Wednesday, October 28, 2009

The Basics for the New Ham, Bob, No. 75

Here are a few questions provided by Mike, KF7DTI for the newer ham...

What is “Legal” (1500 watts) vs. Proper ( 5 to 20 watts) and why…
 First of all, let's look at what the legal limit is: 1,500 watts PEP (Peak Envelope Power) this is defined as the average power provided to the transmission line over one cycle where the envelope is at it's peak.  The envelope is the carrier plus the modulation, so it is the average power of the signal at it's highest modulation.  This gives a good indication of the likelihood of the signal to interfere with neighboring frequencies.

So now we get to the real question, what is proper.  Well the regulations have something to say about that too.  We are required to use the lowest amount of power to accomplish the communications we are trying to do.  This is definitely a gray area and a guideline rather than a hard and fast rule.  Sometimes it can be obvious, you don't need 50 watts to talk on 2 meter simplex to your neighbor a few blocks away.  Sometimes it is not obvious at all, just how much power do you need to be heard by that rare DX station in a South Seas island that dozens of other hams are also trying to reach.  There are endless possibilities for arguments here but this is a sort of "good faith" rule.  You need to use your own best judgment to decide how much power is necessary.

The other reason to use less power is personal safety.  I won't go into the specifics but there is good reason that your handheld doesn't put out more than about 5 watts.  If you want to use your mobile rig as a portable, as many of us in emergency communications do, it is important to get the antenna away from your body and anyone elses.  Just how far is another judgment call but it helps if you also have it up high so that when it is radiating primarily in the horizontal direction, it will be above your and everyone else's heads.

Proper handling of my unit .. will my Mobile work OK in the Freezing snow?..  110 degree Desert Sun?... pouring Rain?
Your mobile rig is designed to stay in a vehicle and to operate in one too.  There are a handful of new weather-proof and even water-proof rigs on the market but leaving those out, you should use your rig where it will be kept dry and reasonably clean.  As for cold and heat, you should check your owner's manual to be sure but generally you can do very well in the cold.  When it gets hot you run the risk of overheating your rig when you run full power.  Once again, this is a gray area.  You can run at a pretty high ambient temperature as long as you use low power.  The more power you use, the lower the ambient temperature has to be.

What happens when my batteries get low?.. How can I tell?
I assume you mean your portable here.  You should here a beep to tell you.  HT's are notorious for beeping about 5 seconds before they shutdown.  None of the HT's that I'm aware of have battery charge indicators.  I may be wrong about this and if anyone knows of ones that do please speak up.

Why is my brand new Mobile that I just put in my  old TRUCK so staticy?
There are a couple of possible reasons.  The most likely is the old truck itself.  It is either emitting radiation from sparking or other electronics or it is causing fluctuations in the voltage where you are hooking up your radio.  For this reason it is usually suggested to connect your radio directly to the battery, properly fused of course.  Then all you have to worry about is the radiation caused by your truck.  The only way I know to diagnose and fix it is to try putting some filters on the wires and see what happens.  But this is a well known problem and there is a lot out there already to help diagnose it.  One reason it happens is that mobile and HT rigs usually don't have the good filtering that base stations do.  You can pay a lot for a Motorola or other rig designed for professional use in high radiation environments and do a lot better. 

I can use my old CB Radio Antenna as my Mobile antenna right?
I wouldn't try it.  Antennas are a huge subject that has been covered in various ERN's.  You can check the blog for more info.  In general, you can probably modify an old CB antenna if you know what you are doing to make it work for amateur radio, but you are almost certainly better buying an antenna build to do the job.  Or you can make your own from scratch.  Most people don't make their mobile anteannas though, that is better suited for base operations.

What is SWR and why do I care? (that is a good subject)
 SWR has been covered a few times and Lee has an exhaustive set of lectures on fundamental electronics leading up to impedance.  In short, SWR, the Standing Wave Ratio, is a measure of how much of an electronic signal that you are transmitting, is reflected at a junction.  The cause of the reflection is an impedance mismatch at the junction.  For example, if you connected your transceiver that has an impediance at it's output of 50 ohms to 75 ohm cable, you will get an impedance mismatch that will cause a high SWR.  Since most of us know to use 50 ohm cable the mismatch almost always comes at the connection to the antenna.  The impedance at the connection to an antenna is a very complex subject and can depend on the antenna height above ground and other factors.  For VHF/UHF it is simplified by the fact that the antenna is high above the ground compared to the wavelength so there is little variation.  That's why you can buy an antenna with a 50 ohm connector and be pretty confident that it actually is 50 ohms.

What does QSL, QTH, QRV, 73… etc. mean?..   When is OK to use “Shorthand” like that?
QSL, QTH, QRV and other three letter combinations starting with Q are known as Q signals.  They come to us from the days of CW where it was worthwhile to have a shortcut for some commonly used phrases.  Q was chosen since it is almost always followed by U so that by creating these combinations, not using U you could be assured that it was not a word.  If the Q signal is followed by a question mark it means that it is a question, if no question mark then it is a positive statement.

For example, probably the most common one heard is QSL.  You will hear it in place of Roger, Acknowledged, etc.  It means, "I acknowledge receipt" or with a question mark, "Do you acknowledge receipt."  This is also the reason for QSL cards, which are an acknowledgment of receipt of a contact form another station.  These are used to prove that you made a contact with that rare DX station.  By the way DX is just shorthand for distance and means a long distance, usually international.

73 goes back a long way as well and just means, "Best Wishes"

There are no hard and fast rules about using these.  The most important thing to keep in mind is that you want to make yourself clearly understood.  If the person or people you are communicating with understand the Q signals it is fine to use them.

Wednesday, October 21, 2009

ASCII one oh one, Lee Bond N7KC

October 21, 2009 Educational Radio Net, PSRG 74th Session

Have you ever wondered about the relationship between computers and data entry? What really happens when you hit a key on your computer and the corresponding character pops up on the monitor? If you are old enough to remember the Mits Altair or IMSAI 8 bit microcomputers then you will have no problem answering these two lead in questions.

Surely one of the oldest schemes for encoding alphabetical characters and numerals is the code developed by Samuel Morse and is known as Morse code. Early amateur radio operators had no choice but to learn the code in order to communicate with their fellow hams. The railroad telegraphers code is a variant of the Morse code and both the radio and railroad schemes were the backbone of the early communications industry.

As telecommunications technique improved the mechanical tele-printer based on the 5 level Baudot code was introduced. Communications was much easier when typing replaced the telegraph key and the distant output was in easily read text. Since only 5 symbols were used the number of possible combinations was limited to 32. If you count all the letters of the alphabet, both lower and upper case, and the numerals 0 through 9, and various punctuation characters it is clear that even a shifted 32 will not do the job.

During the late 50’s, when the early mainframe computers were evolving, it was obvious that something had to be done to improve the encoding of alpha-numerical character information that would be fed to the room sized digital monsters that glowed in the dark.

Enter ASCII, pronounced ass-key, the acronym for American Standard Code for Information Interchange. ASCII is a 7 bit code hence 128 unique bit pattern combinations are possible. Enough combinations to represent all the upper and lower case alphabetical characters plus numbers plus punctuation plus special formatting characters in use at the time. The first meeting of the committee which adopted this code was in 1960. The code later became known as US ASCII since it was only good for English systems.

During this time frame IBM developed a proprietary code known as EBCDIC which was based on all possible combinations of the 8 bits in a byte. There are 256 possible unique combinations of 8 bits so EBCDIC offered twice as many possibilities as did ASCII. EBCDIC was used in the large mainframe computers that IBM produced and ASCII became the standard coding scheme for the micro-computing industry.

From the late 50’s until recently the use of US ASCII dominated the microcomputer industry and information exchange on the Internet. Today ASCII is taking a back seat to the Unicode in its various implementations as UTF-8, UTF-16, or UTF-32 as in Unicode Transformation Format. Using 16 bits, or a word, offers over 65 thousand unique possibilities so numerous languages can be represented in addition to English and this makes the encoding truly universal and a natural for Internet use.

Historically ASCII is a 7 bit code. Always has been and always will be. However, that inviting 8th bit in the word could be useful and double the number of coding possibilities. Implementations of ASCII using all 8 bits became known as "extended" ASCII and found much use for formatting characters and such when word processing came to fore. Other names were "upper" level ASCII in contrast to the original "lower" level scheme.

Let’s look at 7 bit ASCII in some detail to see how it is structured.

