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Old March 4th 07, 03:35 AM posted to rec.radio.amateur.boatanchors
John, N9JG John, N9JG is offline
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First recorded activity by RadioBanter: Aug 2006
Posts: 83
Default Duty factor for Drake L-4B

Yes it does. Drake did an excellent job when they designed and manufactured
the L-4B.

"Dave" wrote in message
. ..
Does the L4B use the Eimac tube chimney and matching tube socket?

The tube pins can get so hot the soldered connections on tubes without the
chimney/socket [i.e. Heathkit Cooling] can and do melt at 100% duty cycle
at full power.

K3HVG wrote:

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