Borrowed a Rohde & Schwarz FSH8 handheld spectrum/network analyzer for
the weekend to try and track down a nagging issue that has been
bothering me on 160-40m.
The noise is wideband covering all 3 bands and takes the form of period
rapid increases in noise level. On the Icom 7700 receiver it takes the
form of background noise rising 3-4 S units in a seemingly random
pattern and pulsing at a maximum rate of perhaps 10 Hz. At other times
it may be several seconds before a series of spikes arrives. The desire
signals all remain the same level and weaker ones just get masked by the
noise.
On the spectrum analyzer I confirm the ambient noise peaking 12-20 dB
across the 1.6 = 11 MHz range. It almost looks like the signal is some
kind of wideband modulation.
Walked the neighborhood over a mile in all directions. (Boy you get some
strange looks carrying a spectrum analyzer down the street). The effect
was found everywhere, some spots stronger than others but no clear
source.
Inserted bandpass filters in for each of the ham bands and the noise
peaks remain in band.
The only clue I have is this only happens after dark. 7 days a week. My
first thought was the sodium street lights but I visited one that is
failing (turning off and On) and the noise was no worse.
Anyone have any suggestions?
Ed
VE4EAR
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