Re: Low output from 2nd crystal filter and SA602 product detector

Posted by Don Wilhelm-4 on Feb 01, 2011; 8:45pm
URL: http://elecraft.85.s1.nabble.com/Low-output-from-2nd-crystal-filter-and-SA602-product-detector-tp5979986p5982573.html

  Bob,

Yes, that seems quite good.

On your transmit problem, count the turns on the toroids in the Low Pass
Filter.  Count the number of times the wire passes through the center of
the core.  Many builders do not pick up on the fact that a straight wire
through the core is one turn while a full wrap around the core is two
turns - they end up with an extra turn and the Low Pass Filter's cutoff
frequency is too low.

If you have an antenna analyzer, I can tell you how to check the LPF easily.

73,
Don W3FPR

On 2/1/2011 2:09 PM, n7zf wrote:

> Don,
> AGC was on,  T7 is 5:20, crystals are the -S flavor.
>
> With a -130 dBm signal, Spectrogram shows the signal about 20 dB above the
> noise floor, so I guess I have nothing to worry about.  Can easily hear the
> signal with headphones.  This graph is with AGC on, and the AGC off chart
> looks about the same.
>
> http://elecraft.365791.n2.nabble.com/file/n5982289/minus_130_dBm_signal_at_10.1_MHz_with_agc_on.jpeg
>
> I will go back to the original problem I was chasing:  on transmitter tests,
> the K2 draws about 50% more current than it should.  I am guessing that I
> need to work on the transformers in the PA circuit.
> Thanks,
> Bob N7ZF

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