KX2 ---> PA temperature

When operating the KX2 in pure sunlight it gets rather hot (I think it is the same with the KX3 …). On today’s activation weather was great, a nice summer day with high temperatures.

The PA temperature went up to 50°C during TX with 10W … the manual only tells me that the KX2 will reduce power or turn off when getting to hot.

Can anyone of you tell me at which temperature the KX2 will automatically reduce power? And switch off completely?

73 Martin, OE5REO

Hi Martin,

While living in Australia I got worried about my FT-817’s case getting too hot to touch while operating in the sun. I resolved the problem by applying some sticky-backed white plastic (sometimes known by it’s original product name “fablon” I think), to the case. This made a vast improvement on following activations. I was also able to remove the plastic without any marks being left on the case when I moved to Europe.

73 Ed.


Judging by the block diagrams the KX2 is virtually identical to the KX3 in terms of hardware, it uses the same final transistors (FETs) anyway.

60°C it will back the power down to 5W from 10W on the KX3. I would be surprised if its that much different on the KX2 considering its basically the same radio in a smaller box… with less features :wink:


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thank you for the info jonathan … 73 de martin, oe5reo

A simple solution to sunny hot days is to carry a light colored towel to cover the radio. I’ve done this for years while operating portable anywhere and the sun is a factor.
Now a days I use an old piece of a windshield cover that protects your dash board from the sun. When I bought a new one, I just cut a section out of the old one and lay it over the radio.
The silver side reflects the sun, it also has a foam backing, no more problems with the radio getting hot because of the sun beating down on it.
Keeps my KX2 cool here in Florida where we have our share of hot sunny days !

73 de Ed
Bradenton, FL


This is not a problem I expected in UK but it happened to me last week. Few replies so lots and lots of CQ and a progressively rising temperature. I then gave up; few replies at 10W, so a lost cause on 5W :frowning:

I was hot too and nearly gave up on hill number 2.


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Or an umbrella if there is not a gale blowing. Although I have not done so there are those half moon beach shelters available.

Thinking of one for the coming summer as once the KX3 flashed up an over temperature message last summer and had to stop and wait for it to cool.

You’ve never been to Scotland then? :grin:

You need to get an external PA Rod for SOTA, I drive my home brew amp with a comfortable 4.8W from the KX3. Doesn’t push the PA too hard in the KX3 as a consequence of the reduced drive.

It is however, an utter pain using the KX3 for WSPR with its temp trip as it can cut the PA in mid transmission !

I have one, Jonathan, but only carry it on very short easy walks. I have to reduce the weight I carry. It’s all right for you fit youngsters; I used to carry an ft-857 and two batteries :slight_smile:

Get your sherpa to lug the batteries and you carry the radio. She’s only got a handy with her! :imp:

Unless she has all the chocolate and cake and yummy stuff in her bag. In which case don’t use value cake space for batteries!

I think your still doing good in your youth Rod, besides your completing more mountains then me at present :wink:

Sadly I am not allowed any cake at the moment, assorted nuts are a pretty good mountain substitute snack I find !


Geoff M0PYG and I will be splitting the weight when we are walking in the Czech Republic next week. We will be carrying an FT857 and 7 AH LiFePo etc between us…

73 Phil

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Hi Martin,

same with the KX3. I got my KX3 before Elecraft increased the size of the metal plate they call a heat sink. In summer at air temperatures around 30°C I get up above 50°C PA temperature by prolonged CQ calls at 10 W SSB. This does not require the KX3 being exposed to the direct sun.
My record is 55°C when I got scared and reduced power to 5 W.

73 de Michael, DB7MM

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You know when I have the KX3 in pieces I often wonder why they didn’t mount the finals underneath the RF board and fit a small serrated heatsink on the back face of the radio, it would dissipate better then that covering plate.