issues with my cb...need advice

@DirtJersey,
I'll second what MsJamie says about coax. The urban myth about magic coax lengths seem to be self-perpetuating. When I do an install, I leave an extra foot or so at each end and tuck the slack away neatly. I do that for a couple of reasons.
One is that, if the user is a tinkerer, constantly swapping amps and meters and different things in and out of the line after the radio, he/she/it will eventually flex the coax enough times where it goes into its connector that either the braid or the center connector will break. If I leave a little slack, there will be enough extra coax to pull out to put a new plug on, even a couple of times. Same thing goes for the antenna end, where the connector is exposed to the ravages and vagaries of Mother Nature, vandals, and brigands.
Another reason for doing it is so that I, or another shop with a large wattmeter or antenna analyzer (well, larger than the little $10 mini-meters) will have enough room to get my/his/her/its jumper to the radio and still reach the meter with the running line to the antenna at the time of install, or sometime in the future. If the line is precisely the right length and PL-259's shell snugs up the last millimeter of slack, I/he/she/it will have to drop the radio out of the mount to meter it.

If it were possible to know the *exact* frequency you were operating on (withing a channel or two) and measure the coax *precisely*, and you know the velocity factor of the coax, then an electrical halfwave in length of coax will show you the same SWR at the "radio end" as it sees at the "antenna end". But stray, even a little bit on any of those measurements, or in the fabrication of the feedline, and you end up with just a random number on the meter.

I tune an antenna with the shortest feedline that will let me get out of the area of influence of the antenna, typically from inside the vehicle, through a window. If you're tuning from the radio with a fully installed radio/coax/antenna system, just tune for minimum reflected voltage as shown on the SWR meter, whether it's the one on the radio or an external one. In the real world, the difference between 1.5:1 and 1.3:1, while measurable on a meter, will never be noticed on the air. As long as it's low enough that the radio is not in jeopardy, the actual number is really only good for bragging rights.

By the way, I was born & bred in Noo Joisee. At the time, most of my radio gear was old and tube powered, except for my old Courier TR-5 mobile, and it had pretty worn-out pots. When I first got the Courier, even in NJ, on October mornings, the pots were pretty stiff in the mornings until the car warmed up some.

In 1972, I moved to Bareflanks, Alaska. One of the things I bought there was a new JC Penney Pinto 23. At -40 (F or C, same) the pots wouldn't turn, the mic cord wouldn't bend, and the RX audio was terrible if I'd left it "on" (it was on a ignition relay switched line to the battery) before I shut the pickup down the night before. It took longer to warm up than it did in NJ, but once it did, it was fine.

I'm guessing that the controls on your Cobra turn OK after the vehicle warms up? It seems to be an issue of the materials used in the manufacture and/or what kind of cleaner-lube someone before you has used on the controls. In the whole time I had mine, I never used anything but 97% isopropyl alcohol in mine when they got noisy, but they still got stodgy when the mercury plummeted.

Hope that helps some.
73,
Handlebar

 

This creates an "RF Choke" and de-tunes the antenna system, in some cases to the point of not being able to get the SWR down to an acceptable level.

 

Huh?!? You make it sound that an RF choke is a bad thing. A choke does nothing to the signal on the inside of the coax. If you've got some sort of antenna that is designed to run without a ground plane and uses the coax braid, then it might interfere with that then, but for the typical antenna, there's nothing you can do to the outside of a feedline that will affect the signal inside, short of bending it so far (smaller than the minimum bend radius specified by the manufacturer) that the spacing between the inner and outer conductors changes, thereby changing the characteristic impedance of the line at that point. If changing the shape of the feedline changes the SWR, than something was already wrong, and there was "RF in the shack", with RF riding on the outside (braid) of the coax.
I would think that a Figure-8 is more likely to do just that at the tops and bottoms of the "loops" unless it's really, really loose.
73,
Handlebar

 

I learned this back in 1968 with my first CB install. And if you look around you will find that the Experts still recommend it today.

