[Elecraft] KPA500 Temperature

[David Yarnes]

So----is anyone monitoring the peak temperature on their KPA500?  I'm kind 
of doing that, and it seems like mine gets up to the mid 50's C before it 
more or less stabilizes.  It's kind of neat how the fan speeds up as needed, 
although I really can't hear it that well.  Compared to other amps I've 
used, this one is S I L E N T!
I had some concern that just one fan would move enough air to keep the 
temperature down, but I think it does the job appropriately.  What's neat is 
you can override the auto feature for fan speed with a menu setting.  I 
suppose that might be necessary if you were running RTTY or something.

If I make a relatively long transmission (on CW), the temperature on the amp 
goes up into the mid 50's C.  I assume that is normal.  The fan speeds up 
sufficiently to keep it at, or near, that temperature as far as I can tell 
at this point.  As soon as I stop transmitting, the temperature drops like a 
rock!  I think the fan keeps going for a while to help accomplish that.

Per the manual, the heatsink temperature rating is something like 90 C., so 
I'm not even close to testing that.  As I've said before, I'm not very smart 
about amps, but I assume a lot of amps run temperatures much higher than 
this one does.  Besides, since it seems to, more or less, level out in the 
mid 50's, I assume that is more than reasonable.  Hopefully I'm right about 
that.

I have adjusted my drive to about 27 watts from the K3.  That gives me 480 
watts plus out of the amp, according to the amp's internal wattmeter.  My 
objective is to run this thing somewhat conservatively, and hopefully that's 
what I'm doing.  I can easily get 600 watts out of the amp, but why do it? 
I'm getting an S unit and a half, more or less, improvement by running the 
amp.  600 watts would be a negligible increase over that.

Right now the amp is showing about 35 C. while it is idle.  That's the same 
that my K3 shows when it is idle.  On a somewhat extended transmission my K3 
PA temp goes up to the mid 40's C, and the amp goes into the mid 50's.  That 
seems reasonable intuitively, but I'd be very interested to hear whether or 
not that's what others are experiencing.

I also assume that if I were running RTTY, or some other intensive mode, I 
would need to back off of the power on the amp, just as I do with the K3.  I 
don't operate that mode very often, but I know it's hard on PA's.  The 
manual doesn't say much about that--it only says "500 watts output" without 
indicating any difference by mode.  Most other amps I see have a reduced 
power rating for RTTY, etc.  For now, I'll assume that's an oversight.

The main thing I haven't tested yet is the amp's performance on 6 meters. 
My operation on that band is pretty casual, but it was a major factor in my 
decision to make the investment.  6 meters can be  a bunch of fun when 
conditions are right.  I think making this amp 6 meters capable was a very 
smart move.

I have one question at this point--when I switch my K3 to 30 meters the amp 
recognizes that fact, and displays that band.  However, there is no 
indication that the amp works on 30 meters, and there is not an optional 
band switch for 30 meters--probably, at a minimum, because that band is 
limited to 200 watts.  I haven't even tapped the key on that band with the 
amp on.  So, my question is whether or not the amp is "30 meters capable", 
even though it would probably violate the power limitation rule.

Well, I'm obviously having fun with the amp, but I'll probably have it 
turned off much of the time.  Amps like this give you a nice boost, but I 
prefer to go "a cappela" for the most part.  I've never felt amp usage 
should be automatic.

Dave W7AQK








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