23cm PC Board Yagi

I wanted a bit more “oomph” from my 1W 1.2 GHz HT, so I purchased a PC board Yagi to get another 6 dB.

I have a Yaesu FT-911 1.2 GHz HT. It is a 1990’s rig gifted me by the wife of a Silent Key at my work. It is a sweet handheld, but with limited power.

WA5VJB makes a variety of PC board antennas. The 1.2 GHz 3-element Yagi is $6, which was hard to resist. He also makes other nice microwave antennas: log-periodics, patch arrays, wheels, vivaldis, etc.

I went to HSC Electronic Supply and picked up a PC mount BNC and a right-angle BNC by navigating this aisle.

23cm yagi 2

I found a short, stiff BNC cable from this bin.

23cm yagi 3

I soldered on the BNC chassis connector and epoxied it to the antenna. The PC board is beat up because I’ve been carrying it around in my backpack for ARRL Field Day. It was pristine when I got it. Nice design, the feedline attaches at the edge of the board, then there is a stripline to the driven element. The reflector element is on the back side of the board. You can just barely see it in this photo. The shield of the coax attaches to a thru-hole pad that goes to the stripline on the other side of the board. That is hidden by the connector in this photo.

23cm yagi 1

And now I have a 1.2 GHz “flamethrower” HT.

23cm yagi 4

I need to find something to stiffen that bit of coax so I don’t have to use my hand to stabilize it. Other that than, pretty sweet.

Speakers for my Elecraft KX3

Want speakers for your rig? No need to wait. For about the cost of a tank of gas, you could be sitting back and enjoying armchair copy.

The internal speaker in my KX3 is good but not great, plus the rig has stereo effects which you can’t hear through the single speaker. The headphone jack provides 100 mW per channel, which is not enough to drive speakers to a reasonable listening level.

This is my under $35 setup for an external audio amp and stereo speakers. Of course it would work for any other rig.

The KX3 has stereo output, so this is a 15 Watt per channel stereo amp that runs off 12 V, plus a pair of simple 3 inch speakers. The amp is mounted on top of one of the speakers with 2 inch wide velcro. The power lead has Anderson PowerPoles, so it plugs into the rest of my station power bus.

IMG 0221

Let’s walk through the parts list. You can choose your own speakers, of course. I was looking for some vintage Radio Shack Optimus Pro-X44AV speakers on eBay, but ran out of time before JOTA last October. I have one of those speakers on my Lowe HF-150 Europa.

The Pyle speakers are compact, inexpensive, and sound fine. I’m sure there are lots of other small speakers that work.

Item Cost
Pyle Home PCB3BK 3-Inch Cube Speakers, Pair 21.38
DROK Audio Amplifier (TDA7297 15W+15W) 8.50
Velcro 2″ by 4″ strips (optional) 2.77
Belkin Rockstar Headphone Splitter (optional) 10.99
Speaker/power wire had it
Anderson PowerPoles had it

The DROK stereo amp varies in price on Amazon, sometimes around $8, sometimes around $11. It is built around a TDA 7297 integrated amplifier. It works with a DC power supply from 6.5 V to 18 V, perfect for ham use. In small quantities, the IC is under $4. Add in the heat sink, board, pot, and connectors, and even $12 is a fair price. It is a pretty cute little amp, really.

A separate volume control for the speakers is handy. I can turn those up or down as I’m in, or not in, the “shack” (our bedroom).

The blue “power on” LED is very bright, so it is normally taped over with some black photo darkroom masking tape. I removed that for these photos.

stereo speakers and audio amp

I also use a headphone splitter so I can leave everything plugged in—my headphones (Yamaha CM500), the amp for the speakers, and the USB audio A/D device (not plugged in for this photo).

Belkin Rockstar Headphone Splitter

Here is the velcro that I used to mount the amp on top of a speaker. I have extra for other stuff that needs stuck down. The next candidate is my MFJ UTC clock. After that, who knows? I have plenty of velcro left.

two inch wide adhesive Velcro

Finally, here is the whole grand setup in the shack. Such as it is.

KX3 station with speakers

SOTA at Philmont

There are ten summits inside Philmont Scout Ranch that are listed in the Summits on the Air (SOTA) amateur radio program. There are another three summits within the Valle Vidal region to the north of the ranch. Only six of these thirteen peaks have been activated by SOTA operators.

