[hpsdr] Pandora Fan Orientation?

[w3sz]

I don't know anything about these issues ;)
but I mounted the fan as an exhaust fan rather than having the fan blow 
air onto the LPU heatsink, reasoning that the heatsink and the 
vertically mounted power resistors were positioned between the fan and 
the nearby Mercury/Ozy/Pene boards, and I didn't want the fan 
potentially blowing the hot air from the heatsink and the power 
resistors onto the much more expensive and difficult to replace boards. 
  I figured that the fan was close enough to the heatsink and had a high 
enough flow volume that it would entrain sufficient air flow around the 
heatsinks to cool the heatsinks when it was operating in the exhaust mode.

But it could well be that because of the position and dimensions of the 
LPU heatsinks that little or none of the hot air from the heatsinks 
would have in fact reached the boards if I had used the fan to blow air 
into the cabinet instead of having it mounted as I did.

I have had my units running for hours and have not had any problems with 
the configuration I used, but I don't have a temperature probe and I 
haven't approached 100,000 hours of use yet.

Pending further data I will keep my fans mounted as they are ;)

73,

W3SZ
Roger Rehr
http://www.nitehawk.com/w3sz

On 7/11/2009 1:12 PM, Albertson Chris wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
> The purpose of a fan is to exhaust the hot air and thereby reduce the
> ambient temperature of the inside of a chassis.
> You would see these exhaust fans mounted near the top of the enclosure.
> If you have a specific heat sink that needs cooling it's best to mount a
> small fan directly to that one heat sink.
>
> The fan will move more air if the side blowing is unobstructed
>
>
>
> On Jul 11, 2009, at 9:59 AM, John Ackermann N8UR wrote:
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> We haven't done any serious testing on airflow, but it intuitively
>> seems the right thing is to have air blowing into the cabinet, so that
>> it's directly hitting the LPU heatsinks. However, intuition isn't
>> always correct, so it would be interesting to hear from anyone who
>> really knows this stuff.
>>
>> John
>> ----
>>
>> n3evl said the following on 07/11/2009 12:08 PM:
>>> ***** High Performance Software Defined Radio Discussion List *****
>>> I have my fan mounted in Pandora and noticed that it is mounted such
>>> that it blows air out of the cabinet. I'm guessing it needs to draw
>>> air into the cabinet and needs to be turned around?
>>> BTW, LPU is complete and operational. I mounted the two 6.8ohm 10w
>>> resistors in parallel instead of the single 2.2ohm - voltages all
>>> look good. Thanks again to those that shared their photos of the
>>> constructed board.
>>> Pete, N3EVL
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