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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