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. G3YRO

    G3YRO Ham Member QRZ Page

    Well, regardless of what it says in the various Manuals, we always set the S Meter to read S9 when fed from a calibrated signal generator giving 50uV . . . this was on ALL original series FT101s, from Mk1, Mk2, Bs, Es and Fs. (all the British Fs were still badged as Es)

    On the very early ones, that usually corresponded to the Calibrator reading approximately S9 on 20m . . . But I'm just remembering that increased to S9 + 20dB, I think on the Mk2s. . . and then when the B came out, it was S9 + 25dB. So the Buffer emitter resistor mod gave about 5dB increase in output . . . but not sure why the Mk1s had a much lower Calibrator output.

    In fact, we adjusted ALL HF rigs we had in for repair or re-sell part-exchange (regardless of make) to read S9 for 50uV ! (it was a kind of mission to set a uniform standard!)

    Roger G3YRO
     
    Last edited: Jul 19, 2018
  2. HAMHOCK75

    HAMHOCK75 QRZ Member

    My calculations show that to read S9 +25 at 14.2 MHz, the calibrator voltage would have to increase nearly 18 times ( using PB1179 as the reference ) at that frequency but it is possible that doubling the gain caused the amplifier to limit creating stronger harmonics. A spectrum analyzer would be able to tell very quickly if the amplitude of the harmonics came up that much. It would be 2.5 divisions on a 10 dB/div standard display.

    That answered my question. You set later units to S9 +25 on the calibrator because for reasons that are still not entirely clear, the amplitude of the calibrator increased 25 dB over 50 uV.

    I too prefer to use a frequency synthesizer to set up 50 uV = S9.
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Yes, I think you must be right . . . although the Buffer's gain wasn't increased by 20 or more dB, probably it was clipping much harder, so the harmoics were a lot stronger.

    Whatever the reason, the way the Handbooks were re-written (in Japanese English!) is rather confusing . . .

    The point is that, regardless of what strength the Calbrator signal was on 20m, that setting was such that S9 still corresponded to a 50uV signal (and NOT S9 + 25dB equals 50uV)

    So if you don't have an accurate calibrated Signal Generator, using the Calibrator as a reference to set the S Meter is pretty close.

    Roger G3YRO
     
  4. HS0ZED

    HS0ZED Ham Member QRZ Page

    Must be something wrong with this one then. It's a late model calibrator regulator board, PB-1547B but it puts out pretty much dead on 50uV and agrees with a sig gen of known calibration state. Similar level from the 100KHz and the 25Khz settings
     
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Not quite sure how you would read the output level of the calibrator board, as it's probably so full of harmonics . . .

    If you set your S Meter to read S9 when you feed a 50uV Signal Generator signal in, what does your Calibrator read on 14.200? (mine reads S9 +25dB)

    Roger G3YRO
     
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    Any reading above or below S9 will not be correct.

    That is the way most radios are.

    Setting the radio for S9 +25dB when the signal is really S9 is silly.

    But people you give signal reports to will be happy.
     
  7. G3YRO

    G3YRO Ham Member QRZ Page

    I agree . . . but why would anyone do that?

    Actually both my main rigs (FT101E and TS-930S) track fairly well above and below S9 . . . certainly from S5 to about S9 + 30dB.

    Roger G3YRO
     
    Last edited: Jul 19, 2018
  8. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    That seems to be more of an SSB problem. On CW I give real RST reports and typically get a real one back, unless it is some pileup DX'er or something then of course everyone is 5NN even if you ask to repeat info, hi!
     
  9. HS0ZED

    HS0ZED Ham Member QRZ Page

    Mine reads S9, both the 100KHz and the 25KHz
     
  10. G3YRO

    G3YRO Ham Member QRZ Page

    Something odd going on then . . . also the 25 and 100kHz Calibrator signals are usually quite different in strength.

    I always give proper S Meter signal reports, whether on CW or SSB . . . all my serious operating is on 160m, where people are genuinely interested how strong (or weak) their signal is.

    That's why I've always made sure my S Meters are properly calibrated.

    (obviously in contests, you usually just give a standard 5/9 or 599)

    Roger G3YRO
     
    Last edited: Jul 19, 2018

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