Topband: Input Impedance of the FT1000/S-Meter Calibration issues

[Sinisa Hristov]

Rick Karlquist wrote:

> There is not 10-20 dB of variation in the S-meter.  The
> worst case mismatch you show is 10+j16.  Even this 5:1
> SWR only results in a 3 dB mismatch loss, still not much
> in the overall scheme of things.  (You can find mismatch
> loss on any decent Smith chart).

Mismatch loss doesn't apply to this case.
The variation was observed with a constant current source,
not 50 Ohm source. Power delivered to FT1000 input is
R * I ^ 2, where R is the real part of input impedance.


> Also, you can easily fix even this 3 dB by using your
> own external attenuator

No, it cannot be fixed this way.
This will only ensure that constant power is delivered
to the external attenuator, but the original problem
repeats itself between external attenuator and RX input.


73,

Sinisa  YT1NT, VA3TTN