SWR. going to yank the CB out by the wires.

[E412B]

I've been fighting the SWR on this van since day 1.

CB is Uniden 510XL.

Dodge CV RAM company van (like a dodge caravan) with ladder rack and 2 ladders (12ft and 8ft A-frame fiberglass).
Have tried 2 Little Wil no luck.
This is the current setup.
18' RG58AU coax. PL 259 plug on one end and lugs on the other.
I tested 0 ohm end-to-end on center conductor. 0 ohm end-to-end on outer conductor. center to outer WFO.

New mounting bracket. Mounted to center front of ladder rack. 8 guage wire bonding mounting bracket to side door jam.

4" spring (parking garage access) and a FireStick knock-off

testing SWR with Astatic PDC2 meter. All I have.

With all antenna parts connected. Testing with multi-meter at PL-259.
There is 0 ohm between outer plug and the front door jam. so ground is good.
There is no continuity between center conductor and door jam.

I started SWR on 1 at 2.5:1 and 3.5+:1 on 40.


Now the SWR on channel 1 is 2.4:1 and channel 40 is 1.3:1

Need to get SWR down before installing new Cobra. I know I may need to re-adjust. but if I cant get this one down I don't want to install the Cobra and a K40.

I'm out of ideals.

 

[The DB]

There is 0 ohm between outer plug and the front door jam. so ground is good.

This isn't necessarily as true as many people think it is. To your transmitted signal, a dead short on a standard multimeter can appear to actually be an open circuit, and an open circuit on your multimeter can appear to be an dead short to the transmitted signal.

Unlike your multimeter, RF is not DC, and it doesn't usually act like DC either.

Now the SWR on channel 1 is 2.4:1 and channel 40 is 1.3:1

According to this info, your antenna is to short.

You might also consider reporting on the SWR on channel 20.


The DB

 

[E412B]

Thanks for the reply

20 is something like 1.9:1 I cant remember off the top of my head.

If the multi meter is showing a 0 ohm short from coax shield side to frame of van and that means nothing for a RF signal. How can I check the ground plane? Already too much money in radio stuff all at one time.

 

[E412B]

I can tell you how to make a Cisco roll over console cable but RF is a killin me.

 

[222DBFL]

Antenna is def too short. Need to add some length like The DB states looking at your vswr readings, ch1 is 2.4:1, ch20 is 1.9:1, and ch40 is 1.3:1. This means your antenna is too short and needs to be either lengthened or if there is a tunable tip, screw the tip out to add length. This is with the firestick knockoff if it has a wire inside you may have to add a longer spring (6" vs 4"), or find a way to make the antenna taller if there is no adjustment screw at the top. Also the Lil Wil antennas are about as bottom of the barrel as it gets. About like having a clothes hanger up. Been there and done that. They are very narrow banded and best I could ever get one to tune to was vswr readings of 1.3:1-1.4:1 with the whip cut, adjusted and so forth. This was on a work van that had plenty of metal under the antenna. A taller antenna would work better than the current setup, something like a sirio performer 5000 mag mount. Understsnding money being tight, but the antenna is one area you don't want to skimp on. JMHO on that. But at any rate like said, the current antenna is too short and needs to be lengthened. Hope this helps and have a good one.

 

[E412B]

The firestick knockoff just has a wire you pull out and cut.
I could drill out the center. Stick the copper down the hole. Add a nut and bolt or a long wood screw as long as it is not painted or something. Yep, redneck all the way.

Think i will put the K40 on. It has the adjustable tip. I think the stinger (?) is about 3-4 inches long.

Will get some pics and post tomorrow.

Other things I thought of.
I think the hood of the van is aluminum. The Little Wil would stick to it.
There is more of the roof behind the antenna than in front.
Would the rungs of the fiberglass ladder mess with the SWR?

got to get up and gone in 5 hours so got to go.
A 3hr drive goes a little easier with a radio.'
Later this week have 5+ hrs one way for an hour of work. The life of a traveling tech. got to love it. Windshield time ain't easy.

 

[222DBFL]