Referring to the Bits, Nybles, Bytes, and Words (presentation 71) a few weeks ago we know that computers like to operate with patterns of 4 bits (a nyble), 8 bits (a byte), or 16 bits (a word). If ASCII requires 7 bits then the best choice for a pattern would be the next largest set or byte consisting of an assemblage of 8 bits. The extra 8th bit became useful as a rudimentary error detecting bit and was called the parity bit. More on this later.

A table of the ASCII characters is generally shown as 16 rows and 8 columns. The multiple of 16x8 is 128 so this array matches all the combination possibilities of 7 bits. The first two columns from the left contain all of the, so called, formatting characters, the third column from the left is where you find the various punctuation symbols and math symbols, the fourth column from the left lists the numerical symbols, and the last four columns are the upper and lower case alphabetical symbols.

To identify any one of 16 rows requires 4 bits and the lower 4 bits of the 7 bits is used as the row identifier where bit 1 is least significant. To identify any one of the 8 columns requires 3 bits and the bits 5, 6, and 7 (most significant) are used for this purpose. So, to recap… bits 1, 2, 3, and 4 are used to identify in which row a character is located and bits 5, 6, and 7 are used to identify in which column a character is located. Every box in the array is uniquely identified by a bit pattern. Bit 8 is always a zero unless the optional parity possibility is in play.

The data entry and identification process goes like this. Suppose you depress the capital or upper case "H" key on your keyboard. Bit 7 is forced to a "1" and 6 and 5 remain at zero. Bit 4 is forced to a "1" and bits 3, 2, and 1 remain at zero. Finally the "H" is coded as 01001000 or 48h in shorthand hexadecimal notation. This bit pattern is sent to the computer where it is checked, pattern by pattern, against a table looking for a match. When the match is found the computer proper knows which key was pressed.

Any error in this transmission process is serious since the computer will interpret your intended bit pattern incorrectly. The 8th bit or parity bit allows a low level error check as follows. Parity can be defined as even or odd. If you choose even then if the sum of the 7 bit 1’s is odd you just force bit 8 to a 1 and the overall number of 1 bits is even. If the sum of the 1 bits is even then leave the 8th bit at zero. This same process holds for odd parity. On the receiving end the system will check the count to determine if parity is correct. This scheme will detect all 1 bit errors or odd multiples thereof.

In summary, bits 5, 6, and 7 determine a column and indicate if the symbol is formatting, a number, or alphabetical character. Bits 1, 2, 3, and 4 determine which character of the alphabet or which number or which formatting symbol is to be used.

This concludes the set up discussion for ASCII one oh one. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

Tuesday, October 20, 2009

The Future of the Educational Radio Net

Lee and I are considering ending our involvement with the Educational Radio Net.  If we do, it will very likely end the net itself.

This has been a labor of love for the two of us.   It is a fair amount of work to come up with new subjects each week, research them and write the scripts for them.  Getting on the air and doing the net is the payoff.  What has kept us going has been the interest and participation of the hams checking in to the net.  Lately that interest has fallen off somewhat.  We both agree that we do not wish to continue as it is going now.

We are soliciting ideas, suggestions, questions, etc. to assist us with creating future nets.  We are also looking to add to our base of regular contributors.

To give your suggestions, please contact Lee Bond:

We are very grateful for the contributions from those listed below.  They have helped sustain the net.
John Pollock, K7MCX
Jim Hadlock, K7WA
Brian Daly, WB7OML
Curt Black, WR5J
Boone Barker, KC7RK

Wednesday, October 14, 2009

Extra Class Exam Grab Bag, Bob, No. 73

Tonight was supposed to be about current use of Spread Spectrum in Ham Radio but I couldn't find any information about it.  If anyone on frequency knows about it or knows where to point me to look please let me know.

Instead, tonight I will discuss a few test questions from the Extra Class exam. 

E9B08 (C)
How does the total amount of radiation emitted by a directional (gain) antenna compare with the total amount of radiation emitted from an isotropic antenna, assuming each is driven by the same amount of power?
A. The total amount of radiation from the directional antenna is increased by the gain of the antenna
B. The total amount of radiation from the directional antenna is stronger by its front to back ratio
C. There is no difference between the two antennas
D. The radiation from the isotropic antenna is 2.15 dB stronger than that from the directional antenna

The important point to take away from this is that the total radiation depends solely on the amount of power that is transferred to the antenna.  What the antenna design can do is shape or focus that radiation so that more goes in the direction you want and less in the directions you don't want.

E9D06 (C)
Why should an HF mobile antenna loading coil have a high ratio of reactance to resistance?
A. To swamp out harmonics
B. To maximize losses
C. To minimize losses
D. To minimize the Q

The reactance in the loading coil doesn't contribute to heat loss.  All heat loss comes from resistance.  Resistance acts directly on current, converting it to heat.  Reactance, being out of phase with current, doesn't produce heat and doesn't contribute to losses.
E9D08 (B)
What happens to the bandwidth of an antenna as it is shortened through the use of loading coils?
A. It is increased
B. It is decreased
C. No change occurs
D. It becomes flat

Which of the following types of conductor would be best for minimizing losses in a station's RF ground system?
A. A resistive wire, such as a spark-plug wire
B. A thin, flat copper strap several inches wide
C. A cable with 6 or 7 18-gauge conductors in parallel
D. A single 12 or 10 gauge stainless steel wire

The reason for the thin, flat copper strap is that it increases the Capacitive reactance vs. the Inductive reactance making the strap less likely to become resonant.  For similar reasons the RF ground strap should be as short as possible.
E9D15 (C)
Which of these choices would provide the best RF ground for your station?
A. A 50-ohm resistor connected to ground
B. A connection to a metal water pipe
C. A connection to 3 or 4 interconnected ground rods driven into the Earth
D. A connection to 3 or 4 interconnected ground rods via a series RF choke

We want a very low impedance path directly to earth ground.  We are not trying to match impedance here, just reduce it, so no resistors or chokes.  The metal water pipe might serve as a safety ground, although today, more and more pipes are PVC so don't count on that metal pipe you are connecting to, to be metal the entire length.  But even so, an all metal pipe system in your house makes a pretty active antenna system in itself.  This is not what you want for your RF ground.  The short-run ground strap to interconnected ground rods in the Earth is the way to go.

Tuesday, October 6, 2009

Digital Summer Notes, Boone Barker, KC7RK, No. 72

Notes from Curt Black's “Summer of Digital Communications Fun”

By Boone Barker, KC7RK October 3, 2009

I was a student in the ham radio class taught by Curt Black WR5J during the summer of 2009. Included in the class were Lee N7KC, Bob K9PQ, Tammy WA7TZ, Glen K7GLE and others. We learned about and experimented with a variety of digital communication modes, many of which could be useful for emergency communications. I know that everyone who participated enjoyed the challenge of learning about digital communications. We all owe Curt a huge debt of gratitude for his success in making this a fun experience.

This paper is my effort to recap the summer sessions and some key points that I wanted to remember. Full descriptions and more are in the WA-DIGITAL Yahoo Group site at‑digital/ .


Students met Wednesday evenings from June 6 through August 26, 2009, on the PSRG Seattle repeater (146.960 MHz) for the Educational Radio Net hosted by Curt Black, WR5J.

All 12 sessions were written and led by Curt– Environmental Scientist – ham for ¼ century—had a packet network then in Texas. Also a naturalist – birds and bats and nature in general – Sound Recordist.

Curt emphasized that nearly everything came from the internet somewhere and sources were cited each time. Only of little of the information was based on direct communication with the authors of the software—only when he had questions on how to make something work or what was the current best approach for achieving some objective.

Training purpose: explore and experiment with a variety of digital communication modes over radio.

The WA-DIGITAL Yahoo Group established at‑digital/ for this topic has extensive files and messages on this topic, including a Blog Post script for each session. The information below is only a very brief summary of each session; go to the corresponding Blog Post for complete directions and information.

Session scripts were also posted on the PSRG Educational Radio Net blog at and are still there.

Participants were asked to have a computer, VHF and HF radios and—eventually—a sound card interface, home-brew or purchased.

Session 1 - Intro to Digital Communication, Software and Modes

Planned activity for the summer

Session 1 Intro to Digital Communication, Software and Modes

Session 2 Intro to FLDIGI – Install, Setup and Mode Selection

Session 3 Using FLDIGI – Starting with PSK-31 and Transmitting a Good Signal

Session 4 More FLDIGI – RTTY, the WRAP Utility and RS-ID

Session 5 WSPR – Weak Signal Propagation Reporter

Session 6 MMSSTV Slow Scan Image Transmission

Session 7 Digital SSTV EasyPAL

Session 8 WSJT-JT65A – Terrestrial HF

Session 9 WSJT-HS-Meteor Scatter

Session 10 Packet Radio Using Flex32

Session 11 Packet Radio Using AGW Packet Engine

Session 12 WINDRM – Digital Voice

Soundcard to radio interface options

  • Acoustic coupling: microphone feeding shack audio into your computer and the rig audio softly coming out of a speaker in the room with you fairly close to the mic
  • Hardware: range from very simple ones for a few bucks to $100 for a Tigertronics SignaLink USB. If you want to keep going you can go up to a $369 US Interface Navigator - Lots of choices.

