|[AMRadio] Ranger driving SB220|
w5jo at brightok.net
Tue Feb 12 12:12:11 EST 2008
>It is also easy for the modulator
> to over modulate because it doesn't need to deliver as much current.
> John, WA5BXO
This is probably the main cause of trouble using an amp with a driver as
described. I constantly hear crappy audio on the bands with the
configuration. Many do not understand meter readings of Class A, AB and
B amps anyway so they tend to overdrive them with audio.
Not only that they do not monitor the output waveform. Additionally
many do not know how to interpert what they see. So all in all, I
believe, the best way to avoid hidden troubles is to operate an exciter
or transmitter is near its design parameters and reduce power with the
Last night was a perfect example. One station who was using a solid
state exciter to drive a tube amp was splattering all over the place and
the person (s) he was in contact with could not hear the problems. If
they did, they either wouldn't tell him or did not know what was
happening. I was about 5 kc below and when I heard the buckshot tuned
up to see who it was. They were all telling him that he sounded fine
and what the meters should read. Wrong of course.
All this assumes the exciter is operating properly. That can be a crap
shoot with a lot of this old gear. Especially a transmitter pulled from
a barn and put on the air with mimimual rework.
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