Friday, December 3, 2010


The receiver used in Solidarity is an upgrade of that used in my November 27, 2010  station. The detector now operates in the vicinity of 2.87MHz with improved frequency stability. Furthermore, the addition of the frequency-converter stage introduces isolation between the detector and the antenna.

My earlier receiver was also plagued by microphonics. While a vibration damping mount for the CK5875 detector tube would have greatly reduced the problem, I decided to side-step the issue entirely by switching to a remarkable, Soviet-made, subminiature pentode.

The 1Ж24Б (1J24B, 1SH24B) is a marvel of ingenuity dating from the 1950's. Examining the close-up photos on this German site, one might be tempted to exclaim, "Where are the grids?" In fact, three grids are present, only, they aren't helically-wound, neither are they ladder or screen structures; they're collinear! This device is the product of some clever electron optics (see post #7) involving tiny sheet beams.

Another virtue of this tube is its extraordinary emission efficiency; a definite plus given my eventual goal of building a minimalist's vacuum tube-based portable QRPp station. 

Details of the 1Ж24Б are covered in this 1962 Soviet vacuum tube manual. An article on the topic of these tubes appeared in the July 1960 edition of the journal, "Радио." Please click here to download this magazine issue. The article begins on page 34 (page 40 of the scanned document). 

Aside from the vague speculation they may have been been used in the MIG-25 (Foxbat), it's clear these tubes were used for portable military equipment of the Warsaw Pact nations; an example of which may be found here. They were used for similar applications, and during the same time-period as the likes of my Raytheon subminiature tube was used in NATO equipment. 

I rather like the idea of melding the CK5875 and 1Ж24Б - these former Cold War adversaries - into a single radio.  

The 40mW transmitter amounts to a simple, crystal-controlled, Miller oscillator followed by a high-pass, L-network for impedance matching. For maximum efficiency L1 needs to be a Hi-Q inductor. 

The regenerodyne receiver IF tunes from 2.877 to 2.807MHz in order to provide 20m coverage from 14.000 to 14.070MHz. L2 and C4 constitute a 16.877MHz trap filter. Adjust L2 for maximum 16.877MHz energy at the filament. VC2 cancels the residual trap reactance at 14MHz. On paper it improves the sensitivity by 4dB; it's not strictly necessary. While tuning across the band VC3 needs to be re-peaked every 10kHz or so. VC4 is the main-tuning variable capacitor. VR1 is the regeneration control. 

The CK5875 filament draws 100mW at 1.2Vdc and the 1J24b's each draw 15mA. Altogether, the receiver only consumes 217mW of input power. Not a peep of SWBCI has been heard on this receiver in several weeks of operation.

Despite poor band conditions, last week Solidarity provided me with several pleasant QSOs. On Thursday, K9IS replied to my CQ with his Elecraft K1 from Wisconsin. Steve was running 3w to a dipole. He was 579 on the regenerodyne and he gave my 40mW signal a 339 report. 

An hour later N4KGL/4 answered my call. Greg was operating his little, Wilderness SST @ 3w into a Hamstick dipole that he mounted atop a 20' mast. Greg was on his lunch hour and operating from the parking lot adjacent to his office. Details of his setup may be found here, here and here. Greg wrote later

"I had good copy at the beginning for the essentials and then fading in and out....When I turned on the rig I was hearing nothing in the SST's 8 khz receive window. So you were the first signal that I heard."

Working a guy standing in a parking lot on his lunch hour (a stone's throw from the Gulf of Mexico) with 40mW and some vintage pencil tubes stuck in a plastic protoboard here in snowy Vermont is just plain cool! 

A few minutes after I signed I heard K9IS calling me again. He'd heard Greg's and my QSO. In fact, he'd continued to copy my CQs on a variety of rigs ever since our contact. He said that my signal had peaked briefly at 559. The most exciting news was that despite a slight frequency offset in our crystals, he'd copied me on his RockMite. Steve then switched to the RockMite (at 350mW) for the remainder of our contact! I gave him a 559 (an easy copy here aside from the QSB fades). He copied me at 329. Just amazing...

These great QSO's were the "shot in the arm" I needed to go on calling, even as the band conditions appeared to further deteriorate. Tuning around, I only heard a couple of signals on the band now; besides it was nearly sundown. But you know how it is...just a couple more calls  :o)

And suddenly, big as life, I hear FG8AR calling me! I quickly send off a 599 report; feeling my pulse all the way to my sending wrist. FG8AR replies with a 539 report. He says his name is Olivier and asks, "PSE UR PWR?"  I reply, and he responds, "GUD GUD WITH 40MW." 

It took me a moment to recover after we'd signed; I kept looking at the tiny CK5875 envelope while trying to visualize the geographical location of the island of Guadeloupe. 

Most exciting of all is the thought of what will be possible with Solidarity when the conditions on 20m are actually good! 

So thanks for your interest, guys. I hope to be QRV on 14.060MHz with this rig come next Tuesday (12/7/10). I hope to hear from you!




