PDA

View Full Version : CB Coax, what to do with extra cable?


Rezarf
04-25-2008, 03:43 PM
Howdy friends. I have remounted my CB antenna to clear my roof line and hoping to get a little better reception by being higher. I added a grounding strap to my swing out and things are coming along nicely.

I was wondering what to do with the extra 2' of cable. I remeber in the HAM class it was said not to coil the extra up. I have looked at my cable and it looks like I could run it down my rear crossmember (the one that the shocks attach to on the 40) and zip tie the cable making a long U shape. Is that okay? It looks like my best shot right now.

Any other tips while I am there? FWIW, I cleaned all my connections with air.:thumb::cheers:

MDH33
04-25-2008, 03:54 PM
I always thought it was OK to coil the extra cable, just don't cut or shorten it. (?) Mine is coiled in my glove compartment and I think I get pretty good reception.

Rezarf
04-25-2008, 03:58 PM
Thanks Martin, that is good to know,I am sure one of the wise guru's will chime in soon. :bowdown:

Here is my new mount placement...

MDH33
04-25-2008, 04:04 PM
looks clean! You're getting some skillz with the welder! How many :beer: 's to help me fab up some soft half doors from an old set of Bestop soft full doors? :D

About the co-ax, I checked on the Walcott CB site and they suggest loosely coiling it serpentine style (like a climbing rope I guess) and securing in the middle. Since you only have a couple of extra feet, it should work fine. I had about 10 extra feet since my CB is in the dash and the antenna is only a few feet away on the cowl. :o

corsair23
04-25-2008, 04:39 PM
About the co-ax, I checked on the Walcott CB site and they suggest loosely coiling it serpentine style (like a climbing rope I guess) and securing in the middle. Since you only have a couple of extra feet, it should work fine. I had about 10 extra feet since my CB is in the dash and the antenna is only a few feet away on the cowl. :o

x2

Nathaniel or Dave may chime in but according to Nathaniel you do NOT want to just coil the excess coax (bad ju ju) up. What Nathaniel showed us at the antenna building party was to coil the excess coil up and then secure it right in the middle with a zip tie so it comes out looking like an "8" or the infinity sign :thumb:

I'm going to try this with the 2-3' of excess I have coiled up in my PS footwell area on the LX and see if that helps with my high SWR levels.

Mendocino
04-25-2008, 06:13 PM
In another post I think Dave said to coil it like a bowtie and not to use a circular coil because that acts as an inductor.


x2

Nathaniel or Dave may chime in but according to Nathaniel you do NOT want to just coil the excess coax (bad ju ju) up. What Nathaniel showed us at the antenna building party was to coil the excess coil up and then secure it right in the middle with a zip tie so it comes out looking like an "8" or the infinity sign :thumb:

I'm going to try this with the 2-3' of excess I have coiled up in my PS footwell area on the LX and see if that helps with my high SWR levels.

corsair23
04-25-2008, 08:34 PM
In another post I think Dave said to coil it like a bowtie and not to use a circular coil because that acts as an inductor.

Yep...Bowtime, figure 8, infinity sign....Any of those as long as it isn't in a circular shape. :thumb:

Groucho
04-25-2008, 08:54 PM
"...there are a couple of things to keep in mind when installing an antenna on a vehicle.

2. Keep the feedline (coax) clean and short. No big loops of extra coax bundled up anywhere. These become loading coils that will mess with the resonant effects of your antenna. Don't kink the coax. It too will mess with the impedance..."



"The way to "coil" up any excess coax is to loop it and then tie it together in the center of the loop to form a kind of figure "8". That way, you minimize the effect the coil will have on the antenna. (Basically the coil would aid in "matching" the feedline to the antenna, so the impedance is the same at the feed point of the antenna and the coax.) Without knowing what your impedance is at those two locations, you don't want to coil up your wire."

Martin, if you have 10 feet coiled up in your glovebox, I would recommend that you cut it to length and teach yourself (I would help and I'm sure Dave would too) how to solder a new Amphenol PL-259 on to the end. Don't worry about the coax you cut. If you figure out that putting a new connector is not that hard, you can use it other places. Even so, coax from Radio Shack is not that expensive. If you do this your signal will almost certainly improve.

BTW--Just because you hear people, doen't mean you have a good antenna/signal. A long wire 50 feet long will be a moderate receive antenna. It is how you are set up to transmit thats what counts. A long piece of coax actually has more db loss than you think, especially when it comes to the piddley 5 watts CB has to work with. Plus, at the right length, the coax may act like it is resonating as an antenna, really screwing things up.

MDH33
04-25-2008, 10:31 PM
wisdom much appreciated. :D

I'm usually hard to hear in person, so if I can can get assist via gadgets, it's all good. :bowdown:

Rezarf
04-25-2008, 11:30 PM
How about this? I have about 2' left over, what if I run it down the frame rail, along the crossmember, make a U turn and back to the frame rail and continue. Is that better than the figure 8?

