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Penrider
Intermediate Member
Username: Penrider
Post Number: 197
Registered: 1-2007
| | Posted on Tuesday, August 07, 2007 - 1:18 am: | 
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I just aquired a used Realistic aluminum 5/8wave groundplane base antenna. Swr is 3:1!! All coax is perfect. I took the base of the antenna apart and replaced the SO-239 with a new one (the old one was pretty nasty). I STILL have a reading from center to ground, but All connections are clean and read clear.
Inside the base is what appears to be some type of wound coil. 4 turns of #20 red-coated copper wire around a 1 1/4" core. The path APPEARS to be as follows...
2 strands of copper from the center of the so-239
4 turns around the core (or 2 each??).
1 strand to feedpoint of antenna tube, 1 strand to ground of so-239.
The coil had a layer of electrical tape around it, so I have no idea if certain strands were supposed to be isolated or not.
The antenna mount/groundplane radial mount is isolated from the antenna vertical by thick plastic bushings (in good shape, not rotten, no continuity between them).
Is that coil some kind of impedance match??
Should I be getting continuity between center and ground??
Should I be getting the same exact reading from center to ground as I do from center to center and ground to ground??
I haven't taken apart or modified that coil and all that Appeared to be wrong was a bad so-239 and some dirty connections. The coil was clean and looked like it hadn't been harmed or messed with.
Any help would be appreciated!!! I don't want to completely reassemble the antenna until I know I have it right.
Sean
CEF867
Two tin cans and a string, it's still a contact...BTW, I need my can back when we're done!
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Marconi
Advanced Member
Username: Marconi
Post Number: 743
Registered: 11-2001
| | Posted on Tuesday, August 07, 2007 - 9:41 am: |
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If the SO-239 was bad, how did you check the SWR? How long is the vertical element and is there a wire static device at the top? I think HyGain made one about 20' long and the Super Penatrator was about 23' long. I'm just guessing, but I think the one you have should be a bit over 23' long. Again I am just guessing, but that length is probably from the feed point to the tip.
I think you have an old CLR II and if so, then your OHM meter reading, center to shield, is probably correct. |
Penrider
Intermediate Member
Username: Penrider
Post Number: 198
Registered: 1-2007
| | Posted on Tuesday, August 07, 2007 - 7:35 pm: |
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Since my coax is good, all antenna assembly connections are clean/shiny/tight, tower and antenna mount are well grounded, and the swr is too high to be a tuning issue with a non-tuneable antenna, the next logical place to check is the so-239. It was corroded inside and the center plastic isolator was cracked and rotten, so I replaced it. They are too cheap to bother with trying to clean it/shine it up inside. I don't know yet if that was the issue or not. I have not checked the swr again, because I don't want to reassemble the bottom section until I know if all is well. And, yes it has (3) 6" static radials at the tip.
Sean
CEF867
Two tin cans and a string, it's still a contact...BTW, I need my can back when we're done!
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Marconi
Advanced Member
Username: Marconi
Post Number: 744
Registered: 11-2001
| | Posted on Tuesday, August 07, 2007 - 10:50 pm: |
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I'm like you Penrider, what else could it be. The coil is giving you the right OHM's response. Bolt that bugger together and give it a try. However, I would re-tape the coil and re-check the continuity after assembly.
Good luck! |
Penrider
Intermediate Member
Username: Penrider
Post Number: 201
Registered: 1-2007
| | Posted on Wednesday, August 08, 2007 - 7:32 pm: |
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already reassembled nice and neat, and I used a piece of heat shrink on the coil instead of tape. Don't ask where I got heat shrink that big, lol. Am putting it up and testing it tonight. Yeah, Curt I thought it looked familiar.
Sean
CEF867
Two tin cans and a string, it's still a contact...BTW, I need my can back when we're done!
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Penrider
Intermediate Member
Username: Penrider
Post Number: 202
Registered: 1-2007
| | Posted on Wednesday, August 08, 2007 - 10:22 pm: |
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I think maybe I fixed it!!
1.2:1 on ch1, 1.3:1 on ch40!!
I think I'll leave it alone.
Receive blows the doors off my a-99, and since I don't have a local to compare to I can only go by the 5 AM contacts I just made on ch13. I normally have a lot of trouble getting out on the am side.
Sean
CEF867
Two tin cans and a string, it's still a contact...BTW, I need my can back when we're done!
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