SOTA is an award scheme for radio amateurs that encourages portable operation in mountainous areas. I think it is a great match for Scouting, combining the outdoors, technology, and world fellowship. Grab a radio, hike to the top of a mountain, and talk to people.

Here is a map of the Philmont South Country, which has most of the SOTA summits.

Philmont SOTA South

Starting at the north and moving south, these are the SOTA summits. If the summit does not have an official name, SOTA uses the altitude. An unnamed summit that is 8820 feet tall will be “Point 8820”.

Philmont Region Summit Name SOTA Reference Number of Activations
Valle Vidal Little Costilla Peak W5N/CM-001 1
Valle Vidal Ash Mountain South W5N/CM-005 0
Valle Vidal Point 11100 W5N/CM-007 1
North Country Baldy Mountain W5N/CM-002 4
North Country Point 8820 W5N/CM-023 No longer valid
South Country Point 8988 W5N/CM-018 0
South Country Phillips Mount W5N/CM-004 3
South Country Bear Mountain W5N/CM-011 No longer valid
South Country Schaefers Peak W5N/CM-016 5
South Country Black Mountain W5N/CM-010 0
South Country Garcia Peak W5N/CM-009 0
South Country Point 8881 W5N/CM-021 0
South Country Mesa Urraca W5N/CM-026 0
South Country Trail Peak W5N/CM-013 3
South Country Burn Peak W5N/CM-014 0
South Country Lookout Peak W5N/CM-015 No longer valid

I used CalTopo.com to make maps with the Philmont boundaries and the SOTA peaks overlaid. CalTopo is a fantastic, free tool for making custom maps. For a modest subscription ($20/year), you can unlock more features. But the free version is still very useful.

The PDF maps are geospatial PDFs, so you can use them with a mapping app like Avenza Maps (free).

  • Map of all of Philmont with SOTA peaks, in PDF, JPEG, and on CalTopo.
  • Map of the Valle Vidal with SOTA peaks, in PDF and JPEG.
  • Map of Philmont North Country with SOTA peaks, in PDF and JPEG.
  • Map of Philmont South Country with SOTA peaks, in PDF and JPEG.

I don’t have a ride this year, but I want to go back to Philmont, with a radio!

Updated May 2022: Removed three peaks that are no longer valid SOTA summits and updated the activation counts. Fixed all the URLs to point to the new, different summit URLs. Tweaked the text to match the new summit counts. There have been 12 activations since this was originally published in February 2017, not bad for four years (no treks in 2018 because of the Ute Park Fire). Back then, only Baldy and Scheafers had been activated.

Short Podcasts for the Beginning Ham

Since 2011, Onno (VK6FLAB) has been producing weekly podcasts for beginning Australian amateur radio operators. The podcasts are short, from one to three minutes long. I’m no longer a beginner, but I really enjoy the podcasts. They are full of curiosity, advice, and encouragement. They make me want to get on the air.

The first series of podcasts, What use is an F-call? ran from 2011 through June 2015. These were about operating with with the Australian Foundation Licence, the entry-level license there.

The second series, Foundations of Amateur Radio, is still for Foundation Licence holders, but has a name that makes a bit more sense to non-Australian hams.

Each podcast has a text transcription, which helps with handicapped accessibility. Those are available on the website and I can see them in my iOS Podcasts app.

There are a few terms unique to Australia and amateur radio there, so I’ve compiled a short glossary.

  • The ACMA is the government agency that issues amateur radio licenses.
  • An F-call is an Australian call sign with a four-letter suffix starting with “F”, like “VK6FLAB”. All Foundation Licence holders have F-calls.
  • The Foundation Licence is the entry level amateur radio license. Unlike the US Technician license, it allows operating on HF bands (80, 40, 15, and 10) with voice and Morse at 10 Watts. It does not permit data modes, homebuilt transmitters, or automatically controlled transmitters. Other license classes are Standard and Advanced.
  • Holden is the Australian arm of General Motors, so a “Holden vs Ford discussion” is like a Chevy vs Ford discussion.
  • The LCD (Licence Conditions Determination) is the set of rules and regulations for amateur radio operators.
  • The WIA (Wireless Institute of Australia) is the national association for amateur radio, similar to the ARRL in the US.

Whenever I start one of Onno’s podcasts, I listen to three or four. I’ve listened to over eighty so far and I think I’ll be sad when I finish the backlog and have to wait a whole week for the next one.

