[Elecraft] KX2 Heatsink

[Josh Fiden]

Sorry if this is argumentative, but your post seems to be in conflict 
with Wayne's post earlier today.

Wayne: "...heat sinking that is entirely adequate  in all modes at full 
power, even from a 14 volt external supply."

The manual also says "all modes" which I don't see why that would 
exclude JT65. JT65 is *not* 100% duty cycle. It transmits about 50 
seconds out of the 1 minute interval, then receives for 1 minute. Sounds 
to me like slightly less than 50%.

Wayne's results were 7 mins key down until reduced power at 25c ambient. 
Running JT conditions of 1 min xmit and 1 min receive, how long does it 
take to reduce power, if ever? How much is this performance reduced at 
30 or 35c? Without this data I don't see how we evaluate whether an 
additional heat sink is required.

Thanks & 73,
Josh W6XU

On 5/14/2017 2:18 PM, Howard Hoyt wrote:
> Hi Kev,
>
> The issue is related to the fact that Elecraft, as do virtually all 
> amateur radio manufacturers rate power output with 50% duty cycle 
> SSB/CW modes only.  As is stated in the KX3 specifications and here 
> copied from the KX2 manual:
>
> /"80-17 meters, 10 W PEP max (+/- 1 dB); 12 and 10 meters, 8 W PEP max 
> (+/- 1 dB).//
> //Recommended transmit duty cycle: 50%, all modes. (If power amplifier 
> temperature or//
> //current drain is too high, power will automatically be reduced.)//
> //NOTE: When using over 5 W in SSB, DATA-A and AFSK-A modes, the//
> //recommended supply voltage is 12 V or higher to minimize transmit 
> intermodulation//
> //products. Higher power with lower voltages should be used only when 
> necessary."/
>
> I believe many or most of the requests we have had to make an 
> aftermarket heatsink have come from hams using these rigs in digital 
> modes such as JT and desire full-power operation, which Elecraft does 
> not explicitly endorse, but which is possible with additional 
> cooling.  Elecraft designs and specifies operation of their rigs very 
> conservatively compared to many other manufacturers, and the KX2 and 
> KX3 specifications are spot on.
> Also as is stated in the specification, the KX2 internal battery, at 
> 10-11V depending on state of charge is considered adequate for 5W or 
> less, and we have supplied many Kx33 14V supplies to KX2 owners who 
> want to use the rig at 10W power when AC power is available.
>
> I conclude many of these KX2 rigs are being used in digital modes from 
> fixed location AC power, not from batteries.  I can't blame the hams 
> who do this, the KX2 is a fantastically full-featured rig for fixed 
> operation, I have used it at home to check into local 10M SSB nets 
> driving a KPA500 and no one was the wiser compared to my K3.
>
> Cheers,
> Howie - WA4PSC