CB install, SWR very high, help me!!!

[fifthcircle]

OK, so I have searched a ton, read a ton, and have troubleshot a ton....

THE SITUATION:
2006 Tacoma with Fiberglass cab high camper shell,
Cobra 75 WXST, 18' firestik coax, stainless hood channel mount, 3' wilson

I also have a second coax, 4' firestik, and another mount in the bed that I used prior to the topper....

Long story short, my SWR is very high (in the red, 5 to 10). I have good ground showing using my multi-meter. All continuity is where it should and/or shouldn't be. I have tried both mounting locations with both antennae and both coax. My next step will be to try the Cobra 29ltd. It does have a built in SWR, not that I ever even knew it... LOL!!!

Now, I don't have the paint scraped off under the mounts, should I?

I do have marginally better SWR once in a while, for apparently no reason, the best I have seen is ch1=5, ch40=3.



In the past, I just hooked up the CB and slapped on the antennae, never tuned with an SWR meter, and just went with it. Never had a single problem with several different radio's and different mounts. The mount in the back of the bed (painted metal just inside the tailgate) with a Cobra 29ltd had awesome range (compared to several other people I knew with jeeps and other units). Was I just lucky?

I am quite frustrated at this point, and just about to say the heck with it, and just roll....I am sick of messing with it. :ar15:

 

[kb7our]

Seems like the base of your mount may not be making good contact with the body. Do you have the body tied to the frame via braided strap to increase the effectiveness of your ground plane? What type of SWR meter are you using and how are you using it? A few pics would be most helpful. If you will be at OX11 on the Sat I may bring my MFJ SWR meter and could give it a check for you.

 

[fifthcircle]

Seems like the base of your mount may not be making good contact with the body. Do you have the body tied to the frame via braided strap to increase the effectiveness of your ground plane? What type of SWR meter are you using and how are you using it? A few pics would be most helpful. If you will be at OX11 on the Sat I may bring my MFJ SWR meter and could give it a check for you.

I am at work...I could maybe grab some pics in the AM.

I am suspect of the mount and proper bonding, but didn't want to start grinding off paint just to have that not work. The mount is screwed onto the drivers side front hood channel ~1' in front of the windshield via 5 screws. I also ran a small jumper from one screw to the ground for the battery that is on that quarter panel just under the hood channel ~1' fwd of the mount. This didn't help...but it is just a small jumper, and not a proper bonding strap.

It is a friends SWR meter, and he tuned his install (Jeep) with it the same week. It is a cheap one that he got with his CB kit from RightChannelRadio.com

Not gonna be at OX11, but heading to Moab in less than 2wks! :wings:

I am thinking about snagging a magnetic mount antennae from WalMart for under $20 and giving that a try. Grinding the paint would be cheaper, but much more permanent...nothing some rattle can red can't fix since it's under the hood. :Wow1:


EDIT: I found some pictures that illustrate almost exactly the way mine is installed...antennae mount anyway. Right off the FireStik site:
http://www.firestik.com/Instl-Text/ford174.htm
The only difference is that I have sheet metal screws (5 total) and no bolts/nuts on the mount.

 

[trump]

Isolation washer on the top or bottom?

 

[fifthcircle]

Isolation washer on the top or bottom?

Isolation washer is on the top, with the Firestik "firering" fitting on the bottom with the protruding vinyl up (into the mount). I double checked this and have tried putting the firering on the top of the mount, with the isolation washer on the bottom of the mount...same result.


After thinking about it all day, and looking everywhere online....I am pretty sure it is a problem with RF grounding. On Firestik's site, they don't say you need to remove any paint for proper grounding, but without doing so, I don't believe it's getting a proper grounding surface for RF (even though I show continuity, electrically).

 

[xtatik]

After thinking about it all day, and looking everywhere online....I am pretty sure it is a problem with RF grounding. On Firestik's site, they don't say you need to remove any paint for proper grounding, but without doing so, I don't believe it's getting a proper grounding surface for RF (even though I show continuity, electrically).

^Do this....Also bond the hood to the rest of the vehicle. Run a short braided strap from the hood to body at each of the hinge points.

 

[fifthcircle]

^Do this....Also bond the hood to the rest of the vehicle. Run a short braided strap from the hood to body at each of the hinge points.

Yeah....damnit. I was hoping it was an easier solution. Being lazy is HARD! :coffeedrink:
It's not on the hood though, it's on the drivers quarter panel (hood channel). Not sure what bonding the hood will do for me?

Where do I get some good wire braid? Not looking forward to spending more money either. What a pain! Maybe I can scrounge some up at work. Gotta be some at a Telecomm company. If not, I am still thinking a cheap mag mount on the roof would be MUCH easier...at least for now.

 

[Hedge]

Not sure what bonding the hood will do for me?

It should help make the hood a more effective counterpoise/ground plane for your 5/8 wave antenna, which needs a ground plane. This will in theory improve both reception and transmission ranges.

Where do I get some good wire braid?

"The shield from RG8 works well if the length of the strap is short (under 10 inches or so). Just take care when you strip off the outer jacket that you don't cut through the shield itself. Discard any that is corroded or discolored. Flatten it out by pulling it over a rounded surface. A large, round screwdriver shaft works well for this purpose." (http://www.k0bg.com/bonding.html)​

 

[fifthcircle]

It should help make the hood a more effective counterpoise/ground plane for your 5/8 wave antenna, which needs a ground plane. This will in theory improve both reception and transmission ranges.

"The shield from RG8 works well if the length of the strap is short (under 10 inches or so). Just take care when you strip off the outer jacket that you don't cut through the shield itself. Discard any that is corroded or discolored. Flatten it out by pulling it over a rounded surface. A large, round screwdriver shaft works well for this purpose." (http://www.k0bg.com/bonding.html)​

I have a ton of coax that I can use the shield from (RG6 and RG11...the good stuff as far as CATV goes )

UPDATE:
I changed the mounting location a tad. I moved it back a few inches and used a bolt that is part of the hood channel. Found the idea from another similar install that worked = PICTURE. Seems to have helped a LOT! I can now tune the antennae within reason, and safe usage. This is great, and I am not looking for perfection, just not wanting to fry the txmtr :smiley_drive:

So, I did some really quick tuning before work. I have it tuned almost a perfect 1:1 on about ch15. The issue is how much it swings from ch1 to ch40. Ch1 = 1.6, Ch40 = 2.5
What's up with that? Darn antennae seems really sensitive to minor adjustment of the tuning screw. Still need more grounding maybe?

 

[1911]

So, I did some really quick tuning before work. I have it tuned almost a perfect 1:1 on about ch15. The issue is how much it swings from ch1 to ch40. Ch1 = 1.6, Ch40 = 2.5
What's up with that? Darn antennae seems really sensitive to minor adjustment of the tuning screw. Still need more grounding maybe?

Your antenna is too long. Adjust the length until Ch 1 = ch 40.

 

[fifthcircle]

Your antenna is too long. Adjust the length until Ch 1 = ch 40.

Yeah, I get that. I was just wondering if my total range is excessive? Looking at the Firestik site, I see that a fairly large swing from one end to the other is pretty normal...at least per their "Off Center Tuning" tech doc: http://www.firestik.com/Tech_Docs/Off-tune.htm

 

[1911]

Every antenna tunes in a parabolic curve. You can only have an ideal multiple of the wavelength for one single frequency; everything else higher or lower is a compromise. In the cb band, it's always best to tune so that 1 and 40 are equal, this will give the best average performance over any/all channels. The lowest dip in SWR will not be exactly in the middle this way but it doesn't matter. The low dip marks the single frequency that particular antenna is an optimal length for.