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SWR climbs as Radio warms up.

DavidZak

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I need some help troubleshooting an issue with SWR signal. Is it normal for my SWR to start out at 1.1 when I start my radio and the more I transmit it climbs up in the 2.4 range as it warms up? If not, what could be the issue?
 

prcguy

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It could be the radio is drifting in power and the SWR measurement takes into account the power level during setup. If you cal the SWR meter and increase the power afterwards the SWR will appear to increase.

What kind of antenna? I've seen a number of antennas that have a coil in base or in the whip that heats up with lots of power and the VSWR changes. This should never happen with a stock radio unless the coil is wound with #36 wire or smaller.



I have one in the radio and also one that is inline. Whether I run an amp or not the results are still the same.
 

DavidZak

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It could be the radio is drifting in power and the SWR measurement takes into account the power level during setup. If you cal the SWR meter and increase the power afterwards the SWR will appear to increase.

What kind of antenna? I've seen a number of antennas that have a coil in base or in the whip that heats up with lots of power and the VSWR changes. This should never happen with a stock radio unless the coil is wound with #36 wire or smaller.
It could be the radio is drifting in power and the SWR measurement takes into account the power level during setup. If you cal the SWR meter and increase the power afterwards the SWR will appear to increase.

What kind of antenna? I've seen a number of antennas that have a coil in base or in the whip that heats up with lots of power and the VSWR changes. This should never happen with a stock radio unless the coil is wound with #36 wire or smaller.
Antron 99.
 

prcguy

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I think the only way to get to the bottom of this is to use a power/SWR meter you can trust and with a dummy load. Or use an antenna analyzer with its built in RF source. I would first test the radio by transmitting for a minute into a load to see if the power is stable. Then repeat the SWR measurement on the antenna with the known good meter and also double check power over time into the antenna.

I think you will find either the radio is changing power, or the antenna SWR really is changing (unlikely) or your current SWR meter(s) have a problem. It could also be your test method and you could be making a mistake calibrating the SWR meter or doing something we can't see to comment on.


Rg8 or rg213 is correct. The large stuff.
 

DavidZak

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Bunnlevel NC
I think the only way to get to the bottom of this is to use a power/SWR meter you can trust and with a dummy load. Or use an antenna analyzer with its built in RF source. I would first test the radio by transmitting for a minute into a load to see if the power is stable. Then repeat the SWR measurement on the antenna with the known good meter and also double check power over time into the antenna.

I think you will find either the radio is changing power, or the antenna SWR really is changing (unlikely) or your current SWR meter(s) have a problem. It could also be your test method and you could be making a mistake calibrating the SWR meter or doing something we can't see to comment on.
Would using another radio in the same set-up be a good indicator for troubleshooting? If the swr does not go higher after warm up that should tell me the problem is in the radio?
 

prcguy

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Yes, that would eliminate one possible thing that could be causing a problem. If another radio gives stable readings that would point at your first radio as a suspect.

Would using another radio in the same set-up be a good indicator for troubleshooting? If the swr does not go higher after warm up that should tell me the problem is in the radio?
 

prcguy

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A solder connection would have to be right on the edge of failure to show up when transmitting with just a few watts. If you don't have other test equipment then swapping the radio, jumper cables, etc, might find the problem by process of elimination.

I've used different many pl-259s. But I think you're on to something. Maybe cold solder joint SO-239 (socket); ?
 

DavidZak

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Messages
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Location
Bunnlevel NC
I will be swapping out the radio tonight calibrating the swr meters and giving it a good work out. If the swr doesn't climb up I think I'll have to take a closer look at the 2000 gtl. I'll keep you all informed of my results. Thanks for all the help!
 

ThomasB3131

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Feb 23, 2018
Messages
140
It could also be water in the coax. I've had that happen on a 2 meter antenna system. At first glance SWR would be fine, then as you started to transmit little by little the SWR would get worse and worse.
 
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