Ft901 is there a way to adjust all bands to agree w display?

Discussion in '"Boat Anchor" & Classic Equipment' started by KG7HVR, Jan 20, 2018.

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  1. KG7HVR

    KG7HVR Ham Member QRZ Page

    When I set the mark and adjust on 75M so that my display is correct when I go up to 40 or 20 it's not even close so I constantly have to adjust with the marker which is not very accurate and hard to tell when it's at zero beat anyways.
    there must be some way to adjust each band so that when you change bands you don't have to recalibrate the digital display.
    I cannot find any information in the service manual about this.
    I just need to be able to nudge each band a few kc so they all match up.
    There is a vco for each band. there are several for the 10 meter band. I don't really care about the 10 meter band I don't use it. I just want to be able to switch from 40 to 20 or 75m without having to guess where I'm at at the band and recalibrate the display. Also USB and LSB are off.
    any advice would be helpful I have two of these radios actually
     
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Probably not. That is why these radios have a marker. So you can calibrate the dial and be more accurate.

    A full alignment would give you the most accuracy, but I cannot guarantee that you would not have some dial inaccuracy.

    How far off is the dial reading? What are you doing that you need particular precision? :)

    In the end the only solution is an alignment. You can't go just tweaking things with a screwdriver. Sorry.

    [edited for clarity]
     
    Last edited: Jan 20, 2018
  3. KG7HVR

    KG7HVR Ham Member QRZ Page

    If I'm on say 7.204 lsb and switch to USB ill be on 7.201
    Then switch to 80m I'll see a display of 3.700
    Tx will be on 3.70391 and so forth
     
  4. KG7HVR

    KG7HVR Ham Member QRZ Page

    I seem to remember adjusting each band on the 101 series to match the dial you wouldn't recalibrate your dial every time you change the Bands
     
  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Ok, so you have split of 3kc between USB and LSB. That can be corrected by aligning the USB/LSB.

    A Tx/Rx split of 391 Hz is worth doing an alignment. Tx and Rx SHOULD be quite close at all times on all bands. A full alignment is warranted.

    There is no simple way to calibrate all the bands from the front panel. A full alignment per the Service Manual is the correct way to address the inaccuracies. However, given the technology, you will still see some difference from band to band of at least tens or hundred Hertz or so, on each band and perhaps more between bands.
     
  6. G3YRO

    G3YRO Ham Member QRZ Page

    No it can't ! LSB is generated around 3kHz away from USB . . . so if you change from one to the other, you will ALWAYS have to re-calibrate the dial - this is not an error ! (and again if you go to CW)

    Secondly, if you adjust the Heterodyne Crystal Oscillator for each band, it WILL move the resultant frequency slightly. The Trimmer is there to resonate the tuned circuit, ie peak the output, NOT to adjust the frequency. But you can usually compromise in the adjustment of the Het Osc trimmers, such that the frequencies are pretty close as you change from band to band.

    By the way, all of this is the case with ANY conventional VFO/crystal mix rig.

    Only synthesized rigs using sophisticated PLL systems allow you to change Band and Mode and the frequency stays as indicated.

    EDIT - all my above comments were relating to the FT101 (which I thought you were talking about!) Some apply to the FT901 . . . but having looked at the circuit, I see they have no trimmers to adjust each band's crystal oscillator !

    If you were bothered, you could fit a small trimmer on each one, so they're aligned the same when you change bands.

    Roger G3YRO
     
    Last edited: Jan 20, 2018
    W4NNF likes this.
  7. KG7HVR

    KG7HVR Ham Member QRZ Page

    correct I read in the manual about the 3kc difference on upper and lower.
    There is a crystal unit on the bottom of the radio with transformer cans
     

    Attached Files:

  8. G3YRO

    G3YRO Ham Member QRZ Page

    Well the circuit diagram didn't show the Tuned Circuit with any ferrite cores . . .

    But as they HAVE, you may be able to align the frequencies by adjusting each one.

    Roger G3YRO
     
  9. KG7HVR

    KG7HVR Ham Member QRZ Page

    hmm. Ill try it on the parts radio with the bad IF board
     
  10. KG7HVR

    KG7HVR Ham Member QRZ Page

    It had no effect
     

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