Re: Blowing a masthead SSPA

Paul G8AQA

There is a spray product called Midas Spider EX that is supposed to keep the spiders out of things.  I have tested it for flies and it works very well. I now use it on all box on the tower.  Read the can for precautions. Ideal for outside heat sinks.

Paul G8AQA

On 20/02/2021 15:13, John Quarmby via wrote:

For my 3 and 6cm systems the heatsinks are external to the diecast waterproof box, sealed round the edges with non-corrosive silicone sealant. The 3cm section has forced air cooling with a hood over the fans, the heatsink fins are covered so air is pulled up through the fins from bottom to the top and then expelled by the two minature fans into the hood which keeps water off. It does need annual maintenance to remove spiders webs which tend to gum up the fans. This arrangement has worked for 20 or so years with the box outside on the tower throughout that time. The heatsinking is compromised a little by having the diecast box body in between the PA and heatsink, it wouldn't be too difficult to calculate the resulting increase in thermal resistance.


John G3XDY

On 20/02/2021 13:48, DAVID G4ASR via wrote:
Hi everyone,

Has anyone built a masthead SSPA with integral blowers?   I'm just looking for ideas of how to bring air in & out without bringing in rainwater.

Its actually going to be used on 70cm, bringing my total of masthead transverter/lna/sspa boxes to a total of 5, up to the 3cm band.
It won't be permanently on the tower. Just fired up for 1-day a month, maybe on the tower for 3 days or so.

On my 1296MHz masthead transverter/sspa I have 2 blowers and bring the air in/out on 32mm plastic plumbing fittings that I can swivel so that the inlet/outlet
point downwards.   

As an aside, I'm going to be rebuilding my 13cm masthead system with a 3xLDMOS sspa and will be shifting a fair bit of air.
Ideally I would love to have the heatsink fins external to the masthead box but can't see a way of making it waterproof and able to be easily removed when I blow it up.
Maybe some type of flexible gasket? 
Be interested to see how you do it ?         

73, David G4ASR


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