Hello all
I have read many posts but have not been able to find a answer to a problem i am having. I just fabricated a CB antenna mount out of aluminum. I installed the mount right next to the third light on my F350 crew cab. I know this is not as good as mounting in in the center of the roof but i believe this is a good location. The Cb I am using is a Radio Shack TRC 447. I am waiting to buy a better cb so I will use this one for now. anyway I have installed a spring in between the antenna and the mount. I had used a couple of wrenches to tighten the coax connector to the spring and then i tightened the antenna in the same manner. I have a grommet in between the spring and the mount so as to separate the ground. the cb has a built in SWR (i know its not the best but i am waiting for my friend to bring his by) I read the instruction on the cb radio i have on how to calibrate the swr and after i did my initial check i had a SWR above 4 moved the grommet to in between the spring and antenna and checked it again still above 4 I thought for sure i was having a grounding issue so i installed a ground wire from the mount bolt to the truck itself not only did i do that but i sanded off the paint behind the mount.... still above 4 I took the spring off and used only the antenna to the coax adapter still above 4. During all this at one time i must have not re tightened the mount and when i checked the SWR I was at about 2 on both channels. So the spring is on and the antenna is mounted to the spring i have the grommet between the mount and the spring i only hand tightened the spring down but it seems that if i do any off road driving this might loosen up too much. So back to the original question How tight should the antenna, the spring be ?
how tight of a conection
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mikegolden
- Mud-Duck Sr.
- Posts: 6
- Joined: July 23rd, 2010, 10:56 pm
I forgot to mention i have a wilson silver load FGT antenna and i have tried using the wire that comes with the antenna when everything was real tight but still did not work. I understand the concept of adjusting the tip but really this was only meant to see where i was with the stock SWR meter i will fine tune the antenna when i get my friends SWR meter but i am afraid that the spring is not tight enough so i am not sure if any of you gurus can see something that i have done wrong. Thanks
Mike G
Mike G
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231
Hi Mike,
Well, first of all there should be a stud assembly as part of the whole thing, too. You haven't mentioned a word about that. If you are using a stud assembly that has only a single insulator (grommet as you called it) it should be placed on the top to insulate the antenna from ground. The bottom portion of the stud assembly should be touching the mount. That is, if you have it as I'm picturing it.
To answer your question, I use flat and/or lock washers when snugging up. That's all you want, is to snug them up rechecking maybe in a day or so to make sure they are still snug, then maybe a week later, etc. It just depends on the installation, the abuse they might see, etc. as to how needy they might be. I know on my offroad rig it flops around alot and snug was fine for it.
Welcome to the forum and good luck on the system.
Well, first of all there should be a stud assembly as part of the whole thing, too. You haven't mentioned a word about that. If you are using a stud assembly that has only a single insulator (grommet as you called it) it should be placed on the top to insulate the antenna from ground. The bottom portion of the stud assembly should be touching the mount. That is, if you have it as I'm picturing it.
To answer your question, I use flat and/or lock washers when snugging up. That's all you want, is to snug them up rechecking maybe in a day or so to make sure they are still snug, then maybe a week later, etc. It just depends on the installation, the abuse they might see, etc. as to how needy they might be. I know on my offroad rig it flops around alot and snug was fine for it.
Welcome to the forum and good luck on the system.
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mikegolden
- Mud-Duck Sr.
- Posts: 6
- Joined: July 23rd, 2010, 10:56 pm
Thank you for the reply
LOL ok so now i know what it is called. the Coax adapter is what i was calling the stud assembly. So if i am correct in my assumption from your post i can screw the spring directly to the stud with a lockwasher then use the insulator (grommet) between the spring and the antenna and just check the connection every now and then to make sure its not too loose. Thanks again.
Mike G
LOL ok so now i know what it is called. the Coax adapter is what i was calling the stud assembly. So if i am correct in my assumption from your post i can screw the spring directly to the stud with a lockwasher then use the insulator (grommet) between the spring and the antenna and just check the connection every now and then to make sure its not too loose. Thanks again.
Mike G
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'Doc
I'm afraid I don't understand what you're explaining. Any spring added to an antenna that I've ever seen has become part of the radiating portion of that antenna. So, there need be no insulator between the spring and antenna whip. The spring usually threaded into a base of some sort, probably containing a load. any insulator would be at the bottom of that load, not between it and the spring. Or instead of a load, there's just a stud mount, insulated at the bottom, directly connected to the spring and whip. So what am I missing?
As far as how tight the spring should be tightened? Basically, tight enough so that it won't come loose with normal vibration/usage. Stop before stripping any threads?
- 'Doc
As far as how tight the spring should be tightened? Basically, tight enough so that it won't come loose with normal vibration/usage. Stop before stripping any threads?
- 'Doc
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231
Not really. Working from the PL-259 coax connector:mikegolden wrote:Thank you for the reply
LOL ok so now i know what it is called. the Coax adapter is what i was calling the stud assembly. So if i am correct in my assumption from your post i can screw the spring directly to the stud with a lockwasher then use the insulator (grommet) between the spring and the antenna and just check the connection every now and then to make sure its not too loose. Thanks again.
Mike G
SO-239 coax receiver (bottom of the stud assembly and mount) --> mount -->//Top of mount--> Insulator --> Spring --> Antenna. The bottom of the stud assembly grounds to the bottom of the mount. The top portion of the stud assembly is used with the insulator to insulate the antenna and spring from ground. Once you add the spring, it effectively becomes part of the antenna itself and lengthens it. Inside most springs is a braid of copper wire.
