Elecraft Power Ratings

[Jim Brown-10]

Those concerned with the design and ruggedness of the new KPA500 might
take comfort in the behaviour of the K3 in keydown modes like RTTY. For
years, on the advice of a free-lance engineer who works for Elecraft
(and is working on the KPA500), I've run my K3s at full power for 100W
RTTY contests (like NAQP).  That often involves near-continuous CQing
near the end of a contest, when you've already worked everyone on a band
that you can hear, or when you're hoping that 10M will open. He was able
to give me that advice because the K3 is very well protected against
overheating, and because the power handling devices are conservatively
rated and run conservatively.

I ran an NAQP RTTY contest yesterday, and after CQing on 20M for a while
as it was closing, looked at the PA temperature.  It was only 45 degrees
C, well below the point where fans would turn on and/or speed up to
provide more cooling.  The K3 is not alone in conservative design -- my
vintage IC746, which I bought many years ago to use on 6M and 2M,  is
also rated for 100W in keydown modes, even on 2M.

73, Jim K9YC
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[Dave Hachadorian]

At 45 degrees Celsius, the K3 fans were probably running at speed 2.

I don't like to hear the fans throttling up and down, so I set mine to run
at speed 4 before yesterday's RTTY contest. Not only did they run at
constant speed, keeping things cool, but they gave me the feeling that I
was running big power with all that fan noise. The noise at speed 4 sounds
quite pleasant to me.

The following is a copy of a reflector posting I made on 20090312:

I did an experiment on my two K3's - key down at 100 watts
for four minutes while noting PA Temp and fan speed. Both K3's
behaved
identically and both leveled off at PA Temp = 64C after
about 3 minutes. For the record, here are the results (best
viewed with Courier font):

Time   Temp  Fan
0:00    26C    0
0:26    37      1
0:44    41      2
1:19    50      3
1:45    55      4
2:40    60      4
2:50    62      4
3:15    64      4
4:00    64      4

Room temp was 77F.

According to the manual, the PA is set to drop into bypass at
84C, so it didn't even come close.


Dave Hachadorian, K6LL
Yuma, AZ




-----Original Message-----
From: Jim Brown
Sent: Sunday, February 27, 2011 11:01 AM
To: Reflector Elecraft
Subject: [Elecraft] Elecraft Power Ratings

I ran an NAQP RTTY contest yesterday, and after CQing on 20M for a while
as it was closing, looked at the PA temperature.  It was only 45 degrees
C, well below the point where fans would turn on and/or speed up to
provide more cooling.  The K3 is not alone in conservative design -- my
vintage IC746, which I bought many years ago to use on 6M and 2M,  is
also rated for 100W in keydown modes, even on 2M.

73, Jim K9YC

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