Building a Dummy Load

If you plan to transmit on your radio, you need a way to test your transmitter without radiating a signal. You do that by transmitting into a “dummy load”. I had a 20 Watt dummy load, but I needed one to handle 100 Watts, so I built a $40 kit in June. This was the first serious soldering I had done in years, maybe decades.

I built the Oak Hills Research RFL-100 kit. A pre-built 100 W dummy load is usually $150-200. This kit is $40.

The dummy load is twenty 5 W resistors in parallel. Here are the first two resistors, ready to be soldered.

Dummy load 1

And here we are, with half of the resistors soldered onto the board.

Dummy load 2

Here we see all the resistors soldered, the board installed in the nice enclosure, and soldered to the the input connector. I chose a BNC connector instead of the standard UHF connector. My ham shack is cabled with BNC. The enclosure is marked up under the connector mounting nuts because I ground off the paint with a Dremel tool. That was much easier than sanding the paint off.

Dummy load 3

Is it 50 Ω? Well, let’s see. Hmm 49.9 Ω is within 0.1%. My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω.

Dummy load 4

Finally, let’s connect it to my new 100 Watt power amplifier on the ANT 2 port. Looks great, handling 100 Watts continuous with a 1:1 SWR.

Dummy load 5

If you have a transmitter and need a dummy load, I highly recommend building the Oak Hills Research RFL-100.

International Radio Scouting Badges

Radio Scouting is an international activity, and the World Organization of the Scout Movement (WOSM) has patches and pins for it. I love the classic design, and I also love the price, with the current exchange rate.

The WOSM Radio Scouting emblem looks a lot like the World Scout Crest, but with a radio twist. It has the same purple background, but instead of the circling rope, it has dots, like Morse Code. The fleur-de-lis is at the bottom, and the center is a globe with headphones, a neckerchief, and some lightning bolt lines. It sounds complicated, but it says “Scouts on the radio around the world” without using words.

Radio Scouting patch Radio scouting pin

Right now (late 2016), the cloth badge (patch) is $1.29 (£1.04) and the metal badge (pin) is $1.81 (£1.46). You can work out the shipping cost yourself, but I think it is worth it to wear the world-wide symbol of Radio Scouting.

Send your name in Morse code!

This sounds like great fun for Boy Scouts or any youth-oriented radio activity. Here is the description from Dan Romanchik’s blog (kb6nu.com) about teaching Morse at the Ann Arbor Mini Maker Faire.

As usual, I had my collection of keys and was teaching kids (and some adults) how to send their names in Morse Code. I have a chart of the characters (see right) that I tape to the table next to the key, and when someone approaches the table, I ask if they’d like to learn to send their name in Morse Code, and if they say yes, I ask them to tell me the first letter in their name.

After they tell me, I show them the character on the chart and then show them how to send it. Once they’ve successfully done that, I tell them to look up the rest of the letters and then send them as well. If they successfully do this, I thrust out my hand and say, “Nice to meet you, Joe (or whatever name they just sent me).” The look on some faces is priceless.

I love the way this goes straight to “do” with a minimum of “tell”, then gives an immediate reward. The “tell me the first letter” method is really clever and makes it almost like a magic trick. You can also manage several people at the activity, as long as you can copy very slow Morse.

Send your name in morse code

Chart in PDF and in Microsoft Word formats.

Quoted with the kind permission of KB6NU.

Update: Don mentioned two things that make it simpler for the participants. First is to use “dit” and “dah” instead of dots and dashes, to start them on sound instead of pictures. Second is to leave off the numbers, since few people have numbers in their names. I’ve updated the chart to follow his excellent advice.

History of Morse Code in the Boy Scouts

Morse code has been in and out of the Boy Scout requirements for over a hundred years. During that time, Morse has changed from a career skill to a rewarding hobby, from a vocation to an avocation. Also during that time, radio has grown to include voice communications, data communications, and broadcast.

Morse interpreter strip

I’ve gathered all the requirements I could find: rank, merit badge, or skill award. Morse was a requirement for First Class for 61 years, 1911 to 1972. It returned as an option from 1979 to 1990 during the skill award period of BSA advancement.

For context, I’ve included a few historical milestones from amateur radio, digital communication, and other radio services.

1910: Boy Scouts of America founded.

