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Wednesday, September 30, 2009

AA1TJ's Nifty Fifties Pixie

Once again great things are happening in the underground lab of Michael, AA1TJ. Michael has temporarily put aside his work on Iron Pyrite-based receivers, and is now working the world with 50's era point contact transistors. I can feel the enthusiasm, even all the way over here in Rome. I particularly liked Michael's description of the QSO in which the other guy heard his backwave. Backwave is the very small signal that is sometimes put out when the key of simple transmitter is up. For example, the oscillator on my old VXO-controlled 6 watter (from "QRP Classics") ran all the time -- I just keyed the amplifiers. Sometimes guys would report hearing some of the RF from the oscillator even when the key was up. (By the way, the term backwave reminds me of a word used sometime by Billy and Maria: backwash. As in, "No Maria, you can't have a sip of my soda -- you always leave backwash!")

In his e-mails, Michael mentions that the physics of the point contact devices are a bit of a mystery for him. I recall that the book "Crystal Fire" by Riordan and Hoddeson had some pretty good info on how these early transistors worked.

Here are some excerpts from Michael's e-mails on this project:

I haven't had time to document this pyrite/tunnel diode receiver on account of a phone call that I had two weeks ago from Jack Ward at the Transistor Musuem. Jack approached me with an idea to recreate the first ham radio contacts using transistors. Of course, the point-contact transistors involved are now pretty rare items. No problem for a fellow with a transistor museum though!
Jack kindly sent me a couple of Western Electric, 2N110 "relics." I had some initial trouble with "squegging," and I wasn't able to produce oscillation above 380kHz. To read a recent tale of one fellow's trouble trying to tame the 2N110, please see
I especially liked where he wrote, "I did seriously consider giving up at this stage and taking up heavy drinking." ;o)
However, I located an old textbook that discussed circuit design theory using point-contact transistors (the physics of these devices are still clouded in mystery). What I learned made all the difference. A few more hours at the bench and I had an 80m transmitter putting out 10mW.
The story gets better though, Ned. A circuit briefly described in another old book really caught my attention. It was pretty much the same circuit as was used by George Rose, K2AH, in his first transistor QSO. Only, a circuit (designed by G3IEE) showed a pair of headphones in dotted lines, next to the collector resistor. The text merely said
"As indicated, the circuit also functions as an oscillating detector type of receivere for local continuous wave operations whith head phones plugged into the collector circuit instead of resistor R3. Good reception and break-in operation were obtained."
That got my blood moving! Positive results came right away on the bench. The received signals were every bit as strong as with my Reggie and the Cub Scout heterodyne (what I started calling, "Chester," after the name of the mine where the pyrite was found).
I had my first QSO last week using Jack's point-contact transistor (made in 1956) in the transceiver designed by G3EII (in 1954). Jim, W1PID, was my first contact. Since then I've made over a dozen QSO's with five different stations.
FYI, I'll paste a message below that I sent to Jack Ward this weekend. One thing I forgot to add is that W1VZR copied my 10mW signal on his Cake Pan regenerative receiver over in Maine last week. Aside from my three QSO's with VE3DJX at a distance of 319 miles, the other notable results to-date were hearing both W1DFU and W1PID - in the course of separate QSOs - when they dropped down to an output power of 100mW.
Again, I haven't had a chance to post much on my web site, but I do have the current schematic up, and you can see both K2AH and G3IEE's circuits in scans from the old transistor book. G3IEE's circuit is shown in Figure 16.2 in the second jpeg image.
One more thing, Ned. I hooked up this past week with G3JNB. Victor was one of the fellows (he was only 21 at the time) working with Tony, G3IEE, back in 1954 to make the first-ever, UK ham radio QSOs using transistors. Victor has already posted an envelope containing copies of his log, the QSL card from G3IEE and the original, 1954, Wireless World article describing their results. In the course of our Skype video call last week, Victor held up to the camera the RAF telegraph key that he used for his QSO with Tony. Pretty neat, eh?
I've got to get back to work here. Congratulations on getting your Reggie up and running, Ned. I look forward to seeing the photos and I'd surely like to hear about any contacts you make with it. Speaking of which, I have some photos of Jim, W1FMR's beautifully constructed Reggie that I've been meaning to post on my web page. Once I get around to it would you mind if I include one of your photos as well?
Best wishes,
Mike, AA1TJ
Hi Jack,

