Some Audio Shielding

As I was aligning my "23/24 Re-cycle" 17 meter SSB rig, I noticed the tell-tale sounds of RF getting into my audio. (I guess I should be pleased -- my amplifiers are now producing enough RF to cause some trouble!) So this morning I went in and battened down the hatches in the AF part of the rig. Lead lengths were reduced. Unshielded cables were replaced with RG-174 (with due attention to "Murphy's Whiskers"). A ferrite bead was placed on the wire that carries voltage to the op-amp chip. I wrapped some foil (actually some of that conductive tape used to protect windows in alarm systems) around the plug on the D-104). And finally I cut out two pieces of PC board and made a shield for the whole AF section (see above). I think all this has had the desired effect. The audio sounds clean. I have the day off today, so if there are no Coronal Mass Ejections I hope to make some contacts on 17. Stay tuned!

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My .02 KW Linear Amplifier

Once again, die-hard QRP guys should probably look away at this point...

My Cycle 23/Cycle 24 refurbishing project continues. The JBOT amplifier in the 17 meter SSB rig is now working nicely, but unfortunately just as I got ready to make some contacts, the Coronal Mass Ejection hit us and conditions on 17 deteriorated badly. Looking for something to do, I noticed that in some pictures of my old Azores station, sitting alongside the SSB transmitter there was a small cabinet with a QRO/QRP switch on the front panel. Ah yes! My Ramsey Kit linear amplifier! This is a MOSFET-based device. Mine was designed for 20, but I changed the low pass filter and put it on 17. Later, in Italy, it went on 20 meters and for some reason I went back to the 20 meter low pass filter.

Yesterday I blew the dust off this thing, pulled out the 20 meter LP filter and replaced it with a filter that will let my 17 meter RF reach the antenna. Today I fired it up. Wow! 20 Watts! Look out 17 meters!

I really like the QRO/QRP switch -- it gives me the opportunity to lean back and say (just like the big guns) "Wait a second Old Man, let me turn on my LINEAR!" I even have a little fan in the box that you can hear when I go to the QRO position. Unfortunately it doesn't make the lights flicker. But we can dream...

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Putting 17 Meter SSB Station On the Air

Magnificent, don't you think? The sun is rising over Northern Virginia, and 17 meters is starting to come alive. Yesterday I finished the tweaking and peaking of the JBOT amplifier for the transmitter. It is nice and stable now. (And yes, Steve, it has a low-pass filter!) On top of the transmitter cabinet is the receiver. It is a Barebones Superhet designed by Doug DeMaw and built on a FAR circuit board by Dale Parfitt, W4OP. I changed it to 17 meters and broadened the filter response for use on SSB. Both the transmitter and the receiver use variable crystal oscillators, with two crystals in each (switch-able from the front panels). The frequency coverage of of the transmitter and the receiver match up fairly well (good thing!). Wish me luck! Today I will venture forth amidst the coronal mass ejections and try to make a few SSB contacts on good-ol' 17.

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A Good Deal on SolderSmoke -- The Book 30% off!

Thirty percent off from Lulu! That's pretty good! Offer ends on January 31.
See "SolderSmoke -- Global Adventures in Wireless Electronics" at:
http://soldersmoke.com/book.htm

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Some Amazing German Knack

Michael, DL4MGM, sends us this report from a country in which "the knack" has deep linguistic and cultural roots. Wow, that's my kind of hamfest! Test stations for homebrew gear. And the key-powered transmitter is a great idea. I know there is a lot of energy going into those straight keys -- as a kid, my arm would hurt after an afternoon of unanswered CQs. Thanks Michael!

Hi Bill,
I do not know how big your german listener base is but in any case I want to draw your attention to the "Amateurfunk Tagung München" on 10th and 11th of March 2012. It is a german amateur radio convention which takes place every other year at the University of applied sciences in Munich. There is one speaker track with, mostly german, talks on a wide spectrum of topics related to our hobby. The organisers did a particularly good job in getting Joe Taylor, K1JT, as a speaker to talk on "Recent Advances in Amateur Weak Signal Communication" (10. at 17:00 local time). Needless to say that I'm looking forward to this. Apart from the talks there will be booths and exhibits from various groups and also some well known commercial sources of RF/microwave components, modules and the like.

Another highlight are the lab places, including personnel, where you can have your home brewed stuff tested up into the high double digit GHz range. I always take home new ideas from just strolling around there and looking at the things people bring for testing...