  1. We call those pencil tube pentodes the
    1 "" little spider "" followed by the number ...
    The zhe letter of the Cyrillic alphabet does not exist
    in our Latin alphabet amigo Mike, so we name it
    "" the little spider"" or the aranita ... letter.
    Seasons Greetings from Havana
    Your friend
    Arnie Coro

  2. Hi Arnie,

    Ha, now that you mention it, that "zhe" symbol does look like a little spider! Gosh, but what a brilliant design, eh?!

    I hope to see you on 14060kHz soon, Arnie.

    Seasons Greetings from atop snowy Mt. Mansfield.

    Your pal,
    Mike, AA1TJ

  3. That "zhe" symbol is not a spider (spider has 8 legs), but a bug, the Glowbug exactly :)

    Great project, thanx for share, 73!

  4. Andy,'ve got such a cool blog! I especially like the "Evergreen Sender." You're a real artist, OM!

    Tis' the season for brightly colored glowbugs :o)

    Mike, AA1TJ

  5. Thank you so much, Mike, I have to write more often :)

    Another note about the "zhe" letter - BUG in Russian means "ЖУК" (sounds like "zhook"). So, I'm quite sure that that letter in the tube name is not a little spider, but a Glowbug itself :)

  6. Astounding work, Mike! It's hard enough work finding these obscure little devices nobody has heard of - but to make radio with them too!

    Have a joyous holiday OM

    73 Dave NM0S

  7. Hi David,

    Thanks very much for your kind thoughts!

    Best wishes for a very Merry Christmas and a Happy, Healthy New Year.

    Mike, AA1TJ

  8. Great info.
    What made you to use T1. Why is it better than just one more link turn to T2.

  9. Thank you Petro,
    I agree it is tempting to combine T1 and T2; both for the sake of simplicity and to eliminate the need to re-peak T1 as one tunes across the band. However, V2 ought to have a high-impedance load at 2.8MHz in order to produce a decent conversion-gain. More importantly, the Q-multiplied tank circuit of which T2 is a part should not "see" a heavy external load, otherwise the virtues gained from Q-multiplication would be diminished or lost altogether. My solution was to use two lightly-coupled resonators. But as you suggest, there may be simpler options. Good luck and have fun, OM!


  10. Thanks Mike for clear explanation.

  11. There is one more tube you can use in mixer. 1j37b has two separate grids. But I guess you are aware of it.

  12. Dear Piter,

    No, I had not seen the 1j37b; what a lovely little vacuum tube! While it draws considerably more filament current than does the 1J24B, the extra grid would be very useful indeed! Thank you for bringing it to my attention, OM.


  13. The 1Zh24B or 1P24B was apparently used in the transmitter on Sputnik, which emitted 20 and 40 MHz unmodulated carrier. Have you ever seen a circuit diagram for that transmitter (called D-200).

  14. Hello Don,

    Thanks for your comment. I would be thrilled to see the schematic of Sputnik's little transmitter; especially as both Sputnik and me were "launched" the very same year! However, it's my understanding that nobody knows what became of it. What a pity. Think how much fun it would be to put a replica of the world's most famous QRPp transmitter back on the air.

    "It took a little over an hour for the satellite
    to return back around the Earth. Once again,
    Lappo picked up the signals, the insistent
    “beep-beep-beep”. He screamed: “It’s there!
    It’s there!"

    BTW, I have the schematics for the solid-state transmitters used in the American Vanguard and Explorer-1 satellites. In fact, I've used similar circuits - equipped with roughly comparable vintage transistors - to make a number of over-the-air contacts with my radio amateur brethren.

    If the Sputnik transmitter circuit should ever come to light it would be great fun to "beep-beep" around the world with it on 15m CW!

    Mike, AA1TJ

  15. Havana's newspapers carried the news that radio amateurs CO2OM and short wave listener Arnaldo Coro Jr. had picked up the Sputnik transmissions, near 20,000 and 40,000 megaHertz...
    Oscar's Super Pro receiver was the type that went up to 40 megaHertz.
    My receiver could only pick up signals
    up to 30.000 megaHertz.
    It was quite an achievement for a 15 years old Arnie Coro to be quoted in one of the most important newspapers of Cuba !!!

  16. I picked up the Sputnik 20,000 plus or minus about 3 kiloHertz.
    It made a news headline at one of Havana's most important newspaper published after 4 October 1957
    Quite an achievement for a 15 years old radioaficionado !!!
    It helped that my dad was a friend of the guy that ran the science column of the newspaper HI HI !!!

  17. I believe all the components of the sputnik transmitter are still manufactured. I have a couple photos that show the guts of the Sputnik radio unit, if you're curious. Maybe you can deduce something about it.

  18. Hi Arnie,
    What a wonderful memory that must be, and what a great way to begin your radio career! Hearing those little beeps must have sent shivers down your spine. Thanks for sharing, OM!

    Mike, AA1TJ

  19. Hello Don,
    Thank you, yes, I'd be very interested to see those photos! I would also appreciate hearing what you've unconvered on the type of vacuum tube that was used.

    I came across your excellent webpage and blog last evening. I especially enjoyed reading your Sputnik-1 page.

    Don, you can reach me at mjrainey at

    BTW, good stuff on your work at Bell Labs and high-fives on the Shostakovich. This link comes from my web site

    Mike, AA1TJ

  20. Interesting,

    But perhaps you might like to try this little QRP, comrade..?