A True SWR Mystery

[Riverman]

My SWR has been 1.1 for as long as I've had this antenna up. (Measured with amp on).
Three days ago this began happening:

In the mornings when I first turn the equipment on, SWR is 1.5.
As the day goes on, it slowly lowers until early evening when it is back to 1.1.
Equipment is a Royce 619 and KL 203. They are not on all day. I only turn them on when using them. Maybe 3-4 times a day.

Any ideas?

 

[144inBama]

Possibly moisture at the antenna connection and as you use it/sits in the sun, it cooks out and it's back to normal.

 

[Riverman]

Possibly moisture at the antenna connection and as you use it/sits in the sun, it cooks out and it's back to normal.

The connection was weatherproofed with coax seal when installed. It is still sealed.

Thought my coax might be the problem. It has a few scraped places on it (came from the seller that way). However, I just inspected it and find nowhere where the shield is exposed.

Weather is is lows in the 40s and highs in the 60s. No precipitation. There is some dew in the mornings.

 

[144inBama]

How long has it been up? Weather proofing does break down over time. It only takes a pinhole size opening for moisture to wick its way in. The coax moving could break the seal over time. Cold weather can make it more stiff and if the coax moves, it can woller it out enough for a drop to get in. Then once it's in it stays in, it just evaporates, then when it cools off again, it condenses causing them same issue. Just something to look at. As far as the scraped places, the same applies, if water can enter the jacket, it can cause the same issue.

 

[Riverman]

How long has it been up? Weather proofing does break down over time. It only takes a pinhole size opening for moisture to wick its way in. The coax moving could break the seal over time. Cold weather can make it more stiff and if the coax moves, it can woller it out enough for a drop to get in. Then once it's in it stays in, it just evaporates, then when it cools off again, it condenses causing them same issue. Just something to look at. As far as the scraped places, the same applies, if water can enter the jacket, it can cause the same issue.

10-4.
Failed to mention when I inspected it, I replaced the coax seal with a fresh wrap.

 

[sp5it]

How it's behaving on dummy load?

 

[Riverman]

How it's behaving on dummy load?

Don't have one, Mike.

Wish I did.

Or are you referring to my antenna?

 

[sp5it]

Not your antenna
With dummy load is easy to rule out/find faulty component.
Now all we can do is guessing.
Mike

 

[DXman]

The 1st thing I would do would be to remove the amp. when the swr is high, then recheck. Then you will know if it's in the feed line, antenna or amp.
It might also be in the radio..........

 

[hotrod]

sounds like ya had mositure or water in ya coax or antenna

 

[Shadetree Mechanic]

Could be a bad shield connection on a PL plug. I tore my shack apart one time looking for a bad connection and ended up finding a 2 foot jumper that was fine at 4 watts, but the swr would start climbing as the power was rolled up. Try swapping out or removing jumpers, bypass meters and coax switches. Hook the main coax straight up to the rig if possible. Check the easy stuff first, and use the process of elimination to figure out what is what.

 

[Rwb]

wrap the pl259 with that rubber tape you buy at hardware stores,start the wrap from bottom.then buy the best grade of 3m electrical tape you can find.wrap it again from bottom to top. never use less than 3m tape. learned that years ago. i dont like to rinse wipe rinse wipe. do it rite first time

 

[144inBama]

wrap the pl259 with that rubber tape you buy at hardware stores,start the wrap from bottom.then buy the best grade of 3m electrical tape you can find.wrap it again from bottom to top. never use less than 3m tape. learned that years ago. i dont like to rinse wipe rinse wipe. do it rite first time

3M 130c (rubber tape) finished with 3M 33+ (electrical tape) and you are 100% correct on only using 3M. It cost more but it's the only tape that doesn't just fall off in cold weather or break down in a year or two.
1st: back wrap the 33+ (sticky side out)
2nd: wrap it with the 130c (when using the 130c, you need to streeeetch it as you wrap it).
3rd: Wrap it again with the 33+ (sticky side down).
This keeps the sticky goo off of the connector and coax so you're not fighting it if you need to remove it later.
This is how we make motor splices and they're 100% water and moisture tight.

 

[Eldorado828]

Don't have one, Mike.

Wish I did.

Or are you referring to my antenna?

Well did you come to a conclusion on what the cause is? You got me wondering.

I myself was thinking expand and contract with a connector. Some of those pl259 or so239 center connectors available today aren't as snug as they should be.
That's just my hypothesis.

 

[Riverman]

Well did you come to a conclusion on what the cause is? You got me wondering.

I myself was thinking expand and contract with a connector. Some of those pl259 or so239 center connectors available today aren't as snug as they should be.
That's just my hypothesis.

Sorry I haven’t updated, Ed. Too dang forgetful.

I replaced the PL259 that connects to the antenna and that did it. Problem Solved!

My thanks to you and all who responded.