[Elecraft] Powering a K3s from a battery?

[Wes (N7WS)]

Good points all.

Something else to note, even at 14V, running a K3 at 11-12 watts is a disaster.  
Just because you're using "low power" doesn't mean that the amplifier isn't 
distorting. IMD is also frequency sensitive. One frequency measurements tell you 
nothing about IMD performance.  At 30 watts output on 3.8 MHz my K3 IMD was 17dB 
lower than at 14 MHz.

At 24 MHz the IMD at 10W was 29 dB worse than 30W!   In all cases of frequency 
or output power the IMD was worse at 10W output.


  On 12/29/2015 5:00 PM, Bill Mader wrote:
> Actually, IMD in the PA increases significantly as battery voltage drops!
> For example, during Field Day a few years ago someone kicked off the
> generator power to our SSB station which kept operating on the back-up
> battery.  Sometime later the CW captain stopped by asking if we had changed
> anything.  He could hear "splatter" from our 20m signal on his 20m rig.
> This was not the case earlier in the day.
>
> I checked everything and discovered the AC power issue.  I turned the outlet
> switch back to On and checked with the 20m CW operator.  His reception had
> immediately cleaned up!  He no longer heard anything from 20 SSB the rest of
> the (non-contest) event.  BTW, we went on to take 4th place overall with
> just six transmitters (2012).
>
> When driving a KPA500, this is much less of an issue since the K3 runs
> typically under 30 Watts for 500 Watts from the KPA500.  NC0B has spoken
> frequently, in less than glowing terms, about IMD issues in 12 VDC (nominal)
> PA's.
>
> I've seen a number of comments recently that some folks don't care if their
> radios' TX IMD is high.  That attitude is exemplified in many DX pileups.  I
> have raised my power supply's voltage in an effort to keep my TX IMD as low
> as possible based on my reading and empirical evidence related above.
>
> 73, Bill, K8TE
> Albuquerque DX Assn
>