The last thing I want to mention is the current "operating and construction challenge" because it so right up our alley. It is something like an "Energy harvesting transmitter key". The task is to build a 2m, 80m or 10m transmitter which is completely powered by the energy put into the key movement. In order not to stifle inovations, a lot of liberties are granted such as keying by foot. It will be allowed to pre-charge the energy storage component by keying up to to 10 "v"s with the transmitter turned off. As proof of operation, a 160 character random text message will have to be send to an adjoining room. Ranking criteria (in descending order) will be: - Peak transmitter power during transmission of the last character. - Construction and handling - Message errors - Keying speed / total transfer time - Tone quality and frequency stability Sounds like it will be a lot of fun... Here the link to the german site: http://www.darc.de/distrikte/c/amateurfunktagung-muenchen/

That's all for now.
Keep going!
Kind regards from southern Germany de Michael, DL4MGM



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Toroidal Travails II

Steve Smith sent me a good article on broadband transformers. Reading through it, it occurred to me that perhaps using a heavier gauge wire in that PA output transformer might help. So I rebuilt the FT-50-43 transformer and put it in the final. No joy -- output was still down around 1 watt. Then I tried adding two turns to the secondary (on his web page Farhan advises experimenting with the turns ratio in an effort to improve output). Again, no joy. So I went back to the FT-37-43 transformer with 12 turns on the secondary. This yields the best results so far: about 2.5 watts. Still a bit low, but for some reason, the smaller cores seem to do better. Toroidal transformer tweaking to continue... Stay tuned.

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Toroidal Transformers: Does Size Matter?

I continue to tweak and peak the JBOT amplifier in the Azores 17 SSB transmitter. On this version I used some FT-50-43 toroidal cores instead of the smaller FT-37-43 cores recommended by Farhan. This morning I was experimenting with the output transformer. I seem to get noticeably more output with a transformer made with four FT-37-43 cores than I do with one made with four larger FT-50-43 cores.

I noticed something similar on my previous JBOT: performance improved when I switched from some relatively large binocular cores and went to the recommended FT-37-43.

So, what do you guys think? Could there be lower losses using the smaller cores? Any other reason why the smaller transformers seem to be doing better?

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Some unbridled Australian enthusiasm... (Two Videos from Oz)

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JBOT Installed in Azores 17 Meter SSB Rig

Even though one of their Coronal Mass Ejections is due to hit us soon, the radio gods have been quite kind to me this morning. I installed the JBOT amplifier board in the 17 meter SSB transmitter that I had built out in the Azores during the last solar cycle. The board went in without any trouble. And I was a very surprised when it DIDN'T break into oscillation and instability! Holy Cow! This one was stable from the start! Even when connected to my antenna! Eureka!

The rig still needs some peaking and tweaking. I'm only getting about 2-3 watts out and I should be getting 4-5. I did a quick and dirty "by ear" alignment --- I just listened to my own signal with my trusty Drake 2-B and moved the carrier oscillator freq around a bit until the SSB audio sounded good (you never have to do that with DSB!).

For those of you not familiar with this rig, here is some background:
-- Built on the chassis of an old Heath DX-40
-- Crystal filter at 5.174 MHz. Filter rocks and carrier oscillator rocks from an old Swan 240 I picked up in the Dominican Republic from Pericles Perdomo HI8P (SK).
-- Based on a design published in SPRAT by Frank Lee, G3YCC (SK).
--Heterodyne oscillator is a G3RJV Universal VXO circuit running at around 23.3 MHz.
-- That orange cord to the big meter that you are no doubt wondering about is just a little circuit that monitors total current drawn by the rig. It bounces up and down as I talk. I put it in there mostly because I wanted to make use of a beautiful old Simpson meter that I picked up in 1973 at the Crystal Radio Club (W2DMC) in Valley Cottage, New York.

Going around, clockwise from below the meter: G3RJV VXO, carrier oscillator and two diode balanced modulator board, crystal filter (with NE602 mixer and post-filter bandpass filter to the left), JBOT PA. Audio amp (using op amp) below the chassis. T/R relay in the center (antenna changeover relay below the chassis).

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The Father of the CK722 (and RadioShack!)

Steve Smith of SolderSmoke's West Coast bureau sent us the link to this article about a very interesting guy who made enormous contributions to the radio art. Three cheers for Norman Krim!
http://tinyurl.com/7qsdq22

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DIY at the V&A (Victoria and Albert Museum)

http://blog.makezine.com/2012/01/17/the-power-of-making-at-the-va/

Power of Making from Juriaan Booij on Vimeo.

