SPE say 1.5KW SSB and CW, no limit. Continuous duty modes, should be
used on the lower 1KW or 500W ranges.
This will by my 6M amp / instant on HF / backup HF amp. I plan to limit it 1KW.
From the manual :
"Note: ATTENTION: Never stress the amplifier with long periods in
key-down transmission,
as this can stress the amplifier components. However, sophisticated
Software avoids
transmitting a continuous signal in the "MAX" condition for long
periods by switching
to "MID" power.
Note: In SSB, use of high compression is not encouraged as this can
cause a rapid increase
in the temperature of the amplifier."
"Appears when a continuous signal is transmitted in
"MAX". After 15 sec. the amplifier will switch
automatically to "MID"."
- Paul
At 08:49 AM 12/24/2017, Jim Thomson wrote:
Date: Sun, 24 Dec 2017 01:01:39 +0000
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Subject: Re: [Amps] NXP 65V LDMOS 1K80H-1800W
<I checked the website for SPE, looking for duty cycle specs but didn't
<see any. Does anyone know what they are?
<73, Bill W6WRT
### Excellent question. And ditto with the new Flex...power
genius..with its mystery 100% ICAS rating.
IMO, 100% ICAS means talk on ssb or cw all day long.... but dont do
something stupid, like a rtty contest.
## These SS amps are typ 50% eff at best, so with 1.5 kw out
requires 3 kw dc input.
Dissipation of course is 1.5 kw. Thats a bunch. And a huge
amount if running rtty,
FT8, any other digital mode, or FM etc.
## any tube amp running just 60% eff, would only require 2.5 kw dc
input...and dissipation
is now down to just 1 kw.
## On the lower 3 bands, with the same tube amp on
160-80-40, 68-70% eff is readily achievable.
Now the diss is down even more, to just 706- 643 watts.
## helluva big difference between 1500 watts ccs diss on the SS
amp..and the 643- 1000 watts
CCS diss of the SS amp.
## It would require some exquisite heat sink design to be able to
dissipate 1500 watts CCS of heat.
This is where the SS amp should be using a 19 inch wide rack mount
heat sink, very deep, and very tall,
like 12 inches or more, and lotsa air on it. Loads of fins, and
very thin fins.
## that or some elaborate cooling setup, with a liquid cooled heat
sink and an external air cooled radiator +
mating water pump.
## ideally the way to manage heat is to generate less of it in the
1st place, like through higher eff, which
appears is not going to happen any time soon with typ class AB SS amps.
## I would like to see what both these amp manufacturers have to
say about duty cycle.
If they are 1.5 kw ICAS, I will pass on em for now, not for the
$7K price tag.
Jim VE7RF
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