VFO stabilizers

Discussion in '"Boat Anchor" & Classic Equipment' started by KM1H, Oct 9, 2017.

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  1. KM1H

    KM1H Ham Member QRZ Page

    Has anybody used one of these on a hefty TX VFO such as an early or late Meissner Signal Shifter, aka drifter? They use a 6F6 straight thru on 160 or as a multiplier on all other bands for the early plug in coil version. A 6V6 drives a 807 on the postwar EX version
    While Ive done many TC reworks to receivers and transceivers it can be very time consuming and if the UK X-Lock is as good as it looks I'll get one to start with.

  2. KE0ZU

    KE0ZU Ham Member QRZ Page

    Hi Carl,

    Who's kit are you considering?

    I can't be of any help here since I never built one, and the only one I've even used was the one in the HP8640 which seemed to work pretty well. However I'd be interested in seeing what the results of your experiment are, as I have a post war EX coming up in the Queue.

    As you know there are lots of circuit variations out there, and some are pretty simple, should you decide to copy or roll your own.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Wish I could find somewhere to buy ordinary temperature compensating capacitors to make an oscillator stable.

    In the past, I have made VFOs very stable by selecting the correct value (usually an N750 coeffcient capacitor)

    I want one for my external digital display for my FT101 . . . the crystal conversion osc in that drifts MORE than my FT101 !

    (I know there are companies in the USA that sell them . . . but they want $25 dollars to ship ONE 50 cent capacitor!)

    Roger G3YRO
    Last edited: Oct 9, 2017
  4. SM0AOM

    SM0AOM Ham Member QRZ Page

    I would suggest that you read the material on the Hans Summers website
    where some of the limitations of the frequency lock loop are discussed.

    Ages ago, I tried the original PA0KSB circuit and found that there is a limit to the drift rate
    that it is able to correct. As long as this limit is not exceeded, the principle works "as advertised".

    The limit is derived from the control voltage characteristcs in Hz/V, time constant of the integrator in the loop and the spacing of the lock points.

  5. W1GCI

    W1GCI Ham Member QRZ Page

    Carl, how much drift over the operational time period?
  6. K6AFS

    K6AFS Ham Member QRZ Page

    Hi Carl,
    Yes, I use a VFO stabilizer on my Collins KWS-1. The stabilizer is completely transparent and unseen, leaving the operation of the KWS-1 absolutely stock. The only clue to its existence is that drift is controlled to within 1hz over the stabilizer's +/- 0.1ppm OCXO reference. It unlocks when spotting, locks when set to operate. When locked, the stabilizer controls frequency via a varactor diode that I installed to replace one of the small fixed capacitors in the VFO tank. The stabilizer uses an MCU running like a frequency counter reading the frequency output of the VFO in 1hz resolution. Once drift is detected, it outputs a control voltage to the varactor to reverse the drift. For the past several years, I use my KWS-1 on fixed frequency mulit-hour rag chews. Nowadays I hang around on 3913. I spot the TX to frequency when I start, and never touch the VFO thereafter no matter how many hours I operate. People I talk to never get a clue I am using a boat anchor. I grow a nice grin when sometimes someone asks me, after talking for a few hours, what type of Yaesu or Kenwood am I using and I tell them I am using a transmitter made in 1956 running barefoot. Some details on my Qrz page.

    Btw, I have followed many of your wonderful posts on other forums the past 20yrs... Thanks for being a ham.

    PA3AAT, KM1H and KD2ACO like this.
  7. KM1H

    KM1H Ham Member QRZ Page

    KD2ACO likes this.
  8. KB4MNG

    KB4MNG Ham Member QRZ Page

    I really like your qrz page. I had no idea that was where the "gold dust" term come from. Very interesting! Looks like you really use the vintage radios. Have you ever had major issues with them that had to be fixed?
  9. K6AFS

    K6AFS Ham Member QRZ Page

    The misconception that the black twins were called gold dust due to their value is a byproduct of modern interpretation by hams today. The original interpretation was lost when Fairbanks went out of business. The one major issue with the KWS-1 (and most other boat anchors) is drift. It was not an issue back in the day but most hams today make an issue of it. The vfo stabilizer I installed works similar to the X-lock described by Carl.

  10. N2EY

    N2EY Ham Member QRZ Page

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