[ARC5] Lopsided modulation

[Brian Clarke]

Hello Neil,With what are you modulating? Shrader says that voice
modulation is always lopsided. If you're using a close-mic technique
with the original carbon mic, that will increase the lopsidedness.
As others have commented, the stiffness of your power supply may be a
cause. As you are both using plate+screen modulation. use a CRO to
look at the DC rail after the modulation transformer where it feeds to
transmitters. Also check the bias on the 1625 finals and compare with
the PA output - like, is the carrier symmetrical?
73 de Brian, VK2GCE

On Sun, 25 Feb 2018 09:38:20 +1300, you asked:

A friend and I are running Command transmitters on the local 75 meter
AM net, with full plate and screen modulation. 
We monitor our transmissions on the local SDR receiver site which has
a waterfall display. In both cases, the lower sideband shows as
considerably stronger than the upper, and this has us perplexed. Our
stations are the only ones affected.

I have never seen anything in the literature to explain this. Downward
modulation is a problem with AM, but articles do not indicate whether
lopsided modulation results.

My transmitter is the AN/ARC-5, absolutely unmodified and running 40W
input due to dynamotor constraint. H
is is the SCR-274 modified for plate & screen modulation and running
twice that.

Anyone suggest a reason for the unequal sidebands?

Neil ZL1ANM

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