[Elecraft] K3 sensitivity below 40 meters

[Richard Fjeld]

In all fairness, I have to append this.  I held off saying what I wanted to 
because I knew of someone who would be watching this reflector, and I didn't 
want my comments out to 'the group'.

I said  "I believe it is due to resonance" and it is as far as the antenna 
is concerned.  I also believe it is due to the K3.  I bought it for my last 
sun cycle, and it has been a pure enjoyment for me.  I'm not a 'nectar' 
drinker, if you get the connection.  It just wouldn't be right to not 
acknowledge the excellent receiver.  The NR is effective for man-made noise. 
I would like to see it better on atmospheric noise, but I don't know if that 
will be possible.

I bought the K3 for it's operating conveniences, and it's reputation as a 
good receiver which I have found to be accurate.  I am especially pleased 
with the filtering.  Since I got the P3 and can see the signals beside my 
passband that I am not hearing, I have been amazed.

In summary, even a good radio needs a resonant antenna.

Rich, n0ce

----- Original Message ----- 
From: "Richard Fjeld" <rpfjeld at embarqmail.com>
To: <kt5d at charter.net>
Cc: "elecraft posting" <elecraft at mailman.qth.net>
Sent: Tuesday, November 13, 2012 11:39 AM
Subject: Re: [Elecraft] K3 sensitivity below 40 meters


>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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