[See and,21.msg23/topicseen.html#new for DIY soundcard interfaces.]

Software now available

  • Multifunctional: Multipsk, MixW, Ham Radio Deluxe and FLDIGI
  • Specialized: Digipan, MMSSTV, EasyPal, WSPR, WSJT, Flex32
  • Interface: AGW Packet Engine, Packet Engine Pro
  • Winlink: Airmail, Paclink

Assignment: install FLDIGI and get ready to receive at the next session.

Session 2 - Intro to FLDIGI – Install, Setup and Mode Selection

The group owes much of what we know about FLDIGI and the Narrow Band Emergency Messaging System (NBEMS) to the Pennsylvania group at .

Fast Light Digital Modem Application (FLDIGI) Software by W1HKJ and Friends ( )


  • CW AFCW (A2).
  • DominoEX: (4,5,8,11,16,22)
  • Hell: Feld Hell, Slow Hell, Feld Hell 5, Feld Hell 9, FSK Hell, FSK Hell-105, Hell 80
  • MFSK: from 4 to 64 tones
  • MT63: 500, 1000, 2000 Hz bandwidths
  • Olivia: – several flavors from 250 to 1000Hz bandwidth and with from 8 to 32 tones
  • PSK: BPSK-31, QPSK-31, BPSK- 63, QPSK-63, BPSK- 125, QPSK 125, BPSK-250, QPSK-250
  • RTTY: 45 baud, 50-baud, 75-baud
  • Thor: (4, 5, 8, 11, 16, 22)
  • Throb: (1, 2, 4)
  • WWV: calibration of soundcard oscillator)
  • Frequency Analysis: measure the frequency of a remote signal that is transmitting a steady carrier.
  • Tune: generates a continuous single frequency audio signal at the exact frequency to which the waterfall cursor has been set

To Install the Software:

See Blog Post 2 in the WA-DIGITAL group files for detailed instructions. A summary: Go to the web site at . Follow steps on the left side of the page to get the FLDIGI software, install, and configure it. Calibrate your sound card offsets by downloading and running CheckSR from . Also download and install NBEMS macros from .

Application Notes

  • Win XP users should load FLDIGI 3.12.4. Vista OS users should install FLDIGI 3.11.4-WinV (available at ) until bugs in the later version are fixed.
  • Bookmark fldigi on-line help at and go to it for info on various modes, and for an index of sights and sounds of digital modes.
  • Install QuickMix by Product Technology Partners at .This is a simple applet that allows you to store all or part of the current state of your audio mixer in a settings file, and to restore the mixer to that state whenever you want.

Try out FLDIGI using some of the following modes and frequencies.

PSK – narrow band low symbol rate modes using single carrier differential Binary Phase Shift Keying, BPSK, or Quadrature Phase Shift Keying, QPSK. This is the most popular digital mode by far. Common PSK31 frequencies: Daytime: 14.070 MHz/USB, 10.140 MHz/USB, 7.070 MHz/USB Evenings/Night: 3.580 MHz/USB, 7.070 MHz/USB, 10.140 MHz/USB

MT63 employs a unique highly redundant Forward Error Correction system which contributes to it robustness in the face of interference and fading.

Olivia is a very robust mode with low error rates, but can be annoyingly slow.

  • HF USB ops – (500Hz/16 Tones): NBEMS recommended USB frequencies: 3.584, 7.074, 14.074 MHz

[See for a full list of Olivia calling frequencies.]

Domino The mode is normally used without Forward Error Correction, as it is very robust. The default speed (11 baud) was designed for NVIS conditions (80m at night), and other speeds suit weak signal LF, and high speed HF use. The use of incremental keying gives the mode complete immunity to transmitter-receiver frequency offset, drift and excellent rejection of propagation induced Doppler.

  • Default calling mode - DominoEX11. NBEMS recommended USB frequencies: 3.583, 7.073, 14.073 MHz

Feld Hell frequencies 3.580, 7.037, 10.137, 14.0635, 21.063, 28.120 MHz

Session 3 Using FLDIGI – Starting with PSK-31 and Transmitting a Good Signal

Recommended reading: Clint Hurd KK7UK presentation at Alaska Hamfest in 2008: go to and click on Digital Communication Basics.

Hints to new PSK users from that presentation:

  1. Make sure you are putting out a pure signal. Don't overdrive the rig.
  2. Ask on the bands for a report from others – the software of the person receiving your signal can report your IMD – should be less than minus 24dB.
  3. Don't type in all caps.
  4. Lower your power to a level of 50% of what your rig can produce so you don’t burn out your finals.
  5. Tune a little above the PSK activity and call with Hell or MFSK16 or Olivia 16/500.

All PSK31 frequencies

160 meters 1.838 MHz

80 meters 3.580 MHz

40 meters 7.035 MHz

30 meters 10.140 MHz

20 meters 14.070 MHz

17 meters 18.100 MHz

15 meters 21.080 MHz

10 meters 28.120 MHz

6 meters 50.290 MHz

2 meters 144.144 MHz

1.25 meters 222.07 MHz

70 centimeters 432.2 MHz

33 centimeters 909 MHz

Note: you will frequently see the wider signals of PSK63 just a little higher.

Session 4 More FLDIGI – RTTY, the WRAP Utility and RS-ID

More features of FLDIGI described in Blog Post 4

Macros: content can be edited by right clicking on the button. Other sets can be accessed by clicking on the end of the bar. Left or right clicking on the mode button brings up options.

Waterfall: the size can be adjusted and magnified.

2-minutes buffer: constantly saving the audio so that a new signal in a different mode can be selected for decoding of that last 2 minutes.

Signal to noise and intermodulation distortion of a received signal are displayed on the bottom of the screen.

The Wrap Utility (downloaded with FLDIGI)

Wrap allows you to transmit a text message, image, or binary file to either single or multiple stations and allow each receiving station to verify that the transmission was received without error. Blog Post 4 has detailed instructions for configuring FLDIGI, converting and sending a “wrapped” message, and receiving and decoding wrapped messages.


The "RS" ("RS" for "Reed-Solomon") identifier allows automatic identification any digital transmission done in one of the RX/TX modes handled by FLDIGI if the sending station is using the feature. In receive mode it can be activated by clicking on the RSID button in upper right.

RTTY (Radio Teletype) is the second most common digital mode.

Look to the following websites for RTTY guidance:

RTTY frequencies:

80 meters: 3580 - 3650 (3520 - 3525 in Japan)

40 meters: 7080 - 7100 in the US (see note below)

30 meters: 10110 to top of band

20 meters: 14080 - 14099 (avoid the NCDXF beacons at 14100)

15 meters: 21080 - 21100

10 meters: 28080 – 28100

Note: RTTY allocations for 40 meters vary greatly all over the world. In the US, RTTY is permitted between 7000 and 7150, although most US activity is between 7080 and 7100. DX activity is often found between 7020 and 7045. The ARRL promotes 7040 as the RTTY DX calling frequency, but the CW QRP’ers use it as their calling frequency too.

Three main digital packages are:

FLDIGI by David Freese, W1HKJ and Skip Teller, KH6TY:

HRD/DM780 by Simon Brown, HB9DRV:

MULTIPSK by Patrick Lindecker, F6CTE:

Patrick’s MULTIPSK is a great technical achievement. He offers the most sensitive modems and detection routines available and many modes (such as ALE-400) that are not available in any other software. The challenge is his user interface is very dense and can be tough on a first-time user. His philosophy is he wants all the controls in one place – and they are.

FLDIGI is a very elegant package that is fully featured but simple to setup and use. HRD is not so simple, but is a great package and when used with DM780 is very fully featured. MULTIPSK offers the most sensitive modems and detection routines available and many modes (such as ALE-400) that are not available in any other software. The challenge is his user interface is very dense and can be tough on a first-time user.

Other packages of significance

WINWARBLER, part of the DXLAB suite and available here:

DIGIPAN – by Skip Teller KH6 and one of the authors of FLDIGI and a founding father of digital modes in amateur radio:

MixW – updated in Jan, 2009 after a long hiatus. Payment of $50 required after a 15-day trial period.

