Cobra 29LX and Wilson Little Wil- SWR Help (Extremely High)

Allof75

Pathfinder
Hi all, I just installed a Cobra 29LX and Wilson Little Wil magnet mount antenna on my pathfinder, it appears everything is hooked up correctly, and yet I keep getting SWR readings of 3 and above on channels 1, 20, and 40. I go through the Cobra factory recommended procedure to check and calibrate to SWR every time, and I understand the radio's meter is not as accurate as others, but I don't think it'd be reading a 3 when it's actually a 1.5. The antenna is preferrably mounted in the center of my roof, and even with trimming it, moving it to other locations on the roof, seeing if coiled wires were affecting the reading, and moving the whip up and down in its mount, I keep getting the same extremely poor results.

Any help?
 

Vegas_Nick

Adventurer
Honestly, I'd get your hands on a real SWR meter and check it. That is high for a lil Wil, even out of the box. Radio SWR meters are hardly accurate. IIRC, the 20 did have an SWR cal adjustment as well, but that only goes so far.
 

Allof75

Pathfinder
Honestly, I'd get your hands on a real SWR meter and check it. That is high for a lil Wil, even out of the box. Radio SWR meters are hardly accurate. IIRC, the 20 did have an SWR cal adjustment as well, but that only goes so far.

I realize it's an inaccurate measurement, but I'd be really surprised if it was reading a 3 and it was significantly lower. Do you mean the radio itself might have a SWR calibration for the SWR meter itself?
 

4x4junkie

Explorer
Yeah I've never seen a built-in meter that was more than a few points off (worst I've seen was maybe 1.4 when it was actually 1.7, for example).

All connections tight?
Can you try a different antenna? (or a dummy load, which would rule out the meter being bad).
 

Allof75

Pathfinder
Yeah I've never seen a built-in meter that was more than a few points off (worst I've seen was maybe 1.4 when it was actually 1.7, for example).

All connections tight?
Can you try a different antenna? (or a dummy load, which would rule out the meter being bad).

Exactly, and so far as I can tell, I double checked everything. I don't have another antenna handy at the moment ️haha. I'm thinking it may be an issue with the cobra itself? Does anyone think the placement of the antenna with the roof rack sticking up 6" above the base, about 1' away on all sides would make a difference?
 

4x4junkie

Explorer
Does anyone think the placement of the antenna with the roof rack sticking up 6" above the base, about 1' away on all sides would make a difference?

That certainly could be affecting it... Very short antennas (especially base-loads such as a Little Wil) are more affected by nearby metal objects than a taller antenna would be. If you can't change it's location, I say get a taller antenna for it (a 5½' high top-loaded whip such as a Francis CB-26 Hot-Rod should do fine there). A taller antenna will have FAR better range anyway (a spring on it's mount should alleviate concerns of damage from overhead branches/drive-thru ceilings).

Another option might be a permanent-mount of some sort to attach the antenna straight to the front or back of the rack.
 

CCPAJeeper

Observer
The antenna needs to be grounded. I had a mag mount previously and could not get the SWR adjusted close to the recommended range. I then talked with a local CB guru who advised as to the importance of grounding the antenna. I got a solid mount and grounded it properly. The SWR was easily adjusted to the optimal end of the range and the radio works great.
Hope that helps you out. Good luck.
 

whowey

New member
Some metallic paints will mess with the swr reading. You are making sure to check the swr with all the doors closed. This will affect it also.
 

Allof75

Pathfinder
4x4, I'm planning on replacing it if I can't seem to get a handle on it, I'll look into those; thanks!

CCPA, how did you ground your mag mount?

Whowey, I made sure to close all the doors, and my paint does have flake in it but I'd be surprised if that small amount killed the communication.
 

BigJimCruising

Adventurer
Oh my does this thread bring back memories (nightmares?) of chasing down high swr's! So sorry you're going through this! Doors open, wrong paint, to close to racks! Enough to make you take up drinking! Well it did for me anyway. Let me throw in my $.02 worth just to make it a little worse. Lets get back to the basics for a bit and check a few things out first.
1. Check your power wire. I know I know but check it anyway.
2. Check your ground, both for the radio chassis and the ground to power the radio. Did you run a proper ground wire or just find a screw under the dash and add an eyelet? Is the radio properly grounded to the chassis? These can cause just the kind of problems your having.
3. Recheck all the connections on the back of the radio. Power, negative and antenna. Is the antenna connector really seated or is it kind of loose?
4. Have you checked the antenna coax? This part can really suck if you've already hidden the coax behind panels but it has to be done. (Sorry) You need to inspect the entire antenna coax, from the connector to the antenna. Is the coax firmly attached to the connector? Now inspect every inch of coax. Look for punctures, cuts, kinks or sign that there might have been a kink, for the coax ever being crushed or anything else that might have harmed the inside of the coax. Find your inner "Columbo" here and look for any signs of coax damage as any of these things can cause your swr to suck while fooling you into thinking it's not the coax.
5. Do the same for the antenna. You'd be surprised how many antennas over the years have been bad right out of the box. Don't forget to check how it screws into the mag mount. Make sure everything is tight and feels solid.

