[Elecraft] K3s - 80W on 160 - Resolved

[Gary Smith]

Hi Jim & the others who replied,

This is a follow-up for someone in the 
future who looks for the same solution. 

Yeah, the small amount of difference in 
the wattage is insignificant but 
considering all the radios I've owned, the 
low end of the bands were always the 
highest output. 10M was usually the lowest 
output & with the K3/K3s, 6M was always as 
good as the other bands watt wise and 160 
was full output. This not being the case, 
I was concerned.

I had done the calibration and raised the 
output to 87W but that was it. As was 
suggested, I raised the voltage from the 
PS to give me 13.8V on transmit which 
required 14.6V resting. I'm using the 
cable Elecraft supplies and I'm suspecting 
it could be just a tad lower gauge/thicker 
copper to reduce the resistance but on 
160M, I am now getting a 115W reading on 
the P3 and 113W on the LP-100A.

So the increased voltage was the 
difference in my case. A thicker wire 
would certainly require less voltage than 
14.6 and that's what I am going to look 
into. With the power Pole connector, I'll 
have to look a little deeper into what 
will work best. I have no crimping tool 
for Power Pole so that makes it more of a 
challenge.

Anyway, thanks Jim & all who suggested the 
higher voltage, it was the answer in this 
instance.

73,

Gary
KA1J


> On Fri,12/16/2016 9:27 PM, Gary Smith wrote:
> > With the ATU in or out it gives 81W out on 160, SWR is 1.28
> >
> > All other bands except 6M give around 98W, 6M gives 87W
> >
> > Any ideas what might be causing the lower output on 160?
> 
> 81W is 0.9 dB less than 100W; 87W is 0.6 dB less than 100W.  On 6M,
> it's probably a simple matter of efficiency -- power amps are slightly
> less efficient on 6M than on the lower bands.
> 
> And there may be a power calibration issue. There's a procedure in the
> manual for doing that.
> 
> Or even error in the power measurement itself. Few power meters are
> specified for better than 5%. Bird wattmeters are specified as 5% of
> full scale, and a condition of that is that the slug is in
> calibration. If, for example, you're using a 250W slug, accuracy is
> +/- 12.5W. I use an N8LP LP100A, which specifies 5% at any power level
> from 1W, and quotes 3% typical. 5% is 0.22 dB.  3% is 0.13 dB.
> 
> Low DC voltage can also be an issue, either due to the power supply
> itself or IR loss in the power cable (or even the connector(s). Use
> the built-in metering function to check DC voltage with just the RX
> running and keydown. Short, fat copper is your friend. :)
> 
> 73, Jim K9YC
> 
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