Splicing RG58

[Brian McVickers]

During a recent vehicle project I found my CB cable and decided to follow it.
The previous owner installed the CB and its two antenna mounts, one front and one rear. Along the length going to the rear mount I found two taped up connections that turn out to be splices joining three separate lenghts of cable to make one.

These splices are done by twising the center braided wires together and then the outer braded wires together, then it's all taped up!

Seems a bit sketchy to me. Does this work or should it be done another way?

What is the proper way to splice RG58 together? :confused:

[DaveInDenver]

Funny! You most certainly can not treat coax like regular wire. Splices are no good pretty much under all conditions. There is absolutely no way to guarantee your impedance at the splice by striping, twisting and soldering the connection. That will be a huge discontinuity and probably will result in a horrible reflection. Have you ever tried checking the VSWR of your feed? Bet it's ridiculous.

If you must join two lengths, the only way to do it reasonably is putting connectors on each section and adding a bulkhead in the middle. This is less than perfect, but far better than trying to join them like regular wire.

Your best bet is buy a roll of cable and run new, unmolested feeds.

[BajaTaco]

I can't understand what the purpose of splicing 3 cables together would be. Do I understand correctly, that basically, this is a "strand" of 3 cables all terminating at a single point at either end (where the splices are)?

As far as I know, the proper way to splice RG58 would be to use a barrel connector (http://www.firestik.com/Catalog/AR-4.htm)and then two PL-259 connectors (http://www.firestik.com/Catalog/T6-259.htm) at each end of cable. Process the connectors and cable ends as shown HERE (http://www.firestik.com/Tech_Docs/Coax_Procg.htm).

[Brian McVickers]

That's what I figured, these twisted splices are just ugly!

I have terrible transmit and receive, maybe a 1/2 mile!!
I just got an SWR meter and was going to try and tune the system but then found the splices and decided that needs correction before worrying about the SWR.

I’ll need to look into replacing it with a solid length, Radio Shack seems to be my only convenient option and they have 20 and 50 foot lengths with connectors on the ends but I will most likely have to cut the connectors off of at least one end to run it, and then replace the connector.

Now with my other project, I am needing to run a second coax but one end has a special soldered connection that I can’t duplicate. This coax is not long enough so I have a 20’ extension that I will have to connect with a bulkhead. Hopefully It wont result In too much loss.

All of the CB type shops near me keep inconvenient hours so they are hard for me to get to. Any other ideas besides Radio Shack?

[Brian McVickers]

I can't understand what the purpose of splicing 3 cables together would be. Do I understand correctly, that basically, this is a "strand" of 3 cables all terminating at a single point at either end (where the splices are)?



Correct. It seems as if the installer needed a 20 foot lentgh of cable but only had a 7', 8' and 5' lengths to work with so he connected them end to end!

[DaveInDenver]

I can't understand what the purpose of splicing 3 cables together would be. Do I understand correctly, that basically, this is a "strand" of 3 cables all terminating at a single point at either end (where the splices are)?
One reason people try to splice coax is to feed two antennas from one source. There are probably correct ways to build a harness to do that, but other than truckers with their CBs I'm not personally aware of anyone who does that (other than commercial broadcasters, but that's a little more sophisticated). It's hard enough optimally tuning a single antenna, forget dealing with two radiators! With co-phased antennas you need to be super careful about the distance between the two whips and it'll really only works well at a relatively narrow bandwidth. The two whips probably should not be flopping around in the wind, either...

[DaveInDenver]

I have terrible transmit and receive, maybe a 1/2 mile!!
I just got an SWR meter and was going to try and tune the system but then found the splices and decided that needs correction before worrying about the SWR.

Since you haven't yet burned up your radio, keying it one more time is probably not a big deal. I'd measure the SWR of the feed as it is, just to see. But I'm curious in that way.


I’ll need to look into replacing it with a solid length, Radio Shack seems to be my only convenient option and they have 20 and 50 foot lengths with connectors on the ends but I will most likely have to cut the connectors off of at least one end to run it, and then replace the connector.