Yes the firestick with the tunable tip should work much better then the current one as you have some adjustment. The current knockoff one, if it's just a wire, then you need to either add piece of small gauge wire, maybe 1" or so, or get a 6" spring if you have a 4" one now. Now the firestick should be much easier to deal with as it does have the tunable tip that pulls out. What height is this antenna? If it's the 5ft one with the adjustable tip and is heavy, it's probably one like this pictured below I take it?? If so you should have good rx and tx with it. They aren't too bad of an antenna. Actually have been suprised at how well the one I have worked. It needs a new top whip for tuning as the old one rusted into place and the Allen head stripped whilst trying to get it out. Needless to say, SS is not fun to drill through! The outer brass bullet went smooth, but boy I had a time getting the rest of the antenna piece that was cut too short and left in the antenna to rust by a previous owner. It doesn't get much use but when I 1st got it and the tri mag mount that came with it, the antenna worked well as I recall. Anyway, keep us updated. Here is the photo of the one I have, is yours like this one, the K40?? Mine is the 5ft one with the tunable tip that pulls out. I just don't have my whip inserted. Anyway, again, keep at it and you'll get it right. Take your time and make sure to follow proper procedures when measuring VSWR.
1. Find a large field or parking lot and get away from any obstructions for about 50-75ft all around.
2. Then, set mic gain to 0 or all the way down.
3. Key radio on AM and calibrate swr meter, then flip switch or whatever is needed to get vswr reading.
4. Check these readings on channels 1, 20, & 40. I start with channel 20 and then go to 1 and 40 and see which way the vswr is going. If it rises when I go to 40, and falls when I go to channel 1, the antenna is too long normally, and needs to be cut down a bit. Cut in 1/8" increments. Seems tiny, but sometimes it's all that is needed and it will help keep from cutting antenna too short. If the readings are high on 1 and low on 40 the whip needs to be lengthened. You want to try to balance the readings between the 3 channels, 1, 20, & 40.
Hope this Brick wall of text helps. And again, keep at it and just be patient..

 

[M0GVZ]

With all antenna parts connected. Testing with multi-meter at PL-259.
There is 0 ohm between outer plug and the front door jam. so ground is good.

No it isn't. From what you've described with your mounting you basically have no ground at all. Its the metal DIRECTLY UNDER THE ANTENNA which counts for a ground and you effectively have nothing but air. You can't make up for it by putting a bit of thin wire to a part on the body. 8 gauge is not that great for RF, even 0 gauge is not as good as just flattened out braid from RG213 coax.

The antenna needs to be lengthened to make up for the fact that you have no ground.

Your next problem is the ladders. Unless they're made of wood they are going to have a massive effect on the antenna tuning when you have them on the rack.

 

[E412B]

To all thanks for the replies.

Got some more meter reading to share a little later.

See if I getting a little better understanding of this stuff.

I have a good short from the shield side of the coax to the ground (frame, body, or negative post of battery) of the van BUT, RF doesn't care about that ground. RF needs a "ground plane" (metal) connected to the shield of the coax to reflex the signal transmitted by the antenna which is connected to the center conductor of the coax.

Now, I could just make sure that my antenna mount has a good connection as close to center (left to right and front to rear) to the ladder rack. Then make sure that all parts of the ladder rack has a good connection to each other. Then remove the wire I have going to the body from the antenna mount.

Close?

Now the readings. I still haven't had time to make any changes to the system. The only thing that has changed has been the weather. Monday is was rain off and; on and the SWR way way high and all 40 channels. I did have to use the ladder. But the SWR was high before the ladder was moved and after it was replaced. Couldn't check while the 12 footer was off. and I did notice the Watt side of meter stayed around 2+.

Now today it rained all day. The SWR on
channel 1 was 2.3:1
channel 20 was 1.7:1
channel 40 was 1.6:1

I understand that the antenna is short. I'm guessing that the rain helped the ground plane issue? Or the rain helped drain off the signal that was being returned to CB?
I don't think the rain got into the coax. I used liquid tape around the shield and dielectric where the lugs were.

 

[M0GVZ]

To all thanks for the replies.

Got some more meter reading to share a little later.

If its from your multimeter then don't waste your time as it measures DC and not RF. You need an antenna analyser.

I have a good short from the shield side of the coax to the ground (frame, body, or negative post of battery) of the van BUT, RF doesn't care about that ground. RF needs a "ground plane" (metal) connected to the shield of the coax to reflex the signal transmitted by the antenna which is connected to the center conductor of the coax.

Correct.

Now, I could just make sure that my antenna mount has a good connection as close to center (left to right and front to rear) to the ladder rack. Then make sure that all parts of the ladder rack has a good connection to each other. Then remove the wire I have going to the body from the antenna mount.

Close?

Not even close. The ground starts at the mount. The whole idea is we want RF to flow over as best a conductor it can rather than the lossy ground. Ideally you'd have a large sheet of horizontal metal there, ie the roof of the vehicle. The ladder rack is not a large sheet of metal, its a small bit of box section.

Now today it rained all day. The SWR on
channel 1 was 2.3:1
channel 20 was 1.7:1
channel 40 was 1.6:1

I understand that the antenna is short. I'm guessing that the rain helped the ground plane issue?

No. The rain affected the antenna making it appear electrically longer to RF. RF flows on the surface of a conductor so anything touching that surface, whether it be insulation or water affects how RF travels over it.