Check out this repository of digital and other ham radio software:

Session 5 WSPR – Weak Signal Propagation Reporter

Joe Taylor, K1JT, of Princeton has written a series of programs for brilliantly combining Digital Signal Processing (DSP) and ham radio to allow us to plumb the depths of weak signal work. WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter." This program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands. Users with internet access can watch results in real time at

Downloads for Windows and documentation are at Follow the Quick Start Guide to install and configure.

Application notes

Soundcard: In Configure>Options, enter the numbers from the “Audio Device” list on the black WSPR screen that comes up at startup. Note that power is in dBm.

Frequency settings are automatic. Just choose the band.

Install Dimension 4 from Thinking Man Software at to keep your computer clock accurate to within 0.01 sec.

This is a weak signal mode – it really doesn’t need much power – try 1 watt (30 dBm) and see who hears you and where they are.

Try operating at local sunrise or sunset to really see what happens as the bands change.

Session 6 MMSSTV, Slow Scan Image Transmission

Download MMSSTV from

Install and configure it using the Help file in the program, or instructions in the WA-DIGITAL Yahoo Group files.

Most common modes: Scotty 1 or Scotty 2 in US. Martin 1 or 2 for DX.

Suggested SSTV frequencies:

· 10 Meters: 28.673 28.677 28.680=calling frequency 28.683 28.686 28.690=K3ASI repeater 28.700=ON4VRB repeater

· 15 Meters: 21.334 21.337 21.340=calling frequency 21.343 21.346 Avoid SSTV around 21.350 because there is a Phone DX Net running

· 20 Meters: 14.230=calling frequency 14.233 14.236 14.239 Avoid SSTV on 14.227 because there is a Phone DX Net running there.

Application Notes

Soundcard oscillator calibration is critical to avoid transmitting slanted images. See “Slant Correction” in the Help menu.

To use this software, just go to the SSTV watering holes at 14.230 or 14.233. This is the best known and possibly the best defended frequency in all of amateur radio.

The Ten Commandments of Slowscan by Dave Jones - KB4YZ

  1. Use voice before sending SSTV.
  2. Wait for voice and SSTV traffic to finish before sending SSTV.
  3. Choose an SSTV mode that is proper for the image to be sent, band conditions, and the receive capability of the receiving stations.
  4. Announce the SSTV mode used prior to sending.
  5. Transmit on frequency as confirmed by calibration of the VFO with WWV.
  6. Send straight pictures as confirmed by calibration of the clock timing with WWV.
  7. Send quality pictures with call sign on image.
  8. Send full frame.
  9. Avoid sending a CW ID unless required by regulations.
  10. Describe the picture only after it is confirmed that it was properly received.

Session 7 Digital SSTV: EasyPAL

EasyPAL is a piece of software by Erik VK4AES that uses DRM encoding and allows us to send any type of file on your computer, including images. We can request “fills” or retransmission of any blocks not received perfectly. Or you can Reed-Solomon encode everything you send to increase the probability your information will make it through the first time.

Download the software from and go to the help file on that web site for configuration instructions and help files.

SSTV frequencies are listed above.

Application notes

Soundcard volume settings are critical. Too high or too low a signal level from your Receiver via your Radio Interface to your PC soundcard will result in Total or partial LOSS OF RECEIVE SIGNAL. EasyPal will correctly receive and decode when ALL RECEIVE INDICATORS SHOW GREEN. Get it right and then use QuickMix to save settings for this application.

Go to Setup>Calibrate Waterfall (WWV) to use WWV signals to calibrate waterfall frequency scale.

[N.B. EasyPal could be a powerful tool for emcomm. It could be used to transmit a standard ICS form along with photos from the field to the EOC.]

Session 8 WSJT-JT65A – Terrestrial HF

The WJT Software was also written by Joe Taylor, K1JT. It facilitates basic digital communication using protocols explicitly optimized for a number of different propagation modes. Specifically:

  • FSK441 for meteor scatter
  • JT6M for ionospheric scatter
  • JT65 for EME at VHF/UHF, and for HF skywave propagation

Download for Windows is at . The user’s guide is included with the download.

JT65 has three sub-modes known as JT65A, B, and C. They are identical except for the spacing between transmitted tone intervals. At the present time JT65A is generally used on HF and 50 MHz, JT65B on 144 and 432 MHz, and JT65C on 1296 MHz. JT65 uses 60 second transmission and reception intervals.

Andy K3UK has an excellent JT65A guide at

By far the simplest method of figuring out where the action can be found is to use your web browser and go to the JT65 Terrestrial Link web site by N0UK at‑bin/jt65talk .

The most commonly used JT65A frequencies are: 14.075 to 14.076 7.075 7.076 in North America 7.042 to 7.043 7.025 LSB for Europe and Oceania 3.576 (North America) 3.796 (Europe) 18.102 & 18.106 10.147 21.076 24.910 1.805 to 1.808.

14.076 or 10.147 or 7.076 are the best places to start. These are DIAL frequencies.

Application Notes

Important: use the WSJT7 black and white DOS-like window to check your input and output device numbers –then transfer that info to the colorful WSJT7 by K1JT window - look under the SETUP menu - OPTIONS choice and enter the AUDIO IN and AUDIO OUT device numbers you got from the first column on the DOS-like black window.

As before, input volume level is critical.

Soundcard oscillator calibration is also important. See the help files.

Operating with WSJT

By longstanding tradition, a minimal valid QSO requires the exchange of call signs, a signal report or some other information, and acknowledgments. WSJT is designed to facilitate making such minimal QSOs under difficult conditions, and the process can be made easier if you follow standard operating practices. The recommended procedure is as follows:

1. If you have received less than both calls from the other station, send both calls.

2. If you have received both calls, send both calls and a signal report.

3. If you have received both calls and a report, send R plus your signal report.

4. If you have received R plus signal report, send RRR.

5. If you have received RRR — that is, a definite acknowledgment of all of your information — the QSO is “officially” complete. However, the other station may not know this, so it is conventional to send 73s (or some other conversational information) to signify that you are done.

Typing the F5 key will cause WSJT to pop up a screen that reminds you of the recommended procedures.

Digital on Six at promotes the use of digital modes on the 6 meter band. A weekly event is the JT65B activity on Friday evenings in 2 phases: 9:00 pm Eastern and then 8:00 pm Pacific time. Default Mode JT65B on 50.294MHz. When the "Band Is Open" QSY to PSK / Olivia / etc. on that mode’s appropriate calling frequency. 50.260 WSJT Modes (Calling Frequency) 50.290 PSK31 50.2925 Olivia 50.294 JT65B & Friday Activity Period Calling Frequency 50.300 RTTY and MFSK

Session 9 WSJT-High Speed-Meteor Scatter

WSJT/FSK441 is now the primary meteor scatter program and mode over nearly all the world.

Go to for Standard Operating Procedures for FSK441 meteor scatter communications within the Americas. Read this!

Go to Ping Jockey Central at and click on “read this!” at the top of the page to see Ping Jockey Etiquette. On that page are messages from ongoing HSMS scheds and contacts.

Go to for the WSJT Group –information and news about meteor scatter, including Random Hour operations on Saturday and Sunday mornings. See also the WSTJ Yahoo group.

Application Notes

Computer clock must be accurate.

In North America, 50.260 MHz and 144.140 MHz are calling (CQ) frequencies—not operating frequencies. Schedules should always be made at least 5 kHz away from the calling (CQ) frequencies.

"CQU5" means "I'm listening and will reply Up 5 kHz." "CQD8" means "I'm listening and will reply Down 8 kHz". The offset frequency is always relative to the CQ frequency.

“CQ123” means "I'm listening and will reply on 144.123 MHz."

The commonly-accepted (and expected) exchange for all HSMS operation is the burst duration-signal strength report ("2-number" report).

First Number: Ping Duration

Second Number: Signal Strength

1 - Ping with no info. (Not sent)

2 - ping, up to 5 sec in length

6 - up to S3 in strength

3 - 5-15 sec in length

7 - S4 to S5

4 - 15-60 sec burst

8 - S6 to S7

5 - over 60 sec burst

9 - S8 and stronger

Best time for MS operations is in the morning hours, around 0600 local time, when that part of the earth is facing the same direction as the direction of travel of the earth in its orbit around the sun.

Session 10 Packet Radio Using Flex32 and Paxon

Soundcard packet makes amateur packet radio available to any Ham with a VHF transceiver and a soundcard-equipped computer, at little or no expense.

For the classic “Introduction to Packet Radio” by Larry Kenney, WB9LOZ, go to .

