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

[Jim Thomson]

Date: Wed, 28 Dec 2011 18:03:36 -0500
From: "Roger (K8RI)" <k8ri at rogerhalstead.com>
Subject: Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY!
.

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.

###  any Collins KWM2 has  -48db pep  IMD-3.   
Tx's....like my old Drake T4XC, with sweep tubes, were
-30db pep [and that's with 70ma ZSAC @ 700vdc =49 watts, each
tube only has 26 W of diss, for a total of 52w. To even get the lousy -30db pep
IMD-3, they have to run the idle power at 94% of it's max diss rating ]
If you want to see lousy IMD from the 70's, check out a Swan 700CX, or
the yaesu FTDX-400/401/560/570 xcvr's.   The various sweep tube
amps from that era were nothing to write home about. 

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/buckshotting more on one side than the other it's probably 
related to IM as IM can be much more prevalent 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".

##  I switch the xcvr  from LSB  to USB  on 75m on the main RX
in my MK-V, on my left ear, [while listening in LSB on the sub RX
in my right ear]... and I hear nothing on the opposite sideband of
a friends MK-V.  Yet, I hear all sorts,  of crap on several Icom's.
The fellow with the yaesu  was a lot stronger than the folks with the
Icom. 


later..... Jim  VE7RF


73

Roger (K8RI)

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