[AMRadio] Re: Carrier with one sideband


John Coleman jc at pctechref.com
Fri Feb 8 12:18:31 EST 2008


I think most of the modern rice boxes are actually full double sideband.  By
modern, I mean in the last 5 years.

I have not seen any lately that or not full double SB, but I am sure there
are still a few that use the filter and are SSB with carrier insertion
regardless of mode.

Actually TV is a mix mode thing.  The first 250KHZ of modulation is full AM
DoubleSB but then the rest of the 4.1 MH of modulation is SSB.  At 3.58MHZ
is the suppressed color subcarrier (not transmitted except in bursts)with
double Sideband I/Q addition out to 500KC above and below the 3.58MHZ mark
then another 500KC upper but only at the phase that produces skin tone.  At
4.5MHZ out is the full FM audio subcarrier that is 150KHZ wide

Interestingly the IF bandpass of the TV RCVR is a bell or flat top shape
with the main carrier tuned at 50% down on one slope and the 4.5MHZ audio
subcarrier in a trap right before after the sound IF takeoff.      
John, WA5BXO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Bob Macklin
Sent: Thursday, February 07, 2008 5:39 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] Re: Carrier with one sideband

The method of generating AM with a SSB transmitter by reinserting carrier
was a common mode of operation in the late 50's and early 60's. The TV video
signal works this way.

It is my understanding the modern RICEBOXES that generate AM do it in the
exact way.




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