No, it doesn't "push" an Astron 20 amp supply to drive a K2/100 at all. =
An
Astron 20 amp supply is LOAFING well within it's mfg's specs when =
driving a
K2/100.=20
The K2/100 demands intermittent currents up to about 16 A at 100 watts =
(mine
runs 16 amps at 108 watts 'wide open'). That's total drain for the K2 =
and
KPA100. And those are intermittent peak currents up to 16 amps.
The ASTRON 20 amp supply is rated for 16 amps continuous! So even if a =
K2
were to draw 20 amps at full power, it would still be within the =
"normal"
working range for the Astron 20 amp supply.=20
The K2 can only make full power output (and consume about 16 amps of
current) with fairly low duty-cycles - SSB peak or CW (if you don't want =
to
see the KPA100 smoke, you'd better not hold the key down too long in CW
mode).
That's why Elecraft recommends a 20 amp supply. What seems to catch =
people
is the comment in the KPA100 manual about using a supply rated at 20 =
amps
"or higher". What they are saying is that if you have a supply with a =
higher
current rating it won't hurt your K2/100, but it is not any 'better' to =
do
so.=20
Remember, the K2/100 is de-rated for high duty-cycle loads like PSK, =
etc.
Which drops its current demands well below the peak levels, so a 20 Amp
Astron is "loafing" under any set of conditions that the K2/100 can
withstand.=20
But, even if I wanted to see my K2/100 melt down by putting a book on =
the
key until it died, the Astron 20 would still be running within its =
current
ratings. You'll understand if I don't want to demonstrate that. However,
when I first built my KPA100, I only had a Ten-Tec 11 amp (ICAS) supply =
on
hand. It ran the K2/100 just fine for a couple of weeks at full power =
before
I picked up my Astron 20. I kept an eye on the heat sink temperature and =
it
stayed well within it's normal operating range. Clearly, the Ten Tec =
supply
was build like an Astron - lots of excess capacity.=20
If you put a good-quality but too small supply on a K2/100, what you =
will
most likely see is that the rig will suddenly shut off when you go above =
a
certain power level. Most supplies have a "crowbar" circuit that shuts =
off
the output if a certain current is exceeded. That protects the supply =
from
damage in the event of an accidental short.=20
Where the 35 Amp supply might be handy is if you wanted to run several =
rigs
from the same supply. Driving a K2/100 wide open, a 20 amp Astron has =
about
4 amps continuous current capacity for other things. IF you need more =
than
that, the bigger supply might be better.=20
With the bigger supply come more weight, much stronger magnetic fields =
that
must be kept away from the K2, and more noise. The big ones tend to =
"hum"
noticeably because the field around the transformer vibrates the case.
Personally, I prefer two or three smaller supplies to one BIG one.=20
Ron AC7AC
-----Original Message-----
I went with the VS-35M for mine.... What drove my decision was that the
K2/100=20
would be pushing the RS-20 beyond the 100% rated load and into the=20
50%ICAS.
=20
Tim Raymer
73 de KA0OUV