Yes, I had great fun with our little 2N110's this past week. Of of now, I've had well over a dozen radio contacts with five different stations. I used 10mW of output power to make these contacts. The distances shown are all "as the crow flies."

W1PID, Sanbornton, NH, 67miles; lowest power used on his end 100mW
VE3DJX, Smith Falls, Onatario, 319 miles; 10watts on his end
W1DFU, Wallingford, VT, 42 miles; his lowest power was 100mW
W1VZR, Limerick, ME, 100 miles; 40w

Pete, the last fellow listed, heard the 2N110 while it was running as a "beacon" with a continuously looped Morse code message. Having received my call-sign he located my email address and shot off a reception report. I saw his message pop up on my computer and quickly looked up his telephone number. He was still at his radio when he picked up the phone. I found him pretty excited as my signal strength had sharply risen in the last few minutes. He asked if there was a problem with my keying circuit as he could still hear a faint tone on my frequency when my transmitter should have been silent. "Ha!" sez I, "You're hearing a 100 microwatt back-wave radiation!" The distance separating us divided by the 100uW power is equivalent to 1 million miles per watt; a very impressive figure!

One more station answered my CQ this past week from near Hartford, CT. However, I can't recall his call sign and I'm currently at work but my logbook is at home. My output power was up to 17mW during that contact; on account of a temporary change that I made to the circuit. However, pushing the transistor to that power level reduced the quality of the keying, and so I returned to 10mW following that contact (earlier, I'd reported that my output power was 12mW, but a more careful measurement indicated that I was only putting out 10mW).

You might have noticed that I've posted the schematic to my web site. However, I expect the circuit will change over the next week, or so, as I still want to tinker with the keying circuit. By all reports my signal is good but it has just a touch of keying "chirp." Chirp is what hams call a variation in the received signal tone when the telegraph key is first depressed. Again, I expect to have that sorted out before long.

Yes, it was a real pleasure talking with Victor, G3JNB. FYI, I'll send you copies of all the documents that he provides. He said that he's including some original data sheets for point contact transistors that he's held on to these past 55 years. I'll keep copies and send the originals to you.

I asked Victor if he'd like me to build a duplicate radio for him using the second 2N110 that you sent me. I think he was thrilled to hear my offer. Don't you think it would wonderful if he, of all people, managed to make a contact using a reproduction of the point-contact transmitter that he and Tony, G3IEE, used in those pioneering days?

The order of business next week is to finalize the circuit design and begin building two identical circuits into permanent radios. Of course, I'll take time off, now and then, to try and make more contacts. I'm already astonished that it was possible to span a distance of 319 miles (not once, but thrice!) using your ancient transistor relic.

Acting on your suggestion, I looked up the other fellows mentioned in K2AH's article. It turns out that Tommy Thomas, W2UK, was quite a radio pioneer on VHF.


Unfortunately, I've learned that he passed away not so long ago. The call signs of the other two fellows are not currently in the FCC database (I suspect because they are gone as well). A quick search on the Internet turned up nothing on them.

Victor, G3JNB, remarked that he believes that he is the only one left of his original group of transistor enthusiasts. Doubtless, one reason is that he was only 21 years-old at the time of the experiments with G3IEE.

Victor reports that Tony, G3IEE, worked as an engineer for Mullard. I guess that explains where his transistors came from. Victor used a standard vacuum tube transmitter for his first contact with Tony, but sometime later he built his own one-transistor transmitter following Tony's design. Victor says that he used it to make one or two contacts across town before he put it on the shelf. Again, I'll be very interested to see the photocopy of his station log from that period.

