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RF in 12v Supply

Mark M
 

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 amateurradiokits.in. 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
Gordon Gibby
 

Sprinkle 0.1 ufd capacitors from supply lines to ground. They¡¯re cheap, and they¡¯re great!

On Jun 29, 2018, at 13:17, Mark M <junquemaile@...> 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 amateurradiokits.in. 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
 

Try RG58 for the supply.


On Fri, Jun 29, 2018 at 7:17 PM, Mark M <junquemaile@...> 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
 

That's apart from Gordon's suggestion

On Fri, Jun 29, 2018 at 7:20 PM, Lawrence Galea <9h1avlaw@...> wrote:
Try RG58 for the supply.


On Fri, Jun 29, 2018 at 7:17 PM, Mark M <junquemaile@...> 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
Gordon Gibby
 

¿ªÔÆÌåÓý

Make sure the ground is a healthy healthy healthy connection as well, either a chassis or some pretty thick wires and lots of them, arrange so they all connect at some point called single point ground. ?


On Jun 29, 2018, at 13:21, Lawrence Galea <9h1avlaw@...> wrote:

That's apart from Gordon's suggestion

On Fri, Jun 29, 2018 at 7:20 PM, Lawrence Galea <9h1avlaw@...> wrote:
Try RG58 for the supply.


On Fri, Jun 29, 2018 at 7:17 PM, Mark M <junquemaile@...> 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
 

0.1 mfd across the power leads at the power supply and again at the uBITX power
connector.? It could be that RF is modulating the 12V power lead and that causing
RF in the power supply regulator.? Bypassing the DC power at the power supply
should stop that if it is the problem.?

Arv
_._


On Fri, Jun 29, 2018 at 11:20 AM Lawrence Galea <9h1avlaw@...> wrote:
Try RG58 for the supply.


On Fri, Jun 29, 2018 at 7:17 PM, Mark M <junquemaile@...> 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
 

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 amateurradiokits.in. 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
 

This sure sounds like a good arrangement.

tim ab0wr

On Fri, 29 Jun 2018 14:41:50 -0400
"Bill Cromwell" <wrcromwell@...> wrote:

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 amateurradiokits.in. 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
 

I've build SS amps for radios up to 350W and never had RF get into a power supply.

I could understand if the antenna was poor and you had high shield currents but?
a dummy load?? No.

I'd suspect the wiring of the antenna connection from the board to the load
has the ground and RF hot reversed.? If you did that you would have RF all
over the place and possible ill effects.

I have two Astrons and they are not particularly RF sensitive.

Allison

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