[Elecraft] [KX3] Portable operation - heating with sun loading

[Dominic Baines]

Gary, Matt,

Other than trying to get your KX3 into shade, which is a good idea 
anyway.... you 'CAN' also add an extra heatsink to the current tiny one.

There are plenty of after market (Google "KX3 after market heatsink"... 
for you US guys) resellers out there selling heatsinks that are 
specially for the KX3.

I just used a 6" length of a finned Ali heatsink and bolted it with heat 
sink compound applied underneath to the current heatsink strip that the 
PA are also bolted to and underneath the KX3. I did not disassemble my 
KX3 to add it but I did have to drill into the chassis/heatsink strip 
and use self tapping screws (short ones!!).

I remove when not needed.

My KX3 runs very warm with it still with the PA at c49'C (win-test 
sending 5sec repeating cqcqcq etc into a dummy load at 10W) after a 
while at 28'C ambient but it does not fold back! I added this after 
experience that a high ambient temp caused me issues. (31'C in 6W) You 
can also open the case slightly and force blow air through it (small 
ex-CPU 12V fan is easiest).

Note do NOT put heatsink between the PA tabs and the chassis (i.e. 
INSIDE the case) as the PA transistors tabs need to be connected to the 
chassis, unless you add a lead to make the connection. If you do you'll 
get high curr errors and all sort of issues I am sure.

None of this are official mods etc and I am sure Elecraft might have a 
very good reason to invalidate any warranty if you do anything that 
approaches this sort of modification so approach with caution. The

72

Dom
M1KTA


On 24/02/2014 17:31, Matt Zilmer wrote:
> Hi Gary,
>
> For the frequency drift issue you noticed, you might want to perform
> the temperature compensation procedure.  See
> http://www.elecraft.com/KX3/kx3_app_notes.htm for more details.  The
> procedure results in much improved freq drift characteristics.  OTOH,
> you may already have been through this and know all that.
>
> If your main issue is the PA temperature protection, I'm not sure
> there's a lot you can do about that except get the KX3 under shade.
> I've had to do that a number of times when operating portable,
> especially in the summer season.
>
> 73,
> matt W6NIA
>
> On Mon, 24 Feb 2014 09:09:18 -0800, you wrote:
>
>> This is just a FYI but when operating portable and the KX3 is subject to
>> warm air temps and being in the sun for a prolonged period of time,
>> internal heating can lead to minor drift in freq (as reported by the
>> radio) and the possibility of powering down it's output.  Obviously,
>> making sure the radio stays out of the sun is one way of mitigating this
>> issue but if there's ever a chance to further improve cooling it might
>> be worth looking at.
>>
>> The KX3 is proving to be an excellent portable SOTA radio.  I have
>> modified mine to include the Side KX panels and cover
>> (http://gemsproducts.com/) and use it with as Zippy 30C Series 4200mah
>> LifePo battery.  Capacity and voltage stability of this battery allows
>> full power SSB operation of my KX3 for several hours without any need
>> for voltage dropping circuit.
>>
>> Gary (K6YOA)
>>
> Matt Zilmer, W6NIA
>