[Elecraft] KPA-500 fan noise

[Jim Brown]

Harry,

Harry,

I didn't see this this email until just now --  it got stuck in my spam 
filter.  The subject line says KPA-500, so that's what I was talking about.

 From what you've written here, it does, indeed, sound like you/ve done 
a pretty good engineering job.

73, Jim K9YC

On 6/3/2014 12:17 PM, Harry Yingst wrote:
> As I stated I do Not have a KPA500 It is in the future plans but I 
> need to get some antenna work done first.
>
> As I stated I replaced the Fans in my K3
>
> I went with the Noctua brand because they are known for making a 
> quality fan that is very quiet.
>
>
> New Fan: Noctua NF-A6x25 FLX
> Airflow: 17 cfm (29.2 m3h converted to cfm)
> Noise: 19.3db
> Speed: 3000 RPM (at 12 v)
> Static Pressure: 2.18 mm
> Current: 120 mA  (.12 A)
>
> Original Fan: UTEC AT6015L-12L2B-ND2
> Airflow: 15.4 cmf at 24.8db
> Noise 24.8
> Speed 3000 RPM (at 12v)
> Static Pressure: 2.21mm
> Current 100 mA
>
> Yes I hear the air rushing but not the bearings
>
>
>
> ------------------------------------------------------------------------
> *From:* Jim Brown <jim at audiosystemsgroup.com>
> *To:* elecraft at mailman.qth.net
> *Sent:* Tuesday, June 3, 2014 2:21 PM
> *Subject:* Re: [Elecraft] KPA-500 fan noise
>
> On 6/3/2014 7:19 AM, Harry Yingst via Elecraft wrote:
> > Replacing the fans was a worthwhile improvement and made copy easier.
>
> Something does not compute. The fan in my KPA500 is pretty quiet on RX,
> and only gets loud during long transmissions, continuing for a short
> time (a few seconds) after that. How does a fan that is noisy only on TX
> make copy difficult on RX?
>
> Another thing that doesn't compute is that a lot of the noise I'm
> hearing is air flow. Perhaps the replacement fan is running slower,
> which would reduce air flow, which would reduce cooling. Again, I would
> approach all of this with great caution. Cooling of power devices is as
> important an element of the design of amplifier as any of the rest of
> the circuitry.
>
> I think it's a mistake to think that we hear the fan because it's a
> "cheap" or inferior one. We hear it because it's working.
>
>
> 73, Jim K9YC
>
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