Now with my other project, I am needing to run a second coax but one end has a special soldered connection that I can’t duplicate. This coax is not long enough so I have a 20’ extension that I will have to connect with a bulkhead. Hopefully It wont result In too much loss.

All of the CB type shops near me keep inconvenient hours so they are hard for me to get to. Any other ideas besides Radio Shack?
A bulkhead-type splice is fine. You do get some loss, but it's not horrible and in a mobile rig it's really not enough to bother worrying about.

As far as rolling your own, don't shy away from crimped connectors. They are not as good as solid soldered connections, but if you take time and keep things tidy and organized, they can work fine. I carry crimp connectors and coax tools in my spares kit, never know when you might need to make a repair. Your feed is going to be better if trimming off one pre-made connector allows a cleaner installation and trimming the coax to the right length is better than coiling up extra cable.

[Brian McVickers]

One reason people try to splice coax is to feed two antennas from one source. There are probably correct ways to build a harness to do that,

Ok so here's the kicker,
this setup has one connection that goes into the back of the radio as normal. That connector has a rubber boot on it with two holes. Out of each hole comes one cable to there are two cables going to the one connection that attatches to the radio. One cable runs forward to the front bumber antenna mount and the other runs to the back to the spare tire carrier antenna mount.

Thing is I only have one antenna. I believe this set-up was to allow the one antenna to be positioned for driver preference, in the front or in the back. So one antenna mount is always empty.

Does this make sense???

[DaveInDenver]

Ok so here's the kicker,
this setup has one connection that goes into the back of the radio as normal. That connector has a rubber boot on it with two holes. Out of each hole comes one cable to there are two cables going to the one connection that attatches to the radio. One cable runs forward to the front bumber antenna mount and the other runs to the back to the spare tire carrier antenna mount.

Thing is I only have one antenna. I believe this set-up was to allow the one antenna to be positioned for driver preference, in the front or in the back. So one antenna mount is always empty.

Does this make sense???
Makes sense, although the preferred way to do this is an antenna switcher. Keep in mind that the coax is a part of the antenna system, so leaving it unterminated or poor connections have as much or more effect on the TX and RX as the whip itself. If I understand, you have at all times one of the feeds left without an antenna, right? That is basically, well, really bad. That looks like a very high impedance to the coax, which is best compared to a perfect mirror electrically and all the energy is reflected back from that leg. This is bad, bad, bad for the radio.

[Brian McVickers]

Thanks Dave, this is great info.

OK so the system has been this way since well before I had it. The radio still seems to TX and RX well within short distances so I don't think its fried.

I'm thinking of three solutions:

1 - Snip off the double connection going to the back of the radio and put a PL259 connector on each lead, one front and one rear. Then I would connect the lead coming from the active feed, mount with antenna, to the radio and leave the inactive feed, mount with no antenna, disconnected. That way I could just switch connections if I ever have the desire to swich antenna locations. --- Question, will each antenna location have it's own SWR reading ant therefore possibly need it's own antenna? Maybe I should just pick one location!?

2 - Get a second antenna so that each feed is active. However I would then need to tune the set and ther may be no benefit to such a setup.

3 - Get a dummy load to fill the inactive empty antenna mount.

I think I like Option 1, what do you think?

[DaveInDenver]

OK so the system has been this way since well before I had it. The radio still seems to TX and RX well within short distances so I don't think its fried.
Probably OK, at least not burned up. Probably not an ideal situation, but CB radios are usually pretty rugged units and can take quite a bit of abuse.


1 - Snip off the double connection going to the back of the radio and put a PL259 connector on each lead, one front and one rear. Then I would connect the lead coming from the active feed, mount with antenna, to the radio and leave the inactive feed, mount with no antenna, disconnected. That way I could just switch connections if I ever have the desire to swich antenna locations. --- Question, will each antenna location have it's own SWR reading ant therefore possibly need it's own antenna? Maybe I should just pick one location!?

2 - Get a second antenna so that each feed is active. However I would then need to tune the set and ther may be no benefit to such a setup.

3 - Get a dummy load to fill the inactive empty antenna mount.

