Thursday, November 10, 2011

Something Crazy's Going On

I've been out of the saddle for some weeks now due to family issues. At last, this afternoon I lowered myself down into the Hobbit Hole with the aim to have some much-needed fun. Well, I did that plus some; only, I'm a little confused right now.

Once in my shack I quickly threw together a 40m, crystal-controlled, Pierce oscillator using a germanium grown-junction alloy transistor. This one was made by General Electric back in September of 1956; type 2N78. As the maximum data-book 3db-down cutoff frequency is only 6MHz, I'm pushing it a bit. With 12V on the collector the RF output power is 5.6mW. Not much, on the other hand the worst harmonic is -45dBc with just a simple LC tank in the collector...no extra LPF required.

1957 Radio Shack Catalog

Next I built a one-transistor regenerative receiver using the same type 2N78 transistor. It even has the same date-code. For simplicity I placed my 1950's Czech military surplus "4k Ohm" headphones directly in the collector return to the +6V supply line.

Likewise, I plumbed my Czech mil-surplus straight key to the transmitter. The antenna was my usual 135' end-fed wire erected at 35' on the ends.



The band was busy so I ended up calling CQ at 7041.6MHz; smack between some "letter" stations. I called for about an hour with no luck. Having only three 40m quartz crystals, I kept checking the lower two frequencies for a clear spot. Eventually there was a lull on 7014.7kHz so I began calling there. It didn't last long. In less than five minutes I found myself buried in a resurgence of DX activity. But now I noticed my third quartz crystal frequency was open so I QSY'd up to 7029.7kHz, where I took up calling CQ again.

At 2134z a strong station answered my call. It was K8CIT calling from Michigan (554m/891km). Art was 589 to 599 here with his 100w and 80m loop at 60'. He gave me a 429. We ended up having a great QSO lasting until 2150z. Art copied everything I sent: details about my rig, the transistor type, my receiver, etc..


When I came up to the house for dinner I decided to check the RBN to see if any of my calls had been captured. Indeed, I was logged a number of times by RBN receivers in NH and PA, with SNRs from 1 to 5dB. But right at the top of the list was a RBN capture at a SNR of 14dB. The RBN station that logged me was DL8LAS near Kiel (3599m/5792km)! Everything about the logging seems correct: frequency, sending speed, etc.. It appears that my antique transistor was heard in Germany this evening on 40m...all 5.6 milliwatts.

15 December 2011 Update: Peter, DL3PB, may have solved the mystery!  There appears to be a bug in the RBN software that occasionally prompts it to capture your call sign as sent by another station, and present it as though it had heard you calling CQ. This would make sense as the DL8LAS listing of my call is approximately the time that K8CIT would have been signing-off with me. It very well may have gotten my call sign from K8CIT. Thanks Peter!

K2LP answered my CQ on 15 November 2011. The reports were 599/559. Bud's strong signal blocked my little regenerative receiver so badly that I resorted to copying the "thumps"...no tone heard whatsoever! ;o) 

6 comments:

  1. I've noticed such mystery propagation several times before, I names it "warmholes", but can't explain its nature. Thank you for sharing, it is very interesting.
    73! uu1cc

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  2. Michael

    The greatest mystery to me is where you managed to get your set of "1950's Czech military surplus 4k Ohm headphones". Is there a source you can share?

    Mark VK6WV

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  3. Hey Andy,

    It's good to hear from you. Yes, it almost seemed like Sci-Fi. In fact, G3XBM wrote to say, "I reckon you are TXing through a wormhole in the space time continuum and that way he is just down your lane." ;o)

    Hello Mark,

    The phones and hand key are much appreciated gifts from Martin, OK2MR. Both of these were used on the RM 31 field radio; circa 1952 thru the 60's.

    http://greenradios.blogspot.com/2011/02/tana-liben-supertana-mana-trinec.html

    I occasionally see the keys for sale so perhaps the phones surface from time to time as well?

    Best wishes,
    Mike, AA1TJ

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  4. I think G3XBM was right. There are at least no mysteries any more. A pitty! But on your part: Well done! and we will meet on the next greyline which is coming through.

    But I had this kind of propagation when connecting a satellite. The signal goes up and is not reflected back to earth as normal, but travels in a kind of tunnel between the d and f-layers before it comes down in good old Germany.

    And here you are of course welcome and the signal is happy to see some light at the end of the tunnel.

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  5. Gruß Hajo,

    Thank you for your suggestion that ducting might be responsible for the DL8LAS RBN capture of my miniscule signal. At your prompting I read through a basic description of the phenomenon at

    http://www.antennex.com/prop/prop0806/prop0806.pdf

    I look forward to meeting you on the bands, Hajo. Until then, I wish you all the best!

    73/72,
    Mike, AA1TJ

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