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-   -   yet another swr ? (http://www.wranglerforum.com/f40/yet-another-swr-135612.html)

Badass_TJ 01-26-2012 12:48 PM

yet another swr ?
 
hi, im new to cb radios. im only looking to talk to my buddies on the trails. I bought a

Cobra 19 ultra 3
4' firestik 2
radio shack antenna stud
20' radio shack coax
workman swr-2t meter

I cleaned all the paint off my rear bumper (to bare steel) installed the stud as directions said with insulator on top and antenna (bumper has tab for antenna) ran the coax, ran a power wire directly to the battery to power the cb. ive been trying to tune the antenna, I can get channel 1 and 40 even at 2.5 if i adjust the tip up or down the swr on either of the channels goes up or down. i cant get anything lower than 2.5 any ideas? ive searched this forum and the net for hours trying to figure this out... thx

30-284 01-26-2012 08:03 PM

If your antenna is mounted to the bumper, then it is very close to the tub and top for almost the whole length, this can keep your SWR somewhat high. 2.5 across the board is not the end of the world tho. It is also best to check your SWR out in the open when not too close to anything.

Donn

The Toolman 01-26-2012 08:22 PM

Like Donn said, make sure you are out in the open at least 50' from any buildings, etc. Also, as much as I like Radio Shack, their coax is a bit sub-standard at best & might be contributing to the bad reading. Probably not the only issue, but can be part of it.

Any chance you can post pics of your install?

Remus_Redbone 01-26-2012 10:33 PM

Quote:

Originally Posted by 30-284 (Post 1964746)
If your antenna is mounted to the bumper, then it is very close to the tub and top for almost the whole length, this can keep your SWR somewhat high. 2.5 across the board is not the end of the world tho.

^^^ yes. A 4 footer on the back bumper has about 50% of it's length just inches from the tub / tailgate which could be the issue. With equal SWR on 1 & 40, it does sound like it could be the problem.

psouza 01-27-2012 12:31 AM

Quote:

Originally Posted by The Toolman (Post 1964831)
Also, as much as I like Radio Shack, their coax is a bit sub-standard at best & might be contributing to the bad reading. Probably not the only issue, but can be part of it.

Any chance you could point us to some professionally generated data (non commercial) on co-ax quality and particularly Radio Shack? What, in your opinion, are the typical failings of that "quality" of cable?

Phil

The Toolman 01-27-2012 12:53 AM

Quote:

Originally Posted by psouza

Any chance you could point us to some professionally generated data (non commercial) on co-ax quality and particularly Radio Shack? What, in your opinion, are the typical failings of that "quality" of cable?

Phil

Just what I have seen many times when repairing other peoples coax. I do not go off of what I read on the net, I go off of what I have repaired. When I have to swap out someone's coax, it's either stock coax on a big rig, cheap no name coax, or Radio Shack coax. Most everything Radio Shack has I like & trust, just not their coax & a few other odds & ends.

Typically with Radio Shack coax, (50 Ohm coax with PL-259 ends)I have found that the PL-259 ends are incorrectly installed &/or there is a break in the center conductor or a breech in the insulating sheath between the outer ground braid & the center conductor causing a short in the cable.

Now, back to the subject by the original poster, I did not pay close enough attention to the fact that you are using the 4 ft antenna. I agree with Don & Remus that you may need a 5 foot top load type antenna "Firestick" or something similar that will raise the antenna's loading point just a bit higher for less reflect, which in turn, will give an unfavorable SWR reading.

sparky 01-27-2012 08:46 AM

I would also try bonding the bumper to the frame and the tub.

IE: running braid / ground strap / heavier gauge wire, from the bumper to the frame and tub to create on solid ground plane. The ground is part of the antenna system and without a good one you can have problems getting it setup. As a start try temp connections with wires just clipped on (bare metal), or under screws. See if it help, if it does then do a good permenant connection.

And, yes being close to the tub with the antenna is not helping.

The Toolman 01-27-2012 08:53 AM

Quote:

Originally Posted by sparky
I would also try bonding the bumper to the frame and the tub.