1911: Second Class requirement 3 is “Elementary signaling: Know the semaphore, or American Morse, or Myer alphabet.” First Class requirement 3 is “Send and receive a message by semaphore, or American Morse, or Myer alphabet, sixteen letters per minute.” [Myer is the same as “wigwag”.]

1911: Signaling merit badge requirement 1 is “Send and receive a message in two of the following systems of signaling: Semaphore, Morse, or Myer, not fewer than twenty-four letters per minute.”

1912: First amateur radio licenses in the US.

1916: First regular radio broadcasts in the US.

1918: Wireless merit badge introduced, requires Morse at ten words per minute.

1927: First Class requirement 4 (from Revised Handbook for Boys), “Send and receive by Semaphore Code, including conventional signs, thirty letters per minute; or by the General Service Code (International Morse), sixteen letters per minute, including conventional signs; or by Indian Sign Language Code, thirty signs per minute; or by the Manual Alphabet for the Deaf, thirteen letters per minute.” [In Morse, this is about three words per minute.]

1930: Radio merit badge (replacement for Wireless) lowers the requirement to five words per minute. Requirement 1 is “Receive and send correctly a straight text at not less than five words (25 letters) per minute.”

1947: First amateur radio contacts over SSB at Stanford University.

1948: First Class requirement 6 (from 5th edition handbook) is “Know the International Morse code, including necessary procedure signals. Using this code, send and receive, by any suitable means, a message of twenty words (one hundred letters) over a distance of at least 100 yards.” [No speed requirement, change from American Morse, requirement is unchanged in 6th edition]

1948: Signaling merit badge requirement 2, “Send and receive in the International Morse code, by buzzer or other sound device, a complete message of not less than thirty-five words, at a rate of not less than thirty-five letters per minute.” Requirement 3, “Demonstrate an ability to send and receive a message in the International Morse code by wigwag and by blinker or other light signaling device at the rate of not less than twenty letters per minute.” [35 cpm is 7 wpm, 20 cpm is 4 wpm]

1965: First Class requirement 4 (from 7th edition handbook) is “Send and receive a message of at least 20 words, using either international Morse or semaphore codes and necessary procedure signals.” [No speed requirement]

1965: An amateur radio license is accepted as proof of Morse competence for Radio merit badge.

1967: Viterbi decoder invented, beginning of modern digital communication.

1972: First Class drops Morse requirement in 8th edition Boy Scout Handbook.

1979: Morse returns as an option for the Communications Skill Award (9th edition handbook), requirement is “Signal by two of the following methods: silent Scout signals, manual alphabet, sign language for the deaf, Indian sign language, sports signals, Morse code, semaphore code, Scouts trail signs.” [This long list of options requires fourteen pages of documentation in the Handbook. Oddly, the handbook includes the Braille alphabet, though it is not one of the signaling systems listed in the requirement.]

1981: Space Shuttle STS-1 mission uses digital voice communication.

1984: Broadcast and SWL options added to Radio Merit Badge requirements, Morse dropped.

1990: First Class drops Morse requirement (again).

1991: FCC introduces no-code Technician license.

1992: Signaling merit badge discontinued.

1999: Morse replaced by satellite for global maritime distress calls (no more SOS).

2007: FCC drops Morse requirement for all amateur licenses.

2010: Morse returns for one year in the centennial Signaling merit badge.

2012: BSA adds Morse interpreter strip.

2015: Morse returns yet again as part of the Signs, Signals, and Codes merit badge: “Send or receive a message of six to ten words using Morse code.” [No speed requirement]

There are probably many choices for the beginning of modern digital communication. I chose the invention of the Viterbi decoder, because that supported low-latency error correction in hardware for digital codes. And it is really cool technology.

All the BSA requirements after 1965 are from my bookshelf. Earlier requirements are from scanned handbooks checked out from The Internet Archive.

Radio Scouting: The Operator Patch

My wife doesn’t understand the patch thing, but Scouts know that it isn’t real Scouting until there is a patch. The BSA patch for licensed radio amateurs has been available since 2013 and has an official spot on the uniform. If you have an amateur radio license, you should wear this patch.

BSA radio patch

This is not a temporary patch. It goes on the right sleeve below the Quality Unit patch. If you don’t wear a Quality Unit patch, it goes below the Patrol emblem. If you don’t have a Patrol emblem, well, figure it out. I hear that the new Guide to Uniforming and Insignia is nearly ready.

