[Amps] FCC Denies Expert Linears' Request for Waiver of

[Jim Garland]

You're right Jim. I was remembering wrong. I have a C-Line set up on one of
my vintage station tables and just repeated the experiment. I loaded the
T4XC to maximum output (measured with an LP-100A) and got 119W into a DL on
20m. Then I shorted the ALC, and the output only went up to 128W.  However,
talking into the microphone caused the average plate current meter reading
on the T4XC to about double with the ALC shorted, even though the peak
output power hardly changed. Evidently, there was severe flat-topping in the
T4XC PA. It would have splattered all over the band, and probably would have
been barely intelligible. 
73,
Jim W8ZR

> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Jim Thomson
> Sent: Tuesday, January 03, 2017 03:56 PM
> To: amps at contesting.com
> Subject: [Amps] FCC Denies Expert Linears' Request for Waiver of
> 
> Date: Tue, 3 Jan 2017 13:31:37 -0700
> From: MU 4CX250B <4cx250b at miamioh.edu>
> To: jim at audiosystemsgroup.com
> Cc: "amps at contesting.com" <amps at contesting.com>
> Subject: Re: [Amps] FCC Denies Expert Linears' Request for Waiver of
> 15 dB Rule
> 
> I remember that with the Drake C-Line, some ops would short the T4XC ALC
line, which
> would increase the power output to 175W. Most vacuum tube transmitters I
am familiar
> with did not have a power adjustment.
> Even the mighty solid state Collins KWM-380 lacks a power adjustment.
> 73,
> Jim w8zr
> 
> ##  I owned several new C lines.... and you wont get any 175 watts out of
any of them with
> the ALC shorted out. All that shorting out the ALC line did...was increase
the talk
> power a whole bunch on ssb.   Pep out stayed the same.  Average went way
up.
> 
> ##  For ALC between the xcvr and amplifier in question to even work
correctly, the time
> constant in the xcvrs  alc  has to match the time constant in the amps
alc circuit.
> The drake L4B wont work with the Drake TR7.   Ditto  with a drake L7 and a
drake
> T4XC.   An  ALC  cap has to be swapped out to a different value in both
those amps.
> 
> ##  T4XC  + L4B  require no cap changes, alc is matched  for time
constants....
> ditto with TR7 +  L7.
> 
> ##  If the amp in question doesnt have adjustable ALC,  it still wont work
properly.
> Both the L7 and L4B have adjustable alc.  There is NO power output control
on the drake
> T4X series, nor the TR3 /4 series.   The adjustable ALC on the drake amps
was the only way
> to tweak the po of the exciter.
> 
> ## there were several of the kenwood  SS xcvrs, like the  TS-450 I believe
that had no PO
> control.
> They ran flat out.... so again, if driving amp, the alc line to the amp
had to be installed..and
> the amp had to have adjustable alc.
> 
> ##   back then using a xcvr that put out 130 watts pep, with an amp that
required 100w of
> drive would work
> fine, with the alc line installed and tweaked correctly.   The problems
started when some
> bozo tried to use his
> swan 500-700 CX to drive a SB-200,  or  8877,  then  try and rely on the
alc connection
> between em..to keep things
> under control.   Didnt work.
> 
> ##  even on the older  SS xcvrs that had no PO control,  you could still
control the output
> on ssb mode, by inserting a low value of  dc voltage on the alc buss  on
the back of the xcvr.
> -9 vdc  from a battery, through a 50k pot, tweaked
> correctly works just fine.  Then you can dial up exactly how much pep out
u want on ssb
> mode.   You have already
> developed the ALC voltage.   Scream all u want, but you wont exceed
say.... 65 watts, or
> whatever its tweaked to.
> 
> ## another method is to use limiters and distortion cancelled clippers in
the audio chain,
> results are the same.
> 
> Jim   VE7RF
> 
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