[Amps] Cheap auxiliary amp cooling

[Jim Barber]

Thanks, George.

In this particular case, I haven't noticed any RF *yet*, but my antennas 
are some distance from the shack, with common-mode chokes on all the 
cabling.

I'm still slowly digging out after a move, but when time and space 
permit I'll get the spectrum analyzer and EMI probe set up - then we'll 
see what flavor of noise we're getting from it.

73,
Jim N7CXI


On 3/30/2012 6:12 AM, GeorgeWallner wrote:
> On Fri, 30 Mar 2012 00:29:21 -0700
>> Jim Barber <audioguy at q.com> wrote:
> <a 250mm (10"!) 12V PC case fan has a
>> brushless (no RF noise) DC motor,
>
> Jim,
>
> That sounds like a good fan and it will likely prolong the life of you
> amp. Do not automatically assume, however, that "brushless" means no RF
> noise. The brushless commutation is achived using high speed switching
> transistors, which can generate RF. I usually add a .1 uF cap across the
> fan's terminals, a small 2 mH common mode choke in series with the 12 V
> DC power feed and a second .1uF cap on the other side of the choke for a
> perfectly RF quiet fan. Sometimes a single cap is enough, but you would
> have to test for that.
>
> 73 es GL,
>
> George, AA7JV
>