One more thing, Jack. I'm fortunate to count George, G3RJV as a pal-o-mine. George is a recently retired Anglican vicar, but he also founded the GQRP; what began as a society of UK amateurs interested in low power operation. Since then, it has become something of an international institution. I had a message of congratulations this week from George; saying that he's keeping a watchful eye on our project. In return, I inquired if George might be able to put me in contact with folk that might help shed light on what was going on at that time (transistor-wise) in the rest of "Hamdom". That is, I'd like to assemble a folder on the topic of "first transistor QRP QSOs" for Japan, Western and Eastern Europe, Australia, etc.. I'll keep you apprised of any news.

That's all from here, Jack. Once again, I'd like to express my thanks to you for including me in your project. It's already been great fun and a real pleasure to meet some wonderful people.

Kind regards,
Mike, AA1TJ

Tuesday, September 29, 2009

Sunday, September 27, 2009

SolderSmoke Podcast #116


27 September 2009
Wild Boar Hunting Season Opens
SPRAT and QQ on Kindle?
Kite Antenna Day -- An idea whose time has come!
Doublet antenna in Ponticelli
Ponticelli QSOs on 40, 20, and 15
Steve Roberts -- Knack on a Bike
AA1TJ goes Iron Pyrite and Point Contact
Princess Elettra Marconi
SolderSmoke Book: Price Reduced AND Oktoberfest Sale!
Prices reduced on T-Shirts, coffee cups, bumper stickers

Saturday, September 26, 2009


Lulu is running an Oktoberfest sale. You can save 20% on SolderSmoke (The Book). Please help spread the word to those who (gasp!) might not be checking this blog every day. Promo 1: Enter coupon code 'PROST' at checkout and save 20% on the purchase price of any order up (maximum discount $25. Promo 2: Enter coupon code 'OKTOBERFEST' at checkout and save $50 on the purchase price of any order of $200 or more. Discount cannot be used to pay for, nor shall be applied to, applicable taxes or shipping and handling charges. Promotional codes cannot be applied to any previous orders. No exchanges or substitutions allowed. Only one valid promotional code may be used per account. Offer expires on 09/27/09 at 11:59 PM GMT. Lulu.com reserves the right to change or revoke this offer at any time. Void where prohibited.

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Friday, September 25, 2009

Meeting Princess Elettra Marconi

Last night at a diplomatic reception in Rome I had the privilege of meeting Princess Elettra Marconi, daughter of the inventor. She is a charming lady. We talked about ham radio, about her dad, and about some the recent books that have come out about him (including Thunderstruck.) Above is a photo of Princess Elettra on her eighth birthday, onboard Marconi's yacht Elettra. This must be a very poignant photo for the family -- the caption indicated that the inventor died later that day.

Wednesday, September 23, 2009

Auroral Memories from W7ZOI

Hi Bill,

I was really on top of it this time and listened to Soldersmoke 115 yesterday evening, the same day I got it from the Internet. I was intrigued by your description of the aurora in 1972. I don't recall that one. By then we were in Oregon. We have had some strong ones down this way, but missed them visually because of cloud cover, a common problem in Oregon. But I have fond memories of the first and most spectacular show I ever did see. This happened when I was trying to go on the air in eastern Washington. I knew that I had put something in my log about it, so last night I pulled my log books of that day and started looking. It took a while, but it was there. QTH at the time was Richland, WA, which is in the SE corner of the state, right on the Columbia River. The station is the first B&W photo on my web site.

I see in my log that on 9/12 of 1957 I had been active. I called a ZL at 1:40 AM on 20M CW. (All times are Pacific time. Probably daylight time.) Then I had worked w2gqn in NJ at 18:11. But the band became quite noisy after that. I have log entries for September 13th, '57, starting just after midnight:

0020. "Tremendous Northern Lights display. Approx 300 degrees of the sky was colored. Sky had green tinge to the north and red in east and west which extended almost to the direct south. Noise level on 14 mc very high. Noise had the character of an electric shaver. Noise masked all signals except W6ULS on 14.048. Noise cleared at 00:44 and heard KG6AAY (Guam). Static crashes remained. 7 mc seemed unaffected by the noise."

