QROoooooooo!

Here's a rig that will never be featured in SPRAT or QQ! Welcome to the Gates HC-114: http://www.transmitter.be/gat-hc114.html
(Stephen, G7VFY, sent me this, so blame him if this exposure to QRO causes any psychological trauma.) I note that the rig does have a five element low-pass filter.

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The Knack, defined

Of course, our British cousins will have some problems with this. (We already have some lexicon problems there -- I can sense many of them wincing every time I say "SodderSmoke"!) But I'm sure they will be understanding here. And indeed, the Knack can sometimes leave you Knackered! (BTW: I currently have an annoying little soldering iron burn on the tip of my right finger.)

Hi Bill,

Maybe I'm not the first to think of these two words, but here goes:

Knacking v/n. as a noun, the act of artfully and cleverly designing, building from scratch, or repairing devices using, usually electronic in nature, specifically amateur radio related...not related to hacking As in: "My knacking was a success and I finally got my Drake 2B working on 30 meters" Somewhat redundant, since knacking IMPLIES extreme cleverness, knacking ALWAYS has a successful result, by definition!

as a verb (as in "Googling") to artfully and cleverly design, build, or repair a device, normally electronic in nature as in "I was knacking my JBOT amp yesterday and successfully added a new low pass filter" Implies high level of cleverness and determination and a modicum of luck


knacker n. one who artfully and cleverly designs, builds or repairs electronics, especially amateur radio related, implies high level of accomplishment and can be used by knackers to describe themselves without embarrassment or outright bragging. Knackers do not need formal training in electronics to fully qualify. Knackers always know who they are and can be identified by burn scars on their fingers from soldering accidents.

Keep your great blog and podcasts going.

73

Steve Silverman
KB3SII

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Hard Core! Wisdom and Ideas on Toroids

Gerard ZS5AAC

This morning the BITX20 mailing list has an interesting discussion of toroidal cores. I especially like Gerard's use of the cores from old CFL bulbs. Farhan wraps it up with a great explanation of why we use ferrite cores in broadband transformers:
------------------------------
Over the years I built quite a few BITX's. In the beginning I used the
toroids salvaged from CFL lamps. These worked quite well for the mixer
coils. For the filter coils I used 6mm bakelite slug tuned coils that were
stripped from old PYE radios. Wonder if anybody else experimented
along the same lines. I build my BITX's Manhattan style and they work from the start with few minor tunings. Happy BITX'ing, Gerard, ZS5AAC.
---------------------------------------
Bob
The purists may attack us on this, but what you propose is very
possible. I have been using a wooden-core toroid for several years as part of an antenna tuner.

http://qrp.webhop.net/Pictures/Webcam-1293651325.jpeg

http://qrp.webhop.net/Pictures/Webcam-1295140555.jpeg

I'm also using small plastic and wooden beads as toroid cores for
several other projects. Half inch long sections cut from thick-wall (schedule-40 or schedule-80) PVC pipe also makes good toroidal forms. Beauty of using non-metallic cores is that the core can be split to allow winding wire through the slot without having to thread it through the hole.

http://qrp.webhop.net/Pictures/Webcam-1289957121.jpeg = 1.4 uh

Bending an inductor back on itself in toroidal form concentrates the
magnetic field in the center, whether the core is metallic or non-metallic. This gives you similar self-shielding properties when using either type core material.

With non-metallic cores you no longer have to worry about core saturation, so running high current finals is not a problem.

Key to doing this is being able to measure inductance of 5 turns, 10 turns,
and 20 turns, so you can calculate and plot the effective AL of your wooden core toroids. Once you know this value you can make up a chart to tell how many turns are required for a specific inductance.

Twisting wires together to make a transmission-line for bifilar or
trifilar windings is interesting because the impedance of that transmission line might affect performance of your transformer. It may require a bit of experimentation with an SWR bridge to tell when you have the best balance between twist pitch, wire diameter, and insulation thickness.
Arv - K7HKL
---------------------------------------------

Robert, Arv,
There are two types of coils used in the bitx - the broadband
transformers and the RF coils in the bandpass filter and oscillators.
You could easily substitute the rf and vfo/bfo coils with just about
any kind of coil - as long as you are hitting the same inductance and
Q. But there is a catch : a few years ago, I finally got down to
measuring the Q of the nylon tap washers that I had originally used.
The q was quite modest at 70. Wes made independent measurements with similar results (his paper is on www.w7zoi.net under technical stuff). In short, for good performance use good old air coils wound on a
cylindrical formers if you don't use toroids.

About the broadband transformers. These need a material that has very
low loss, very high permeability. The reasoning is like this :
1. We need an transformer's inductance such that the reactance is
at least 200 ohms at the lowest frequency. This puts the inductance at
around 30uH at 4MHz.
2. If we achieve 30uH through lots of turns (say 100), each turn will
exhibit capacitance with it's neighbor and the large number of turns
will add up the capacitance so that the coil will provide enough
self-capacitance to resonate at an unintended frequency in HF leading
to pretty bad mixer performance.
3. The only way out would be to achieve the required reactance with
lower number of turns. This means using ferrites.
- farhan VU2ESE

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Success on Seventeen Sideband!

Wow, sometimes scratch-built homebrewing can be a frustrating masochistic activity. Who among us at one point or another hasn't sat back from the bench and wondered why he didn't take up stamp collecting? But then sometimes the radio gods are smiling on you, the smoke stays inside the components, the antenna rope doesn't break, oscillators osc and amplifiers amp and all is right with the universe. I had one of those days yesterday.

The RF feedback measures I described earlier took care of that problem very nicely. Conditions on 17 were not that good yesterday, but as soon as the sun was up I started hearing stations. I called Phil, K5ACR, in Oklahoma and he came right back to me. He said the signal sounded OK, but he thought I might have been driving it a bit too hard. I backed off a bit and he said it sounded very nice.

Our weather was really disturbingly pleasant yesterday (we're not supposed to be out in T-shirts on January 31). I took advantage of it and went out with my fishing pole and sling shot (the neighbors love it) and got a line over just the right branch. This allowed me to turn my low-to-the ground 17 meter inverted Vee into a proper dipole, up about 15 meters or so.

Back to the shack and K5USI said I was booming into Mississippi's Gulf Coast. I turned off my 20 watt linear and he could hear me just fine barefoot. Then I worked K2BQ in Florida. All stations report that the signal sounds very nice.

I remembered that I did a QST article about this transmitter a few years back. I can't find it on the web, but here is an old page that describes it as it was in the last solar cycle:
http://www.gadgeteer.us/17SSB.HTM

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SolderSmoke -- The Book 20% off. And available for Ipad and Nook

Save 20 percent through February 3. Through the Lulu site you can get the book in the print or e versions.

The book is also available from Kindle, the Ibook store, and for the Barnes and Noble Nook.

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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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