[Amps] Fwd: Linear Amplifier Tuning---PROPERLY!

[Gary Schafer]

Hi Roger,

Actually the Collins rigs were substantially better than most of today's
rigs as far as IM goes. They used negative feedback in all of their finals
which reduced IM about 10 db. ALC overshoot was not so pretty though.

IM if produced, will be the same above the wanted signal as it is below the
signal. An easy way to check for IM is to just switch side bands on the
receiver. That will show you the close in IM present on the opposite side
which will be a mirror of the IM on the active side band.

It sometimes may seem that a station is buckshoting more on one side than
the other but remember that your receiver pass band is offset from the
carrier and so is the transmitted signal offset from the carrier.

73
Gary  K4FMX
 
> Just think what the bands would sound like if we were still using SSB
> rigs from the 60's<:-))  Even the Collins and Hallicrafters were not all
> that great.  There were exceptions, but not many.
> 
> Of course it's not just crappy IM from many of today's SS rigs. Many of
> them give the operator so much control over the signal they end up
> generating garbage up and down the band quite a ways trying to find what
> they think is the perfect, tailored audio.  "I think" if you find
> noise/splatter/buchshoting more on one side than the other it's probably
> related to IM as IM can be much more prevelant on one side than the
> other. OTOH over driving the amp usually ends up with buckshot and
> splatter pretty much equal on both sides. Neither is likely to result in
> a nomination for "ham of the year".
> 
> 73
> 
> Roger (K8RI)
>