[Elecraft] K3 sensitivity below 40 meters

[Richard Fjeld]

I think it may be due to my final comment, but first, some info.

My pre-amp is off and the ATT is on 90% of the time.  I seldom turn on the 
pre-amp. With the pre-amp off, and the ATT on, I consistently hear guys 
breaking in that the others in the group do not hear, and they run good 
equipment. They comment on it, and believe it is due to my antenna.  The 
apex of my antenna is only 40 feet high. One of them has a 100 foot tower. 
I believe it is due to resonance. Read on.

I would suspect antenna not resonant, or working with a swr that is not 
optimum for the frequency.  (You need both.)   Emphasis is given to swr for 
transmit out of concern for the finals, but I discovered years ago how 
important a 1.0:1 swr is for receive. Anything less is a compromise in 
receive performance.

You say "to 'hear' an S9 signal".  That has me curious.  S9 is RF, hearing 
is AF.  Still pondering....

The K3 is calibrated for S9 at -50 uV with the pre-amp on. This may be the 
answer to your question. It could also be that you need to calibrate your 
S-meter.  The XG-2 works well for that.

Good luck,
Rich, n0ce


----- Original Message ----- 
From: <kt5d at charter.net>
To: <elecraft at mailman.qth.net>
Sent: Tuesday, November 13, 2012 8:39 AM
Subject: [Elecraft] K3 sensitivity below 40 meters


>
> Conventional wisdom historically has been that a receiver preamp is not
> used at 40 meters and below primarily because it is not needed, indeed
> it would typically degrade receiver performance. So why is it necessary
> to engage the 20 dB preamp on the K3 to get it to hear an S9 signal at
> the appropriate level of other receivers?
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