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Discussion Starter · #1 ·
Rastus, please add this to the tech section.
Setting the VSWR:

Some facts and pointers:
As the frequency of operation increases the radio wave gets shorter so a 1/4 wave antenna at CB frequencies is nominally 108"
As you have noticed the are plenty of 2', 3', 4' and 5' "top loaded" fiberglass antennas on the market. The manufacturer simply winds or loads the top of the antenna with the magnet wire so you still have 108" of antenna it has just been shortened. Now for you fellow electrical engineers out there I know this is oversimplified but the readers here do not want a bunch of technocrap, man we have too much of it here just explaining the basics, lol.
So on to setting the VSWR or tuning the antenna.
1st and this does need to be mentioned once again, CUTTING THE COAX to tune VSWR is not acceptable, you only are fooling the wattmeter by giving it a false reading of the forward to reverse voltage it should be measuring.
Hook up the wattmeter to the antenna and radio and tune the CB to ch. 40 and take a reading then go to ch. 1 and take a reading. If the VSWR is higher on ch. 40 than on ch. 1 then the antenna is too long so loosen the tip and slide it in some, not much go SLOWLY. If you have the type of commercial antenna where you cut some off the bottom then do so at the rate of 1/4" at a time. Repeat the measurement process till you have the best match on both ch. 40 and ch. 1 If the VSWR was higher on ch 1 you will have to slide the tunable tip out.
So what if you have slid the tip out as far as is possible and the VSWR is still very high on ch. 1 and high but not as high on ch. 40? this shows that the antenna is still a little short so try using a spring which will lengthen the antenna and also give you extra flex.
If you have done all the above and VSWR is still way high then you need to see if you have shorted the connector , easy to do, make sure you trimmed the braid neatly no single strand toughing the center conductor, even the tiny single strand can short the coax. If this was not the problem then you need to check the entire run of coax for a nick or see if it has gotten against the exhaust pipe and melted? I have seen some instances of just plain bad coax from a manufacturer. My recommendation is always use Belden or Tram or Andrew heliax brand coax, they are very high quality.
Happy Trails

Mark
 

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spankn You forgot the ultimate cheat! a matcher :) I've been usin' 1 for years. of course I expect my 2 ways to do better than a mile or so. I run a 19LTD ( slightly adjusted) with a wilson 1000 and the matcher. the erp is basically 20w and with the whip style I ain't skeered of trees! The tin roof at the sonic is another story.
 

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Discussion Starter · #3 ·
yep

I fergeted a lot nowadays, lol
BTW, Wilson is another great antenna!!! And a good companion on a cast a way island I hear, lol
I know a lot of folks like the stainless steel whips for use on the trail but I just hate that clanging noise when they hit limbs. Which reminds me of a safety issue. If you are helping a buddy tune an antenna never touch it during TX you will get a nasty RF burn.
 

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thanks again man, when i get home looks like i got some tuning to do on my cb and antenna....now where can i get a wattmeter?
 

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Discussion Starter · #5 ·
wattmeter

Radio shack sold them at one time, mine are somewhat pricey commercial models that will do multiple bands. Make sure you get one that is good down to 26Mhz and you might find one on eBay looking under ham radio equipment.
 

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Discussion Starter · #7 ·
most likely

IMHO yes, because even though the actual spring itself is not doing the conducting of the signal, a braided wire inside the spring is and this braided wire is most likely gone if the outer spring is very rusty. Also if the spring is very rusty then it may snap off at a critical time.
 

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OldGoat said:
IMHO yes, because even though the actual spring itself is not doing the conducting of the signal, a braided wire inside the spring is and this braided wire is most likely gone if the outer spring is very rusty. Also if the spring is very rusty then it may snap off at a critical time.

mines still chrome with some surface rust ... but at k-rock for the first day my CB did not work so good (at first the little gauge on it said 0) but as the day(s) went on it got better at the end I could talk to camp from the other side of the ranch ...I just wondered if it was the rust inbetween the coils of the spring ???
 

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Discussion Starter · #9 ·
CB antenna

Flex the spring open and see if the center braid is in good shape, you could clip a test lead to the antenna rod and the other end to the base of the antenna and use on ohm meter while flexing the spring to see if you get anything other than 0 ohms if so the center conductor is bad.
Next thing to check would be to remove the coax from the radio and take a measurement with the ohm meter from the center conductor of the coax to the outer conductor and it should not show a short with the whip type antenna, if it does start looking down the coax fromn the connector to the antenna for maybe a cut into the coax or maybe a burned spot where it got against the exhaust?
Now, based on the fact that it did better as the day warmed up I would check all my connections even the power connections because if they were just barely making contact while it was cooler and they got a better "grip" as the sun came out it might explain the situation.
Mark
 
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