Don't worry, its a very complicated subject. I'm trying to find a way to explain without getting into a lot of theory but I can't. Suffice to say its probably better just concentrating on best practice than the hows and whys.

Read the following:
http://k0bg.com/ground.html
http://k0bg.com/antmount.html
http://k0bg.com/bonding.html

 

[222DBFL]

Read the material that M0GVZ linked to and you will have a much better understanding of how and why things work the way they do. Your antenna is one of the most vital parts of your radio station. This is where majority of people slack off and end up having a mediocre setup and wonder why thier $300 radio isn't "gettin out" or hearing anything. Takes some work to get it right and if you spend the time doing it the right way, it will reward you with much better rx/tx 99.9% of the time. There is always Murhy's Law, but even that can be overcome with some perseverance. JMHO. Get that antenna setup corrected and you'll be much happier!!

 

[rabbiporkchop]

I've been fighting the SWR on this van since day 1.

CB is Uniden 510XL.

Dodge CV RAM company van (like a dodge caravan) with ladder rack and 2 ladders (12ft and 8ft A-frame fiberglass).
Have tried 2 Little Wil no luck.
This is the current setup.
18' RG58AU coax. PL 259 plug on one end and lugs on the other.
I tested 0 ohm end-to-end on center conductor. 0 ohm end-to-end on outer conductor. center to outer WFO.

New mounting bracket. Mounted to center front of ladder rack. 8 guage wire bonding mounting bracket to side door jam.

4" spring (parking garage access) and a FireStick knock-off

testing SWR with Astatic PDC2 meter. All I have.

With all antenna parts connected. Testing with multi-meter at PL-259.
There is 0 ohm between outer plug and the front door jam. so ground is good.
There is no continuity between center conductor and door jam.

I started SWR on 1 at 2.5:1 and 3.5+:1 on 40.


Now the SWR on channel 1 is 2.4:1 and channel 40 is 1.3:1

Need to get SWR down before installing new Cobra. I know I may need to re-adjust. but if I cant get this one down I don't want to install the Cobra and a K40.

I'm out of ideals.

you forgot to measure 0 ohms from the rooftop down to the negative side of the battery and from the rooftop to the frame and from the frame to the negative side of the battery only then will you be in a position to adjust the antenna

 

[The DB]

you forgot to measure 0 ohms from the rooftop down to the negative side of the battery and from the rooftop to the frame and from the frame to the negative side of the battery only then will you be in a position to adjust the antenna

Neither your vehicle's roof or frame need a connection to the negative terminal of the battery for the antenna to work. Further, weather or not there is a good connection between the roof/frame to the battery makes absolutely no difference in how a mobile antenna functions. The ground terminal on the battery has nothing to do with a ground plane. In most vehicles you will have this connection simply because that is how vehicles are designed, but it is not required.

A connection between the frame and roof is also not required, however it is a good thing. That being said, simply having a 0 ohm connection as reported by a multimeter is not always enough, and to be sure it needs to be properly RF bonded.

As stated above, RF acts different than the DC a multimeter uses for continuity testing. You cannot assume that a 0 ohm connection reported by a multimeter will be 0 ohms at 27 MHz.


The DB

 

[rabbiporkchop]

Never said it was required but it definitely eliminates a bunch of potential problems and by eliminating potential problems right at the beginning you're automatically taking a bunch of guesswork out of the equation simultaneously. There is a step by step process I follow on every installation and I never seem to have those same issues because I do everything in a specific order.

Neither your vehicle's roof or frame need a connection to the negative terminal of the battery for the antenna to work. Further, weather or not there is a good connection between the roof/frame to the battery makes absolutely no difference in how a mobile antenna functions. The ground terminal on the battery has nothing to do with a ground plane. In most vehicles you will have this connection simply because that is how vehicles are designed, but it is not required.

A connection between the frame and roof is also not required, however it is a good thing. That being said, simply having a 0 ohm connection as reported by a multimeter is not always enough, and to be sure it needs to be properly RF bonded.

As stated above, RF acts different than the DC a multimeter uses for continuity testing. You cannot assume that a 0 ohm connection reported by a multimeter will be 0 ohms at 27 MHz.


The DB

 

[rabbiporkchop]

Sucking 80 amps through an 18 gauge wire has a tendency to catch vehicles on fire which is precisely why I follow my step by step process before I even attempt to tune an antenna because there's other factors at play besides worrying about the antenna amperage draw is another thing to take into consideration. Nothing wrong with killing two birds with one stone

Never said it was required but it definitely eliminates a bunch of potential problems and by eliminating potential problems right at the beginning you're automatically taking a bunch of guesswork out of the equation simultaneously. There is a step by step process I follow on every installation and I never seem to have those same issues because I do everything in a specific order.