One of the many perks that I enjoyed during my four years in London was living near that city's amazing museums. I was more of a Science Museum or Natural History Museum guy, but the we also loved the V&A. Each day on my way to work, the 414 bus took me past the V&A's magnificent facade. I always tried to get a seat that would allow me to get a good look.
The Maker Blog reports that the Victoria and Albert recently had an exposition on people who make things in their own private workshops. We are not alone! The video imbeded above is some sights and sounds from the world of DIY. The link below takes you to another video that includes some nice interviews with folks who are making things.

http://blog.makezine.com/2012/01/17/the-power-of-making-at-the-va/

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Another JBOT Amplifier

Over the weekend I built another JBOT 5 watt linear amplifier (design by Farhan). I used a nice piece of copper-clad board that Dave, W8NF, sent me (thanks again Dave).

This time I chickened out regarding the possible conductivity of the anodized heat sinks. I didn't have any trouble with this on my first JBOT, but I worried that if the anodized layer gets flaked away, a heat sink might short one of those collectors to ground. To be on the safe side, I put small squares of Gorilla Tape on under the heat sinks. (PLEASE don't tell me that Gorilla Tape is conductive!)

For T1 and T2 I used FT50-43 toroids instead of the TV baluns used by Farhan. He had recommended FT37-43's as an alternative to the TV baluns, but I went with the slightly larger toroids. For T3 I rolled my own binocular core using four FT37-43 toroids stacked 2X2.

The amplifier has passed the smoke test. Next I have to put in the low pass filter (Steve Smith: Please note that I have left space on the board for the filter.) Then this version will face its real test when it goes into the 17 meter Azores SINGLE sideband rig.

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Sunspots: As Good As It's Going to Get

The good news is that conditions are not a lot better than they have been. The bad news is that they won't be getting much better. But take heart guys: the next few years should be pretty good. Now is the time to get those rigs and antennas for the upper HF bands in shape. Construction of a second 17 meter JBOT amplifier begins today (this one for the Azores SSB transmitter).

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Warning! QRPers May Find This Disturbing!

Greg, KC2DWF, sent me this link to a really great web site about the AM broadcast station WLW (aka "The Nation's Station"). Brace yourselves guys, for we are now moving out of QRP land: The exciter on this baby is 50 kilowatts! The modulator could produce 400 kilowatts of AUDIO! The article is very well written, obviously done by an aficionado of high power RF. There are some great lines in there. Here is a sample:

This brings up the real fun part of 1934 AM broadcasting - NO LIMITERS! WLW, like any big-time station at the time, gave the Full Monty: 100 per cent modulation. Now, radio textbooks always have cute little pictures of sine waves at 100%, but people don't talk in sine waves. They don't beat drums, play hillbilly music, or yodel in sine waves. If the studio asked the big rig for some outrageously asymmetrical upward modulation barely crossing zero at all, the DC-sucking beast said FEED ME and obliged - briefly. Voltmeters dipped at the power company, antenna current went haywire, cows felt funny tingles in odd places, and various shotgun-loud bangs and sparks filled the transmitter building.

Have fun, but don't get any QRO ideas...

Here's the link to the article:
http://www.ominous-valve.com/wlw.html

More info and pictures here:
http://www.oldradio.com/archives/stations/cinc/wlwpix.htm

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SolderSmoke Podcast #140

Universal VXO

A new episode of the SolderSmoke podcast is now available:

http://soldersmoke.com/soldersmoke140.mp3

January 9, 2012

-- Santa Claus: Ice Skates, Brownie Box Cameras, and Piper Cubs
-- On the air with 17 Meter Azores DSB rig
-- Seeking balance (with antennas)

-- 23/24 recycling of Azores SSB Rig: Adding Soul to the Old Machine!
-- Attacked by my own soldering iron!

-- RG-174, swarf, and other insidious threats to the homebrewer
-- Inspiration from QRP Quarterly
-- G3RJV validates the D-104
-- T/R admonition from the 1973 Handbook (words to live by)
-- The Woz on electronics and teenage social isolation
-- BANDSWEEP: Straight Key Night at WA6ARA
-- MAILBAG
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Helliwell and the Whistlers

Paul, W2IOG, alerted me to the passing of Robert Helliwell, one of the discoverers of the "whistlers" and an expert on VLF phenomena and the magnetosphere. Paul met him and tells me that he was a real gentleman. His obit is fascinating:

http://news.stanford.edu/news/2011/may/robert-helliwell-obit-052011.html

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Homebrew SSB Portable from Australia

Peter Parker, VK3YE, is one of the true gurus of QRP phone. When I first started building DSB and later SSB rigs, I frequently found inspiration and ideas in Peter's articles and web sites. This morning I came across this amazing video, produced just days ago, showing Peter and his new SSB transceiver in operation from a beautiful Australian beach. The rig is a 40 meter version of Farhan's BITX-20. (I really like the frequency dial.)

