[AMRadio] AM vs. broadband line noise


Jim Candela jcandela at prodigy.net
Sat Sep 15 18:14:26 EDT 2007


Mike,

    The broadband noise needs to be your first effort to remedy. Why go through all kinds of stuff with your equipment when there is a bug zapper across the street that constantly is sizzling away? Find the source and see if you can eliminate it. I once had total noise ( S9 + 20 or higher) from broadcast AM thru 6 meters. I found the culprit and here it was:

http://pages.prodigy.net/jcandela/Pole/Pole.JPG

   Don't skimp on station grounding or overlook a noise source withing your own home. When you switch a coax switch that closes off a receiver that receiver should be free from line noise. If not your shielding is poor or you have a ground loop.  This can be fixed. In my case I fought a noise that was from my garage door opener. I was mad at the power company when in fact the noise source was in my house.

    I currently have 3 receivers, a ICOM R75, Hammerlund SP-600 and a Gonset G-76 (xcvr). When things are bad from line noise I always resort to the ICOM R75 since it has multiple IF passband filters (I have 3 for AM, one I added), a Noise Blanker, and DSP noise reduction. I can also receive AM with the synchrous detector while using a narrow filter and offset tuning to select only one sideband. The folks at Kiwa have mod's for the ICOM to make things even better. 

   Other folks using the Flex Radio using SDR (software designed receiver) have an assortment of bells and whistles to eliminate noise to a level unheard of just a few years ago.

My two cents
Jim
WD5JKO

----- Original Message ----
From: Michael Mertes <fnerks1 at yahoo.com>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Saturday, September 15, 2007 1:53:32 PM
Subject: [AMRadio] AM vs. broadband line noise

It occured to me that I have too much line noise here.
I am not shy about transmitting with my low power AM
setup, but I'm not going to do that if I can't hear
anything. I've had this problem for just over a year,
so it is something I will have to chase down soon
enough, but I just don't have the time right now.

So I have a question for the group; since I have never
really pursued AM seriously before. It is this: How
does line noise affect AM as opposed to SSB. It seems
as though I have much better reception with SSB on the
same bands and can work SSB; where AM is just wiped
out. One point certainly is the wide bandwidth and
less signal/noise on AM, but that doesn't seem to be
the whole of it. Does anyone have an educated guess,
or is it just my observation only?

Thanks,

Mike/KZ5M


       
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