I think I like Option 1, what do you think?
Option 1-
This would work just fine, kind of a pain but would work. Yes, the length of coax affects the SWR you'll get. So when you tune an antenna, the coax length determines ultimately the length of the whip. It's relatively unlikely that they'd be perfectly identical, but if the feeds are similar you might find that on one mount the SWR is good and the other it's not too bad, though.

Option 2-
If you have two whips, then tune each and then it's just a swap at the radio, that is fine. You could stick a switcher at that location and that would be easy.

Option 3-
This works, too. A dummy load, though, absorbs energy and so you'd be losing transmitter power just heating the resistor in the dummy load. This saves the radio at the expense of lost range. In real terms, this would be no worse than what you have now and might result in some increased range if your radio is designed to fold back its output when it see a poor load. Most CBs are dumb, but rugged enough to tolerate a bad SWR. Others are smart (most ham radios in the past decade or two operate this way) in that if they see too much reflection, they reduce their power. This protects the radio.

My $0.02 is to pick a convenient mount location, run fresh coax and tune it up (so, yeah, option 1). There is no perfect spot. The best ones electrically are rarely the best ones physically. I have mine on the roof and it works great, just bangs trees a lot. On the bumper it was less likely to hit stuff, but it did not do all that great facing forward.

[Brian McVickers]

Last night I pulled out the old spliced cable and ran a single piece of new cable about 18 feet long. This will connect the radio to the rear antenna mount wich will now be the primary antenna mount.

I attempted to put a connector on the leftover coax running to the front mount but it turns out to be RG-59 and it would not accept my PL259 connector since the cable is too thick.

I'm hoping to test the SWR today but this morning on the way to work the weather channel came through stronger than ever before. I tried a radio check but no one was listening!

Now my only concern with the CB antenna is its lenght in relation to its location. It is mounted on the spare tire carrier and the tip of the antenna does not clear the top of the vehicle -- so I'm concented that this clearance issue may act as a barrier to TX range.

Would it be better if the tip of the antenna cleared the top of the truck -- the signal is transmitted fromt the very tip of the antenna correct?

[DaveInDenver]

Would it be better if the tip of the antenna cleared the top of the truck -- the signal is transmitted fromt the very tip of the antenna correct?
Doesn't matter all that much. An antenna radiates along it's whole length, so getting just the tip above the roof will make a marginal difference. The more of the length above the roof the better. If the antenna is competely blocked, then you're getting very little going that way, but getting just a couple of inches above the roof line isn't going to suddently equalize the radiated energy in all directions. You'll still be getting very little energy radiated across the roof.

[Brian McVickers]

SWR Readings:

Ok, the antenna is completely below the roofline and about three inches off the back door's vertical plane.

I just checked the SWR readings:

Ch-20 = 7
Ch-40 = 4.8
Ch-01 = 12.5

The % of reflected power is in the red on the meter. Red starts at SWR of 3 and is equal to 25% of power reflected, so my readings are over 50% reflected.

According to the directions: If reading is higher at ch40 than ch01 antenna needs to be shorter. If readingis lower at ch40 than ch01 antenna needs to be longer.

So I need a longer antenna. Is there more to it that I am missing?

Oh, and thanks by the way this is great help!

[Brian McVickers]

Also note, I can hear the weather band bleeding over to the regular CB channels ever so slightly!????

[Brian McVickers]

I think I figured out what the previoius owner attempted to do with the antenna setup --- http://www.firestik.com/Tech_Docs/SNGL-or-Dual.htm

There was one mount on the front bumper and one on the rear tire carrier. The vehicle is a mix of aluminum and steel, steel roof, steel passenger doors, aluminum front and rear quater panels, aluminum hood and rear door. So the ground plane is pretty bad!

Using the two mounts he may have been attempting to rig a co-phased antenna which requires RG-59 cable to be used. The front mount had RG-59 cable running to the radio wher it joined the other cable in a joiner plug that went to the radio. The problem I see was that the cable going to the rear mount was RG-58 and it had two very bad hand wound splices in it. This system would have requred him to have two antennas installed at all times!