00:49. called KG6AAY. No luck.
00:56. called ZL2AHA. Again, no luck.
No more entries until 16:25 when I worked a local friend, Wn7JII on 7 mc.

Yea, I know; the frequencies were in mc back then.

Thanks for stirring up some really fun memories.

73, Wes

AA1TJ's Point Contact Contacts

I was very glad to see that Mike, AA1TJ, is back in his underground shack and once again pushing the limits of QRP technology. This may be one of his greatest QRP-capers:


It was one of those rare days on the bench where everything I touched
turned, if not to gold, at to least silver. At the end of my last shop
session on Friday I could only get Jack Ward's point contact
transistor to oscillate as high as 385kHz. And that was without a
load. I brushed up on the theory over the weekend and set upon the
circuit today after lunch with a vengeance.

Better yet, over the weekend I found a wonderful circuit in a
transistor handbook dating from 1956. This circuit first appeared in
"Wireless World" in may of 1954 ("160 Metre Transistor Transmitter").
At first glace, the circuit looks identical to George Rose, K2AH's
historic circuit. However, Mr. Cockle (don't yet know his call sign)
shows a dotted transformer and headphones next to the collector bias
transistor. He'd figured out the point contact oscillator could double
as a direct conversion receiver! A 1954 vintage "Pixie," only
simpler! The key to it all is the signal tank in the base circuit.
That is to say, the transmitter output power is picked off the base
circuit tank. It sounds daft, but bear in mind the circuit has more in
common with a tunnel diode oscillator than it does a feedback
oscillator that most of us are familiar with.

I'll cut to the chase as I want to get back on the air ASAP. The
Western Electric point-contact transistor is sending 12mW up the
transmission line. The same circuit is working FB as a receiver with
full break-in and 800Hz RIT offset. I put it on the air at 2234 this
evening. At 2247 K1IQI answered my CQ. He first sent a "QRZ?" so I
repeated my call several times. He came right back with my call and
gave me a 219 report from Monson, MA. Unfortunately, QSB wiped out my
next transmission. He returned with an apology, wished us better luck
next time and then he was gone. Close but no cigar!

I'm headed back to the shack once I send this message. I'm rock-bound
on 3533.6kHz. I'll be calling CQ and listening until 0300, or so.

Right, here I go.

Mike, AA1TJ

Monday, September 21, 2009

"I didn't care. I had a secret life..."

Dreams of Escape…

It began in Kentucky in the early ‘60s: I was a ham radio operator known as WN4KSW, a skinny burr-headed prisoner of school, isolated in the cultural drought of the Midwest. I was theoretically a smart little bugger, according to test scores, yet I kept hearing that I had attitude problems and wasn't working up to my potential. With the exception of science fairs, my academic performance was apparently disappointing to authority figures. Oh well. I didn't care: I had a secret life.

Thus begins the really amazing and inspirational story of Steven K. Roberts, N4RVE, the "Knack on a Bike" guy whose videos I mentioned last week. Stop whatever it is you are doing, and proceed to his web site. Read his story:


And don't miss the other great content on his site. Click on his resources link.

Weekend QSOs from Ponticelli on 40, 20, AND 15

When we returned to the Ponticelli site on Saturday I found that one end of my new doublet antenna had fallen down. No problem. One throw of the old rock-and-string and we were back in business. On Sunday I fired up the solar-powered HW8 and worked four stations on three bands: OZ8SW and US7IVW on 20, S59DDR on 40, and --icing on the cake-- OY1CT in the Faeroe Islands on 15 meters (the picture above is of his QTH). I haven't had a contact on 15 in a long time. I really like the frequency flexibility of the twin-lead doublet antenna.

