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Mobile problem...sort of a RF grounding theory type question

B

Bobcat

Member
May 24, 2005
34
2
18
Deer Park, TX
Back in June I resurrected my old '87 F150 Stepside bringing it back from the dead. In so doing I had to troubleshoot a taillight/brake light problem that wound up being that the bed was not properly grounded to the frame (never could find a ground strap and, when I jumpered the lamp ground the the bumper everything works!). The largest wire I had at the time was about #14 maybe #12 so I took that with two appropriate sized ring connectors and put it under a good solid bed bolt and a good solid frame bolt. Voila, the light problem was fixed. ( Afterwards, I thought about getting one of the cables like a Ford uses to go from the solenoid to the started since it is a heavy #4 wire with good heavy ends, but I never did it.)

Now....to the CB part of this story.

I put in a Cobra 21LTD that is used, once my father inlaw's, a new 4' Firestick(tuneable), and new RG-8/X coax.

The problem is, I could never get the SWR down any further than about 1.6:1 maybe 1.8:1 which I know is not real good, but I could at least sandbag but I don't transmit much.

I've been thinking lately about that little bitty ground wire...

is it possible that that little bitty wire is not sufficient to provide grounding for the antenna at RF frequency?

It may be a dumb idea but I thought I'd see if I could raise another opinion.

Thanks in advance
 

i think we need more details. like were on the truck it is mounted. could be to close to the cab and just be a little reflect. 1.8 should not stop you from transmitting.

anyway a picture if possible or a better description of were and how it is mounted would be great. :)
 
I can get a pic but until I do.....

This is an '87 Stepside. The antenna mount type is abody panel mount stye (read that..... hog a hole through the metal, stick it in the top, put the big washers and the nut on from below, tighten it down good, and screw on your coax.

I have it mounted on the bed rail ( the 4" wide or so rim of the bed box ) about 6" back from the front of the bed. That puts it just about 8" or so from the cab.

Extra info: my last antenna was a 5' Firestick and I had no problem getting it to 1.2:1 or 1.3:1 in that area.... That one eventually bropke a few years ago. I just recently bought another but the shop did not have another 5' so I bought a 4'. (the shop clerk said that's all they ever sell and that is why he doesnt keep 5'ers in.)

That, of course, does bring the loading coil down closer to the cab.......
 
Boy.......... I never dreamed....... two things I guess I didn't learn along the way:

1) tunable Firesticks.......you had BETTER put the red cap on between tuning tweaks, and

2) apparently Radio Shack coax assemblies with the "part metal part rubber" plugs...... stinketh greatly.

ON point #1....... I fought that antenna for a half hour it just did not want to set correctly.....it just didn't have the right "feel". Well...when I was done I put the cap back on and took one more reading.......kaPOW it jumped like crazy. I had to shorten the tuning screw by,ohhhhhhhh, maybe 6 turns total. BUT what I noticed.... with the red cap on it behaves much more smoothly. I was able to "walk it right in to the best possible value I could get which wa 2:1 on Ch1, 1.7:1 on Ch20, and 2:1 on Ch40. The 21LTD deadkeys 2 and whistles to 6 so that aint too bad. (I just checked ... it is a Dynascan).

Now, on point #2...... I know I considered getting raw RG-8/X and a couple of PL-259s..... but I had a senior moment. I couldnt find any RG-8/X locally..... so I just decided to tolerate the R/S cable for a while. Apparently.....a big mistake. At either end of the cable.....if you hold the connector still....and wiggle the cable.... the radio noise breaks in and out.... as if maybe the braid is not making right..... or the tip is not meeting the inside of the jack just right...... I'm thinking thats good for about -50 on my points.

Sometimes....you gotta learn the hard way.
 

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