One reason people try to splice coax is to feed two antennas from one source. There are probably correct ways to build a harness to do that, but other than truckers with their CBs I'm not personally aware of anyone who does that (other than commercial broadcasters, but that's a little more sophisticated). It's hard enough optimally tuning a single antenna, forget dealing with two radiators! With co-phased antennas you need to be super careful about the distance between the two whips and it'll really only works well at a relatively narrow bandwidth. The two whips probably should not be flopping around in the wind, either...

[Brian McVickers]

DUH! on me!
http://www.firestik.com/Tech_Docs/Mnt-Grnd.htmThe antenna mount is not grounded! :sport_box



SWR Readings:

Ok, the antenna is completely below the roofline and about three inches off the back door's vertical plane.

I just checked the SWR readings:

Ch-20 = 7
Ch-40 = 4.8
Ch-01 = 12.5

The % of reflected power is in the red on the meter. Red starts at SWR of 3 and is equal to 25% of power reflected, so my readings are over 50% reflected.

According to the directions: If reading is higher at ch40 than ch01 antenna needs to be shorter. If readingis lower at ch40 than ch01 antenna needs to be longer.

So I need a longer antenna. Is there more to it that I am missing?

Oh, and thanks by the way this is great help!

[Brian McVickers]

I think the answer here will be to properly ground the mount and then go with a taller antenna that will clear the roof line.

Considering the
FireStik 4' Fire Fly toploaded antenna or
Wilson 4' Flex toploaded antenna

I'm leaning towards the Wilson Flex

Since both are toploaded the majority of the TX power is emited in the top 1 foot of the antenna which will be above the roofline.

[crawler#976]

My best results for CB's have been with a whip type antenna. The Taco has a 1/2 wave base loaded whip, the trail beater a true 1/4 wave 108" with spring mount. Previous to that I used a roof mounted base loaded K40 quick detachable antenna. It worked the best of the three, but was a pain when trailing thru wooded areas. I quit spending large amounts of money on radios - they seem to get beat by trail use anyway, so I buy cheapys and use a good antenna. Seems to work out pretty well - rarely do I have problems w/ RX or TX (until the radios puke...)

The only disadvantage to the whips is having them flop around. I keep the 108" secured at the tip until needed, and when people are around on the trail, point it out and tell'm to stay clear...

As far as grounding goes, I run a seperate ground directly to the mount and connect it to the chassi at the same location the radio is grounded.

[k6uk]

Just read through this thread and I have a few things to add:

1. I'm not sure about those SWR readings. Your swr should be below 2 on all channels. But I'm not sure where you are getting your numbers since most swr meters top-out at about 4 or 5. At any rate - you may have a problem if your SWR is that high.

2. Antenna Height. You definately want to get the antenna above the roof if possible - the more clearance the better. At least try to get 1/3 of the antenna up above the roofline.

3. Grounding.
As far as grounding goes, I run a seperate ground directly to the mount and connect it to the chassi at the same location the radio is grounded.Grounding is super important when it comes to radio equipment. But it is also important to keep you ground runs as short as possible. You don't want the ground to be so long that it becomes an antenna itself - so always ground the antenna as close as possible to the mount.

4. A note about co-phasing and coax length. It is often talked about that coax legnth affects the swr of a given antenna, and there are certain "magical" lengths of coax that CBrs will sometimes swear you must use. This really isn't the case - properly sheilded and installed coax can be whatever length you want (see http://www.signalengineering.com/ultimate/coax_basics.html). BUT in the case of co-phased antennas you would need your runs to be exactly the same length and the same type of coax. In-fact, to do it right you would need to determine the velocity factor of the coax you are using, and cut specific legnths of coax. The reason has nothing to do with antenna length, but rather the speed at which the signals travel through the coax. If your antennas radiate "out of phase" they will cancel each other out instead of increase your gain. Here's a good link to an article on co-phasing (http://www.signalengineering.com/ultimate/co_phasing.html) but as you can see it is really most effective on large base-station antennas. Truckers co-phase their antennas to combat the huge trailer they are hauling which can cause dropouts in signal on one side of the vehicle.

-Mike

[k6uk]

Just read through this thread and I have a few things to add:

1. I'm not sure about those SWR readings. Your swr should be below 2 on all channels. But I'm not sure where you are getting your numbers since most swr meters top-out at about 4 or 5. At any rate - you may have a problem if your SWR is that high.

