[Elecraft] K3 6m noise figure

Edward R Cole kl7uw at acsalaska.net
Fri Nov 15 13:14:55 EST 2013


This was discussed few couple months ago and it prompted me to make 
measurements on 6m & 10m, for both K3 and KX3:
Note the measurements were made at 2.8 KHz bandwidth whereas Elecraft 
specs are for 500-Hz bandwidth (correction factor is 7.5 dB lower for 500-Hz):
I use an ARR preamp but specs are equivalent for the PR6.
http://www.kl7uw.com/HF.htm
scroll down half page

Noise figure can be deduced from these measurements.
For a 8-dB Noise Figure, the receiver sensitivity is -140 dBm at 500-Hz bw
I measured -130 dBm at 2800-Hz which is NF = 10-dB*
*internal PRE is turned on.

With addition of ARR preamp and turning off PRE, sensitivity is -137 
dBm with bw of 2800 Hz (which translates to -144.5 dBm at bw = 500 
Hz) which is NF = 1 dB.
Both ARR and PR6 have spec lower in NF.  -137 dBm was near the lowest 
level I was able to produce in these tests so actual performance 
might be even better with the external preamp.

Caveat:  My measurements were using the XG3 enclosed in a metal box 
with external attenuators to reach lower signal levels.  My 
measurements have a level of uncertainty so should only be used as a 
relative indication of sensitivity.  NF should be performed with lab 
quality Noise Figure meters or using accurate thermal noise sources 
to produce "hot/cold" ratios which are more accurate than signal levels.

My tests affirm the specs given by Elecraft as being close to observed.

73, Ed - KL7UW

---------------------------------
From: Peter Torry <peter.torry at talktalk.net>
To: elecraft at mailman.qth.net
Subject: [Elecraft] K3 6m noise figure
Message-ID: <52860A6A.6030804 at talktalk.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I am trying to calculate my link budget for  50 MHz and was wondering if
anyone has measured the K3 noise figure on this band using the K3 alone
and not with the PR6.  Calculations suggest about 8dB but a measurement
would be most welcome.

73

Peter
G3SMT

73, Ed - KL7UW
http://www.kl7uw.com
dubususa at gmail.com
"Kits made by KL7UW" 



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