Flex32 Software written by Gunter Jost DK7WJ

Go to,21.msg23/topicseen.html#new for a tutorial by Charles Brabham N5PVL with download and installation instructions. Two programs are downloaded: this file contains the Flex32 software, some assorted drivers, and a simple terminal program and this is the soundcard driver module, along with a setup utility.

Installation: See Blog Post 10 for details. Briefly: Unzip into C:\FLEX32. Run soundmodem.config to configure soundcard driver. Run Flexctl.exe to bring up the Flexnet Control Center and add “soundmodem” to the channel parameters. Create a command-line shortcut to Tnc32.exe with parameters “call‑sign 4 4” to bring up TNC32. Key Esc to enter command mode and key H to list available commands. This is a simple terminal program that may be used to connect to a packet network

In Seattle, connect to SEA on 145.010 MHz.

Paxon software written by Ulf Haueisen DG1FAZ

Go to,20.0.html for another tutorial by Charles Brabham N5PVL with download and configuration instructions. The web-site, help files and installation program for Paxon are all in German, but the program comes up ready for English speaking users. However, the help file is still in German.

Paxon download is at for download. See Blog Post 10 for details of installation and configuration.

First Steps are listed in the Help tab

Click on Tools, Settings.

Select General, My Calls, Add.

Enter your Callsign and specify the connectable SSIDs.

Setup your Modems and TNCs: Devices, Device drivers, Add.

Select Flexnet or Hostmode.

Select your devices in the list, and edit their Properties.

Confirm the settings with the OK-Button.

Click on Connect to make your first connect with Paxon. Have Fun!

Try browsing around in Paxon's "Settings" and you will be amazed at all of the nice things this program can do. It can be used for file transfers, remote SYSOP'ing, and as a personal terminal.

Session 11 Packet Radio Using AGW Packet Engine

AGW Packet Engine by George Rossopoylos SV2AGW handles all the traffic between packet applications and the computer/radio interface—TNC or soundcard. It is freeware from the SV2AGW web site at in the “Downloads” section. A lengthy tutorial by Ralph Milnes KC2RLM for installation and configuration is located at . See Blog Post 11 for details.

A full featured version is Packet Engine Pro, with one month free and then $59 license fee. The SV2AGW web site also has software downloads for AGWTerminal and AGWMonitor, both useful accompaniments to AGWPE.

Application Notes

When you configure a radioport in AGWPE for SignaLink USB, select an unused printer port (LPT3) as your PTT port.

Always format packet and WL2K messages in plain text. HTML format adds unnecessary bytes to the message.

For use with Airmail software, download and install AM to PE software by Brian Smith KG9OG from .

Session 12 WinDRM—Digital Data and Voice Using Digital Radio Mondiale on the Ham Bands

The problem with digital voice modes is the loss of the use of a proprietary codec. Digital voice is about dead and probably will remain that way until a MELP equivalent codec is found or some new technology is found. See Blog Post 12 for more information.

If you want to try it, here is the link: .14.236 MHz is the calling/net frequency for digital voice.


At this writing, the WA-DIGITAL Yahoo Group is active—and the group web site at‑digital/ has a large collection of files and information about digital communications for Radio Amateurs. If you are interested in this topic but not yet a member of the group, please consider joining.

October 5, 2009

Wednesday, September 30, 2009

Bits, Nibbles, Bytes, and Words, Lee Bond N7KC

September 30, 2009 Educational Radio Net, PSRG 71st Session

The digital computer is ubiquitous. These computers are everywhere. Kids have their own and, more than likely, so do the grandparents. Most users are very proficient with the keyboard and blaze through the games, documents, spreadsheets, and whatnot without even a thought of what is going on inside that mysterious box called a computer. I am willing to bet that not one in ten users can define a "bit" and I will further wager that not one in 100 users has a good grasp of computer arithmetic or how the rational coding of bits makes their computer tick.

My task tonight is to lead you down that magic path and explore the idea of the "bit" and how it can be used to represent numbers or events. We will then extend the bit notion into nibbles, bytes, and words. Some of the net participants tonight are likely to be expert in this bit world so, if you quality, think of ways to help me clarify the notion when I break for questions or comments.

Let’s start with our very familiar decimal number system and dissect it in a way that I bet few of you have done. We will concern ourselves only with integers so no fractions are allowed in our discussion. Integers are the numbers 1, 2, 3, etc. that have no fractional part. You may call them whole numbers if you please. Integers can be precisely defined but that would muddy the water a bit so we will dispense with such formalism in favor of simplicity. We will start with the integers 1 through 9 and include the notion of nothingness as in zero.

When we think of the decimal integers we must consider the ordering. For example after nothingness as in zero we think of 1, then 2, then 3, etc. in order through 9. Our standard notion of 9 is that it is ‘bigger’ than 8 and 8 is ‘bigger’ than 7 or 6 or 5, etc. In the following discussion throw ordering out the door. We will not be interested in ordering. In fact we will not even use numbers rather we will choose a collection of identical marbles and call then symbols. So, zero (or nothingness) plus 1 through 9 equals 10 symbols which we represent with 10 marbles.

Unfortunately this forum of ours does not include a chalkboard so we must create a virtual chalkboard in your mind. If it helps then close your eyes and imagine the following: in your mind arrange 6 boxes in a 2 row x 3 column array. Each of the boxes in the top row has 10 identically sized marbles and the row of lower boxes have ‘nothing’ or zero marbles. Just so we do not get marbles in the wrong boxes lets choose black marbles for the rightmost box, brown marbles for the center box, and red marbles for the leftmost box.

Ok, lets do something useful with this scheme. Assume that you are sitting on the back porch looking toward the Cascades and you want to tally lightning strikes. When the first strike occurs you move a black marble from the top right box into the box below. At the next strike you repeat the previous operation and move another black marble from the top right box into the box below. As you notice more and more lightning strikes you move black marbles until you have no more black marbles in the top right box. At this point you have used all of your marbles, so to speak, and you indicate this fact by moving a brown marble into the middle box below then move all of the ‘used’ black marbles back into the top right storage box.

The lightning strikes continue and you move black marbles, one by one, into the lower box until you again run out of marbles. At this point you move a brown marble from the top box into the box below and reload the top box with the black marbles. Eventually you will run out of brown marbles in the top center box so you will move a red marble from the top left box to the box below and reload the top boxes with appropriate black and brown marbles.

The point of this mental exercise is to illustrate that you can tally objects with symbols and that every time you exhaust, or cycle through, your symbol set you just indicate this fact by incrementing the symbol set to the left. You can choose as many symbols as you please. In this example, based on the decimal system with 10 symbols, each box to the left is weighted or "heavier" by 10 with respect to its neighbor to the right. As a result, this 10 symbol scheme goes units, tens, hundreds, thousands, etc. so is very convenient for us mortals. Once you know the weighting you can easily figure out how many lightning strikes you tallied by counting the symbols in each weighted box.

In the interest of time let me assert that you can use a set of 12, or 9 or 8 or 7, etc. symbols and the scheme holds true. Now lets examine the case where we have reduced the set to two symbols. Thinking for a moment you realize that "bi" means two as in binary star or binocular. Could the binary number system be as simple as accounting for just two symbols? The answer is, of course, yes. The beauty of using two symbols in numerical computing is that transistors are very good switches and can be used to represent the two binary states perfectly. A SPST switch normally has two states such that it is either on or off. Open or closed. It is a trivial exercise to arrange a circuit with a mechanical switch such that one switch position results in +5 volts and the other position results in zero volts. The symbols associated with a two state switch are zero and one as in 0 or 1.

Now, in a fashion similar to the decimal box exercise above let’s arrange 8 binary boxes side by side in a row. We know that the state of each of these "binary" boxes can be represented by either a 0 or a 1. Assume that the rightmost box is the, so called, least significant box and that all boxes are in the 0 state. Visually the boxes look like 0000 0000. Now, bump the rightmost box to the 1 state and the visual presentation goes to 0000 0001. Well, the rightmost box has now used all of its symbols so to tally the next event it must return to 0 and the box to the left is bumped from 0 to 1 as in 0000 0010. If you carry this process forward you will eventually achieve 1111 1111 and the next event will change all positions back to 0000 0000. The weighting goes by 2 rather than 10 as in the decimal case so each position to the right is ½ of its left neighbor or each position is twice its neighbor to the right. The sequence is 256, 128, 64, 32, 16, 8, 4, 2, 1. These 8 boxes represent a byte and each of the positions is a binary digit or bit. Two sets of 8 boxes as in 2 bytes or 16 bits represents a binary "word". Half a byte as in 4 bits is a nibble (or nybble to some).

