[RFI] Ambient Noise Levels

[Jim P]

I HAVE heard brief, slow rises and falls of broad-band
white noise several times in the last couple of years
on 10 Meters; the first time I thought the rig had
experienced some sort of 'issue'.  The next couple
of times I was primed for it, and I checked a couple
different RIOMETERS *1 located in the same
hemisphere.

It was 'the sun'.

Those RIOMETERS recorded a phenom at the same
time I had experienced those brief noise events.

Fred, I don't but wonder if your noise is due to, by
chance, to "static build-up" on your antenna. Do
you have even a high-valued resistor to ground to
preclude any charge accumulation (provide a simple
leakage path to earth)?

I take it you were able to 'kill' the noise by removing
the antenna from the radio at which time the the
noise level dropped back significantly. (I notice
today's rigs employ two levels of 'preamp' as well
as several levels of attenuator; I find the preamps
generally just contribute additional white noise
with little real improvement in S/N ratio *2. I have
an old Yaesu FT-101EE that has no preamp
function and therefore never sounds like a 'rushbox'
quite like some of the later products do on the
bands.)

Jim P



*1 RIOMETER - normally used to measure variation in the
cosmic radio noise absorption taking place in the D-region
*but* will also record any excess noise produced by any
other source including 'ol sol.

http://www.oulu.fi/~spaceweb/textbook/riometers.html


*2 Receiver Preamp effectiveness;  I will have to test this
premise one of these days having come into possession
of an audio noise/distortion analyzer.




----- Original Message ----- 
From: "Fred Stevens K2FRD" <k2frd at mac.com>
To: <rfi at contesting.com>
Sent: Wednesday, August 09, 2006 10:59 PM
Subject: Re: [RFI] Ambient Noise Levels


> At 9:58 PM -0500 9/8/06, Jim P wrote:
> >
> >I don't know that the heart of the question has truely been
> >answered yet as I have questions as to what is actually
> >and specifically being cited here as the 'source' here of
> >the noise. I contend that the bulk of noise for S4 level
> >noise is man-made from electical and electronic devices
> >nearby (on the order of  3 or 4 residences in any given
> >direction. I've had sources on 20 M half a block away on
> >the same distribution circuit that had noticable impact
> >on the PSK31 20 M subband.)
>
> Not sure it's pertinent here, but I also have high white noise levels (S4
to S6, sometimes more, sometimes less) on 40m with a trap dipole (10, 15,
20, 40m) up 40' in the middle. And I'm located far away (18 miles) from any
RFI noise sources (homes, communities, power lines, neighbors, kids with RC
toys) in the middle of Coconino Natl Forest in northern AZ at 7100'. I'm
also operating off battery power with solar panels for recharge with
everything in my travel trailer turned off except my radios. I've chalked up
the noise to general atmospheric QRN and Asian AM broadcast QRM, especially
at night although there could be other explanations. I've about given up on
40m until Cycle 23 turns into Cycle 24.
>
> -- 
> 73 de Fred Stevens K2FRD, VO2FS
> http://homepage.mac.com/k2frd/K2FRD.html
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