[Central-Electronics] Ce 20A alignment questions

[Robert Nickels]

On 5/4/2026 6:19 AM, Laurence Szendrei via Central-Electronics wrote:
> Also, if you have a local SDR with a spectrum display use this to do your sideband suppression procedure - it’s so much better at telling you directly what is happening regarding sideband suppression than using a scope or any receiver lacking a spectrum display. CE didn’t have these when it developed the procedure in the manual

I'll just "second" what Larry is suggesting here.   Even a cheap SDR is 
more than adequate - just make sure to loosely couple to the transmitter 
so you don't overload it, and choose SDR software that lets you zoom way 
in on the signal so you can clearly see both sidebands and the carrier.  
   You'll see the interaction between controls but as described in the 
manual, it's a process of optimizing to get the best compromise when 
switching between sidebands.

Another very useful method must be credited to Fred Johnson ZL2AMJ who 
first described it.   Think of the spectrum produced by an SSB 
transmitter when modulated by a pure 1 kHz sine wave tone.   With good 
carrier and opposite sideband suppression,  only a single output will be 
produced (this is how many produce CW).    If there is carrier leakage,  
  it will be 1 kHz removed from the desired signa,  thus a the beat 
frequency, a 1 kHz tone,  will be heard in the output when listening 
with an AM detector.    If there is opposite sideband leakage,  it will 
be 1 kHz on the other size of the carrier thus a 2 kHz tone will be 
heard.    The amplitude of the two tones heard with an unaligned phasing 
exciter will give an indication of the unwanted signal components that 
are present.   Nulling the carrier should bring the 1 kHz tone down 
virtually into the noise.  Then as you adjust the audio and RF phasing 
you'll be able to minimize the 2 kHz tone.  It's an iterative process 
because the adjustments interact, and the optimal setting for one 
sideband won't be optimal for the other sideband.   You just have to go 
back and forth til you get a good compromise and as Larry said,  it's 
possible to get 30db or better suppression.  The improved audio section 
of the 100/200V allows greater suppression than with the 10/20A design.

Fred described a simple "crystal radio" type detector with headphones 
but all you need is an AM receiver but using an SDR in the AM mode gives 
the added benefit of a visual indication.

73, Bob W9RAN