[Elecraft] KPA-1500 Fan Noise - measured (sort of)

[Bob McGraw K4TAX]

Using a Sound Level Meter with A weighted scale, measure the noise at 1 
meter in at least 4 different directions.   Preferably done in a "free 
field" such that any acoustic reflections are at least 6 meters 
distant.    I know it is difficult to make measurement outside on a 
piece of equipment such as this.   But with these measurements one will 
have some quantitative data to evaluate.   {One side may be noticeably 
quieter.   Thus turning the amp 90º could make a difference.

Also, an audio spectrum analysis of the noise would be nice. There may 
be certain frequencies related to blade tip speed, or bearing chatter 
which can be addressed.

I know Jim, K9YC will have extensive knowledge about this method of 
evaluating "noise" and can offer some solid advice.

73

Bob, K4TAX


On 6/2/2018 6:12 PM, Chris Codella, W2PA wrote:
> In an attempt to quantify this, I installed OSHA's free NIOSH app, 
> which measures noise, onto my iPhone 7 and tried it out.  It's not a 
> measurement instrument, mind you, so the absolute numbers are highly 
> questionable.  But the relative numbers are interesting.  I held the 
> phone at eye level between me and my computer monitor, about 2 feet 
> from the amplifiers.  Here are the results:
>
> dB measured with NIOSH app, rounded to two significant digits:
>
> 46 - for comparison - an Alpha 89 running as normal
> 48 - KPA1500 at fan level 0 (i.e. PS fans only)
> 51 - fan level 1 (i.e. center fan plus PS fans)
> 57 - fan level 2 (all fans on)
> 64 - fan level 3 (all fans on)
> 67 - fan level 4 (all fans on)
> 76 - fan level 5 (all fans on)
>
> Similar to other comments I've read, I find up through level 2 to be 
> okay.  At 3 and above I need headphones or, better still, noise 
> cancelling ones.  My experience thus far is that on SSB in normal 
> conversation at 1500W it stays at level 0 with an occasional excursion 
> into level 1 if I'm long winded.  In the CW WPX test last weekend, 
> strictly in S&P mode, it stayed at level 0. Experiments with CQing and 
> on FT-8 are yet to come and I'm sure will require higher speeds.
>
> 73,
> Chris, W2PA
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