The total number of distinct combinations of 8 bits from 0000 0000 to 1111 1111 is 256 and goes as 2^8. A binary word composed of 16 bits can assume 2^16 or 65,536 distinct combinations. Recall that we are limiting ourselves to positive integers so we are only able to handle numbers up to 65,536. There are schemes to handle signed integers such as 2’s complement arithmetic and to be completely flexible there are floating point schemes which look a lot like scientific notation.

Four binary bits can assume 16 distinct combinations and is the basis of the hexadecimal number system which has symbols 0 through 9 plus A, B, C, D, E, and F. Four binary bits are also used for BCD or binary coded decimal notation by throwing away the six unused states.

How would one go about doing math operations on a computer? Well, microprocessors are very good and quick at adding or subtracting but clumsy when multiplying or dividing. Early microprocessors required many operations or, so called, clock cycles to produce numerical products and it was common to have a math coprocessor standing by to do the heavy lifting. For example, if you want to multiply a number by 10 in the decimal system you just move the decimal point one position to the right. In the binary system you would shift left (x2), shift left again (x4), shift left again (x8), and then add twice to achieve the 10x product. Clearly, there is a lot of time consuming overhead doing math in this fashion. Contemporary microprocessors are constructed with onboard and dedicated numerical processors with slick routines and which unburden the main unit.

If you look at the schematic of any computer one thing will pop out immediately. There are lots of parallel paths connecting the various semiconductor packages. These parallel wire structures are called busses and might be as wide as 16 bits… possibly more… for memory addressing as an example. There is likely a data buss as well. One line generally represents the buss with breakouts at the ends. Each wire handles one bit of data on the data buss.

In summary, the intent of this presentation is to show that symbols can be used to tally events and that recycling symbols will work in any number system. Starting with the familiar decimal number system and showing that symbol manipulation leads handily to the very simple two state, or binary, number system. A bit is a two state binary digit, a nibble is four associated bits, a byte is 2 associated nibbles or 8 bits, and a word is 2 bytes of 16 associated bits. Modern computers are said to have 32 bit words and, in some cases, 64 bit words.

This concludes the set up discussion for bits, nibbles, bytes, and words. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

Wednesday, September 23, 2009

Phase Shift Keying, Bob, No. 70

Tonight I am continuing with my series on Spread Spectrum Radio. I am going to discuss Phase Shift Keying (PSK), which is the form of modulation used by Direct Sequence Spread Spectrum (DSSS) Radio.

Spread Spectrum Radio Review
Let's have a short review of spread spectrum. The two main kinds in use in ham radio are Frequency Hopping and Direct Sequence. Frequency hopping is relatively easy to understand. Your carrier, rather than being on a fixed frequency, jumps from one frequency to another. As long as the equipment receiving makes the same jumps you will be able to transmit the signal and prevent interference on any one frequency from causing a problem. This can be used for analog or digital transmission but is most commonly used for digital. Note that you must have a pattern of frequency changes that is known to both parties in order to allow the receiver to follow the transmission.

In the other method, Direct Sequence, you only transmit digital information. In fact the name "Direct Sequence" comes from the 11 digit sequence of ones and zeros that is used to modulate the carrier. If your data bit is a zero then you send the sequence normally. If your data bit is a one then you send a one where the sequence has a zero and send a zero where the sequence has a one. For example 101 would turn into 010. I mentioned that the carrier is modulated by this sequence but I didn't say how. It is modulated using Phase Shift Keying.

Phase Shift Keying (PSK)
So, what exactly is phase shift keying? It is a way of changing the phase of a carrier to transmit a digital signal. In essence what you are doing with PSK is phase hopping. In the simplest example called Binary Phase Shift Keying (BPSK) you hop 180 degrees out of phase to transmit a certain piece of digital data. So the signal is either in it's "normal" phase or in it's 180 degree out phase which is to say, inverted. Note that the frequency of the carrier isn't changed but when you change the phase and modulate the carrier you create side-band emissions. The faster you modulate the signal, the wider the side-bands. In addition to BPSK there is Quadrature PSK (QPSK) where the phase can be one of four values, 0, 90, 180 or -90. There is also 8PSK using 8 phase angles and so on. The general term is Multiple Phase Shift Keying (MPSK).

Differential Phase Shift Keying (DPSK)
Basic BPSK has the signal at normal 0 phase to represent a digital zero and at 180 degrees out to represent a digital 1. A commonly used variation on this is called Differential Binary Phase Shift Keying (DBPSK) and instead of a 1 being 180 degrees out of phase, a 1 always changes the phase while a 0 always keeps the phase the same. This way you don't need a reference signal to know which is 0 degrees and which is 180 degrees.

If you want a very narrow signal you are limited to a slow digital transfer rate. This is the case with PSK-31. The 31 comes from the 31.25 bits per second data rate which generates 31.25Hz sidebands. This is pretty much the opposite of spread spectrum. The whole point of PSK-31 was to use such a small slice of the band that you could actually fit many PSK-31 channels in the space of a typical SSB voice bandwidth.

PSK for Spread Spectrum
With spread spectrum you want a very wide bandwidth; by definition, one that is much wider than necessary to convey the information. By encoding each bit of data with the 11 bit sequence used in DSSS you now modulate the signal 11 times for each bit transferred. So for a 1 Mbit/sec transmission, you modulate at 11 MHz. This achieves the spread spectrum you are looking for. This modulation is encoded using DBPSK and a suppressed carrier.

Wednesday, September 16, 2009


September 16, 2009 Educational Radio Net, PSRG 69th Session

What a digital summer we experienced at the hands of Curt Black, WR5J! Curt pulled all the stops on a summers survey of free software downloads for your computer which, more or less, turned your radio into an analytical tool. As impressive as this tour was, one must ultimately realize that the most complex task that your computer performs is based on tiny packets of electrons or "charge" being directed here and there by the software commands. Elemental electrons in motion, or moving electric "charge", is the bottom line idea in electrical theory and all electrical devices including radio equipment.

Let's review what we know about "charge". We know that it enjoys the symbol Q in the literature. We also know that it is an assembly of electrons and can be as few a one electron. We know that a collection of electrons numbering 6.14 x 10^18 is known as a Coulomb of charge. We know that charge will move under the influence of an electric field. We know that the original notion, or conventional notion, of charge was based on the erroneous idea that charge carried a positive sign hence moved in the direction of an applied electric field. Modern theory has reversed the original positive charge idea since electrons are negative entities and, in fact, move counter to the direction of any applied electric field. We know that charge can be motionless as in static charge. We know that an electrical current is charge in motion. It would seem that we know a lot about charge.

The study of charge is best represented by the science of Physics with Physical Chemistry running a close second. The study of charge as it applies to the vacuum tube would come under the heading of Classical Newtonian Physics in contrast to the study of charge in semiconductor materials which would come under the heading of Modern Quantum Physics. In my view the vacuum tube represents the most elegant device for demonstrating the behavior of electrical charge influenced by an electric field. Lucky me to be raised in the heyday of the vacuum tube. As late as 1963 the US Navy destroyer to which I was assigned had a single piece of transmitting equipment that had modern solid state diodes in the circuitry. The selenium rectifier preceded germanium devices and modern silicon devices and required no heater but it is a stretch to include it as more than a rudimentary solid state device. The solid state transistor with all its ramifications is a relative newcomer to the field of electronics. Modern radio equipment's are solid state for the most part and only the old timers can relate stories of warming their hands in the glow of those magnificent glass bottles.

No one has actually seen an electron. These entities are very, very tiny and to image them requires wavelengths small in comparison to the size of an electron. The one common instance of, more or less, stationary electrons occurs in the lattice structure of many crystals and x-ray crystallography has demonstrated diffraction images suggesting that these things are real. The fact that we can manipulate these tiny guys to the degree that we can is testimony to the very clever work of early scientists.

We know that conductors have an abundance of so called "free" electrons. This is in contrast to tightly "bound" electrons which are not available to contribute to electric current flow. For example the neutral copper atom has 29 electrons associated with the nucleus in 4, so called, shells with the innermost shell containing 2 electrons followed by the next shell containing 8 electrons followed by the next shell containing 18 electrons followed by the outermost shell with a single, so called, valence electron. The three inner shells are tightly bound to the atomic nucleus but the outer single electron is easily forced out of place and can contribute to the electric current bumping along a copper wire. Most metals are conductors to varying degrees with silver, copper, and gold at the top. A copper atom missing its valence electron is known as a copper ion.

