SWR question

[edfiero]

I fired up my radio for the first time in a year or two and I noticed that on both the radio's built in power meter, as well as on my external meter, my power output is only about half of what it should be.

I then checked the SWR and noticed it to be way up from what I remember it being back in the day. Today its reading 2:9:1 across all 40 channels, while I recall it being about 1:4:1 previously.

(I tried removing the external meter and short coax extension and plugged the big coax directly into the radio. That didn't change anything. Output only about half of what's expected. Tried another radio too..same thing, only about half output. So I attribute this to the high SWR.

The antenna is a Maco V5/8 Vertical. Its been up about 20 years, with no problems. What causes the SWR to go out of adjustment like this on a base antenna??

 

[Tallman]

Lightning, moisture, heat, cold. If your coax is twenty years old it's time to change it.

 

[Robb]

Don't forget tho check out the coax too.
If it is cheap coax; then it may be failing.

 

[222DBFL]

Coax, antenna connection point, antenna itself, connectors, age of coax and what type used, as stated. Antenna may have broken parts. Many things will and can cause this. Most of the time it's the coax and the type used. Cheap coax most likely hasn't any UV protection, or could be an animal got to it. A lot of things can go wrong after 20yrs. Time to take antenna and coax all down and inspect all of it and like said, replace it if necessary, which will most likely be the case. And don't buy cheap coax. Get some quality stuff made by Belden, Andrew, Commscope, Shireen, Davis RF, Eupen, Times Microwave, 123 wireless, huber Suhner, or any reputable coax company. And also good connectors made by the same companies listed as well as amphenol. Hope this helps. Again l, make sure to also check the antenna itself as well. After 20 years there it's hard to tell what you will find. Too many variables. JMHO.

 

[edfiero]

Thanks for the ideas. Last evening we got some rain, and I noticed that the SWR went DOWN during the rain. Now this morning, its back up again. Does this give us any additional clues to where the problem might be? Coax the most likely culprit?? No visible damage to the antenna itself from the ground.

 

[Tallman]

Thanks for the ideas. Last evening we got some rain, and I noticed that the SWR went DOWN during the rain. Now this morning, its back up again. Does this give us any additional clues to where the problem might be? Coax the most likely culprit?? .

Lightning, moisture, heat, cold. If your coax is twenty years old it's time to change it.

Replace your coax and maybe the antenna.

 

[222DBFL]

Yep. Water is a great conductor of electricity!!!

 

[fourstringburn]

Yep. Water is a great conductor of electricity!!!

Not to mention adding capacitance detuning or possibly tuning the antenna some.

 

[edfiero]

To close the loop on this.... I bought 50ft of new LMR-400 to fix the SWR problem, only to find, with the new Coax the SWR was exactly the same as it was with the 22 year old stuff.

The problem was that one of that clamps that connected the coax feed to the "Hoop" Ring at the bottom of the antenna had rusted. Replaced this clamp with a new aluminum clamp and SWR is back to 1:3:1

While most of the hardware with this antenna was Alumium and Stainless Steel, it wasn't ALL rust free. A 25 cent clamp was the source of the issue.

 

[Beetle]

That should be 1.3:1. Glad you got it fixed. Rusty metal hardware in an antenna's near field can really cause problems. Google "rusty bolt effect".