[Elecraft] New Crystals or Not

[Randy Moore]

I've been very interested in this thread.  My K2 is #337 and the filter
response has always attenuated the signal significantly as the bandwidth
narrows.  So tonight I decided to look at it again with Spectrogram and
use the advice I've seen here to determine whether I should order a new
matched xtal set.  But tonight I did a more extensive job of measuring
than I have before and I'm really puzzled.  Basically, I get a very
different set of measurements when I use a noise source (N0SS's design)
than when I use the birdie at 7.000 Mhz.  Also, I get a different
response depending on whether I have the preamp on/off or the attenuator
on.  Here are my numbers.  I hope the columns line up well enough to
read this.

For all measurements, the VFO was set to 7.000 Mhz, AGC off, audio
filter off, RF gain max, mode CW; the signal amplitude was measured at
my sidetone frequency of 530 hz, which is where I have the filter
maximum set (as best I can using Spectrogram).

With the wide-band noise source (AF gain set to about 8:00):

		PreA ON	PreA Off	Att On
OP1		-29		-28		-29
800 hz	-23		-29		-39		
400 hz	-25		-35		-46
150 hz	-30		-42		-53

With the 7.000 Mhz birdie (AF gain readjusted to about 2:00):

		PreA ON	PreA Off	Att On
OP1		-15		-28		-40
800 hz	-32		-45		-56		
400 hz	-38		-51		too low to measure
150 hz	-44		-57		too low to measure

Can someone explain this to me???  Am I doing something wrong here???

Thanks!

73,
Randy, KS4L