Peter describes his rig this way:

It's made from scratch, ugly style, with 99% being from the original design.
It covers 7 to 7.2 MHz, using a 9.05 MHz IF and a 2 MHz VFO.
I used a different microphone amplifier (I got more and clearer output than
the original with my electret mic) and a BD139 driver transistor.
The PA circuitry is also slightly different.
It's been about my easiest and most trouble-free transceiver project to
date. Performance is excellent and a tribute to Ashhar. The furthest distance so
far was a 5/6 report from ZL (about 2000 - 3000km away).

The grand finale of the video is a four-way contact with homebrew rigs in use at all four stations. Excellent. Thanks a lot Peter.

Here is Peter's web site: http://home.alphalink.com.au/~parkerp/

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Las Cruces QRSS Mafia Attacks Pensacola!

OM Dave, WA5DJJ, writes to us about a different kind of SKN -- I guess this would be SLOWWWWWW Key Night!
-----------
Dear Bill,

Hope you and yours have a very Happy New Year.

I agree that Ashhar Farhan is one of the guys that I also admire
mainly because he is trying a valid approach to get amateurs on
the air. His designs are easy to construct, use simple common
parts and work well. I got really tickled when he said that he
kept his parts in two plastic tool boxes. I have so much I have
a hard time keeping mine in a garage with some spillage over to
the storage shed. But alas, I need to downsize.

Keep up the good work with SolderSmoke podcast. You are reaching
a lot of folks and also making a difference.

Our Las Cruces QRSS Mafia had a New Years 2012 on the air celebration
on 30 meter this New Years. We got 14 transmitters on the air and
managed to jam the Pensacola Snapper with so many signals that Bill
couldn't count them all. I attached the sheet I sent W4HBK to
mark the event. There wasn't much room left but others still got
in the holes. We did have a lot of fun plotting the event and getting
the 15 guys installing antennas, building transmitters, and programming
keyers. So, there was a lot of activity here to do the deed.

Anyway, Keep the soldering hot and the projects going. I like your
rebuild of your 17M transmitter. Nice project.

Take care and have fun in 2012.

73 Dave
David R. Hassall WA5DJJ
WEBSITE: http://www.zianet.com/dhassall/


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2012 Off to a Good Start: Balanced ATU Success!

2012 is off to a good start here at SolderSmoke HQ. I'm planning on putting up an 80-10 dipole fed with open wire (window) line. So I need a balanced ATU. A very simple link coupled design appears in lots of the antenna books and handbooks (1980 ARRL Handbook page 19-8, RSGB's "Practical Wire Antennas" by John Heys, page 86): Just a series LC circuit in the primary and another tuned circuit with a split stator variable cap in the secondary. The junk box was VERY cooperative: I found a big tuning coil (or might it have been two coils?) probably from an old Heathkit DX-40 or DX-60) -- that would work for the secondary coil. Then for the primary I found a smaller coil that would fit perfectly (with one layer of Gorilla tape) inside the secondary. I also found two really pristine 1000 pF air variables (I know, they can't handle much voltage, but, hey, that's one of the benefits of being a QRP guy, right?) I used the HW-7 as a signal generator and this morning did some experiments with different loads. You have to play around a bit with the taps on the secondary, but the ATU seems quite capable of matching loads from about 50 ohms up to at least 10K, and it works from at least 40 meters to 15 meters.

I found it very pleasing to see that SWR meter go down to 1:1. I'll now -- in the finest traditions of ham radio -- wait until the snow starts falling and the wind starts howling before I try to put an antenna in the trees.

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Homebrew Hero: Ashhar Farhan, VU2ESE

I wanted to start off 2012 with something inspirational, and here it is: Ashhar Farhan's work bench. I was visiting his site yesterday and found lots of good info, good humor and, indeed, inspiration. Be sure to check out his RF generator project. And the page that gives his thought on tools and test gear. All of it is wonderful -- you'll find lots of evidence of Farhan's long-term case of The Knack, his efforts to put "soul into his new machines" (his kids are mentioned frequently in his descriptions of his projects), and his obvious qualification for membership in the International Brotherhood of Electronic Wizards. I really like Farhan's efforts to design rigs that can be built with parts available all around the world -- a JBOT amp of his design is percolating nicely in my 17 meter DSB rig, and has been crossing the Atlantic almost every day.

As we were throwing a football around yesterday, I told Billy about Farhan. I mentioned that he lives in Hyderabad -- Billy thinks that's one of coolest city names on the planet and plans to work it into the plot of a novel he is working on.

Here is the site: http://www.phonestack.com/farhan/

Three cheers for Farhan! Happy New Year to all!

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