My First-Ever QSO -- 50 Years After Passing Ham Test

Discussion in 'Ham Radio Discussions' started by G3EDM, Aug 27, 2021.

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  1. W9BRD

    W9BRD Ham Member QRZ Page

    0A2 + 0C2 = 150 + 75 = 225
    0B2 + 0B2 = 108 + 108 = 216

    among others; some VR-tube voltages (90, at least) were not made available in miniature-tube form. Some regulation-voltage values are generally more stable than others as a result of the different gas mixtures used; the regulation achieved is still much better than that possible with a resistive voltage divider.

    0B2s will usually stay close to 108 V. "75 V" regulators may be somewhat off 75 V. The regulation voltage varies from tube to tube, and voltage to voltage, and with aging. The regulation, rather than the exact voltage level achieved, is the important thing. Overcurrent/overdissipation can spoil a VR tube's ability to regulate properly fairly quickly.
     
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  2. W9BRD

    W9BRD Ham Member QRZ Page

    It will "work"; it's just that drive to the 5763 will be lower at the reduced oscillator plate voltage. You'll see higher plate current than before for the same output, assuming that the same output can still be achieved.
     
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  3. G3EDM

    G3EDM Ham Member QRZ Page

    Thanks. I think it is worth trying out oB2 + oB2 (this time I am typing the "zero" properly!). Will place an order. It it turns out to be a bad move, the tubes will surely come in useful at a future date, for another project.

    I honestly don't mind messing around in this way, but not forever! It would be nice to get back on the air.

    However, in general I take your point that a two-tube design like the Boosted Pierce is asking for trouble and can probably never be optimal. Just need something usable on the air....

    Oh, one more thing. In one of the two running threads on this project @SM0AOM rightly points out that, at QRP levels, you might want to eke out all the watts you can get. (That was in the context of accessories that can help you tune/adjust the PA for best output.) But frankly I'd rather have lower power if that is the price for getting a clean signal with the Boosted Pierce. In some ways it defeats the purpose of the original design, but I'd rather have sub-optimal power than a sub-optimal signal.

    Edited to add: Might even try 0B2 +0C2 to get a nominal 183 volts. Once again, I am trying to spare my "restuff" crystals ... while still having enough drive to the PA. Right now with the 0A2 I am measuring 142V on the oscillator plate, which may well be too low anyway even for purposes of the oscillator.

    73 de Martin, G3EDM
     
    Last edited: Sep 21, 2021
  4. G3EDM

    G3EDM Ham Member QRZ Page

    For those interested in the technical nitty-gritty, I did another five hours of work on the transmitter today, modifying it to make precise voltage and current measurements easier, and then making a series of actual measurements. These readings are key to figuring out "what's going on" and trying to improve the transmitter overall.

    I've posted a long, highly technical account, including photos and data tables, in the thread over in the "Homebrew and Kit Projects" forum called "Oscillator/PA Cathode Keying, 'Spotting' Your Frequency, and Chirp". It is post #131 in that thread.

    [​IMG]

    73 de Martin, G3EDM
     
    Last edited: Sep 22, 2021
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  5. G3EDM

    G3EDM Ham Member QRZ Page

    This afternoon I was blessed by the visit to my QTH of @G0CIQ (Simon) who brought his FT-817 and set it up at the other end of our house, to monitor my on-air signal.

    The setup is that he keyed my transmitter, while I listened to the output from the FT-817 and made videos. This was a series of actual transmissions through my full-size 40m dipole.

    Guess what: There ain't much wrong with my signal. It does however depend to a large extent on which of the "improvement" modifications to my transmitter are switched in or out.

    The test was done with two crystals: My best crystal (7004.9 kHz) and my worst (7030.5 or thereabouts).

    The best crystal sounded good regardless of operating conditions; it is a "genuine FT-243" vintage rock.

    My worst crystal is one of the numerous "re-stuffs" in my collection; these are modern, much smaller HC-49 crystals mounted inside empty FT-243 enclosures and they were never designed for the voltages or stress endured by the older ones. But guess what: with the right adjustments to operating conditions, it sounded just as good as my "best" crystal.

    It turns out that I was far too reliant on monitoring my own signal using gear (a regenerative receiver!) that is just not capable of doing that without introducing fake defects.

    Without further ado, here are the videos. I apologize for the fact that most of them are rotated 90 degrees, I was holding the phone the wrong way, and although it is possible to un-rotate them in the YouTube editor, it is unbelievably complicated so I will not bother. Not important because what matters is the sound, not the picture.

    BTW for the entire test, the 250 Hz filter was switched in on the FT-817. The signal never drifted out of filter bandwidth.

    G3EDM - Voltage Divider - "Good" Crystal - High Drive


    G3EDM - Voltage Divider - "Good" Crystal - Low Drive


    G3EDM - Voltage Divider - "Bad" Crystal - High Drive


    G3EDM - Voltage Divider - "Bad" Crystal - Low Drive


    (Another four videos in the next post.)

    73 de Martin, G3EDM
     
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  6. G3EDM

    G3EDM Ham Member QRZ Page

    The previous post, continued:

    G3EDM - 0A2 VR Tube - "Good" Crystal - High Drive


    G3EDM - 0A2 VR Tube - "Good" Crystal - Low Drive


    G3EDM - 0A2 VR Tube - "Bad" Crystal - High Drive


    G3EDM - 0A2 VR Tube - "Bad" Crystal - Low Drive


    I'll be back on the air soon.

    I do plan further technical improvements to the transmitter, to be discussed in the Homebrew forum in the thread called "Oscillator/PA Cathode Keying, 'Spotting' Your Frequency, and Chirp".

    73 de Martin, G3EDM
     
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  7. G3EDM

    G3EDM Ham Member QRZ Page

    @G0CIQ: Simon, our sending tests today were spotted by RBN as "CQs" even though we never actually sent CQ! Also the frequency is higher than it used to be, each xtal seems to have crept up by 300 Hz to 500 Hz compared to previous RBN spottings of my signal. Odd!

    (Can you remember where those two xtals came up on the FT-817's frequency display?)

    [​IMG]

    73 de Martin, G3EDM
     
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  8. GM3ZMA

    GM3ZMA Ham Member QRZ Page

    Lots of good work there Martin, well done.

    I believe that the RBN will also report a TEST signal.
    But having said that, a couple of times when I tried it, the RBN did not report my signals.

    I remember that several posters here on the ZED suggested that you really do need a better receiver, (not another regen).
    I think it is time to take a hike to the storage locker, find the BC453 and some bits to build a simple converter.

    Jim GM3ZMA
     
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  9. G0CIQ

    G0CIQ Ham Member QRZ Page

    Morning Martin, it was good to meet you and Jane yesterday and fascinating to take part in your very methodical series of tests! I can't quite see the display in the videos at the moment, currently whizzing towards London on a high speed train so they won't play properly. I tried a few cq calls with my 20m QCX when I got home then thought to have a look on the RBN as a result of your posts about it on here...heard in 3V8 and VE2 which is not too shabby!
    I'll have to put up something for 40m so we can have a go at that ground wave QSO...
    73, Simon
     
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  10. W9BRD

    W9BRD Ham Member QRZ Page

    If you sent TEST, contest-centric RBN records that as CQ, because TEST -- short for CONTEST -- is sent as a contest CQ by quite a few players.
     
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