Thanks!
D
rew

ScaldedDog
04-26-2008, 09:49 AM
Is this for CB or a ham? ***I know nothing about hams***.

If it's for a CB, why not just cut it off? The whole "gotta be 18'" thing doesn't seem to hold water, and I know it never made any discernable difference in my own installations. Post your question over on cbradioforum.com and see what those guys say.

Mark

Mendocino
04-26-2008, 12:14 PM
As long as you don't change the impediance and as a result the SWR you can cut the cable. I think the bigger issue is that most folks have a difficult time terminating coax properly.

Groucho
04-26-2008, 06:11 PM
Is this for CB or a ham? ***I know nothing about hams***.

If it's for a CB, why not just cut it off? The whole "gotta be 18'" thing doesn't seem to hold water, and I know it never made any discernable difference in my own installations. Post your question over on cbradioforum.com and see what those guys say.

Mark

An antenna is an antenna is an antenna. :blah:The laws of physics do not change regardless if you are a beer stained a-shirt wearing trucker using a CB or if you are a HAM geek in your basement wearing the tighty-whities. :hill::lmao:

If you buy a commercial antenna, follow the mfg instructions on the package. If you made your own, just follow the simple ideas stated above. Coil it into a figure 8 or route it outta the way. Just don't over-think it. Then have a :beer: and get your Moab fix. :thumb:

Pappy
04-27-2008, 09:45 AM
... I would recommend that you cut it to length and teach yourself (I would help and I'm sure Dave would too) how to solder a new Amphenol PL-259 on to the end. Don't worry about the coax you cut. If you figure out that putting a new connector is not that hard, you can use it other places. Even so, coax from Radio Shack is not that expensive. If you do this your signal will almost certainly improve.

What tools are needed to do this? Where do you acquire them? The OCD in me want to clean up the extra cable on both my 2m and CB.

Groucho
04-27-2008, 07:31 PM
There are only simple tools. A soldering iron. A razor blade. Solder. Thats it.

If you are using RG-58 you will need to use the adapter. It is an adapter that allows a smaller diameter coax fit into the PL-259 end. When you get it you will see why it is necessary. RG-8 does not require it because it is so much bigger. The adapter goes on the coax before the PL-259.

Make sure you do not solder the braid so much that you melt the dielectric in the connector. The center wire gets soldered to the niplle on the end. Check for continuity. If you have none, you're good.

Now follow the directions. These aren't the best directions, but...

Questions? Ask.

Rezarf
04-27-2008, 10:27 PM
Nathaniel, any idea why I have a little wire coming off my antenna, what does that need to be grounded to? the body? thanks!

Drew

Pappy
04-28-2008, 07:55 AM
Questions? Ask.

OK, where do you source those connectors? And, I thought you needed to crimp the cable side of the connector. This sure looks a lot easier. And, how do you know what cable you have if it's not labeled?

Groucho
04-29-2008, 08:26 AM
OK, where do you source those connectors? And, I thought you needed to crimp the cable side of the connector. This sure looks a lot easier. And, how do you know what cable you have if it's not labeled?

Ham city $1.95 each (http://www.hamcity.com/detail.aspx?ID=985)

Texas towers--look for PL-259 about 2/3 down the page $2.49 each (http://www.texastowers.com/coaxconn.htm)

Ham Radio Outlet--search for PL-259 $2.49 each (http://www.hamradio.com/)

Radio Shack $5.69 each (http://www.radioshack.com/product/index.jsp?productId=2062628&cp=&sr=1&origkw=pl-259+connector&kw=pl-259+connector&parentPage=search)

Radio Shack ADAPTER for RG-58 $2.69 packet of 2 (http://www.radioshack.com/product/index.jsp?productId=2104054&cp=&sr=1&origkw=pl-259+connector&kw=pl-259+connector&parentPage=search)

The cable will either be about 1/4" in diameter or approximately 1/2" in diameter. The smaller is RG-58/59. The larger is RG-8.

First, with a clean cut end of your coax, place the adapter with the fat end toward the inside of the coax (side opposite the end-the coax end side should be closest to the threads of the adapter). Then place the coupling ring on the coax like the picture. If you do it right, the coupling ring will thread onto the body of the PL-259 and then spin freely to be connected to your antenna or radio.

When you strip the outer insulation off (black plastic stuff) off of the braid, and cut the inner dialectric (white stuff surrounding the center conductor wire) to reveal 13MM of braid, 1.6MM of dialectric and 19MM of inner conductor, fold the exposed braid back over the outter insulation.