Saturday, September 19, 2009

SolderSmoke Book "Pirate Day" Sale! 15% off

Looks like Lulu is running a 15% off sale for "Talk like a Pirate Day." Apparently you just have to write "AHOY" when they ask for a promotional code. Here is what Lulu says:

Enter coupon code 'AHOY' at checkout and save 15% off any purchase (up to $100). Discount cannot be used to pay for, nor shall be applied to, applicable taxes or shipping and handling charges. Coupon codes cannot be applied to any previous orders. No exchanges or substitutions allowed. Only one valid promotional code may be used per account. Orders must be in U.S. Dollars. Offer expires on 09/20/09 at 11:59 PM GMT. Lulu.com reserves the right to change or revoke this offer at any time. Void where prohibited.

Knack on a Bike: Steve Roberts Video

Oh man, this is great! The Winebikko! Gizmology! He even had an Oscar 13 satellite station on the bike. You guys are gonna love this:

Thursday, September 17, 2009

SolderSmoke: The Book NOW ONLY $19.99

I found a way to bring down the price on SolderSmoke -- The Book.
It is now $19.99 plus shipping. Check it out:


This all has to do with paper availability, so this version ships only from U.S. printers. This will be a good deal for most buyers, but for buyers in Europe and Asia shipping costs might make this version too expensive. I will put up a standard version that ships from Lulu printers in Europe in a day or so.

Wednesday, September 16, 2009

Ponticelli QRP Station Gets New Antenna

At the country place I now have a table on the front porch for the HW-8 and assorted gear. In the picture above you can see the Trastevere Flea Market Pi Section antenna tuner (upper left), a Japanese SWR meter (also from the flea market) , HW8 and Radio Shack speaker, Volkswagen Solar Cell, 12 Volt gel cell, key and cans...
I had been using a piece of wire just thrown up in the trees, but I thought I could do a bit better. I had some TV twin lead in the shack, and there was this useful-looking center connector... I had some AC line cord. Next thing you know I had a sorta-doublet antenna supported by a Roman Pine in Sabina (pictures below).
And it gets out! Worked IT0ULN in Sicily on 40 meters. Then I spoke to another QRP station, 2W0NNN in Wales, on 20. Also UU4JDD/P on Tuzla Island. Finally E53AX in Estonia.
Ioan, 2WONNN, sent this report:

Hi Bill, thanks for the email, I look forward to seeing the pics on your blog too. Very interesting reading, same goes for your QRZ page too. I had to laugh at your DX with an astronaut on Mir!!!
Your HW-8 and doublet is certainly working well; I remember you were completely readable with a good signal about 90% of the time, it was only the QSB that made it difficult. To be honest I was surprised to have a QRP QSO with someone in Italy. I was using my FT-817 with a new Par End Fedz that I'd catapulted over a tree. The top was about 15m high but oriented as a sloper to the north west. I've had a fair number of QSOs with East coast US stations so I thought I'd go for an over-the-pole route to the West coast... there in Italy you're pretty much spot on the opposite direction so I'm not sure it's all that directional!
73 and hopefully speak to you again for more QRP/QRP!

Monday, September 14, 2009

Saturday, September 12, 2009

SolderSmoke Podcast #115

Camping in Sabina
Michelangelo's late start
Anniversaries: Internet, SolderSmoke, Hack-A-Day
From Kitty Hawk to the Moon
Carrington flares and childhood aurora
Calculating speed of light (using cheese)
Hubble Space Telescope, Sliding Spring Observatory
Transistor Museum
Understanding Mixer products

Friday, September 11, 2009

Mixing it up

OK, enough of the pretty pictures from outer space, now it's time to go back to mixer math.

