Re: [Elecraft_K3] Re: K3S low power output on 160

Rob Sherwood

I had a discussion with Gerald about his 6700, though it happened to be about transmit IMD, not power output.  He said their rig specifications are with 13.8 V. DC at the radio's power connector  (PowerPole).  I was using an Astron RS-35M with an 8-foot #12 wire cable.  I had to increase the Astron voltage to 14.3 volts to get 13.8 at the back of the radio. 

My Pro III PS-125 has a power cord that is about 18-inches long, I suppose for that reason, as unhandy as it is. 


On Dec 3, 2015, at 1:43 PM, "'John Kaufmann' jkaufmann@... [Elecraft_K3]" <Elecraft_K3@...> wrote:


Ø  Make sure your power supply is at least 14.1v.


I’ve tried two power supplies but both are 13.8 VDC.  I have nothing higher.  One supply is an Astron RS35M linear supply and the other is an Astron SS30M switching supply.  I don’t normally use the SS30M because it generates spurious RF birdies that pollute the amateur bands, even when ferrites and line filters are applied to it.



Ø  The classic response is to run the power calibration routine found in

Ø  the utility program. Also check the input voltage at the rear power

Ø  connector while under load.


I did run the transmit gain calibration routine but that did not change anything.  The voltage under load does drop a bit at “full” power out.  With the SS30M it’s 13.0-13.1 VDC and it’s 12.6-12.8 VDC with the RS35M.  The SS30M clearly has better voltage regulation but the maximum power output is the same with either supply.



Ø  And, first, but not least….. what does it do into a “Dummy Load”?

Ø  Test the radio into a dummy load. If all OK, then test Amp into a dummy load.


All power measurements were made into a 50 ohm dummy load as well as real antennas that are well matched (SWR < 1.5:1).   The power output on 160m is no more than 80W with any type of matched load.


73, John W1FV

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