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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