In the podcast, on this blog, and in the SolderSmoke book I have chronicled my efforts to understand how mixer circuits REALLY work. For some of us, the trig is just not enough. We want intuitive understanding. Ya' gotta draw us a picture. Mike KC7IT, and Dennis W6DWF, both alerted me to a good one. It is from a new book "RF Front-End: World Class Designs", Edited by Jane Sullivan Love. The chapter on mixers is available online here:

I really like figure 9.6 (above). You can really SEE how the switching action that is driven by the LO kind of "chops up" the RF signal and produces the complex waveform that is the IF. The neat thing about the IF waveform in this drawing is that you can clearly see both the sum freq (the smaller squiggles) AND the difference freq (the overall movement inside which the smaller squiggles are present). Go ahead, count them up! Sums and differences!
This is a special kind of mixer: a polarity-reversing switching mixer. When the LO is negative, it inverts whatever is at the RF port. From this you can see why mixers are described mathematically as "multipliers." This mixer is multiplying the instantaneous value of the RF input by +1 (when the LO is positive) and then by -1 (when the LO is negative).
I think it is quite a bit harder to "see" the genesis of the sum and difference freqs when you are working with non-switching mixers, but this diagram is, I think, really useful in gaining an intuitive understanding of what goes on in the mixing process.

Wednesday, September 9, 2009

Hubble Space Telescope: New and Improved!

I know, I know, it is not exactly ham radio, but look at it this way: electromagnetic waves from far, far away! REAL DX. And some very cool gear to receive the signals. And some recent repair and modification work... So you see, this is really not so far afield after all.

I've been a big fan of the Hubble Space Telescope for a long time. When I was closer to the equator (in Santo Domingo) sitings of the HST were quite common. I'm glad to see that the recent repairs and mods worked out so well. Here is a really nice video on the new and improved Hubble: Hubble Space Telescope Video

Saving the world, finding comets....

Well I guess the hours are not great, but how about the job satisfaction! Rob McNaught works at the Sliding Spring Observatory about 400 km from Sydney, Australia. The observatory searches for comets and asteroids that could do to us what they may have done to the dinosaurs (see below). A significant fringe benefit of this job is that Rob gets to discover new comets. He recently set world record by finding his 50th. Congrats Rob!

The mission of the Siding Spring Survey is to contribute to the inventory of near-earth objects (NEOs), or more specifically, the potentially hazardous asteroids (PHAs) and comets (PHOs) that may pose a threat of impact and thus harm to civilization. The identification of the iridium anomaly at the Cretaceous-Tertiary boundary (Alvarez et al., 1980) and associated Chicxulub impact crater (Hildebrand et al., 1991) and perhaps recently the Australian Bedout crater (Becker et al., 2004) associated with the Permian- Triassic "great dying" (although the presence of shock metamorphism has not yet been adequately demonstrated), strongly suggests that impacts by minor planets play an important role in the evolution of life. These are a natural result of the accretionary process that formed the Earth and planets. Indeed, the 1994 impact of D/Shoemaker-Levy 9 on Jupiter provided tangible evidence of this. Although the collision frequency is much lower than in the past, the question is not whether there will be other impacts, but when.

Tuesday, September 8, 2009

Early Crystal Set in Altoids-like Box

Even way back then, British homebrewers had an affinity for Altoids-like boxes!
David, M0VTG, sent me the above pictures, and this description:

I enclose some pictures of a kit produced in the early to mid 1900s of crystals and a holder for use in a crystal radio; unfortunately the cats whisker is missing! The box is marked:

Front: NEUTRON Back: Neutron Ltd
Trade Mark Sicilian House
Wireless Crystal Southhampton Row
1/6 Phone Museum 2017
Catswisker and
Directions Enclosed

The 1/6 refers to the price (one shilling and six pence) pre-decimalization and converts to seven and a half pence today (although the half pence has been dropped thorough inflation). I should add that the box measures about an inch and a half in length.

Saturday, September 5, 2009

Carrington Flares, Aurora, Where were you on August 4, 1972?

Greg, KC2DWF, sent me a really interesting story about the work of the English solar astronomer Richard Carrington. He discovered a kind of solar flare (named for him) that comes along every few centuries and could knock us all off the air.

