Re: RF in 12v Supply

Bill Cromwell

Hi Mark,

I laid out and folded a case of steel for my ubitx. Looking from the front, my antenna connector is at the far right rear corner and the internal connector wire is less than two inches long to reach from the board with just a little slack. The DC power connector is over at the far left back. The volume control is way over on the lower right corner of the front panel along with the on-off switch. I routed the power wires under the ubitx board to take advantage of the mostly ground plane board to help shield it from RF at the finals, output filters, and antenna connector. The power line runs much closer to the front of the radio until it gets to the left side and then back. It only comes out from under the circuit board *AT* the back corner. There is no problem with RF. I hope this is helpful to you and others when they layout and assemble theirs.

On 06/29/2018 01:17 PM, Mark M wrote:
The issue discussed in the 'RFI from uBitx TX after AGC and other mods
installed' thread appears to be caused by RF getting into the 12v supply
and from there into the 5v supply that feeds the AGC board (the
ND6T/K5BCQ kit). At least that appears to be the issue on mine. I
thought I'd start another thread to talk about that.

I have the ubitx in a case from The power comes in
thru a plug in the rear panel at the right of the panel (looking at it
from the front), thru a fuse and then thru three wires twisted together
along the rear panel to the connector on the board at the far left.
There's also a polarity protect diode across the supply. The power
connector is right next to the antenna connector and the supply wires
run past the final transistors and .

I'm running the ubitx on 13.8v from an Astron 20A power supply, The
testing was done feeding a Heathkit Cantenna dummy load.

So, any suggestions on how to fix this would be appreciated. Don
mentioned heavier supply wires and capacitor at the input. I thought I'd
try re-routing the supply wires inside case to get them away from the RF
section. Moving the power connector to the other end of the rear panel
would make the run much shorter. Other than that, I don't know. RF
hardware is not my forte (I'm mostly a software guy).

Thanks.... Mark AA7TA
bark less - wag more

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