Everything above checks out ok? Then as mentioned above go out and buy an SWR meter. You don't have to get crazy here, for CB the light duty SWR meter from your local Radio Shack will do just fine. Don't rely on the radio meter, I have had enough of them not properly calibrated over the years to make me never trust one again. I've been down that rabbit hole chasing bad SWR's due to bad radio meters that I will never ever trust one again! (rant over!)

Now make a graph. Put channels 1, 20 and 40 over their own columns. Take an SWR at each channel and write it down in each column. Start adjusting the antenna a little bit at a time and repeat the readings and write those down. Repeat until you start to see the pattern. After a while you might find that the antenna needs to be at its highest setting to bring down the swr. Or you might discover that a bit of the antenna might have to cut off to shorten it to bring down the swr. If so only cut about a quarter inch at a time and start over. If you have be longer well you might have to buy a longer rod but that rarely happens. This can be pretty time consuming since you'll be repeating this over and over again. But in the end you'll have one of those setups that the other guys just don't understand why you can talk to guys further away then they can!

And last but not least. If you just can bring yourself to start cutting antennas then let me offer this. I see your in the OC. I'm in Garden Grove. I won't be able to help until next weekend but if your still having problems let me know and we'll see if we can find a time between us to get together and try to solve your problems. I would have bypassed all the above if I could have met sooner but I just don't have the time until next weekend. And I'm sure by now you're wanting to make some progress!

Best of luck!!! Jim.

All this still fails? Time to find a radio shop and have the pro's do their magic to solve your problem. Not cheap but worth it.
 

4x4junkie

Explorer
CCPA, how did you ground your mag mount?

I suspect he's implying he "grounded" his antenna by replacing his magnet mount with a permanent-mount.
Certainly that is the best way to go, however I suspect there may have been another issue at play (something preventing the magnet mount from working correctly, or the mount itself being defective)...

A magnet mount antenna's ground works via capacitive coupling (this is why most mounts have a piece of foil over their bottom surface). They do not need a separate ground wire or a physical DC connection to function.
When you place the mount against the vehicle, it's foil bottom in proximity to the car's steel creates a capacitor (with the paint as it's dielectric) that carries the antenna's ground current through to the steel body (even though there's no DC connection, it's capacitance still presents a current path of less than an ohm (often much less) at 27 million cycles/second AC, the radio frequency your CB transmitter operates at).
Some info about how capacitors work here:
http://en.wikipedia.org/wiki/Capacitor
(warning, very technical)


Something that can prevent mag mounts from working properly is the common practice of putting pieces of cardboard or other thick items under the mount in an attempt to protect the car's paint. Such items increase the mount's distance from the steel, which not only decreases the magnet's holding power, it also reduces the capacitance underneath the mount, increasing it's impedance to ground (not sure if that was CCPA's issue, or could it be yours?). Those worried about their car's finish, make sure whatever you use is thin like a single sheet of bath tissue or a piece of cellophane (layered-up paper towels is a no-go here).


Also, I don't disagree with BigJimCruising's comments about checking everything you can, however the power wires shouldn't be something that affects your SWR. A bad SWR almost always is a result of issues with the antenna system. If changing the power wires around did affect the SWR, this would indicate a deficient ground in the antenna system, as under no circumstances should there be RF current flowing on your power wires.
 

Allof75

Pathfinder
Oh my does this thread bring back memories (nightmares?) of chasing down high swr's! So sorry you're going through this! Doors open, wrong paint, to close to racks! Enough to make you take up drinking! Well it did for me anyway. Let me throw in my $.02 worth just to make it a little worse. Lets get back to the basics for a bit and check a few things out first.
1. Check your power wire. I know I know but check it anyway.
2. Check your ground, both for the radio chassis and the ground to power the radio. Did you run a proper ground wire or just find a screw under the dash and add an eyelet? Is the radio properly grounded to the chassis? These can cause just the kind of problems your having.
3. Recheck all the connections on the back of the radio. Power, negative and antenna. Is the antenna connector really seated or is it kind of loose?
4. Have you checked the antenna coax? This part can really suck if you've already hidden the coax behind panels but it has to be done. (Sorry) You need to inspect the entire antenna coax, from the connector to the antenna. Is the coax firmly attached to the connector? Now inspect every inch of coax. Look for punctures, cuts, kinks or sign that there might have been a kink, for the coax ever being crushed or anything else that might have harmed the inside of the coax. Find your inner "Columbo" here and look for any signs of coax damage as any of these things can cause your swr to suck while fooling you into thinking it's not the coax.
5. Do the same for the antenna. You'd be surprised how many antennas over the years have been bad right out of the box. Don't forget to check how it screws into the mag mount. Make sure everything is tight and feels solid.