As I was reading the article, I started to think about a childhood event that I think I mentioned in one of the podcasts. I have vivid memories of a summer night in which the skies were filled with really bright colorful lights. The article about Carrington notes that there was a major solar flare (but not of Carrington levels) on August 4, 1972 that caused auroral displays far into the southern part of the USA. The year is a bit later than I thought (I was 13 at that time) but the time of year is correct. And that flare was big enough to have caused really vivid aurora over New York.
The NASA site "Brushfires in the Sky" provides this very helpful list for people, like me, trying to figure out what we saw, and when:

The Aurora Watchers Handbook lists the following "Great Geomagnetic Storms" of the 20th century when auroras were seen much farther south than usual. If you have a childhood memory of aurora borealis, it may have come from one of these storms.

  • October 31 - November 1, 1903
  • September 25, 1909
  • May 13-16, 1921
  • April 16, 1938
  • February 11, 1958
  • July 8, 1958
  • August 4, 1972
  • December 19, 1980
  • March 13-14, 1989
Looks to me like my event was August 4, 1972. Anyone else have memories of this storm?

Here is the article that Greg sent:

The Transistor Museum

Wes, W7ZOI, relayed to us this great site found by from Jeff Damm, WA7MLH. This is a real treasure trove of transistor history:

Thursday, September 3, 2009

Alaska QRSS Grabber Controlled from CHINA!

Our friend Laurence leads an interesting life...


Hi Bill and greetings from the NE coast of still summery China - actually its cooling down a bit from boiling over to just cooking.

Just been home to Alaska. Whilst and between lumberjacking 20 dead trees on the property I had a few mins to throw up a K9AY and connected it via 250ft of Walmarts best RG6U into the R75 - with a little help of Ham radio delux, Citrix and Skype I have control of the radio from here in China - Mostly on 30m but really shoved it up for the winter lf/mf season but of course WSPR and visual modes have proved very popular. So until a moose walks thru, a Wolf chews threw or wife cuts thru the antennae wire it will be up.

Here in China I'm sporting the second r75 and this supplements the SDR IQ - my antennae are gradually getting blocked towards the states and Eu by every rising high rises just in front and I can actually measure the increasing losses at LF and HF as the beast rise. Still looking for your WSPR signal and keep up the good work.

Laurence G4DMA et al - KL1 X and in BY3A

Tuesday, September 1, 2009

A Good Old VFO (by Rick, KK7B)

Here is another really great message from Rick, KK7B, sent to the emrfd yahoo group: [emrfd] A Good Old VFO Saturday, August 22, 2009 10:29 PM From: Rick To: emrfd@yahoogroups.com For several critical receiver applications in my lab I've used old Collins PTOs converted to solid state (I just replace the triode in the classic Hartley circuit with a J310 and run the circuit from a 9 volt regulator). I have half a dozen of them in dedicated propagation study receivers, and one SSB exciter I occasionally use on UHF. The other day I was changing something else in one of my receivers and connected the solid-state PTO to the frequency counter on my bench. The PTO was set to 3.100000 MHz. From a cold start (it hadn't been turned on for years) it drifted three Hz over the first ten minutes, and then a total of 10 Hz over the next few hours. When I calibrated one of my 144 MHz propagation study receivers 25 years ago, total frequency drift was <18Hz/hour. I expect most of that was aging of the overtone crystal oscillator in the premix circuit. Old Collins PTOs are common (someone at Dayton this year had a box of unknown ones in decent shape for $10 each, and there are R390 PTOs in the current Fair Radio flyer). I've never had one fail, tuning resolution is infinite, phase noise is low, digital noise is zero, and once I build one into a receiver, that part of the project is done--no improvements, software upgrades, needed. My research receivers are connected to a baseband Fourier analyzer (yes...even 25 years ago). The finest resolution I've used for serious experiments is 10 milliHertz, but more often I use 1 Hz resolution, with 1024 channels in the output spectrum. I often average spectra for more than a minute, so frequency drift needs to be less than 1 Hz per minute. The solid-state Collins PTO is much more stable than needed even for those critical experiments. This is not a fluke. Every Collins PTO I've converted to solid state using a U310 or J310 has had similar performance. Sometimes it is useful to remember that the major benefit of digital frequency synthesis is that it is quick, cheap, and frequency agile. No commercial manufacturer could afford to build a transceiver with a Collins Mil-Spec PTO in it these days. But for an amateur with mechanical skills or access to surplus hardware who needs just one good oscillator, the venerable Hartley with a temperature compensated tuned circuit and a JFET can provide outstanding performance. In music, art, architecture, automobiles, motorcycles. .. there are recognized "golden eras" where some combination of factors resulted in technical hardware that is widely recognized as being superior to what is being produced today. Often the difference is directly related to the amount of skilled labor needed during production. As technical hobbyists, we automatically assume that new is better, but as experimenters, we should be open to the idea that sometimes the technology, ideas, and block diagrams of an earlier era are superior to the cost-driven disposable technology coming off fully automatic assembly lines in some out-of-the-way place with inexpensive labor and attractive business tax codes. The idea that old technology designed decades ago by retired guys might be better than new technology is a radical concept in electronics. But NASA is using a brand new, hand built, Traveling Wave vacuum tube in the current Moon exploration mission. After 100 years of radio experiments- -it is fun to look back and find old technology that might actually work better than some of the new things we've been inventing recently. Best Regards, Rick KK7B