That said, the antenna itself is only half of the antenna system, your vehicle is the other half. The coax has two parts, the center lead and the shield. The shielding is connected to the coupling on the PL-259 coax connector which goes to ground (your vehicle). The center conductor goes to the antenna which is insulated. So the two parts work together to make one whole antenna system.
Hope that helps and good luck.
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mikegolden
- Mud-Duck Sr.
- Posts: 6
- Joined: July 23rd, 2010, 10:56 pm
DOH!
Now i get it. I will simply add the lock washer today and keep everything else the same. And no I wont tighten it until i strip threads LOL. I will post pics of the setup just because. Thanks
Mike G
Now i get it. I will simply add the lock washer today and keep everything else the same. And no I wont tighten it until i strip threads LOL. I will post pics of the setup just because. Thanks
Mike G
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mikegolden
- Mud-Duck Sr.
- Posts: 6
- Joined: July 23rd, 2010, 10:56 pm
Well I am back. So I did not tighten the antenna down very much and used the SWR meter that came with the CB and bot my SWR to read 1:5 on channel 1 and about the same on channel 40 after i adjusted the tip. everything was working great I dont live to far from HWY 58 and could pick up the truckers going by my kids loved it. The next day while cruising down to work on HWY 58 I was doing about 80 and decided to check my CB i could barley hear it. I suspected a change in my SWR so i pulled over to check it and as soon as i was doing about 10mph I could hear traffic on the CB so I got back on the HWY and as soon as I got above about 15mph i could no longer pick up traffic. I put the selector to SWR cal and adjusted the dial to calibrate it then switched it to test and my SWR was above 4 I pulled over and continued to Calibrate and adjust the SWR meter as i slowed down I could easily see that the slower i went the better my SWR When stopped it is great but anything over 20mph and its too high. What am i missing. I am going to replace the insulator and the Coax cable this weekend but before I do I thought I should run it by you experts first. Thanks
Mike G
Mike G
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231
Yea, I kinda' think I understand what you are thinking might of happened. And you are right. If the insulator has been over tightened even once, they can sometimes distort and allow the center stud to shift (if only a little). It doesn't take but a fraction of an inch for that to short out either. So I think that's a reasonable place to start. They are cheap enough to replace, might as well get a couple if you can.
If that doesn't solve the problem, while you have it all apart build a jumper wire for across the spring. It's not uncommon for some springs to fail. Most have a braid inside to minimize it's length...and sometimes they fail from bad solder or connection point. A #10 or #12 (or bigger if you have it) jumper wire will fix this (it's only about 4"-6" or so and you'll need to probably re-tune a little). If all of this fails to solve the problem, it's time to start look at each component with an ohm meter.
Looks like you are using a Wilson FGT antenna. I forgot about that. There was a production run they did that was defective a couple years ago (or so) if I recall. It's entirely possible you got one of those...even if it's fairly new. Some stock sits around a long time before it's finally sold. So if everything checks out, treat yourself to a new antenna. Tune it up and you'll probably be good to go.
Just a couple more things to check in addition to your plan. Sounds like you are on the right track though.
If that doesn't solve the problem, while you have it all apart build a jumper wire for across the spring. It's not uncommon for some springs to fail. Most have a braid inside to minimize it's length...and sometimes they fail from bad solder or connection point. A #10 or #12 (or bigger if you have it) jumper wire will fix this (it's only about 4"-6" or so and you'll need to probably re-tune a little). If all of this fails to solve the problem, it's time to start look at each component with an ohm meter.
Looks like you are using a Wilson FGT antenna. I forgot about that. There was a production run they did that was defective a couple years ago (or so) if I recall. It's entirely possible you got one of those...even if it's fairly new. Some stock sits around a long time before it's finally sold. So if everything checks out, treat yourself to a new antenna. Tune it up and you'll probably be good to go.
Just a couple more things to check in addition to your plan. Sounds like you are on the right track though.
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mikegolden
- Mud-Duck Sr.
- Posts: 6
- Joined: July 23rd, 2010, 10:56 pm
Hello again
Just an update. The new coax and so239 have been installed. Still the SWR is sky high. so while at work i decided to make a new bracket because the Aluminum one i made was pretty thick and it did not allow much of the so239 threads to show. I could not even thread my spring on so before i made a new bracket i decided to drill out the back side to open it up and see if i could get more threads to show. I drilled it out using a 1inch bit. this in turn also opened up the hole that the threads protrude through (I did not drill all the way through) Put it all back together and now my SWR is under 2. I finally realized what happened. When i drilled the hole the first time i made it just big enough for the threaded part to slip into......DUH this was causing it to ground out now that the hole is bigger the threaded end does not touch the bracket and everything is working great.
Mike G
Just an update. The new coax and so239 have been installed. Still the SWR is sky high. so while at work i decided to make a new bracket because the Aluminum one i made was pretty thick and it did not allow much of the so239 threads to show. I could not even thread my spring on so before i made a new bracket i decided to drill out the back side to open it up and see if i could get more threads to show. I drilled it out using a 1inch bit. this in turn also opened up the hole that the threads protrude through (I did not drill all the way through) Put it all back together and now my SWR is under 2. I finally realized what happened. When i drilled the hole the first time i made it just big enough for the threaded part to slip into......DUH this was causing it to ground out now that the hole is bigger the threaded end does not touch the bracket and everything is working great.
Mike G
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231
That's great Mike! Glad to hear you got it figured out. Now you'll be talking!!! Thanks for the update.
