Resetting when Transmitting on 6 Meters
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Author:  kx9rt [ Sun Mar 25, 2018 12:06 pm ]
Post subject:  Resetting when Transmitting on 6 Meters

Has anyone had any issues with the amp reseting on 6 meters? When transmitting 1 Watt the amp resets with the firmware revision splash screen cycling if continuing with a keydown.

It seems like there is an issue with RF getting back to the controller board. I may have to play around with moving the ribbon cable and adding bypass caps to the microprocessor. I have been going through all of the bands on the amp and taking power measurement data to confirm output power and linearity. I may share that data in another forum post in the future.


Author:  kx9rt [ Tue May 08, 2018 11:04 pm ]
Post subject:  Re: Resetting when Transmitting on 6 Meters

Now that sporadic E season is in full swing, I tried 6 meters again into a 50 ohm dummy load. It still resets every time I transmit.

- The reset occurs on keydown of the CW key if the drive is greater than 0.5W.
- Turning down the power to 0.2W, keydown, and then increase the drive to 1.0W results in no reset and about 50W indicated on the Hardrock meter.
- I have separated the power cable bending forward over the top of the heatsink to see if there is an improvement and potential RF coupling from parallel coax to 13.8V input. No change.

I'd like to track down some torroids and try them on the cables. Otherwise RF bypass caps sprinkled through through the internal supply lines and uP reset lines. Unfortunately the amp is unusable on 6 at this time until I can find a solution.

Author:  jimveatch [ Wed May 09, 2018 5:10 am ]
Post subject:  Re: Resetting when Transmitting on 6 Meters

Hi Scott,

I'd say that there's something wrong with your amp. I transmit into a load on 6M with many different copies of the HR50, I test them all the time and I have never seen one reset.

Which version of the FW is your amp running?
Do you have the ATU installed?
What hardware version do you have?

The initial splash screen should tell you all of these things.

I'm thoroughly tied up until after Dayton, but I'll be happy to look at you amp when I get back. If you email jim (at) HobbyPCB (dot) com, I'll send you shipping info.


Author:  kx9rt [ Wed May 09, 2018 2:29 pm ]
Post subject:  Re: Resetting when Transmitting on 6 Meters

Setup data:
- Revision 3.0D firmware
- Hardware version G
- KX3 Radio
- HobbyPCB supplied DB9 Breakout board
- PTT and COR mode
- QSK board installed
- No Autotuner

- The resetting isn't 100% repeatable. I can keyup with 1.0W drive and it will reset the display MOST of the time.
- The output power via an external meter is also very low while the display is in the process of resetting.
- There is relay clicking during this reset process.
- I noticed around ~2W drive the display power spiked 70+ watts. Instability?
- Transmitting into a 300W dummy load
- Low resistance DC power cable

I'll hit you up in a couple weeks after Dayton.

It feels like stray RF could be a cause of all this either through cabling or reflections or improper loading to cause the transistor to misbehave? I'll double check the 6 meter output filter windings for possible reflections there.

Author:  kx9rt [ Sat Jun 16, 2018 1:11 pm ]
Post subject:  Re: Resetting when Transmitting on 6 Meters

Just to close the loop in this issue, I was able to solve it.

Long story made short, the root cause was the coax cable between the amp and radio. The shield connections were not soldered and not visible in the PL259 holes. Swapping that out with a known good soldered cable cured all the strange behaviors that I was only experiencing on 6 meters.

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