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

[John Koster]

I would vote for suck, rather than blow the heat from the LPU towards the 
board stack, but what do I know ... had to take thermo twice to pass and 
still hated it!

Seems like we ought to have someone on here that knows how to wire up 
those 3 wire fans to modulate the speed according to the internal 
temperature of Pandora.  Is it more complex than having the right 
thermistor?  

On Sat, 11 Jul 2009, John Ackermann N8UR wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> 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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-- 
73,
John, W9DDD


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