It is a skinny patch and a bit tricky to sew on, but that shouldn’t be a problem, because it stays there.

ScoutStuff sells the patch on-line. It is only $1.59, but the cheapest shipping for me was $7.50. I recommend getting it from your local Scout shop.

This has been a very popular patch. It sold out almost immediately when it was first offered.

Sage Venture made a custom run of the patch with a Venturing Green background and a Sea Scout white background. I’m sure you could custom order from Sage Ventures if you’d like that. You can see the designs here.

Radio Scouting: Hike Safely

The Hiker Responsibility Code says “Be prepared..to stay together” on the trail. BSA rules require adequate supervision. But how do we stay together and be safe on a troop hike with thirty or forty Scouts? We can hike in independent groups, each with two adults and a crew first aid kit. Or, we can stay in touch with radio communications.

Crew 27 in our area has a scheme for coordination on a hike. Each independent group has a radio. The last group, “sweep”, has adults and a radio. All groups check in every 15 minutes. If a group cannot communicate with sweep, they halt and wait for the groups behind them to get closer. A hike group can relay messages to and from a forward group.

T 14 at Henry Coe 2006 crop 1

What kind of radio? FRS/GMRS (Family Radio Service, General Mobile Radio Service) radios are affordable and don’t require a license. They work over a fairly short range, maybe a half-mile in the mountains or a forest for FRS channels (0.5 Watt transmit power) or farther for GMRS channels (1 or 2 Watts).

REI has a good guide to outdoor FRS radios.

If a patrol wants to hike with more separation, each group (including sweep) can have someone with an amateur radio license. An amateur radio HT (Handheld Transceiver, often called a “Walkie Talkie”), has more power (5 to 8 Watts) and a range of one or two miles, especially with an improved antenna. Some HT’s only cost a little more than FRS radios. The least expensive models change frequently, but good models tend to cost between $30 and $70. You pay more for ease of use, ruggedness, and a better antenna.

The test for the Technician amateur radio license is not that hard. It is a 35 question test and you need to get 26 correct answers (74%). All the questions are public, so you can practice as much as you want, free. The hamexam.org site is a good place to practice. It isn’t a trivial test—even though I have the highest level of FCC amateur license, I just missed two questions on a practice test.

Try a Technician test and see how close you are. There are study programs and amateurs who are willing to help (“Elmers”). I’m willing to help.

Radio scouting

Radio Scouting: Emergency Preparedness Merit Badge (and Beyond)

E. Prep. merit badge requires the Scout to take part in an emergency mobilization and make a plan for emergency service. Why not let your local amateur radio ARES/RACES group help out?

Amateur radio operators work with their local communities to prepare for emergencies. They do this with drills, frequent radio practice, and public service (which is also mobilization practice). Many groups have a radio communications net every week. Scouts can also work with CERT (Community Emergency Response Team) and other emergency volunteers.

Let’s look at the three parts of requirement 8 for the Emergency Preparedness merit badge.

8a. Prepare a written plan for mobilizing your troop when needed to do emergency service. If there is already a plan, explain it. Tell your part in making it work.

What kind of emergencies can happen in your town and how can Scouts help? The Palo Alto emergency volunteers just had training to supervise sandbag stations in preparation for potential flooding from the El Niño rains. Some of our residents are older and probably should not be shoveling sand and loading sandbags into cars. This is a perfect opportunity for Scouts to volunteer. They should already know how to work effectively in groups and dress for rain.

Make a plan to provide volunteers to fill sandbags and load them into cars. Find out how many sandbag stations there are, pick a crew size, then make a schedule for shifts. Plan how to contact your troop. After you go over it with your merit badge counselor, you might take it to the city office of emergency services, because it could be a big help.

As part of your plan, you should follow the BSA Service Project Planning Guidelines and the BSA Tool Use Guidelines.

8b. Take part in at least one troop mobilization. Before the exercise, describe your part to your counselor. Afterward, conduct an “after-action” lesson, discussing what you learned during the exercise that required changes or adjustments to the plan.

You can’t really do this requirement unless your troop (not a merit badge midway class) does emergency service. So talk to your SPL about what kind of emergency service your troop can do. Put at least one emergency service event on the troop calendar each year, participate, and this requirement will be easy.

To research ideas, you and your SPL can talk to the Emergency Coordinator (EC) for your local ARES/RACES organization. They’ll have a good grasp of local emergency planning and can give you more contacts.

