[Elecraft] KPA500 thermal clicks

Thu Jul 19 11:43:21 EDT 2018

I'm of the same mind, though a KPA1500 is more my preference to replace 
one of the aging tube monsters here.

Good stuff Sorbothane.

Sorbothane was specifically designed for shock absorption 
<https://www.sorbothane.com/what-is-a-good-material-for-shock-absorption.aspx> 
and is manufactured to outperform every other material on the market. 
What makes Sorbothane the best material for shock absorption?

  * It absorbs more than 90% of shock energy and more than 50% of
    vibration energy;
  * It performs in temperatures ranging from –20° to 160° Fahrenheit
    (–29° to 72° Celsius)];
  * It performs at frequencies ranging from 10 to 30,000 Hertz;
  * It’s damping ratio is 0.344 at 2.34 HZ;
  * It doesn’t support bacterial or fungal growth and is relatively
    unaffected by industrial solvents such as diesel fuel, kerosene, and
    hydraulic fluid;
  * It has an extremely long shelf life; and
  * It has a superior damping coefficient.

But I wonder about that temp rating :-)

On 19/07/2018 21:01, Clay Autery wrote:
> Y'all are making me want to find a unit with this "issue" now just so 
> I can solve the mystery....
>
> IF it is the aluminum fins "creaking" due to rapid thermal 
> expansion/contraction, one possible/probably solution is a small 
> Sorbothane damper attached across the fins in an appropriate spot....  
> Can likely be don without measurably challenging the airflow...
>
> 73,
>
> ______________________
> Clay Autery, KY5G
> (318) 518-1389
>
> On 19-Jul-18 08:18, hawley, charles j jr wrote:
>> The ticking sound is clearly the resonant aluminum heat sink fins. 
>> The mechanical shrinking or expanding is abrupt and resonates the 
>> fins much like a tuning fork.
>> My take on it...
>>
>> Chuck
>> Amateur Radio, KE9UW
>> _____
>> From: elecraft-bounces at mailman.qth.net 
>> [elecraft-bounces at mailman.qth.net] on behalf of Martin Sole 
>> [hs0zed at gmail.com]
>> Sent: Wednesday, July 18, 2018 8:37 PM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] KPA500 thermal clicks
>>
>> I think it sounds "orrible!". I'm quite used to the low rumble of the
>> blower in my Alpha 77D but that ticking would be like Chinese water
>> torture to me. Listening to an individual tick it does seem to have a
>> ring to it. Okay the recording was perhaps not the most acoustically
>> perfect but it certainly does sound as if the ring is from the source
>> and not any sort of artifact. If it is from the source then I think you
>> can probably find a way to damp it. First trick will be to identify the
>> specific source.
>>
>> I had read other comments about a ticking, always imagined it to be
>> minimal and essentially unobtrusive but if what you have recorded is
>> anything like how it sounds sat in front of it then definitely it does
>> sound pretty bad to me and not just in amplitude but also in its timbre,
>> pitch, and repetition rate.
>>
>> Martin, HS0ZED
>>
>>
>> On 19/07/2018 06:25, ANDY DURBIN wrote:
>>> I placed my Android phone on top of my KPA500 and made a recording 
>>> while making a few cycles of FT8 TX/RX.  The audio files can be 
>>> found here:
>>>
>>> https://www.dropbox.com/sh/amfy3dz8pgl083n/AAAKi2GYripXyIDjiLpJ2hDwa?dl=0 
>>>
>>>
>>>
>>> One file is the raw recording.  The second has been processed in 
>>> Audacity to amplify to 0 dB peak.  The file starts before the first 
>>> TX. Next the hum of the transformer can be heard with FT8 modulation 
>>> in the background from TX moni.   As the recording progresses the 
>>> changes in fan speed can be heard. The click are always well above 
>>> the fan noise.
>>>
>>> I used this recording to perform some spectral analysis of the 
>>> clicks.  I took one sample at the click and another sample of the 
>>> noise just before the click.  I then subtracted the noise from the 
>>> click and I think I have a reasonable click signature to use as a 
>>> baseline for evaluating any mechanical changes I make in an attempt 
>>> to reduce the clicks.
>>>
>>> Crank it up and enjoy, especially if you think it's normal.
>>>
>>> 73,
>>> Andy k3wyc
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