Batboard

I have two cdm radio tied together with a rick. The transmitting radio heats up and im wondering if there an other way to hook up the cooling fan rather then have it run 24hrs?

Use a real radio? I've seen several failure with the CDMs in regular mobile use... I can imagine what their performance would be like in a repeater application, especially considering the dismal heatsinking.

Use a 12V 4-5/8" muffin fan (http://www.partsexpress.com) running in series through a 20 Ohm/20 watt resistor to provide low speed. In this case, force air ONTO the rear of the radios- not out or away as you do with an enclosure. You may also use a blower type fan.

Now....

Insall an ELK960 timer to bypass the resistor when the timer is active. Trigger the ELK timer with the PTT/XMT lead. Set the timer for 1-2 minutes.

This will continuously run the fan at a low speed until transmitting, then go full speed for 1-2 minutes when transmit is active, then back to low speed.

Works great.

Take the cosmetic covers off the CDM too.

when running fans, I usually use a ceramic cap on the power feed as well. (especially on kenwoods). this usually stops any noise coming from the fan on TX.

I use a computer power-supply fan that I ordered online. The screw spacing fits perfect when the screws are in place, as it's just wide enough of a spacing to secure itself when pushed gently against the rear PA fins, and works really well.

My VHF repeater (2 Radius Mobiles) uses the same setup, with a resistor soldered inline as well, but runs continuous.

I have several CDMR series repeaters in service. They are all installed in the Motorola cabinet, CDR700, have yet to have any problems. The cabinet does have a cooling fan that is set to run only when it senses heat.

For the money, great setup, customers very pleased.