[Elecraft] KPA1500 SWR meter

Mon May 7 12:18:55 EDT 2018

Yes, this is true

For all these LMDOS amps, you need to dissipate all that heat and the
common way is with a Fan, so you really have no choice but to get used to
it.  You have to move a defined amount of air to do the cooling.  Small
fans need to spin faster to move more air than larger fans spinning
slower.  The more compact the amp is the more air you have to move and it
can be noisy.

Move it further away, invest in headphones, etc.   If it is noisy, maybe
drop down 3db to 1/2 power and 1/2 the heat generation.   Put the amp in
another room if you can.

Like Don said, there is no free lunch.  You can't have big time
amplification without producing heat.

It is all in the math.

Mike va3mw

On Mon, May 7, 2018 at 12:07 PM, Don Butler <n5lz at comcast.net> wrote:

> 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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