I think we now have enough information to appreciate how a two terminal vacuum diode works so let's move on to some apparatus to demonstrate the effect. Forget the little glass bottle for the moment. We are going to use a laboratory bell jar and good quality vacuum pump as a part of our apparatus. Everyone has seen the "bell" jar on a stand with a mechanical vacuum pump attached. For our purposes the bell jar stand needs some electrical penetrations so that we can supply potentials to the bell jar innards. The first of the two inside devices is the filament or heater which also serves as a cathode. There are several schemes for heaters so let me select the one known as the directly heated filament cathode. This will be a tungsten wire section which will glow a bright red to orange when filament voltage is applied. Adjacent to the filament-cathode wire we will position a "plate" of flat metal such that it does not touch the filament. This metallic plate is, in fact, called the "plate" electrode in vacuum tube terminology and serves as the anode. Note that the plate may be cylindrical and surround the filament in real world devices.

Our demonstration diode is complete. We have a filament (cathode) and plate (anode) plus a means of producing a good vacuum so on goes the bell jar but someone forgot to start the vacuum pump. Not realizing that a good vacuum is missing we switch on the filament voltage and sure enough the filament starts to light. Then there is a bright flash as the oxygen in the bell jar contributes to the destruction of the filament. Oops. Off with the jar and we install another filament wire. Ok, this time we turn on the pump and let it run until it chortles. Now when we flip the switch for the filament the wire glows a cheery orange. The chortling pump indicates that the internal vacuum (or pressure) is in the 1 to 10 micron range and suitable for our demonstration. The low internal pressure means that atoms of oxygen and nitrogen are scarce and will not interfere with the electronic process that we are interested in observing.

Let's think about the filament voltage for a moment. I did not mention it but the source of the filament voltage is a battery. Traditionally the battery used for filament power is known as the "A" battery.

So, here is our situation... we have a nicely glowing filament with an unconnected plate nearby and both are within a reasonably good vacuum. The glowing filament is probably heated to 800 degrees F or thereabouts and the thermal energy of the filament has caused lightly bound electrons to break free and form a cloud in the immediate vicinity of the filament-cathode. The thermal energy for breakaway is known as the work function and metals vary in this regard. Some substances such as barium offer very low work functions and are used in cooler, indirectly heated, cathode structures.

Our cloud of electrons is negatively charged. If we cause the nearby plate element to become positively charged with respect to the filament-cathode then the electrons will move toward the plate anode and, since moving electrons constitute electrical current, we can measure a plate current if we insert some current measuring device in series with the plate. With regard to the plate, the battery traditionally used to supply plate voltage is known as the "B" battery hence follows the term B+ for the plate positive voltage supply.

There is a third battery associated with vacuum tubes which is known as the "C" battery however it is not relevant here since we are using a two terminal device or diode and the C battery is only relevant in triode structures and beyond for grid biasing.

At this point we have demonstrated that electrons will traverse a vacuum if the plate is positive with respect to the source of electrons. If the plate is negative relative to the source then the electrons are repelled and no plate current will flow. Herein lies the secret of the rectifying diode. If the plate is alternately positive then negative with respect to the cathode as would happen if connected to alternating mains then plate current only flows on positive excursions of plate voltage. Bi-directional current from AC mains becomes unidirectional current in the plate circuit. A single diode offers half wave rectification and a dual diode (or two individual diodes) offers full wave rectification.

The high vacuum in the bell jar or little glass bottle performs two functions. First the pumping process removes virtually all oxygen so the filament suffers no oxidation. Secondly, the high vacuum is synonymous with low pressure both which equate to few residual gas particles present to hinder electron flow from cathode to plate anode. In reality small glass bottles with high internal temperatures will out gas damaging particles which will poison the vacuum so special devices known as "getters" are used internally to trap these vacuum destroyers.
Special attention must be given to the metal leads going through the little glass tube envelopes. If the glass and wire conductors do not expand and contract in the same manner with extreme changes in temperature then the seal will be broken and the tube will be rendered useless in short order. Special wire alloys which match the glass thermal characteristics are used to avoid this problem.

In summary, the physics and mathematics associated with the classic vacuum tube is elegant and a fun pursuit for the very curious. The concept of electronic charge flow within a triode vacuum tube is easily grasped and directly applicable to field effect transistors. The natural extension from diode to triode by introducing a control grid between cathode and plate made possible amplification and the rest is history.

This concludes the set up discussion for the Vacuum Diode. Are there any questions or comments with regard to tonight's discussion topic?

This is N7KC for the Wednesday night Educational Radio Net

Wednesday, September 9, 2009

Winlink 2000, Boone Barker KC7RK, no. 68

The Winlink 2000 System: E-Mail by Radio for Radio Amateurs
Boone Barker, KC7RK

This paper provides a brief introduction to the Winlink 2000 system—what it is and how it works, and how to become a user.

To start, here are a couple of defining quotes from the Winlink web site at .

“Winlink 2000 (WL2K) is a worldwide system of volunteer resources supporting e-mail by radio, with non-commercial links to internet e-mail.”

“To use the Winlink 2000 system, you must hold an Amateur Radio license or be a member of a supported organization or agency. Use of the system and all software is free of charge for those who qualify.”

So Winlink is global, with access around the world. It is developed and supported entirely by volunteers. It is free. The system provides e-mail services to licensed Radio Amateurs without access to the internet such as mariners at sea or expeditions in remote areas.

In addition, a growing number of government agencies and organizations have included WL2K in their emergency communication plans. Winlink 2000 can provide user -to-user e-mail services in a familiar format from inside a disaster area, using only a radio to connect to the outside world.

Elements of Winlink 2000
At the heart of the WL2K system are five mirror image, redundant Common Message Server (CMS) hubs. They are located in San Diego (USA), Wein (Austria), Perth (Australia), Halifax (Canada), and Washington DC (USA). With this redundancy, the system will remain operational even if large segments of the internet are down.

Connected to the five CMS sites are a multitude of Radio Message Server (RMS) nodes, like spokes on a wheel. Traffic flows between the CMS hubs and the internet e-mail recipient, and between the end users and the RMS gateways.

As an aside, the term “PMBO” (for a participating mailbox) is being phased out, but still shows up in Winlink writings.

The radio network has both RMS HF stations and RMS VHF/UHF Packet stations.

RMS HF stations form a controlled and frequency-coordinated global network of Winlink stations. The HF stations all use Pactor, a digital ARQ mode that transfers text files and graphics quickly and error-free. Pactor 2 and 3, the faster modes, are only available on TNC’s produced by SCS in Germany. The WL2K Development Team is working on WINMOR, a new HF transmission protocol that will be freely distributed. It will complement, not replace Pactor; RMS HF stations will be able to handle both modes.

RMS VHF/UHF Packet stations are also part of the network, providing automated messaging capability using AX.25 packet radio in combination with the WL2K Common Message Servers. Although limited in range, RMS Packet stations are widely available in the United States and a few other countries. RMS Packet can provide regular local access to Winlink, or a temporary emergency portal for radio e-mail users, or for fixed installation at unattended remote locations where it can provide radio e-mail communications to the “last mile.”

The locations of public and emcomm RMS stations are shown in maps on the Winlink web site. Related status tables list station call sign, with frequency and mode and grid locator. Note that information about frequencies used by RMS HF emcomm stations is limited to authorized sysops and users.

WL2K Client Software
Paclink is a Winlink 2000 radio e-mail client that links to common e-mail programs such as Outlook Express and Mozilla Thunderbird. Paclink adds telnet, VHF packet radio, HF Pactor radio and WINMOR HF radio channels for WL2K connectivity to compatible user e-mail client programs. Installation and configuration are relatively easy.

Airmail is the oldest and most widely used e-mail program for sending and receiving messages on the Winlink system. Airmail supports HF Pactor, VHF/UHF Packet, and telnet connections over any TCP/IP medium including the internet and high-speed radio media like D-Star. Airmail also has position reporting capability, and a very nice HF propagation prediction program. It can be linked to common e-mail programs such as Outlook Express. Installation and configuration are somewhat difficult, but a nice guide is available; just Google “INSTALLATION AND SETUP FOR WINLINK AIRMAIL”.

Airmail is a stand-alone e-mail program. The primary drawback of Airmail is that it only works with a short list of hardware modems. But it is well suited for WL2K HF connections using a Pactor modem. And the latest version of Airmail 3.3.081 can be used with AGW Packet Engine and a soundcard to make VHF/UHF packet connections, by installing AMPE software. See web site.

On the other hand, Paclink has to be linked with an e-mail program. But it works with a wide variety of hardware TNC’s and modems and with AGW Packet Engine. TNC initialization scripts can be modified by the user. Also, scripts can be used to connect through a digipeater or packet node. CMS Telnet is simple and easy on Paclink, to send and receive WL2K messages on an internet connection.

