[Elecraft] Solving the heat problem in the KX3

[Jim Bennett]

Dick,

I've run PSK31, JT9, and JT65 with my KX3 for several months, on and off. I'm mostly a CW guy, so was just dabbling in the JT modes in my chase of 5BWAS. Running the KX3 barefoot on digital was not a rewarding process for me. Almost everyone running PSK31 is doing so with 15 - 35 watts, so a 3-4 watt signal isn't going to make a lot of QSO's. I did, but they were few and far between. Even worse on the JT modes, where it is quite common practice to answer a CQ right on top of the caller's frequency. If you are running three watts to a marginal antenna and another guy is running 30 watts to a yagi, and you both answer a CQ on the same frequency, guess who gets the QSO...? :-(

So, I run my KX3 RF output into my KPA500 amp. I set the KX3 at about 2-3 watts output and this gives me about 20-25 watts out of the amplifier, which has given me pretty good success on the JT modes, along with PSK31. I use an 88-foot long doublet, fed with ladder line so I quite often get stomped on by the multi-element yagi guys, but that's life. At least I stand a fighting chance at 25 watts. With the KX3 set at those power levels, I am able to run it all day with zero heating up issues. And of course, the KPA500 certainly has no problem with 25 watts output for the JT modes' 50 second transmit/key down transmissions. Don't know how the KXPA100 performs, but the '500 likes it.

Jim / W6JHB



On   Sunday, Apr 13, 2014, at  Sunday, 7:37 AM, Dick, WN3R wrote:

> I really appreciate everyone's contribution and effort in attempting to
> solve the extensive heat problem running digital modes. I continue to follow
> the discussions on a daily basis.
> 
> 
> 
> I can appreciate the fact that while the KX3 has digital capacities, it was
> not designed with the matching RF capacity to handle the heat.  This caution
> was stated early on in the specs. So no surprise.
> 
> 
> 
> However, it is clear that it would be desirable to be able to run
> continuously 10-20 watts in a digital mode.
> 
> 
> 
> Perhaps, Elecraft will solve this problem and produce an official
> modification or method.  Right now, I am thinking the only currently
> supported solution is the purchase of the matching amplifier. With that
> said, please report your experiences running digital modes with the
> amplifier.  What power levels are acceptable without causing a heat problem
> in neither the radio nor the amp?
> 
> 
> 
> Thanks guys,
> 
> 
> 
> 73, Dick, WN3R
> 
> (I have lots of Elecraft gear)
> 
> 
> 
> 
> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to w6jhb at me.com