[AMRadio] AM vs. broadband line noise


Michael Mertes fnerks1 at yahoo.com
Mon Sep 17 15:31:13 EDT 2007


I would like to thank everyone who replied to my
question both on and off the list. There are just more
SSB who are operating at the right distance and power
to get the signal over the S9 noise local noise here
at my QTH to make the appearance of at greater
difference. Getting the noise problems resolved will
make all the difference, but that is a chore for
another day. 

Thanks,
Mike/KZ5M


--- John Coleman <jc at pctechref.com> wrote:

> Actually that is about it.  In reception, the
> advantage is the signal to
> noise ratio.  By having a 1/2 bandwidth and all else
> being equal then you
> will have a 3 DB drop in noise.in a lot of
> situations the bandwidth on older
> AM receivers is several times what it is on a modern
> SSB RCVRs   The caveat
> here is all else is generally not equal.  In a lot
> of situations the
> bandwidth on older AM receivers is several times
> what it is on a modern SSB
> RCVRs.   Product detection, especially balanced
> product detection, has a
> pretty nice advantage and most modern SSB gear uses
> it whereas most of the
> AM stuff doesn't.  "Full bandwidth AM balanced
> product detection" requires
> synchronization with the incoming AM.  With out the
> SYNC it is pretty
> useless for AM.  But if you ever get to use one you
> will want it.  When the
> going gets rough, I have used regular product SSB
> detection for AM and there
> is an advantage because of the reduced bandwidth. I
> have found it is best to
> use a filter where the carrier insertion is 300 HZ
> from the skirt of the
> filter so that low frequency audio is rolled off
> pretty quick and the
> carrier beat is not detected.  This of coarse, make
> the received audio a lot
> like the majority of SSB signals but as I said it is
> for when the going gets
> rough.  "Full bandwidth AM balanced product
> detection" increases the
> reception so that it is only slightly less
> advantageous in signal to noise
> ratio and sound so much better that standard SSB
> detection.
> 
> Most of us like to run AM because of the "GOOD OLD
> SOUND", experimenting,
> building and camaraderie involved.  Signal to noise
> ratio business is for CW
> and PSK.  A LITTLE JOKE
> 
> John
> 
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf
> Of Michael Mertes
> 
>  It occurred 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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