TS-520 VFO Doesn't stay on freq through range

Discussion in '"Boat Anchor" & Classic Equipment' started by K2HNL, Jan 12, 2018.

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  1. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Used DG-5s are expensive, I understand.

    However there are more "modern" equivalent counters that are way cheaper and still adjust the display to read the actual operating frequency...probably $49 or so. Might be worth it. The new ones won't match the "Kenwood" look but are very functional.

    It's difficult to make a capacitor-tuned VFO hold calibration across 500 kHz; so difficult that Collins (and Drake, and even Ten Tec) went to PTOs instead a long time ago. The Collins PTOs have a camshaft inside, with cams tweaked one-by-one to adjust tracking and keep the dial calibration accurate across the band...very complicated, but it worked.
  2. KV6O

    KV6O Ham Member QRZ Page

    Build your own:

  3. G3YRO

    G3YRO Ham Member QRZ Page

    If the VFO capacitor is similar to that usd in the FT101 VFO, you can get the VFO to track by bending the vanes . . .

    If you look at the outer vane of the moving part of the VFO vanes, you will see it is split into about 6 sections, so you can move that vane in and out slightly. This is to adjust the tracking of the VFO.

    Start at the end of the band where the VFO capacitor is fully un-meshed. Zero the dial against the calibrator at the 100kHz point..

    Now go to the next 100kHz point, and bend the first movable vane in or out to get it spot on . . .

    Then go to the next one, etc.

    It's a bit trial-and-error until you get the hang of it . . . but this is how to get your VFO to track across the band.

    Roger G3YRO
  4. K0MB

    K0MB XML Subscriber QRZ Page

    When my TS-520 was brand-spanking new the VFO didn't track perfectly.I just developed the habit of going to the nearest 25 kc point, and re-zero the dial to the calibrator. And this is what I would suggest you consider,
    KA9JLM and KP4SX like this.
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Why make do, when you can make it work properly?

    When I worked for Yaesu, if anyone's VFO didn't track properly, I would fix it so it did !

    Roger G3YRO
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Everyone does not work the complete range of the dial.

    Kenwood made the Slip Dial adjustment for a reason.
  7. KI4AX

    KI4AX Ham Member QRZ Page

    Don't mess with the VFO Tracking and don't bend the Plates of the VFO. This is normal for the Kenwood TS-520. This is why they provided a 25 Khz Marker Generator - that's what the Marker is for; to calibrate that dial ring. It has to be calibrated every time you move more than 25 KHz (in theory) from the last frequency you calibrated it on. Refer to the Owner's Manual to learn how it works, how to use it, and how to keep the dial calibrated; it is very simple. Do NOT try to adjust the tracking of the main VFO and do NOT bend the Plates of the Main Tuning Capacitor - these are not your problem and most likely you will never get them right (again). Stop before your rig becomes FUBAR...

    Dan KI4AX
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Well that's really crappy if the TS520 dial can't be made to track across the whole 500 kHz !

    The Yaesu FT101 series does it fine . . .

    And as I mentioned, if ever a rig WAS slightly out at one end of the band, it was pretty easy to adjust the variable capacitor to get it spot on. I did this on about ten rigs that we sold, out of the many thousands.

    (I'm pretty sure I did the same procedure on at least one TS520 . . . but it was a long time ago !)

    Roger G3YRO
  9. KI4AX

    KI4AX Ham Member QRZ Page


    I qualified my statement by saying 'in theory.'

    And, from what I have seen the FT101 does not do it fine.... At least no better than the Kenwood TS-520. Even when they were new they did not track exactly. That's why they also have a 'calibration dial' and Marker Generator just like the Kenwoods of that era. The Engineers who designed the FT101 (and the Kenwood Hybrids) knew the limitations of their design and that's why the rig has a Marker Generator. That was 'state of the art' in that time period.
  10. G3YRO

    G3YRO Ham Member QRZ Page

    I'm sorry Dan, but you're wrong !

    I sent out HUNDREDS of new FT101s when I worked for the UK Yaesu importer . . .

    Every one was unboxed and thoroughly tested before sending to customers.

    One of the many functions I checked was the dial accuracy from one end of the band to the other . . . if there was even a 1kHZ error, I would then adjust the VFO capacitor to put it right. Most were spot on . . . but I think I had to re-adjust around 20, in the manner I described in my previous post. (which is how they are set up at the factory.)

    Components in the VFO can age a little, so sometimes they may need re-adjusting after 40 years . . .

    I re-did my own FT101E a couple of years ago, and it is now spot-on, right across the full 500kHz that the VFO covers. (I've also done this recently for a couple of locals)

    So as I said before, there is no need for anyone to put up with dial errors . . . it's not Rocket Science to put it right!

    The other excellent feature of the FT101 VFO design is that it has ADJUSTABLE temperature compensation. There is a split-stator capacitor, so you can bring in more negative or positive temperature compensation. Using a hairdryer, to blow hot and cold air, you can make the rig virtually drift-free.

    Again, I re-adjusted mine a couple of years ago . . . and the rig is actually more stable than my external digital readout !

    Roger G3YRO
    Last edited: Jan 19, 2018

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