[Elecraft] [K3] Using K3 for relative noise survey - followup

[Rick Miller - N1RM]

Thanks to all for the great suggestions (the SNR of the responses was
appropriately high!).

I did some experiments with the RSP2 and HDSDR.  It was very close to what I
was looking for and I will revisit it in the future when I am looking for
specific interferers, but I set it aside when I saw a very strong harmonic
of a local AMBC station well up into the HF spectrum.  This happened with my
very good AMBC filter in line.  I won't be comfortable with this approach
until the software provides some control of the RSP2 front end.  What I want
right now is something to give me general quantitative view of the overall
noise level, not something to identify specific interferers.

The good news is that I now have my K3 doing a very nice survey under
control of a Python program I wrote, and using the AFV and dBV VFOB
Alternate Displays.  I connected ANT1 to my reference antenna (a six foot
untuned whip), and put a 50 ohm termination on ANT2.  After setting Rx
parameters the way I want, it tunes to a frequency, selects ANT2, waits for
the level to settle in AFV mode.  It then switches to dBV mode and once
again waits for the display to settle.  Then it selects ANT1, waits a
second, and then starts reading the dBV value once a second.  If it gets two
readings in a row that differ by 0.1 dB or less, it takes that value.  If
that doesn't happen within 10 readings, it just takes the average of the 10
values and moves on.

I am doing two surveys.  One is every 100 KHz from 1 MHz to 29.7 MHz.  The
other is every 10 KHz within the HF ham bands.  So far I have taken multiple
surveys at my home on consecutive nights and the plots overlay each other
very well, so at least the method is consistent.  It takes a very long time
to walk through all the frequencies this way, but I just set it and forget
it, and then import the data into Excel for plotting.

Two observations:
1. I was reminded vividly of the 8.2 MHz first IF by the hole in the general
coverage survey!
2. I was able to deterministically configure all the settings I wanted
EXCEPT turning off AGC.  It appears that the only control of that is the
SWH18 command which is a toggle, and there is no way to read the current
state of that setting.  I had to manually go to each band to ensure that it
was turned off on all of them.  Does anyone know of a different way to do
this?

Thanks again for all the help and suggestions.  I will do multiple day and
night surveys at both my old and new QTH, just to get an idea of what I can
expect at the new site.

Rick
N1RM



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