Posted by
Don Wilhelm-4 on
Oct 08, 2007; 10:20pm
URL: http://elecraft.85.s1.nabble.com/K2-IF-amplifier-output-fault-tp454319p454323.html
Alan,
Great to hear that you have found success.
Yes, I do believe that manual has an omission. It would be difficult to
saturate the IF amp with the RF Gain set to minimum.
I believe you are reading from Appendix E page 12 - while on page 11, it
says to set the RF Gain to minimum (necessary for item 7 on page 12),
but item 8 should include setting the RF gain to 'maximum' if I
understand what is being tested correctly.
The K2 is quiet with no signal - it was designed to be that way. The
other factor is that most receivers have much more reserve audio output
power than the K2, so one cannot 'crank up the audio' and hear a LOT of
noise, especially with no antenna connected. It makes no sense to
listen to the noise floor of the receiver at a loud level anyway. If
you connect an antenna you should hear the band noise above the receiver
noise level (on the HF bands with any decent antenna).
One benefit to all your trouble - at least you know the K2 will stand a
+23 dBm signal at its input with no ill effects!
73,
Don W3FPR
Alan Ibbetson wrote:
> Don et al,
>
> I think I may have made forward progress.
>
> With or without D40/D41 I cannot get more than about 10mV at the
> output of the MC1350 IF amp when performing the IF Amp Saturated
> Output test. This is with the RF gain at minimum and as much signal
> into the antenna jack as my sig gen can produce (3V RMS PD).
>
> However, why would Elecraft have me do this test with the RF gain at
> minimum? We are trying to produce as much output as possible. So I set
> the RF gain to maximum and now there is 280mV of signal at the output
> of the IF amp, which is what the manual predicts. Although there is no
> figure quoted, I find I need 1mV from the sig gen to produce the 150mV
> for the next test (2nd crystal filter loss measurement).
>
> The receiver goes on to pass all the subsequent tests. Having peaked
> the input filters and re-run the BFO calibration I measure the MDS in
> 700Hz to be -132dBm with the preselector off and -138dBm with it on.
> This is within experimental error of the specs in the manual.
>
> So, the receiver isn't deaf. However, it still sounds very quiet to
> me. 7mV of audio hiss at full volume (yes, within spec) is just not
> loud at all.
>
> Sorry to have wasted everyone's time, although I do think the manual
> either misprints "minimum RF gain" when it means maximum, or they
> really do expect you to pump much more than 3V (+23dBm) into the poor
> thing!
>
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