[Elecraft] [K3] Issue with HI CUR on 12m

[Don Wilhelm]

Bill,

I would suggest that you check the SWR on the antenna before concluding 
it is an RF feedback problem.
Don't forget that the balun may be breaking down with power and show no 
problem at lower power (like from an antenna analyzer).

Don W3FPR

On 10/11/2020 8:53 PM, Bill Coleman wrote:
> Don,
>
> I finally got around to running my K3 into a dummy load.
>
> I had no problem running 100w or even 110w with a dummy load. Current draw from the power supply was 22 A and 23 A, respectively, on the K3 display. No HI CUR indications.
>
> External wattmeter validates the output.
>
> I was getting the HI CUR indication on a trap 30/17/12m inverted V. I had to take it down, and now I’m using a trap 80/40/20m dipole through the tuner. No HI CUR indication on that antenna, either.
>
> Even though I have current baluns on both antennas, I’m thinking that my HI CUR problem may be related to RF feedback in the shack.
>
> Do you concur?
>
> I’m in the process of a number of shack improvements, including antenna replacements and grounding and bonding, so that might take care of it.
>
>> On Jan 11, 2020, at 11:29 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>>
>> Bill,
>>
>> Is this into a dummy load (bypass the ATU or tune the ATU into the dummy load).
>> If it is into an antenna, there are a whole lot of guesses about how the antenna behaves with higher power levels than your antenna analyzer shows.  So check it with a dummy load to eliminate the possibility that the problem is in the antenna.
>>
>> Put an external wattmeter in line with the dummy load to eliminate questions about the calibration on the K3 wattmeter.
>>
>> If you can measure the actual current drawn, that would also be helpful.
>>
>> 73,
>> Don W3FPR
>>
>> On 1/11/2020 11:18 AM, Bill Coleman wrote:
>>> Back in early December, I installed two KSYN3As in my K3 SN 7071. Sometime after that, I noticed that on 12m, I’m seeing a HI CUR indication when I set the power level to more than about 80-85 watts. The K3 will back off on the power level, then slowly ramp back up until it hits HI CUR again.
>>> I don’t remember seeing this before. After the KSYNC3A install, I ran the transmit gain calibration at both 5 and 50 watts, as specified in the instructions. Just in case something went awry, I ran it again.
>>> I’m still seeing this problem. What causes HI CUR at 85 watts? The K3 ought to be able to produce over 110 watts on 12m.
>>> I’m not seeing this issue on other bands.
>>> No issues with calibration
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
>              -- Wilbur Wright, 1901
>