[AMRadio] Re: GB> AM vs SSB???


Gary Schafer garyschafer at comcast.net
Sat Apr 7 17:16:02 EDT 2007



> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of Bob Macklin
> Sent: Friday, April 06, 2007 11:52 PM
> To: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] Re: GB> AM vs SSB???
> 
> RBethman comments:
> 
> <<As to SSB, the KWS-1 IS fine.  As to AM - It transmits a carrier and
> ONLY
> one SIDEBAND.  Thereby being POOR for DSB with carrier since it
> ONLY O-N-E sideband with CARRIER.>>
> 
> This is the same way the video portion of a TV signal has been transmitted
> for over 50 years! What is wrong with SSB-AM? Vestigial SB?
> 
> Bob Macklin
> K5MYJ
> Near Seattle, Wa

Wow! There sure seems to be a lot of SSB bashing going on here lately. Some
of you guys sound like some of the unwashed SSB guys that bash AM. Just
reverse the AM and SSB words and you couldn't tell the difference!
Seems to me all would be better off sticking to the facts rather than
inventing stuff to bolster your preferred points.

SSB AM is not as good as full DSB AM but it is also not as poor as some
believe it is. A properly set up SSB AM rig can sound pretty good.
Modulation level does have to be kept down some as Don says or the receiver
detector distortion goes up rapidly as you approach full modulation. As you
near 100% modulation the receiver detector can't tell the difference between
the carrier and the modulation signal. Second harmonic distortion results.

When I say set up properly, there are few that know how to do that right.
Most that run SSB rigs on AM, in the DSB with carrier mode have a hard time
making them sound good on AM and it is mostly the fault of not setting it up
properly. Some sound very nice.

Want to see what good SSB AM sounds like? Just tune off to the side of a
good sounding AM signal with your receiver so that the filter cuts one side
band off but not enough to reduce the carrier. The audio level will drop a
little and distortion may rise slightly but it will still sound pretty good.
You are hearing the same thing as if it was transmitted with only one side
band. This same trick is often done when there is heavy qrm on one side. You
listen to SSB AM and don't even realize it!

As to Collins S line receivers sounding better than some of the rice box
receivers, I haven't heard one. I have several 75S-1, 75S-3, 75S3A etc.
receivers. All have more distortion than my Kenwood TS430. I measured each
with a distortion analyzer, and you can hear the difference, and the TS430
runs rings around any of the Collins receivers in audio quality. So just
because it's old doesn't readily mean that it is better.

73
Gary  K4FMX






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