8c. Prepare a personal emergency service pack for a mobilization call. Prepare a family emergency kit (suitcase or waterproof box) for use by your family in case an emergency evacuation is needed. Explain the needs and uses of the contents.

ARES/RACES volunteers call their personal emergency service packs a “Go Kit”. In our area, we have a “2-Hour Carry Kit” and a “12-Hour Go Kit”. You can use these Go Kit lists as a starting point: PDF Go Kit list, MS Word Go Kit list. The weather in your area will probably require different gear. In our area, we don’t have snow or sub-zero weather.

How do you find your local ARES/RACES group? Ask your local office of emergency services, usually part of the police or fire department. Or ask the fire chief, they should know. You can also search for “ARES RACES” plus the name of your county. There is often a county group that coordinates city groups, for example, this list of city ARES/RACES contacts is on the Santa Clara County ARES/RACES page. Other examples: Williamson County (TX) ARES, Marion County (IN) ARES, and so on. This list of links to ARES/RACES groups might also help, though some links are old and dead.

If you are an ARES/RACES member, consider becoming a merit badge counselor. This merit badge is required for the Eagle rank, so it is very popular. Last year, 46,069 Scouts earned this merit badge!

Emergency Preparedness merit badge patch  world Radio Scouting patchARES color logoRACES color logo

Note on abbreviations: Amateur radio emergency volunteer groups can be called “ARES” (Amateur Radio Emergency Service, an ARRL-sponsored group), “RACES” (Radio Amateur Civil Emergency Service, a government-sponsored group), or “ACS” (Auxiliary Communications Service, the organizational department name used when deployed). In most cases, there is one group that changes hats for different events, and we call it “ARES/RACES”. For more detailed descriptions and even more acronyms, read the Santa Clara County ARES/RACES FAQ.

Radio Scouting: Patrol Camping

Patrols should camp out of earshot from each other and the adult leaders. But how do we provide adequate adult supervision in that situation? With radio communications, of course!

An ideal troop campout has patrols camping separately, probably 100 feet to 100 yards apart from each other. The SPL and ASPL(s) camp separately. The adults should also be at the same distance. But in that configuration, how do the adults provide “qualified supervision” as required in the Sweet Sixteen of BSA Safety? And how does the youth chain of command from Senior Patrol Leader (SPL) to Patrol Leader (PL) work?

This is the supervision requirement from the Sweet Sixteen:

Every BSA activity should be supervised by a conscientious adult who understands and knowingly accepts responsibility for the well-being and safety of the children and youth in his or her care. The supervisor should be sufficiently trained, experienced, and skilled in the activity to be confident of his/her ability to lead and to teach the necessary skills and to respond effectively in the event of an emergency. Field knowledge of all applicable BSA standards and a commitment to implement and follow BSA policies and procedures are essential parts of the supervisor’s qualifications.

The major part of that is training and experience, so the adult needs to be comfortable with their level of oversight while leaving room for a boy-led troop.

With FRS hand-held radios, the Patrol Leaders can communicate with the Senior Patrol Leader, and the adults can monitor the discussion. FRS radios are quite effective at 100 yards, even through trees.

Patrol Leaders can report back to the SPL, or can ask questions. The adult leaders can listen to the traffic. If quick intervention is needed, adults can break in on the discussion. If the SPL needs mentoring, the Scoutmaster can walk over, perhaps with an announcement on-frequency that they are visiting the campsites.

Radio communication should always be backed up with “management by wandering around”, as I learned at Hewlett-Packard. A casual stroll through the campsites with a few questions can uncover a lot of information.

What does this cost? Good quality FRS radios are available in the $20-40 range. A troop with four patrols would need six radios, one for each PL, one for the SPL, and one for the Scoutmaster.

If the youth leadership has amateur radio licenses, they could use hand-held radios with greater range. Amateur hand-helds (HT’s) start around $50.

Radio scouting pin

Transmit Audio and Compression with the Elecraft KX3

This is long, but it combines multiple recommendations from the KX3 and Elecraft mailing lists into a single procedure.

First, update to the latest KX3 firmware. There was a new compression algorithm in 1.50 and fixes in 1.61 and 2.30.

Then, get your KX3 manual. If you can’t find a paper copy, download the latest KX3 Owner’s Manual. You will be looking up a few menu settings.