Then place the PL-259 over the coax. The braid should just show up in the access holes, and the inner conductor should be visible in the straw-like end of the connector (end closest to the end of coax). Bring the adapter up and screw it into the rear of the PL-259. This should hold everything in place for the time being.

My first thing I do is to put some solder in that straw-like end to get the center conductor soldered in well. Just make sure to apply only enough heat to let the solder flow into the straw and cover the center conductor. Let it cool. Too much heat will melt the teflon insulator inside the connector.

Then I apply heat around the area where the access holes are so as to flow some solder between the adapter and the PL-259 to solder the braid. This will take patience and time, because it will require a steady hand, more heat and quick reflexes. Just get enough solder inside one or two access holes to make sure it is sticking. Again, too much heat and you will destroy the inner dielectric of the coax and the teflon insulator if the connector. This will result in a shorted connector, then you have to scrap that end of coax and start all over with new parts.

Bring the coupling ring up and thread it over the body of the PL-259 until it spins freely and won't fall back over the coax.

That should do it.

I will try to post pictures later of me actually doing this.

The pictures I did use are from www.K0BG.com. They show a cutter that is available, but not necessary. The cable he uses is the RG-8. The first picture shows the idea of removing the sheathing to expose the braid and center conductor, as well as the coupling ring. The second picture shows the center conductor poking its head through the straw-like end of the connector.

Pappy
05-06-2008, 08:29 PM
Excellent. Thanks.

Groucho
05-07-2008, 06:18 AM
In Moab, I noticed a green LX450 driving around with a mag mount CB antenna right in the middle of the roof. The I can't believe it part was when I noticed that there was a significant amount of coax wrapped around the base of the antenna.

I just wanted to clarify something really quick. Will your CB work on the trail with a big loop of coax around the base like this? Yes, it will. Will your HAM radio work with a big circular loop of coax on the floor? Yes, it will. Will either of these two configurations be efficient or effective in short distance communications? Probably, sure. Will you be able to reach the head end of a group a few miles down the trail to let them know you are late, or call for help in an emergency? That is where the uncertainty lies. That is why we try to maximize the efficiency of our antenna setup. Don't any of you be that guy.

Remember, a radio is only as good as its antenna.

I guess you can lead a horse to water, but a pencil must be lead.

Rezarf
05-07-2008, 07:53 AM
Nathaniel, any idea why I have a little wire coming off my antenna, what does that need to be grounded to? the body? thanks!

Drew

bump... :thumb:

Groucho
05-07-2008, 09:15 AM
Nathaniel, any idea why I have a little wire coming off my antenna, what does that need to be grounded to? the body? thanks!

Drew

My bad. The only thing I can think of right off is that electronically the antenna is shorted to ground. I don't know which brand and model of antenna you have, so I am unclear as to how it is set up.

This would be similar to the homebrew 2M HAM antenna. I would connect it to your well set up braid from the tire carrier to the truck. If I was me.

Rezarf
05-07-2008, 09:45 AM
Sounds good, I think it is a Wilson 1000 or something like that. I will run the wire to the tire carrier... you think the strap is the best spot for it to tie into correct?

Thanks man, I didn't have any realy problems in Moab, but I did notice I had trouble reaching the other end of the group when we were really spread out. But by then we were all around corners and out of "line of sight."

Thanks!

Drew

Mendocino
05-07-2008, 10:38 AM
...but I did notice I had trouble reaching the other end of the group when we were really spread out...

When are you taking the Technician's test? The HAM should improve things...;)

Seldom Seen
05-07-2008, 01:40 PM
Nathaniel, any idea why I have a little wire coming off my antenna, what does that need to be grounded to? the body? thanks!

Drew


From Wilson's site:


1. What is that wire at the bottom?
Wilson's exclusive impedance matching transformer is connected through the external wire at the bottom of the FGT and Flex series of antennas. It is NOT a "ground wire" to increase the ground of the antenna, although using the lead does make the antenna DC ground. It is used when you are not able to get below a 2.0:1 SWR even after tuning. This generally indicates a mismatch of impedance between the coax and the antenna. This can be caused by poor ground but is generally attributed to the mounting location. It re-inserts 25 ohms impedance at the antenna feed point and brings the system back to the 50 ohms required. It is not a tunable device, therefore it is not fooling the radio into thinking the system is matched. It is actually matching the antenna and feed point to the required 50 ohms impedance for the coaxial cable. The most often time it will be used is when the antenna is mounted on the top of tool box in the bed of a pick-up, or on the passenger side of a tractor using co-phased antennas.

2. What if I do not need the impedance wire?
You have the choice of either cutting it off or taping it out of the way. In making your choice, consider if you may move the antenna to another vehicle, that installation might require the lead. For the most versatile use of the lead, simply lay it alongside the fiberglass and tape it in place. Using electrical tape will offer the easiest method and offer the best protection against weathering conditions.