2. Antenna Height. You definately want to get the antenna above the roof if possible - the more clearance the better. At least try to get 1/3 of the antenna up above the roofline.

3. Grounding.
As far as grounding goes, I run a seperate ground directly to the mount and connect it to the chassi at the same location the radio is grounded.Grounding is super important when it comes to radio equipment. But it is also important to keep you ground runs as short as possible. You don't want the ground to be so long that it becomes an antenna itself - so always ground the antenna as close as possible to the mount.

4. A note about co-phasing and coax length. It is often talked about that coax legnth affects the swr of a given antenna, and there are certain "magical" lengths of coax that CBrs will sometimes swear you must use. This really isn't the case - properly sheilded and installed coax can be whatever length you want. BUT in the case of co-phased antennas you would need your runs to be exactly the same length and the same type of coax. In-fact, to do it right you would need to determine the velocity factor of the coax you are using, and cut specific legnths of coax. The reason has nothing to do with antenna length, but rather the speed at which the signals travel through the coax. If your antennas radiate "out of phase" they will cancel each other out instead of increase your gain. Here's a good link to an article on co-phasing (http://www.signalengineering.com/ultimate/co_phasing.html) but as you can see it is really most effective on large base-station antennas. Truckers co-phase their antennas to combat the huge trailer they are hauling which can cause dropouts in signal on one side of the vehicle.

-Mike

[Brian McVickers]

Thanks Mike.

I talked to the techs at FireStik and the guys at Apollo Communication CB shop in Phoenix and they wer not overly concerned with coax length either - more with grounding and obstruction clearance.

So I have gone with a Wilson "Flex" 4 foot with a quick disconnect. It clears the roofline about with maybe the top 30% but it is also a topload antenna which primarily uses the top one foot of the antenna.

I also ran a propper ground to the antenna mount from the vehicles frame whre I sanded down to bare metal.

It very well could be that I'm using the SWR meter wrong but the readings seem pretty straigt forward. Now with all I have done to improve things I get readings of 2.5 on ch40 and 3.5 on ch1. The Wilson has an adjustable tip and I have already maxed it out with little improvement to SWR. It should be good enought for the trail but it's not perfect - yet!

My biggest concern with the CB now is that I can faintly hear the WX band when on CB. I can hear the weather report very faintly in the background when close to the speaker. What is causing this - what to do?

[k6uk]

That SWR still is too high.
The Wilson comes with a little pigtail of wire attached at its base.
Did you leave this unattached, or did you ground it?

It's supposed to be left unattached, unless you have problems getting the SWR down low enough... then you ground it and see if it helps.

As for the bleed over from the weather band reciever - this is definately some problem in the radio. What model radio is it? Maybe there is a fix available online somewhere.

-Mike

[Brian McVickers]

:iagree: the SWR is still to high, but :confused: :confused:

I have that wire unattached but I did try it to see if it helps but the SWR just went higher!

The instructions on the Wilson suggest getting a longer piece of stainless steel rod to make a longer adjustable tip if you can't get the SWR down. But I'm not even sure I'm doing it right to begin with! The shop where I bought the antenna will tune it for another couple of bucks but I did not have the vehile with me when I was there, and no time this week.

The radio is a simple Radio Shack unit, a few years old.

[k6uk]

Well I notice on the Wilson website that they will provide you with a longer whip if necessary.
http://www.wilsonantenna.com/tsswrf.htm
(309) 756-4546


But I'm not even sure I'm doing it right to begin with!
Okay. Just so you're sure you're doing it right - here is the procedure.
I am assuming you are using a regular power/swr meter not built into the radio.

Of course the first thing is to attach the proper side of the meter to the Transmitter and the other side to the Antenna, the meter will be marked. This seem obvious, but I've seen people miss this step.

Now... first of all you will measure your forward power. There is probably a switch that let's you choose FWD/REV(or SWR)/CAL or something like that. This switch should be set on FWD for the moment. Now key down and you will see the power of you carrier. With a stock CB you should see about 2~4 watts at this point.

