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

[Jeff Cook]

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.