Comet SBB-14 Tri-Band Salvage

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KK4JUG

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#1
I have a Comet SBB-14 tri-band fold-over antenna that is broken and I want to know if it's salvageable. (It is sometimes still listed as an SB-14. I think they added the letter when they improved the fold-over feature.) It's used for 2m, 6m & .70m. It has two coils and when it arrived, it was broken into two pieces in the middle of the top coil. (The supplier replaced the antenna immediately and didn't want the old one back.)

I tried conductive glue to try to fix it but to no avail. There's probably no way to put it back in original condition short of replacing the coil and that's not practical.

The antenna has a UHF connector and is/was 43" long. The lower coil is 10 1/2" from the base and the coil is 4" long. The upper coil is 25 3/4" from the base and 11 1/2" from the lower coil. The upper coil size doesn't matter because it's gotta go. The longest the salvage antenna could be is 25 3/4".

Is this antenna salvageable to make it usable for either 2m or .70m or both or should I go ahead and toss it?
 
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#2
Maybe on Six

What I'm wondering is if you cut off the top coil, could you add some tubing and put it on Six?
You're saying the original antenna is shorter than a quarter wave on six. That leads me to believe the bottom coil is what brings the antenna in on six.

Like you said, the top coil is no longer in the picture. Cut it off. Get a piece of aluminum tubing with an ID that you can slide over the existing antenna and see if you can bring it in on Six. Looking at the antenna, I'm thinking what you had on top of the bottom coil was a 2/440 dual band antenna. And that's the part that's broke. Getting it on 2 and/or 440 may not happen.
 
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KK4JUG

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What I'm wondering is if you cut off the top coil, could you add some tubing and put it on Six?
You're saying the original antenna is shorter than a quarter wave on six. That leads me to believe the bottom coil is what brings the antenna in on six.

Like you said, the top coil is no longer in the picture. Cut it off. Get a piece of aluminum tubing with an ID that you can slide over the existing antenna and see if you can bring it in on Six. Looking at the antenna, I'm thinking what you had on top of the bottom coil was a 2/440 dual band antenna. And that's the part that's broke. Getting it on 2 and/or 440 may not happen.
To be perfectly honest, the 6m properties aren't that great because of ground plane problems. The replacement antenna was mounted on a roof rack cross bar about 3" above the roof of the car and, though it reached the 6m repeater, it's wasn't what it should be. If I remember correctly, the best SWR I could get was 2.9.

I do have a replacement antenna so I don't want to end up spending more in time and labor than the old one's worth.

What about just cutting it off below the upper coil, hooking it up to the radio then putting an SWR meter on it and work it down from there. A Dremel cutting wheel can do wonders with the length with little trouble. Plus, it's a fold-over so it will be easy to work on the end.
 

vagrant

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#4
An antenna analyzer is your friend, but the cost of one to sweep that one antenna is not really a good return on investment. Someone at a local radio club may have the appropriate analyzer and sweep it for you. Ensure it is mounted wherever you plan to use it when they check it.
 

KK4JUG

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An antenna analyzer is your friend, but the cost of one to sweep that one antenna is not really a good return on investment. Someone at a local radio club may have the appropriate analyzer and sweep it for you. Ensure it is mounted wherever you plan to use it when they check it.
I don't have one but we have one on our mobile command post. I retired several years ago but I still serve as communications officer on the "bus." The analyzer is an MFJ-269C. I haven't used it in a while but I'm sure it'll come back to me.
 
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#6
On second thought

I may have been wrong in my reply saying you couldn't use it on 2 and 440.
I suppose that, based on the picture, you could cut off the bottom coil and, if there's at least 19" left, make a quarter wave antenna for 2. Or whack it down to even more and make a quarter wave for 440.
 

KK4JUG

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#7
If I can't make it for at least 2 & 440, I'll chuck it or give it away. Every mobile I have is at least dual-band and a single-band antenna would not be practical. Sometime in the near future, I'll put the antenna analyzer on it and start hacking away. It'll probably take at least 3 or 4 hours but what the heck. It's not like I have a life. :)

If it works, it works. If not, sayonara.
 
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