It seems to me that these Amp
Suppliers are being Penny Wise
and Pound Foolish.
With the cost of the chips being
a small percentage of the cost,
using two instead of one (or four
instead of two) would produce
the results some of us pine for.
Now, granted, the percentage of
us that run RTTY contests at bttw
is rather small, but it does provide
much more headroom and a lot
more life to the Amp (maybe that's
not such a good idea, ask Apple).
However, I run my SPE 1.3K-FA
at the Mid level (~1 KW out) on
FT8 and have yet to see the temp
hit 45C.
Best wishes for the Holiday Season
to all.
73, Dick, W1KSZ
On Sun, Dec 24, 2017 at 9:49 AM, Jim Thomson <jim.thom@telus.net> 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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