[Elecraft] More Audio OUTPUT please

[Ron D'Eau Claire]

I normally wear headphones and I'm one of the ops who seldom, if ever,
runs the audio above 9 o'clock - and that's with the audio gain control
mod installed. 

Of course, "listening" is very subjective. And I think that here in the
USA anyway we have turned things around. When I was a kid, it was the
OT's who had hearing problems. Now that I'm an OT, it seems to be the
kids who have gone deaf. For example, I have pretty much given up on
movie theatres in the USA - the sound levels are so high that I have to
wear good earplugs because the sound levels are very distracting,
sometimes even painful, and that takes the fun out of the whole
experience. 

Adequate "sensitivity" or RF gain in a receiver is very easy to check,
however. It does not require test equipment. Simply connect the antenna
while listening to the background noise. If the background noise
increases noticeably when you connect the antenna, you have all the
sensitivity and RF gain you can use. Any more RF gain (turning on the
preamp, for example) simply reduces the dynamic range of the K2 making
it more vulnerable to overload. Of course, it is a very good receiver
and in most situations you can compromise it a LOT without noticing any
spurs and other degradation, but that doesn't make it a good practice.
The "best" gain distribution in a receiver has just enough gain ahead of
the IF filter to overcome the noise generated internally in the
receiver. Anything more reduces the performance. That's why the K2 has
both an Attenuator and a Preamp. On the lower bands where you can hear
the background noise is higher, you help the receiver by turning the
Attenuator On. 

Then sensitivity varies with selectivity. You may notice the background
increase when you connect the antenna with a 2 kHz bandwidth, but not
hear it at 400 Hz. That's when you need to turn the Attenuator Off or
turn the Preamplifier On. I do that typically on 15 meters and up. It
will vary according to your antenna and the ambient QRN at your QTH. 

Once there is enough sensitivity to overcome internal noise, then the
right place for any further gain needed to rattle the phones or drive a
speaker should come AFTER the selective filters - at least after the IF
filter and it is best after the audio filters. 

Ron AC7AC
K2 # 1289