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FT-101E Intermittent Audio level/S-Meter level

Discussion in '"Boat Anchor" & Classic Equipment' started by KB3GWQ, Jun 26, 2018.

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  1. HS0ZED

    HS0ZED Ham Member QRZ Page

    Okay I understand but in this case the calibrator is pretty much spot on 50uV. At least it agrees with the sig gen and that is certainly pretty close to 50uV.
    Indeed the pot is right on ground. Will clean the board connectors again, and the relay contacts.
     
  2. HAMHOCK75

    HAMHOCK75 QRZ Member

    The board with the calibrator went through four iterations. The first three iterations used a 100 KHz oscillator followed by a transistor amplifier. The difference was in the 25 KHz circuit where some were discrete transistor designs but the last iteration with a 100 KHz crystal, PB1315, used an IC. The big change occurred in the final iteration ( PB1547 ) where the 100 KHz oscillator was replaced with a 3.2 MHz oscillator flowed by a Fairchild 34024pc CMOS ripple counter for 100 KHz. That design is probably significantly more harmonic rich.
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Yes the models with that board are really FT101F versions (even though most are just badged as an E). I recently bought one of those, and the calibrator signal is actually quite different from band to band (as you suggest). There are a few other changes from the E too, mainly in the Noise Blanker, Processor and ALC.

    My rig that is set up for use is a "proper" FT101E.

    And the reason they changed the instructions for setting the S Meter between the earlier and later models was because they increased the output from the Calibrator buffer amp. (If I remember correctly they did that during the FT101B production run). That's why you set it for S9+25dB on the later models. (and the handbook wasn't updated properly, as they incorrectly refer to this being 50uV, which was only the case on the early models, which you set at S9 against the calibrator)

    Roger G3YRO
     
    Last edited: Jul 18, 2018
  4. HAMHOCK75

    HAMHOCK75 QRZ Member

    I suspect that if you have PB1179, PB1185, or PB1314 for the reg/cal board they will be the 50 uV = S9 but if it is PB1547 it will be the S9 +25

    If you think they bumped the buffer gain up to get the S9 + 25, I will have to examine that buffer. The schematics for all the versions are on the Fox Tango web site. Looks like E versions with s/n 20,501 and up are the ones with the PB1547

    P.S. Good to know that those are really F's. I wouldn't mind having one of those even if it has an "E" badge.
     
    Last edited: Jul 18, 2018
  5. G3YRO

    G3YRO Ham Member QRZ Page

    No, they increased the output in the earlier ones

    Roger G3YRO
     
  6. HAMHOCK75

    HAMHOCK75 QRZ Member

    Is the PB1547 you have also S9 + 25?
     
  7. HS0ZED

    HS0ZED Ham Member QRZ Page

    Aha, pot not on ground!!!
    0.16v minimum to the meter!
    Pot changed to new blue cermet type. S meter can indeed be set right down to zero.
     
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Yes, that's what I set it to . . . (only bought it recently)

    But I noticed it behaved VERY differently from my E, which confused me when re-aligning the RF stages . . . totally different calibrator signal level from band to band . . . and the 25kHz signal is a different level too.

    Roger G3YRO
     
  9. HAMHOCK75

    HAMHOCK75 QRZ Member

    PB1547 uses the same 34024PC divider for both 100 KHz ( divide by 32 ) and 25 KHz ( divide by 128 ). It would be interesting to see if the outputs are square wave or pulses. If square wave, the even harmonics will be low.
     
  10. HS0ZED

    HS0ZED Ham Member QRZ Page

    I see only pulses. The FT-101E here S/N 50345 has a PB-1547B. Just plugging the antenna port into the scope I see some oscillator signal. Think that's coming from the main premix oscillator, didn't stop to look but it varies by band. Short pulses ride on that when the calibrator is on. Not much difference if its the 100kHz or 25kHz.

    100kHz Calibrator level is lowest on 160m but that could be alignment in this rig. It is essentially the same on all other bands. 25kHz calibrator is higher than the 100kHz calibrator signal on 160m, 80m and 40m by the time you get to 20m they are essentially the same and stay that way up to the 10D band position.

    S meter is set to read S9 with a 50uV signal from the sig gen and the calibrator level is essentially the same on 20m. Slight variation band to band but not more than 1/2 an S unit.

    There is a full S unit drop in the calibrator signal if the ant port is not terminated in something close to a lowish impedance.
     

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