[Moon-net] 10GHz WG Switch Temperature Rise

[Chris Bartram]

I'm slowly rebuilding the 'focus box' for my 10GHz EME system. Not before 
time, I'm moving to a WG system, and increasing my power output from +46 to 
around +52dBm with a new TWTA. I should also halve the system noise 
temperature with a new WG input preamp and by losing the losses associated 
with the existing coax antenna switch.

I've acquired a couple of Logus WR75 four-port transfer switches. These were 
designed to operate from 117VAC at 60Hz, but they are easy to modify for 120V 
DC operation, by removing an internal bridge rectifier. Our AC supply is 
240V/50Hz, BTW, but I don't want AC power out at the dish, even via a 
transformer. The 120V DC is supplied from a very elementary PIC-based 
switched-mode power supply which operates from a +28V line already present at 
the antenna.

One of the units is a simple failsafe switch. I'd like to use this, as it 
fits-in with the existing coax-based system. For 30+ years I've energised my 
antenna c/o relays on receive, as I can then supply the preamp power, via 
another +/-5V inverter, from the same supply!

My question is: does anyone actually know what the maximum allowable 
temperature rise of the Logus switches is? In free air, I measure 20 - 25 
degree (C) temperature rise above ambient for about 6W dissipation when I 
energise the switch for a few hours. Is that reasonable?

If anyone has relevant experience/knowledge I'd be very pleased to hear from 
them!

Vy 73 and best wishes for 2008.

Chris
GW4DGU