Everything above checks out ok? Then as mentioned above go out and buy an SWR meter. You don't have to get crazy here, for CB the light duty SWR meter from your local Radio Shack will do just fine. Don't rely on the radio meter, I have had enough of them not properly calibrated over the years to make me never trust one again. I've been down that rabbit hole chasing bad SWR's due to bad radio meters that I will never ever trust one again! (rant over!)

Now make a graph. Put channels 1, 20 and 40 over their own columns. Take an SWR at each channel and write it down in each column. Start adjusting the antenna a little bit at a time and repeat the readings and write those down. Repeat until you start to see the pattern. After a while you might find that the antenna needs to be at its highest setting to bring down the swr. Or you might discover that a bit of the antenna might have to cut off to shorten it to bring down the swr. If so only cut about a quarter inch at a time and start over. If you have be longer well you might have to buy a longer rod but that rarely happens. This can be pretty time consuming since you'll be repeating this over and over again. But in the end you'll have one of those setups that the other guys just don't understand why you can talk to guys further away then they can!

And last but not least. If you just can bring yourself to start cutting antennas then let me offer this. I see your in the OC. I'm in Garden Grove. I won't be able to help until next weekend but if your still having problems let me know and we'll see if we can find a time between us to get together and try to solve your problems. I would have bypassed all the above if I could have met sooner but I just don't have the time until next weekend. And I'm sure by now you're wanting to make some progress!

Best of luck!!! Jim.

All this still fails? Time to find a radio shop and have the pro's do their magic to solve your problem. Not cheap but worth it.

Thank you for the extremely helpful post, I'll run through the checklist (most of it seems solid already) today, and verify if that changes anything. If I keep running into issues, I may have to contact you via PM for the help in-person haha.
 

Allof75

Pathfinder
I suspect he's implying he "grounded" his antenna by replacing his magnet mount with a permanent-mount.
Certainly that is the best way to go, however I suspect there may have been another issue at play (something preventing the magnet mount from working correctly, or the mount itself being defective)...

A magnet mount antenna's ground works via capacitive coupling (this is why most mounts have a piece of foil over their bottom surface). They do not need a separate ground wire or a physical DC connection to function.
When you place the mount against the vehicle, it's foil bottom in proximity to the car's steel creates a capacitor (with the paint as it's dielectric) that carries the antenna's ground current through to the steel body (even though there's no DC connection, it's capacitance still presents a current path of less than an ohm (often much less) at 27 million cycles/second AC, the radio frequency your CB transmitter operates at).
Some info about how capacitors work here:
http://en.wikipedia.org/wiki/Capacitor
(warning, very technical)


Something that can prevent mag mounts from working properly is the common practice of putting pieces of cardboard or other thick items under the mount in an attempt to protect the car's paint. Such items increase the mount's distance from the steel, which not only decreases the magnet's holding power, it also reduces the capacitance underneath the mount, increasing it's impedance to ground (not sure if that was CCPA's issue, or could it be yours?). Those worried about their car's finish, make sure whatever you use is thin like a single sheet of bath tissue or a piece of cellophane (layered-up paper towels is a no-go here).


Also, I don't disagree with BigJimCruising's comments about checking everything you can, however the power wires shouldn't be something that affects your SWR. A bad SWR almost always is a result of issues with the antenna system. If changing the power wires around did affect the SWR, this would indicate a deficient ground in the antenna system, as under no circumstances should there be RF current flowing on your power wires.

Thank you, I understand the process of the magnet mount, and didn't put anything under it when testing it in the first place, it was stuck directly to the paint. But again, I'll attempt to spot anything that may cause trouble.
 

Rigged

Observer
This might sound silly, but you didn't cut the coaxial cable to length right? I've done that before and chased my tail for a while. Make sure not to coil up the excess cable and run it throughout the cabin as well.

Like everyone said before check the grounding plane. One step you can try if you have access to a multimeter/VOM is to check continuity between a good known ground and the mount.

With the multimeter you can also test your coaxial cable by checking continuity between the center conductor and outer shield, you should have none if you do then something is wrong with the cable.

Hopefully you can get it setup properly.

Also if you get this far it is helpful to know:

If SWR is higher on channel 40 than channel 1 then your antenna is too high.
If SWR is higher on channel 1 than channel 40 then your antenna is too short.
 

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