Topics

Strange issues on v6 transmit, display acts like it is being pressed #raduino #v6


Larry Biggs
 

Hi all, my v6.2 unit has had a weird thing ever since I received it. During transmit, the display screen acts like it is being pressed. Some times I see "fast tune" light up. Also, if I have the right side VFO chosen it will change itself to the left VFO. Otherwise the unit seems to work fine, I've used it for FT8 a lot. I did however burn out diode D6 recently and replaced it successfully and wonder if the two things are related. When I replaced the diode I completely disassembled the unit and lovingly reassembled it, and the problem remains on transmit.
Thanks in advance for any ideas!
Larry
K6IET


Gary Anderson
 

Larry,
See if the problem persists using a dummy load instead of your antenna system.
Gary


Larry Biggs
 

Will do, thanks Gary!


 

Bad antenna match! RF floating in the shack! Use a proper dummy load and test and see these things repeat!

At 26/02/2021, you wrote:
Hi all, my v6.2 unit has had a weird thing ever since I received it. During transmit, the display screen acts like it is being pressed. Some times I see "fast tune" light up. Also, if I have the right side VFO chosen it will change itself to the left VFO. Otherwise the unit seems to work fine, I've used it for FT8 a lot. I did however burn out diode D6 recently and replaced it successfully and wonder if the two things are related. When I replaced the diode I completely disassembled the unit and lovingly reassembled it, and the problem remains on transmit.
Thanks in advance for any ideas!
Larry
K6IET


Larry Biggs
 

Thanks all, your are right on target, I had been leaking RF into the room!

I run the ubitx into an old MFJ-16010 antenna tuner I've had since my SWL days into a random long wire around my back yard. Before today I had about two feet of the antenna wire going through my window into the office/shack and would see the problem described. After your advice I put a chair outside the window with the antenna connected to the tuner and ran a short coax jumper in through the window and tested. You are correct, I was bleeding RF into the room which was causing the issue. I had been sadly thinking the low power of the ubitx wouldn't be too affected by the short antenna section inside the house. I hooked all my FT8 toys together, tuned the antenna using a NanoVNA (for now) and turned it on during the nice sunny day lol. I started to receive and then enabled transmit and checking the reception map https://pskreporter.info/pskmap.html for myself on 30meters, I had reports as far as New York state (I am in southern California near Oceanside).

I really appreciate the support from the group! Without your feedback I had been thinking I had something wrong with my radio.

As an aside, using the NanoVNA to tune the MFJ-16010 is like doing safe cracking, body capacitance seems to play a factor and I have to turn the knobs, let go of the tuner, check the display etc. I just got done ordering a MFJ-9219 so I don't have to wrestle with the current setup lol. I also don't currently have a dummy load so with this unit I get a tuner/SWR meter/dummy load in a convenient package.

Thanks again for the help, currently playing with FT8 in the daytime, successfully!

Larry
K6IET


 

Hi Larry,

It's not necessarily the closeness of the antenna lead that's the problem.  Your symptoms point to common mode current coming back on the coax shield to actually be on the chassis of the radio.  This is sometimes called "mike bite" because an operator would get shocked when using a microphone due to RF currents coming all the way back to the mike.  You could keep the tuner inside, but you would want to add a 1:1 current choke unun on the coax cable between the tuner and the transceiver.  This should help a lot with the display problem.

73,


Mark


Larry Biggs
 

Thanks Mark, looking into your suggestion.

On Fri, Feb 26, 2021 at 1:20 PM Mark - N7EKU <n7eku@...> wrote:
Hi Larry,

It's not necessarily the closeness of the antenna lead that's the problem.  Your symptoms point to common mode current coming back on the coax shield to actually be on the chassis of the radio.  This is sometimes called "mike bite" because an operator would get shocked when using a microphone due to RF currents coming all the way back to the mike.  You could keep the tuner inside, but you would want to add a 1:1 current choke unun on the coax cable between the tuner and the transceiver.  This should help a lot with the display problem.

73,


Mark


Larry Biggs
 

Thanks all, I modified my patch cable and the tuner is back indoors. Working properly now. :)
image.png


On Fri, Feb 26, 2021, 8:00 PM Larry Biggs via groups.io <lbiggs=larrybiggs.mobi@groups.io> wrote:
Thanks Mark, looking into your suggestion.

On Fri, Feb 26, 2021 at 1:20 PM Mark - N7EKU <n7eku@...> wrote:
Hi Larry,

It's not necessarily the closeness of the antenna lead that's the problem.  Your symptoms point to common mode current coming back on the coax shield to actually be on the chassis of the radio.  This is sometimes called "mike bite" because an operator would get shocked when using a microphone due to RF currents coming all the way back to the mike.  You could keep the tuner inside, but you would want to add a 1:1 current choke unun on the coax cable between the tuner and the transceiver.  This should help a lot with the display problem.

73,


Mark