The audio adjustments are done in separate steps:

  1. Transmit audio equalization (TX EQ).
  2. Microphone bias config.
  3. Microphone gain.
  4. Compression level.

TX EQ

Adjust TX EQ. The KX3 manual explains equalization settings under RX EQ, which works the same as TX EQ. See the section titled “Receive Audio Equalization” (page 20).

About half of the energy in speech is in the low frequencies, but that only adds 5% to intelligibility. So cut those and put all the power into the high-effectiveness frequency bands.

Several experienced ops gave similar recommendations for TX EQ. These settings are from Jim Brown (K9YC) and I used them without any change.

Freq. Band 50Hz 100Hz 200Hz 400Hz 800Hz 1600Hz 2400Hz 3200Hz
EQ -16dB -16dB -16dB -3dB 0 0 0 +3dB

The 3.2kHz boost is optional, use it if it works for you. I did not.

This chart shows this equalization and compares it to the well-known Heil recommendations for Elecraft. I chose the settings for Heil’s wide-range electret element (iC), since that seemed most similar to the CM500 electret mic. For easy comparison, I subtracted 4dB from the Heil settings. This normalizes them to 0dB in mid-range and uses the KX3 maximum cut (-16dB).

TX EQ

Mic Bias

If you are using a Yamaha CM500 headset or other mic that gets mic bias from both the tip and the ring, you can do one of two things for better transmit audio.

If you don’t know whether your mic takes bias from ring, turn off mic bias. If you still have audio from the mic, it does take bias from the ring contact.

The best option is to use a $6 stereo splitter to disconnect the logic bias from the mic. For details, read my earlier post on better audio from your Yamaha CM500.

If you have one of these mics and don’t have a splitter, turn OFF mic bias. This will increase the mic output. Ring on the mic connector is always biased by the KX3 PTT Up/Down logic. That logic supply is noisier than the mic bias supply, so you may want to adjust TX GATE to 1 or 2. That should kill any low-level buzz between words. This is not needed for the Elecraft MH3 mic.

Mic Placement and Gain

Set the TX power to 0.0. Turn off compression (KX3 manual, page 14).

Choose your mic position. Many people like to position a microphone just off the corner of the mouth. This can reduce pops from plosives (P, B, and T). It also reduces breathing noise so you won’t sound like Darth Vader on the air.

Adjust mic gain as described in the KX3 manual under “Basic Voice-Mode Setup” (page 15). While speaking, adjust mic gain for about 5 ALC bars (see below). Try to get four bars solid and one bar flickering. It is harder than it sounds.

Compression

After all that, turn on compression and find the right amount for your voice.

To evaluate compression, use the two digital voice recorder (DVR) buffers and headphones. Record into a buffer then play it back for evaluation. This is better than listening simultaneously with TX monitor (that includes bone conduction) or on-air evaluation (with even more variables).

Read about how to use the DVR in the KX3 manual under “Digital Voice Recorder” (page 21).

Record a message into one DVR buffer with no compression. I used “CQ SOTA Kilo Six Whiskey Romeo Uniform” with repetitions. That has plenty of sibilants and hard consonants (the “K” and “X”) to make problems with too much compression. I recommend including some K’s, T’s, P’s, and S’s in your test message.

Then record the same message with a medium level of compression in the other buffer. The KX3 manual suggests starting with a level from 1 to 10. Make notes. Listen to the two buffers and choose the winner. Try a different level for the other buffer (make notes). Repeat with different compression levels until you are satisfied.

You may want to come back and recheck in an hour or so. My ears got acclimated after several rounds of A/B comparison.

A final on-air check is a good idea, too.

Then remember to turn the TX power back up!

Final Notes

I ended up with mic gain set at 51 and compression set at 20. Any more compression than that and I heard too much distortion. This was with MCU firmware 2.33.

When you change microphones, turn off compression and reset the mic gain. Then turn compression back on.

If you want to experiment with TX EQ settings, use the DVR A/B comparison method, then recheck compression.

Special thanks to a pair of experienced hams who shared their knowledge. I always read their posts.

  • Lyle Johnson, KK7P: He suggested using the DVR to evaluation compression settings. He also worked out the interaction of the logic bias and mic bias and posted the original detailed analysis and workaround to the Elecraft KX3 mailing list.
  • Jim Brown, K9YC: An experienced contester and audio professional, he is a prompt and patient elmer with help on mailing lists, conference presentations, and papers. It is all published on-line and I recommend you read and study his work.

