Re: K3s noise figure spec

Posted by Don Wilhelm on Jul 01, 2020; 12:44am
URL: http://elecraft.85.s1.nabble.com/K3s-noise-figure-spec-tp7662748p7662751.html

Dave,

I don't know the answer to your question, but if you use a preamp at the
antenna, you will not need to use the preamp in the K3S.
The preamp at the the antenna will set the noise figure for the system.
The preamp at the K3S end of the feedline will have to consider the
feedline loss.

At 50 MHz the difference (mast preamp vs. receiver preamp) may be of
little concern, but at higher frequencies it can be significant.

Many VHF operators run with mast mounted preamps with a separate receive
feedline to the receiver - often with RG-58 feedline because the
feedline loss is not important for mast mounted preamps.  50 MHz is in
the middle ground for that consideration.

73,
Don W3FPR

On 6/30/2020 7:31 PM, Dave Sublette wrote:
> Does anybody KNOW what the noise figure is for the 50MHz preamp on the
> K3s?  It isn't listed in the specifications.
>
> I need to know in order to make system noise figure calculations.  My
> feedline is going to be long (low loss, but long) and I'm trying to
> determine if I will need a preamp mounted at the antenna.
>
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