Sonya's Rig

Stewart, G3YSX, provided us with Part II of his article on the espionage radio work of the Soviet spy Sonya (who had the Knack).

Sonja Continued

A few days after my article on Sonja the Spy was published in the September 2004 edition of the CARC newsletter, I received a letter from club member Eddie Ramm
DK3UZ filling in a few additional details.

The Fuchs antenna that Sonja used was first described by Dr Josef Fuchs, OE1JF, in 1928 and is a half-wave end-fed design.

End-fed half-wave antennas are very efficient and do not need a particularly good ground, but they are very high impedance and need a suitable matching circuit. For a spy the use of a simple, but efficient, antenna of this type would have its attractions.

Eddie then pointed out that the design is of current interest to the QRP community by pointing me to the following URL: http://www.qrpproject.de/UK/fuchs_ant_.htm. This describes a 5 band portable QRP antenna designed by Frank, DL7AQT, based on the Fuchs design. The antenna is a 40m to 42m length of wire and the ATU is a parallel tuned circuit using a pair of toroids and a 200pf variable capacitor. It is worth reading the English version of the manual, which discusses the issue of self-resonance in these high impedance matching circuits. Matching circuits of this type only function correctly below the self-resonant frequency. Frank used of a two toroid arrangement to the move the self-resonance from 18MHz to 60MHz, thereby producing an ATU that operated correctly from 80m to 10m.

The second point that Eddie raised was the term “Three Point Oscillator” that Ruth used to describe her (Sonja’s) transmitter. The German term is “Dripunktsender” (three point sender), which Eddie tells me is the term was used to describe both the Hartely and the Colpitts based transmitters. Both oscillator designs are similar in the way that they use the reactive components in the tuned circuit as an impedance transformer to provide the coupling between the tuned circuit and the amplifier, so the use of the common term makes sense. He included an article dated January 1939, which shows a 3W automatic transmitter for maritime use, which is of the Hartley design and is described as a Dripunktsender. The article can be found at http://www.radiomuseum.org/funkschau/1939/funkschau_12jg_0339_1v2.pdf and the Hartley transmitter circuit is shown above.

We have no way of knowing which type Sonja actually used, although, as I suggested before I would suspect that it was the Hartley. This is likely because the Hartley was popular in the amateur radio world at the time and we know that she improved here spy transmitter by using amateur radio techniques. Secondly, because her transmitter had to fabricated, without raising suspicion, using material found in the field, a Hartley would seem to be the preferred design. A Hartley has no critical capacitors, just a coil which can be fabricated out of an “innocent” piece of wire or metal, and adjusted to give both the right inductance and the right feedback.

Stewart G3YSX
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column