K3s/P3 noise comparisons

Posted by Jim AB3CV on Apr 18, 2020; 6:33pm
URL: http://elecraft.85.s1.nabble.com/K3s-P3-noise-comparisons-tp7659817.html

I'm doing some work on measuring RFI levels on 6m at my QTH.

One tool I'm using is the P3 with averaging set to 20 to make for easier
reading.

With the K3s preamp 2 engaged I read -162dbm on the P3 scale when connected
to a 50ohm dummy load.

I'm trying to correlate that to the MDS numbers for the K3s.

The K3s specification with Pre2 engaged is -145dbm measured in a 500hz
bandwidth.

The effective bandwidth of the P3 per the P3 manual is Scale/450 which for
5K that I'm using is 11hz.

Since noise power scales with the square root of the bandwidth that
should result in a ratio of SQRT(45) or 6.7. 10*log(6.7) = 8.2

Adding -162 to 8.2 only brings me to -153db.

So it seems I'm missing something. The P3 is telling me the K3s is 8db more
sensitive than its specification.

What am I missing?

Thanks

JIm ab3cv
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]