IE: running braid / ground strap / heavier gauge wire, from the bumper to the frame and tub to create on solid ground plane. The ground is part of the antenna system and without a good one you can have problems getting it setup. As a start try temp connections with wires just clipped on (bare metal), or under screws. See if it help, if it does then do a good permenant connection.

And, yes being close to the tub with the antenna is not helping.

Another good idea :thumb:

I have a "grounding / bonding" thread that explains the meaning. If I wasn't on the mobile I'd post a link for ya

Badass_TJ 01-27-2012 11:35 AM

Quote:

Originally Posted by The Toolman (Post 1966222)
Another good idea :thumb:

I have a "grounding / bonding" thread that explains the meaning. If I wasn't on the mobile I'd post a link for ya

ive read thru that thread, ill get some pics posted when its not raining out. like you guys said i think its my coax and my antenna is to close the tub. My antenna is about 2 inches from the tub and is level with my soft top. I was thinking of getting the firewire coax, any thoughts on that coax or could you recommend a good coax? What could i do with my antenna? if i get a 5' instead of the the 4' would that be better? id really like to keep it mounted on my bumper but i will move it i have to..thx...

Badass_TJ 01-27-2012 11:40 AM

Quote:

Originally Posted by sparky (Post 1966202)
I would also try bonding the bumper to the frame and the tub.

IE: running braid / ground strap / heavier gauge wire, from the bumper to the frame and tub to create on solid ground plane. The ground is part of the antenna system and without a good one you can have problems getting it setup. As a start try temp connections with wires just clipped on (bare metal), or under screws. See if it help, if it does then do a good permenant connection.

And, yes being close to the tub with the antenna is not helping.

Ive tried this but i was using a 12ga wire, i also removed all the paint from the mounting tab on the bumper (down to bare steel) How far away from the tub do you think i need to be?

Badass_TJ 01-27-2012 11:51 AM

Ok i got a couple of pics, if anyone wants different pics let me know and ill take more....thx

The Toolman 01-27-2012 01:13 PM

As far as coax goes, RG-58 is good coax & will get the job done, but I always run RG - 8x (or "mini 8) coax because it is a bit more rugged to the elements & will last longer on your Jeep. I will give you some references when I get to my computer as far as the coax.

For now, I would go ahead & bond your bumper to the frame. You might try a 5 foot antenna as well.

sparky 01-27-2012 04:02 PM

From those pics, way to close to the tub. There is a lot of coupling going on. Looks like an inch away.

Personally, I'd use a taillight mounting bracket to get it up higher, even if you have to use a shorter antenna.

30-284 01-27-2012 04:54 PM

I think that tail light bracket creates alot of flex in the body when used with a stiff antenna like a firestick.

Donn

Remus_Redbone 01-27-2012 10:17 PM

Check this fancy antenna mount.

http://www.wranglerforum.com/f40/cb-...on-133384.html

Cheap, easy, works great. 1.5:1 SWR or better with a Wilson 4' w/adjustable tip. For whatever reason, I was also able to use a spring without negatively affecting SWR.

sparky 01-29-2012 01:42 PM

I don't think a fibreglass antenna is stiffer than the steel tub.

The Toolman 01-29-2012 05:12 PM

Quote:

Originally Posted by sparky
I don't think a fibreglass antenna is stiffer than the steel tub.

I will have to agree there

30-284 01-29-2012 09:46 PM

Think what you want but I mounted one on my tub and flexed it just a small amount and was surprised at the amount of flex in the body, I took it off and made something different.

Donn

The Toolman 01-29-2012 10:04 PM

One thing about it, after thinking about this again, it does put a lot of leverage to the mount, even being fiberglass. I don't think the shorter antennas & the use of a spring would have too much of an effect, but a 4 or 5 footer without a spring definitely would on a newer Jeep.

sparky 01-30-2012 10:15 AM

I have a stiff 7' aluminum collinear 2M antenna mounted on the side of my tub with a ball mount, no spring and I do not see any flex in the body. Maybe on a newer Jeep, I have a 98.

The taillight bracket seems popular and I don't think anybody has had any mount/body failures.


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