[hpsdr] To suck or to blow, that is the question.

[John Ackermann N8UR]

Jeff, I'm curious what you used as "draft excluders" around the fan. 
Can you provide more info?

To reduce vibration, I mounted my fan using rubber grommets between the 
fan and the enclosure top, and that helps in one way but the gap is 
probably increasing wind noise.

John
----
Jeff Cook said the following on 07/11/2009 04:22 PM:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Dear All,
> 
> My cup runneth over, HPSDR fully functional, Pandora and LPU arrived, 
> and the little fiddling part necessary to get HPSDR fully functional 
> arrived from America within three days of ordering it here in Blighty, 
> does life get any better?
> 
> I've assembled LPU, and put all my kit and caboodle into Pandora along 
> with a fan, switched on and have something that sounds like a wind 
> tunnel.  Remembering what others have said with regard to the fan being 
> noisy I played around, and have found that with a combination of cheap 
> draft excluder at each corner of the fan to act as a buffer between it 
> and Pandora, and dropping the voltage to the fan from 13.8 V to 9 V by 
> using 8 silicon diodes in series housed in heat shrink tube, the noise 
> is reduced to a quite tolerable level.
> 
> Now then, to suck or to blow that is the question, and it seems very 
> reasonable to conclude that under normal circumstances one would wish to 
> vent hot air from inside Pandora to be replaced by cooler air.  But I 
> wonder if that would work with Pandora, it has so many ventilation slots 
> that I feel very little air would be drawn in from its far end, and 
> would probably be mainly drawn in from the slots closest to the fan.  So 
> I have set my fan to blow air into Pandora and in particular against the 
> heatsink of U2 the 5 V regulator, which I've noticed gets very hot if 
> the fan is not on.
> 
> Any other thoughts?
> 
> Jeff Cook, G0AFQ.
> 
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