Tuesday, July 18, 2023

Monitoring the temperature of our radios

A lot of modern rigs have a readout, somewhere on the display, of the rig's internal temperature - or that of the final transistors/FET's, etc. Even my mcHF has this feature.

With more and more hams operating outdoors during summer weather, it may be useful to know how warm your radio is getting. Even more so for those who operate digital modes.

Several owners of the FX-4CR have mentioned that the case gets quite warm, even when operating CW at a substantially lower power level than the radio's 20W maximum. My past two activations were with the FX-4CR operating CW at 20 watts and the case got downright hot after 20 minutes or so.

But ambient was 85-90F, so maybe a hot case is to be expected.

For those wanting to keep an eye on whether or not their rig is running a dangerously high fever, I recommend a stick-on temperature label like this one. I've used them before for other purposes and found them to be accurate, agreeing closely with an infrared thermometer.

They also make possible easy before.after comparisons of external heatsinks available for some rigs (KX2, etc).

If you want to shop around on your own, be careful to avoid similar products that are labeled "Irreversible". These only read maximum temperature, one time. Irreversible = single-use only.

Also, you'll want to apply it to the warmest part of your radio.




  1. I noticed the same thing with my QDX, and with my Hermes Lite 2 as well - even quite light duty loads really cause the enclosures to feel hot. I guess it's possible Yu's purposely using the case as a heatsink/radiator to get the heat away from the PCB & PA transistors. My FX4CR arrived earlier this week, and just setting it up and running some test transmit cycles into a dummy load, I noticed the case was getting warm. Maybe some mods like the ones N6ARA made to his QDX are in order https://twitter.com/n6araelectronic/status/1566922397868994560?s=12&t=zQQyAoqJpp4U7rpMeOaGNA

    1. Yes, the case is the heatsink but it is so well sealed that there's no ventilation - the case becomes an oven. If it were ventilated, there would be complaints of not being sealed against the weather, etc. Damned if you do, damned if you don't. I can live with the heat...just lower the operating time/duty cycle when using the full 20 watts.


    2. It looks like N6ARA is using one of these to monitor the temperature:

      I wonder what his source was for the thermal pads.