Tony Giacometti wrote in
news:VvSdnQC_g_Sb0qLanZ2dnUVZ_hKdnZ2d@hawaiiantel. net:

So, what to do, I followed the instructions for building the loop from
W2YR and KN4LF and from this link
http://www.hard-core-dx.com/nordicdx.../coaxloop.html

I think you are describing a scenario where, with the loop+preamp, the
receiver system is limited by internal noise rather than external noise.

So, it is a two band design, and that complicates matters somewhat.

Just concentrating on the 160m loop...

My calcs are that the 160m loop alone, tuned for zero series reactance
(should need ~90pF) and loaded with 50 ohms should have equivalent gain
of around -47dBi.

You would have to consider the preamp NF and gain and receiver NF to
evaluate the system noise floor, and you haven't given those details
(though they may be implied... but I am not familiar with the preamp you
are using).

Without using a preamp, the external noise (based on ITU-R P.372-8
Residiential man made noise) with this loop ought be of about the same
magnitude as the internal noise of a good transceiver, give or take. For
a preamp to improve the situation, it would need a NF significantly
better than the transceiver and sufficient gain to overcome the
transceiver noise.

Owen