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RT-100 has a Dead Short

 

Hello All - I have an RT/RC-100 combo that has worked very well for about 3 months feeding it with an ICOM 7600 barefoot at 100 watts. Now the RC-100 status light blinks. In checking, I see a dead short on the coax going to the RC-100. There hasn't been any tower that might have damaged the coax, so I strongly suspect that the RT-100 has the short internally. Has anyone run across this before? Thanks.
Paul WB0GXD
 

Many (most?) antennas measure like a short if you measure them with a DC voltmeter.? That is to be expected.
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You must use an SWR meter or VNA or similar instrument, and do the measurement on-frequency.? Anything else is meaningless.
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Andy
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also, if you have a dummy load, the rc-100 can be checked with that and the swr meter

Dave Garber
VE3WEJ / VE3IE


On Sat, Jul 20, 2024 at 1:37?AM Andy via <ai.egrps=[email protected]> wrote:
Many (most?) antennas measure like a short if you measure them with a DC voltmeter.? That is to be expected.
?
You must use an SWR meter or VNA or similar instrument, and do the measurement on-frequency.? Anything else is meaningless.
?
Andy
?
 

I looked at both connectors (with no cables attached)? on my operating RT-100. Either polarity of the leads show an open circuits. There was a time-constant variation of resistance? on the connector labeled "radio", with a readings of around 1-3 megohms.
Mike N3PM
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Thanks everyone for the responses. I should have mentioned?that the RT-100 is tower-mounted, so checking it at the unit is problematic?for me.?
Mike Z.'s response is what I was expecting to?see toward the RT-100 from the radio end. It seems to me that if you're feeding DC voltage down a coax to supply power to a device that you wouldn't want to see a dead short. The time-constant variation makes sense, as the DC blocking / RF pass capacitor is being charged by the voltage?from the ohmmeter and the only other DC path would be the circuitry inside the RT-100 that might have an indication on the ohmmeter.
It sounds like my RT-100 has a problem. I'll have to arrange with my buddy to come climb my tower to get it resolved.
Thanks again for the responses everyone.
-Paul WB0GXD

On Sat, Jul 20, 2024 at 11:11?AM mike z via <bb1300=[email protected]> wrote:
I looked at both connectors (with no cables attached)? on my operating RT-100. Either polarity of the leads show an open circuits. There was a time-constant variation of resistance? on the connector labeled "radio", with a readings of around 1-3 megohms.
Mike N3PM
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I hope it's in the cable or connectors Paul.
Mike? N3PM
 

Actually, LDG is pretty good about service and removing the unit is the easiest task. If they have to fix or replace the cables or connecors on the tower, that will be a whole lot like real work.

So, *I* hope it is the tuner, as that will be the easiest to fix.

Good luck in any case.



On Sat, Jul 20, 2024 at 15:18 mike z via <bb1300=[email protected]> wrote:
I hope it's in the cable or connectors Paul.
Mike? N3PM
 

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Test the impedance with the test leads connected both ways.? An electrolytic capacitor or reverse polarity diode can look like a direct short.

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Al K5TAN

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From: [email protected] <[email protected]> On Behalf Of Paul WB0GXD
Sent: Saturday, July 20, 2024 2:02 PM
To: [email protected]
Subject: Re: [ldgelectronics] RT-100 has a Dead Short

?

Thanks everyone for the responses. I should have mentioned?that the RT-100 is tower-mounted, so checking it at the unit is problematic?for me.?

Mike Z.'s response is what I was expecting to?see toward the RT-100 from the radio end. It seems to me that if you're feeding DC voltage down a coax to supply power to a device that you wouldn't want to see a dead short. The time-constant variation makes sense, as the DC blocking / RF pass capacitor is being charged by the voltage?from the ohmmeter and the only other DC path would be the circuitry inside the RT-100 that might have an indication on the ohmmeter.

It sounds like my RT-100 has a problem. I'll have to arrange with my buddy to come climb my tower to get it resolved.

Thanks again for the responses everyone.

-Paul WB0GXD

?

On Sat, Jul 20, 2024 at 11:11?AM mike z via <bb1300=[email protected]> wrote:

I looked at both connectors (with no cables attached)? on my operating RT-100. Either polarity of the leads show an open circuits. There was a time-constant variation of resistance? on the connector labeled "radio", with a readings of around 1-3 megohms.

Mike N3PM

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I did.
 

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I did too¡­¡­¡­? maybe¡­¡­¡­.??? not sure what it was since so much of the message was cut¡­¡­¡­¡­..

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From: [email protected] <[email protected]> On Behalf Of mike z via groups.io
Sent: Saturday, July 20, 2024 17:28 PM
To: [email protected]
Subject: Re: [ldgelectronics] RT-100 has a Dead Short

?

I did.

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