Now, you want to switch over to CAL or Calibrate. This can be the same switch or it can be somewhere else, but you want to use the knob on the meter to bring the needle to the CAL mark on the meter face. This should be around full scale.

Once it is calibrated for the channel you are on, flip the switch to REV or SWR, and read the SWR scale. This will give you your proper SWR.

I'm sure this is what you were doing, but better safe than sorry.

-Mike

[Brian McVickers]

Yep thats the procedure I did.
very basic SWR meter with one switch FWD/REV and a CAL knob
Switch to FWD then on ch20 key mike and adjust CAL to the infinity sign on the scal. Then switch to REV and key on CH40 and CH1 for readings.

[k6uk]

Okay.
Well then let me ask. What is the antenna attached to?
For example, if it's mounted on a swing out tire carrier, it may be necessary to ground the bumper/tire carrier with copper braid. Simply running a ground to the mount is sometimes not enough, since there is a difference between RF grounding and electrical ground. Oh, which brings up another question... what did you use to ground the mount? Did you use regular wire or copper strap?
Copper strap (or braid) is the preferred material.

-Mike

[Brian McVickers]

The rear door of the vehicle is aluminum, there is a steel tire carrier mounted just off center on the door, the antenna mount is bolted to the tire carrier.

I then have a 12ga copper strand wire running from one of the bolts attaching the antenna mount to the carrier to the frame of the vehicle attached to a spot where I sanded to expose bare metal.

The roof and 4 passenger doors are steel while the hood, four quarter panels and the rear door are aluminum.

[k6uk]

Here is a great article on Grounding, and in particular Bonding:
http://www.k0bg.com/bonding.html

There is a good chance that the door, and possibly the carrier are not grounded properly to the vehicle body. A couple of ground straps could magically solve your problem Take a quick read this may be your answer. Even if it's not, you can only improve things by bonding the rear door and the tire carrier (and all the other doors wouldn't hurt the situation any).

-Mike

[DaveInDenver]

Yep thats the procedure I did.
very basic SWR meter with one switch FWD/REV and a CAL knob
Switch to FWD then on ch20 key mike and adjust CAL to the infinity sign on the scal. Then switch to REV and key on CH40 and CH1 for readings.

One of my old meters is probably like what you're using, a single needle, switch and a knob. This is a pretty simple SWR bridge.

http://www.walcottcb.com/images/SWR138X.jpg

Set it to FWD and key the mic. When you do this, the needle should swing to the right and you adjust the knob until the needle is zero'd (or infinity). Switch to REF, key the mic again and is the SWR measurement. REF in this case means REFlected power.

[Brian McVickers]

Thanks, I'll have to consider that.

My old boat was fully bonded - partially for the use of the Single Side Band radio and even more so that a lightning strike would disipate without making swiss cheese of your hull!

Thanks again
Brian

[DaveInDenver]

Here is a great article on Grounding, and in particular Bonding:
http://www.k0bg.com/bonding.html

There is a good chance that the door, and possibly the carrier are not grounded properly to the vehicle body. A couple of ground straps could magically solve your problem Take a quick read this may be your answer. Even if it's not, you can only improve things by bonding the rear door and the tire carrier (and all the other doors wouldn't hurt the situation any).

-Mike
Notice what Mike is advising here. There is a difference between an electrical ground and an RF ground. Both could be the same when you measure your grounds with a meter, but to your RF signal they could be different. It is, however, a matter of efficiency between the two in the end. If you have a really solid electrical ground running from the mount to the carrier to the frame, there is most likely an OK RF ground, too. But the rest of your truck needs to be primarily grounded with respect to RF. So your roof, doors, frame, etc. all need to be at the same RF ground. This is usually accomplished by running grounding straps, but even short wire pigtails work OK to get things better. The key is the body of your truck NEEDS to be grounded and in a lot of cases the sheet metal is not grounded well. There are few bolts through rubber hockey pucks and that's about it and this is not a good RF ground. Like Mike said, put a short strap from the door to the body and from the body to the frame and that makes a big difference in SWR (which ultimately is a determination of your RX/TX range).