Topband: Hi Gain Preamps, Noise Figure Comparison (KD9SV 994 x5, W1FB, W7IUV preamps)

[JC]

Hi Don

Measuring noise figure below 1 db is a very complicated work. 

First you need to remove all common mode noise, your noise floor should be
better than  -135 dBm at least with a 40 db preamp connected to the radio
input and a 50 ohms load.

You need chokes everywhere and most important shield on 12V, RF in and RF
out. Check the AM band you hear carrier coming in , noise is also coming in.

 Second the NF is very different on 1.8 MHz , measurement near 10 Mhz, does
not tell you the right NF on low bands.

In order to have Noise Figure Uncertainty near .2db it is necessary a good
quality lab equipment, calibrated and two hours per measurement for each NF
reading. This assuming the temperature does no change during the test.


Your Noise Figure Uncertainty based on your video could be 5db or more.


73's
JC

N4IS