[Elecraft] KPA1500 SWR meter

[Don Butler]

Just to clarify as far as the KPA1500 fan noise is concerned and my experience with s/n 45.  In auto mode the fan kicks on when the heatsink temperature reaches 60 degs C …. I first noted that while I was vigorously chasing a DX station in a split CW pileup.   It kicks on at 60 degrees and switches back off when the temp goes down …. So, in auto mode, it can be rather distracting when it’s right at that threshold and frequently switching back and forth ….. so, in that situation, I have been opting to turn the fan on manually.   There are five selectable fan speeds …. 1 through 5 … speeds 1 and 2 are no big deal as far as noise is concerned …. Just like any other amp … the noise is there but it’s not excessive … when you hit speed 3 the pitch goes up and the noise goes up …. And 4 and 5 are progressively more intense … in both pitch and noise level.   I have never found it necessary to go to levels 4 or 5… but I’m primarily operating CW only …. No full keydown rtty or AM at my station ….  I have needed level 3 to keep the heatsink temp below 60 degs C while continuously CQing in a contest run mode however…. And with all the associated noise good earphones are an absolute must.  It really does not take long to cool things down when the fans are running at level 3 …. The fans work …. And they do the job they’re supposed to do.

There’s no free lunch …. If you’re going to use an amp it’s going to get hot … the more you transmit the hotter it will get … and you need to keep it as cool as possible.  I have no problem with the high noise levels necessary when things get really hot.  I just keep my earphones handy.

Don, N5LZ    KPA1500 s/n45   


Sent from Mail for Windows 10

From: john at kk9a.com
Sent: Monday, May 7, 2018 5:17 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] KPA1500 SWR meter

Hopefully Elecraft can duplicate the apparent temperature related SWR
problem and resolve it.

The loud fan noise contradicts preliminary reviews. Perhaps the early
testers did not run the amp in a contest environment where it heated up.
There are over 125 KPA1500's that have been manufactured so they should be
getting used in all types of environments now. I hope to order one for my
station, eventually.

John KK9A


from: Don Butler n5lz at comcast.net
date: Sun May 6 18:41:31 EDT 2018

contest..... which is the first contest I have operated with the KPA1500
.... the heatsink temperature was down in the mid 40s C at the time .... and
in my case it occurred on 160 meters only .... SWR as per other meters as
well as the digital readout on the 1500 were reading 1.2:1 ... and did not
change even when the LED flashing occurred ..... but I was getting
intermittent flashing of all LEDs on the amp's SWR meter ....

During the contest I was continuously running on CW with hourly QSO rates
running between the 70s and 110s .... I opted to manually switch on the fan
to keep the temperature below 60 degs C ..... level 2 seemed to keep it
there most of the time .... but I did move up to level 3 a few times  (and
BTW, at that speed the KPA1500 is clearly the noisiest amp I have ever owned
.... but, arguably, it may very well be the "coolest" also ..... headphones
were absolutely necessary with that noisy fan ..... clearly much noisier
than the Alpha 9500 sitting right next door ... which I also used during the
same contest...

So Mike, you're not the only one experiencing this phenomenon.... whatever
it is..

Don, N5LZ   (KPA1500 #45)


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