 

Read what Wilson says about the extra coax.

http://wilsonantenna.com/faq.php

 

@IWillNot,
This friend of yours kinda points out that just being a ham does not necessarily mean that one is also a good hands-on technician, or good at theory. Some of my best friends are hams, yet I would not let some of them see the insides of any of my radios unless they were wearing either handcuffs or boxing gloves and I were in the room with them.

When I went to work at the first commercial two-way radio shop of my career, I probably learned more in the first three months there than I had in (at that point) over 10 years as a ham. Things from the theory books got played out day-in and day-out. We had two engineers to do system design, and we got to see the differences that incremental changes in components made to overall performance.

I feel lucky to have had a chance to start learning in a practical environment like that. A lot of things that I thought seemed intuitive at first glance didn't really hold up. SWR, for instance, does not equal efficiency. As one poster mentioned, a dummy load on the end of the coax can show a 1.0:1 SWR and still not get out.

Just my thoughts. And since I'm so old, I try to make a point of writing them down before they escape -- they don't happen to me that often

73,
Handlebar

 

Yes, I've seen that it's what they mention on the Wilson site. A brand which, if I recall correctly, made their name originally largely on the success of their very popular magnetic mount line. With only a capacitive coupling for the return path for the RF, it stands to reason (at least to me) that they count on the coax braid for a large portion of the "insurance" for that path. I have no doubt that, for certain products, it can make a difference.

Having established the practice of one manner of feedline dressing, it may be easier on users to maintain that same method, rather than add any chance for confusion by having them remember which method to use with which kind of antenna. But I don't know; I'm not a manufacturer of antennas with an obvious financial stake in their success.

As for "the Experts" (capitalized or not) I'm apparently not looking around in the right places. The professionals in land mobile with whom I spent a career (up to the 930 MHz range) didn't seem to think it noteworthy.

I suppose it will be one of those bits of the RF black arts over which there will always be differing opinions, though. Magnum vs. Ranger, Cobra vs. Stryker.

73,
Handlebar

 

This was out long before Wilson. Like I said I first learned this in 1968 with my first CB install by a old Ham. And many CB install books say the same. I've installed anything other that CB and Amateur equipment.

 

After reading that, I vow to never buy a Wilson antenna.

If putting an RF choke in line detunes your antenna system that much, then there is something very wrong with your antenna system. You do not want your feedline to radiate; that RF energy is being wasted bouncing around the inside of your vehicle, and not out in the air, where you want it.

I especially LOLed when I read about "stuffing" the coax, or putting it under the carpet. Both will eventually cause the coax to fail, either through kinking the cable or getting smashed underfoot.

And then there's this, regarding vans and SUVs...

I nearly fell out of my chair over this one.

Um, the luggage rack will still be in the near field area of the antenna, even if moved a few feet forward. It's still going to affect the tuning. Once the antenna is tuned to the vehicle, the luggage rack won't make a bit of difference. However, you will be effectively beaming your signal behind you. Most of the time, I want to talk to people ahead of me.

Also, let's move the antenna from the only half-decent spot (from a grounding standpoint) on the vehicle to one with significantly increased ground losses. The only reason I could think to do so is to significantly increase ground losses to cover up antenna design issues.

I guess the loss from the radiating coax alone isn't enough to do it.

 

"Professional" simply means that someone gets paid for it. Those guys with the golden screwdrivers who can set "dead key" to 2W and can "whistle up" 15W of "swing" are professionals, too, but I won't let them near any of my radios. (Anyone who does that to a radio has no clue as to how AM modulation works.)

When I was the manager of the local branch of a national contract transportation company, we would get vans that had the radios professionally installed. As in powering a 14 Amp radio from a 10 Amp lighter socket. (They "fixed" that by putting in a 15A fuse.) Then they would take the excess coax, make a 6" coil, then mash it flat and use wire ties to hold it together. The bends in the coax were about 1.5" across... minimum bending radius of RG8X is 2.5" (5" coil).

Yes, professionals. Easier and faster trumps properly every time.