Better Yamaha CM500 Audio with PTT on Elecraft KX3

With a $6 cable, you can get cleaner microphone audio from your CM500 headset and add a jack for a PTT switch.

The Yamaha CM500 is a very popular headset for amateur radio use. It is rugged, effective, and affordable — $60 at B&H Photo and $55 at Amazon. B&H has a much more accurate description of the product.

The CM500 electret boom mic can be powered by the Elecraft KX3, but it takes bias from both the tip and the ring on the plug, like many headsets and mics designed for use with computers.

If you don’t know whether your mic takes bias from ring, turn off mic bias. If you still have audio from the mic, it does take bias from the ring contact.

The KX3 provides mic bias on the tip, but also provides a (noisier) logic bias on ring. The logic bias is for the PTT/UP/DOWN buttons on the MH3 hand mic and cannot be turned off. The workaround is to turn off mic bias to get more output from the CM500 mic, but this leaves a bit of noise on the audio.

I was about to build an adaptor to clean this up when I realized that an off-the-shelf stereo to mono splitter would do the job! This disconnects the logic bias from the mic connector, providing a low-noise bias supply. The other arm of the splitter is now available for a PTT switch. Bonus!

Plug the CM500 into the left channel (tip) arm of the splitter. Plug a PTT switch into the right channel (ring) arm of the splitter. I like this splitter because the arms are labeled “tip” and “ring”. Also, the “red is right channel” works for “red is transmit” in my head.

KX3 CM500 adaptor

What about PTT? Around this time, my beloved Grado SR-60 headphones died after fifteen years of fine music. I decided to repurpose the excellent cord for a PTT switch (the right ear driver failed, so the cord was fine). I found a hand-held pushbutton for $15 and added that to the project.

Here is the full setup with headset, PTT, and the KX3, of course.

KX3 CM500 overview

For my music headphones, I upgraded to the Grado SR-225e. Very nice.

Many headsets designed for computers have an electret mic that takes bias from tip and ring, so this may work for those, too.

Special thanks to two relentlessly inquisitive hams who shared their knowledge. This would not have happened without them.

  • Lyle, KK7P: He worked out the interaction of the logic bias and mic bias and posted the original detailed analysis and workaround to the Elecraft KX3 mailing list. I always read Lyle’s posts.

  • Fred Cady, KE7X: Author of The Elecraft KX3 Book, where I verified that ring2 (logic ground) and sleeve (mic audio ground) on the mic connector were wired together inside the rig. That was the last bit of information that made this hack work. Otherwise, I’d be wiring a custom TRRS adaptor.

Update: The original version of this article mentioned the Koss SB40, which looks very much like the Yamaha CM500, but costs less. The Koss has a dynamic mic instead of the electret mic on the Yamaha. I asked on mailing lists, and some operators are not pleased with the quality of the dynamic mic on the Koss, so I’ve removed those mentions from the article. If you look closely at the picture with the mic plug, it says “KOSS”, which would suggest that Koss makes these for Yamaha, but with an upgraded mic.

Working All of Palo Alto with 5 Watts

How high can you get your antenna? I used a roll-up J-pole antenna on an 18′ collapsible pole supported by our patio table and could be heard across the city using only my 5W HT.

Every Monday night, I check in to the Palo Alto ARES/RACES training net. I can almost always hear net control, but they can rarely hear me. I guess it is good practice relaying traffic, but it makes it hard for me to contribute substantially.

5W Yaesu VX-6R connected to antenna

Last night, I realized that I could use the umbrella hole in our patio table to support an antenna mast! It worked really well. I got great signal reports from across the city. I was clear enough that I got a report of low audio, so we tested a bit more mic gain.

antenna mast supported by patio table

The pole is a Greenlee 18 foot fish pole that was left behind after some electrical construction. It weighs 2.5 pounds and collapses to under 28 inches long. The sections are friction fit and designed for pulling, so they won’t support a lot of weight.

The antenna is an Ed Fong dual-band roll-up J-pole. You can build your own from Ed’s instructions (downloadable from his site), but he builds them better than I could for only $28. I bought mine at our local Ham Radio Outlet in Sunnyvale.

IMG 9845 crop

If you have a patio table, grab some PVC pipe and get your antenna off the ground. It really helps.