Both programs are free to download from the Winlink web site.

Other software
AGW Packet Engine (AGWPE) handles traffic between your TNC or soundcard and packet programs that are configured to use AGWPE. It is free to download from the web site. A lengthy tutorial for installation and configuration is located at .

Winlink 2000 RMS Packet gateways can also be accessed with regular packet software, to compose and send a message from the keyboard. Just connect to the RMS Packet node and read the greeting. Type H for help and then follow the instructions to compose a message. This is perhaps the easiest way to try out Winlink if you already have a packet setup.

For telnet connection to a CMS, the only hardware needed is a computer with internet access. WL2K e-mail through RMS Packet stations requires a VHF radio, a compatible TNC or modem or soundcard, and necessary interface cables.

To connect with an RMS HF gateway on Pactor 1 requires that you have any one of the hardware TNC’s on setup lists in Airmail or Paclink. Pactor 2 or 3 requires that you have a Pactor TNC made by SCS . These cost $1,000 or more.

How do you get started?
First and obviously, you need an amateur radio license. With that, here is a suggested initial sequence.

Go to, register on the web site, and download Paclink or Airmail—your choice. Install and configure the software for telnet to a CMS site. Compose a test message to your internet e-mail address. Send the message using the telnet connection. When that is successful, reply to your Winlink e-mail address.

Another option: if you already have an operational packet setup, use it to connect to a local RMS Packet node. The Winlink web site has a map that shows all of the active RMS Packet stations. Just zoom in on your local area and pick them out. Then go to the Reports tab on the Winlink Web site, scroll down to RMS Packet Status, and look up frequencies of those stations in the table. Sometimes these local nodes are not functioning. So if you don’t get a connection, try another station.

With your first radio or telnet e-mail you will be registered in the WL2K system. Your e-mail address will be [your call]

You can use WL2K client software with packet and your TNC if it is listed in the setup for Paclink Packet TNC Channels or in Airmail VHF Packet Client Setup. Check out the TNC using a simple terminal program. Then try connecting to one of the local RMS Packet stations.

If you want to use a soundcard for packet, first download and install AGW Packet Engine. Create a new radioport for your soundcard. Then configure Paclink or Airmail to use AGWPE. Remember that Airmail requires that AMPE be running. There is a link to AGWPE is the Airmail TNC list but it is not functional.

You might also want to download AGWTerninal, and AGWMonitor from the SV2AGW web site. They are free. AGW Monitor lets you see all the traffic to and from your TNC/modem/soundcard, and AGWTerminal is a nice simple terminal program. AGWTracker is a simple APRS program, also nice. All require that AGWPE or Packet Engine Pro be running.

If an online course is to your liking, there is a “Winlink for Dummies” course that takes you through all the steps. It can be accessed through www/

Some recommendations
You should always format WL2K e-mail messages in plain text. HTML format adds unnecessary bytes to the message. Attachments should be made as small as possible.

Learn about the Winlink Whitelist and how to work with it. This is an anti-spam filter. E-mails to your Winlink e-mail address need to have //WL2K in the subject line or they will be rejected—unless they come from an e-mail account on your Whitelist. E-mail addresses on outgoing messages are automatically added to your Whitelist.

When you configure a radioport in AGWPE for SignaLink USB, select an unused printer port (LPT3) as your PTT port. It’s easy to hang up at this point in the setup.

Winlink 2000 has been used since 1999 by Radio Amateurs at sea and in the jungles to send e-mail messages by radio. As a result of experience in Katrina recovery operations and other disasters, Winlink has been included in operational plans of a growing number of emcomm organizations such as RACES and ARES units, Red Cross, MARS, Baptist Relief, and the Salvation Army.

Another defining quote from the Winlink web site:

“The WL2K mission is to provide, through a volunteer network, effective last resort communications in civil emergencies and personal communications in non-emergency conditions.”

As a Radio Amateur, you may already have experience with packet radio—that’s all you need to access Winlink by radio. Another simple start involves connecting by telnet over the internet. And if you are already a Winlink user, you might consider becoming the sysop for your own RMS Packet station. Software and guidelines are on the web site.

So have fun setting up Winlink and trying it out. It might well be very useful in an emergency, to you and to your community.

September 9, 2009

Tuesday, September 1, 2009

Spread Spectrum Communications, Bob, no. 67

Tonight's topic, spread spectrum communications, may seem to be the stuff of spy fiction and ultra-expensive military hardware, but you have almost certainly used spread spectrum whether you know it or not and you probably have the sophisticated spread spectrum radio gear right in your own house. I'm talking about wireless networking gear, also known as WiFi. More on that later.

According to the ARRL Handbook, spread spectrum is defined as using an RF bandwidth much larger than needed to carry the signal, and where the bandwidth of the signal is independent of the modulation by the signal. It is a form of radio transmission that makes use of a wide bandwidth to avoid interference by noise or other signals. You can imagine that if you are transmitting a simple AM signal over 100 frequencies at the same time then someone transmititng on any one of those frequencies will only contribute one percent toward the final recombined signal. This would be fine until you had someone else also transmitting an AM signal on the same 100 frequencies. Then you would be back to a big interference problem. Partly in order to allow hams to use the same frequency range, there are more sophisticated ways to use those multiple frequencies. We will discuss those in a moment.

In general, spread spectrum transmissions offer three big advantages:
  • Relative Immunity to Interference
    As described above, unless someone else is using the very same spread spectrum technique and is synchronized with you, you likely won't notice the interference
  • Security
    As we will see, there are sophisticated ways to encrypt a signal. This is why it is still valuable to the military.
  • Lower Power Density
    By spreading the signal over a range of frequencies, the power at any given frequency is so low it can be below the noise floor and unnoticed.
There is only one real trade-off and that is the technical complexity necessary to accomplish spread spectrum.

In a sense you could say that spread spectrum began with the earliest radio transmitters. Spark gap transmitters created CW signals that covered a very broad spectrum. You could charitably say that this signal could get through interfering signals but really, it was more of an interfering signal.

Early experiments with intentional spread spectrum began in the late 20's but it was World War II and the military that really pushed the technology forward. Unfortunately, because spread spectrum is still used by the military, much of the history is still kept secret.

In 1981, a group called the Amateur Radio Research and Development Corporation (AMRAD) began experimentation with spread spectrum. In 1989 an idea was put forth to use the Wireless LAN (WLAN) devices in ham radio, and in 1999 the FCC relaxed their rules about hams using spread spectrum. This relaxation opened the door for hams to use equipment already being made for WLAN.

Analog signals can be carried over spread spectrum transmissions, but nearly all spread spectrum use today is with digital signals and that is what we will discuss.

Frequency Hopping Spread Spectrum (FHSS)
As the name implies, the transmitting frequency hops around in a pre-arranged pattern. In the 802.11 spec, there are 3 sets of 26 such patterns using 75 frequencies. By some clever hopping algorithms you can have 802.11 devices using different sequences, or channels, on the same 75 frequencies without interfering with each other. Because there are only 78 sequences, a receiving device could discover the channel being used by the various transmitters and sync up with one.

Direct-Sequence Spread Spectrum (DSSS)
In this method, a pseudo-random code is used to modulate the signal and drive a phase modulator using phase shift keying. I have to admit this it getting into the fringes of what I know so I am going to leave it at that.
Note that by using a pseudo-random code that is not generally known it would be possible to securely encrypt a signal with DSSS. Of course we are not allowed to do that in amateur radio and we avoid that pitfall by using published codes as can be found on the ARRL web site.

Orthogonal Frequency Division Modulation (OFDM)
This method is more like what you may think when you think of spread spectrum. In this mode, the signal is transmitted on 52 carrier frequencies simultaneously. Four of these are called pilot carriers and they help provide the synchronization. The other 48 each transmit independent bit streams so at any given time, 48 bits are being transmitted at once. The reason it is called orthogonal is that the frequencies and modulation patterns are chosen so that each frequency falls in the null of the neighboring frequencies.

Since this mode is so new and underutilized in ham radio, I'm going to do something I don't normally do and that is predict the future of spread spectrum. It is here to stay until something better comes along and, though it may not happen, I wouldn't be surprised to see it adopted in the low bands eventually. I know some of the new digital modes use it to some degree and I can see the FCC, being the pragmatists they are, expanding the use of it as the technology allows.

I want to acknowledge two primary sources for tonights lesson. The ARRL Handbook, a wealth of all things Ham; and Spread Spectrum Scene which I barely scratched the surface of.