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Old March 2nd 07, 11:08 PM posted to rec.radio.amateur.boatanchors
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First recorded activity by RadioBanter: Aug 2006
Posts: 83
Default Duty factor for Drake L-4B

Probably a good idea since I don't think I'd like the smell of a burned out
plate transformer and rf choke.

"K3HVG" wrote in message
...
FWIW, Although the Drake manual for the L4B says that tuning/operation
for CW and RTTY are the same, in one of my L4B books, there's what looks
to be a 2nd or 3rd generation copy of a Drake letter that speaks to RTTY
activity. The Drake letter recommends that the power level for RTTY be
limited to 400 watts, citing the near 100% duty cycle, when key-down. I
guess you take your pick? I run mine at about 400 watts, just to be on
the conservative side.......

John, N9JG wrote:
I have a Drake L-4B, which I purchased new in about 1975. Recently I have
started to use RTTY mode with the L-4B, and I have some concerns about
what is the safe RTTY power level for this amplifier. The Drake easily
puts out 1 kW into my antenna, but during an RTTY contest the
transmission duty cycle can approach 50%. During a long-winded rag chew,
a transmission might be as long as five minutes (just like the old AM
days!). I am reasonably certain that the L-4B (both the amplifier deck
and the PS) can withstand long transmissions at (say) 500 watts out, but
my concern is with the 1000 watt level.

John, N9JG




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Old March 3rd 07, 01:57 AM posted to rec.radio.amateur.boatanchors
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First recorded activity by RadioBanter: Jul 2006
Posts: 241
Default Duty factor for Drake L-4B

Before I read Jeep's response, I was getting ready to respond that 400 watts
of output is right. Solder melts and things fail. I think that is a
realistic number.

It is not the tube plate dissipation that is the limiting factor. It is
heat - both from the components and from the currents flowing through the
switch contacts and the coils.

Colin K7FM


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