Quantar Ham Repeater & Cold Temps.

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KG4LHQ
Posts: 642
Joined: Wed Sep 29, 2004 1:50 am

Quantar Ham Repeater & Cold Temps.

Post by KG4LHQ »

Hey guys,

My UHF Ham Repeater is a Quantar 25W Repeater going to a 10 IN 200W out Henry Amplifier then feeding to a Celwave 526 series duplexer. The issue that I am having is the repeater is not in a controlled environment as it is in a metal rack cabinet in the middle of a field under a water tower that is 175 feet up. Appears during these winter months after cool/cold nights trying to talk on the repeater is almost impossible as it does nothing but short key ups for 10-15 seconds when it hears a signal like severe desense or someone can be talking for 15-30 seconds and be completely unreadable then out of no where their perfectly clear and readable. It sounds like the duplexers are cold causing desense then once they get warmed up with RF there seems to be no issue if that makes any sense. I have checked the duplexers to make sure their not off on tuning and they seem to be spot on. Again, once its been a couple minutes and we have tried to talk it instantly clears up and all works like it should.

How can I fix?

I know Spring and warmer temperatures are coming but I would really like to not have this problem and get it fixed.

Also since Winter will come around and colder temps will come back what would be the best way to be able to heat the cabinet to warmer temps so I might not have this problem again.

Help would be greatly appreciated.
gopher
Posts: 169
Joined: Fri Dec 22, 2006 11:38 am

Re: Quantar Ham Repeater & Cold Temps.

Post by gopher »

i have a few outdoor metal equipment enclosures loaded with computers. we keep them from freezing by installing ceramic heater like these. they screw in to a normal ceramic light bulb socket
http://www.tempco.com/Catalog/Section%2 ... 20Bulb.pdf
its on a themostat so it shuts off when its up to temp.
k2hz
Posts: 531
Joined: Tue Mar 01, 2005 7:27 am

Re: Quantar Ham Repeater & Cold Temps.

Post by k2hz »

Here is a remote possibility but I have seen it happen a few times -

The cold causes the center conductor of the coax to contract enough to pull the center pin of a type N connector back to the point that the connection is intermittent. Once things warm up - trouble goes away. In the cases involving a coax run up the tower there have been aggravating issues with poorly dressed coax bends and/or poor support. Workmanship on the connector installation was also questionable.

If that is not the case, I would suspect a cracked solder connection in a duplexer or some other system component that opens up when it get cold.
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Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Quantar Ham Repeater & Cold Temps.

Post by Bill_G »

gopher wrote:i have a few outdoor metal equipment enclosures loaded with computers. we keep them from freezing by installing ceramic heater like these. they screw in to a normal ceramic light bulb socket
http://www.tempco.com/Catalog/Section%2 ... 20Bulb.pdf
its on a themostat so it shuts off when its up to temp.
Thanks for the link!
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Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Quantar Ham Repeater & Cold Temps.

Post by Bill_G »

KG4LHQ wrote:Hey guys,

My UHF Ham Repeater is a Quantar 25W Repeater going to a 10 IN 200W out Henry Amplifier then feeding to a Celwave 526 series duplexer. The issue that I am having is the repeater is not in a controlled environment as it is in a metal rack cabinet in the middle of a field under a water tower that is 175 feet up. Appears during these winter months after cool/cold nights trying to talk on the repeater is almost impossible as it does nothing but short key ups for 10-15 seconds when it hears a signal like severe desense or someone can be talking for 15-30 seconds and be completely unreadable then out of no where their perfectly clear and readable. It sounds like the duplexers are cold causing desense then once they get warmed up with RF there seems to be no issue if that makes any sense. I have checked the duplexers to make sure their not off on tuning and they seem to be spot on. Again, once its been a couple minutes and we have tried to talk it instantly clears up and all works like it should.

How can I fix?

I know Spring and warmer temperatures are coming but I would really like to not have this problem and get it fixed.

Also since Winter will come around and colder temps will come back what would be the best way to be able to heat the cabinet to warmer temps so I might not have this problem again.

Help would be greatly appreciated.
You are going to have to be on site during a failure, and try to troubleshoot it through a process of elimination. Come with a BIG dummy load and a wattmeter to handle your RFPA.

Start at the antenna port. Put the dummy load on, and key up. If problem goes away, put the antenna back on to verify it returns. If so, it's your line or antenna.

If problem doesn't go away, then put the dummy load on the output of the rfpa. If problem goes away, put the rfpa back on the duplexer to verify it returns. If so, it's your duplexer.

If problem doesn't go away, then put the dummy load on the output of the Quantar. If the problem goes away, put the Quantar back on the rfpa to verify it returns. If so, it's your rfpa.

If the problem doesn't go away, it's your Quantar.

Hopefully you can accomplish this before it fixes itself.
KG4LHQ
Posts: 642
Joined: Wed Sep 29, 2004 1:50 am

Re: Quantar Ham Repeater & Cold Temps.

Post by KG4LHQ »

I honestly do not think the quantar is the problem because the Kenwood 851 did the same exact thing during cold weather, get alittle RF and all was completely fine. I am hoping it is not a coax issue going to the top of the water tower as there is no telling the cost of that replacement.

Being on the site when the issue happens is nearly impossible as it is random and usually lasts only a few seconds or a couple transmissions before its perfectly clear.
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Bill_G
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: Quantar Ham Repeater & Cold Temps.

Post by Bill_G »

Well, at least bypass your monster amp to see if the problem changes.
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