Looking for a fair CB antenna need help

[sLcREX]

Interesting stuff, so when you say grounding to the frame or grounding to the battery, you're referring to the black wire on the CB correct? Not the Fuse block?

 

[frieed]

My guess is even with a horrible SWR, for the short distances of trail use, you could get by, but
Bottom line is:

If you are concerned about the longevity of your radio, then check the SWR. If it's OK then good, if not, then tune the antenna length. It is a simple process and some on here will help you with that, myself included.
-Frieed

p.s. unless you're DAA that is

 

[sixstringsteve]

Interesting stuff, so when you say grounding to the frame or grounding to the battery, you're referring to the black wire on the CB correct? Not the Fuse block?

Hickey is recommending grounding directly to the battery. Or, in other words, ground your fuse block to the battery, then attach your black wire to the ground on your fuse block. The fuse block makes it more complicated than it needs to be if you're not real familiar with wiring.

Here's what you need:

ground wire (black wire) directly to the chassis OR negative battery terminal. Hickey stated that he prefers to go straight to the battery. I choose to ground it to the chassis, but I always remove all paint/coatings when I do that.
+12v (red wire) goes to the battery +. For safety, to prevent a fire, and to protect your CB, you'll want to make sure there is a fuse on this wire. The closer to the battery the better.

I'm sure there are tons of people on here who would be happy to help you wire that. It takes about 20 min. I'd be happy to help, but I know you live a ways away from me. You can probably find someone a lot closer.

 

[gijohn40]

With a magnet mount, you throw it on and it's grounded.

So tell me how this is grounded? the magnet does not make a ground... the only thing your grounding is the antenna to the cb.... so the ground plane really is not there which is why magnetic mounts are not better then an actual physical ground to the car... I will stick to my fiberglass antenna any day with a proper ground at the coax mount.

Now having been a Ham radio operator since the early 90's and working with radios since the 70's... You do have some things correct like making sure the bulk of the windings in the antenna are above the vehicle. and that the best place for the antenna is dead center of the vehicle to get a circular pattern around the vehicle. but if you want a pattern where the majority of your signal goes to the front of the vehicle then placing the antenna in the front is going to give you best results. This is due to the metal of the vehicle will act as a reflector sending the signal to the front.

ok sorry if this seems like an insult... not ment to be one... no sleep for days makes me brain dead...

 

[sixstringsteve]

Oh good, the electrician has entered the building. Thanks for setting the record straight, I don't feel insulted, just foolish for being wrong. Now I know that mag mounts aren't grounded. Is that a problem? I know it works better than a fiberglass one that isn't grounded. My SWRs are below 1.3 with my mag mount antenna. Is mounting to the car and getting a good ground better? I realize that a non-magnetic antenna doesn't work well when it doesn't have a good ground. Why do the magnetic antennas work so well without a good ground? (just trying to understand)

I love the easiness factor for people new to CBs. A lot of guys I've helped didn't realize that paint was keeping them from getting a good ground. They didn't want to scuff up the paint for their bracket, so they got a bad ground. Maybe I'll switch to a solid mount one day for my wilson 5000. For now, I'm loving my mag mount.

 

[gijohn40]

the magnet does make a Fake ground by the magnetism... in non technical terms... kind of like the way a current going thru a transformer will produce another current in the secondary windings which are not physically connected to the primary windings... look up the word "inductance"

 

[gijohn40]

Maybe if you give me some advance notice I can put together a class on radios for your next training day.... I have several different styles of antennas and could even bring some meters to help set up some antennas.

 

[frieed]

It's been quite a while since electromagnetic field theory classes and I have little direct experience with CB's, but I'll step into this a little bit and probably will get ass handed to me:

The ground plane is very different from the DC ground to the battery measured by volt/ohm meter
(rf finds the lowest impedance path 'at it's frequency' which may not be the same as for DC)

A ground plane is an RF reflective surface that makes your 1/4 wave mono-pole antenna look like a 1/2 wave dipole and is mostly unrelated to grounding the antenna (imagine putting the base of the antenna on a mirror, what you see with your eyes (the antenna and it's reflection )is how the antenna works at radio frequencies)

Typical fiberglass antennas are top loaded and (I think) more sensitive of ground plane because most of the "length" (the coil) is farther from the ground plane and thus better DC connection helps (this is speculation)

Typical mag mount antenna is base loaded (coil at the bottom) and close to the ground plane and less sensitive to the dc connection (speculation here as well)

Both of the above are a compromise to the better 102" whip antenna since it actually matches the 1/4 wave length vs coil trickery

some/most antenna models assume an infinite ground plane in all directions

If the ground plane is not symmetric, the radiation power and reception sensitivity are biased towards over the ground plane.
Specifically, I have my antenna on the driver side of my hood, the best transmission and reception are to/from the passenger side.

SWR is a measure of the power reflected back to the radio by the antenna and cable

Changes in impedance cause reflections

Tuning the antenna changes the length/impedance of the antenna to match the radio and reduce reflections

Impedance of a cable is a function of the material used for the insulator between the center conductor and the shield and the geometry of the cable

DC shorts will definitely show a fault in a cable, absence of them does not prove a good cable

Smashing the cable may not cause a short in the cable that you can detect with an ohmmeter, but it will change the impedance and cause reflections.

These reflections will affect your SWR

Lastly, there are no fixed solutions, SWR varies with antenna, antenna placement, cable, routing, and radio. Check your SWR or the world will explode!!!! ok, maybe not, but your CB might, well not explode, but it might just poof....

Sorry, long winded post

Fire away


-Frieed

 

[sixstringsteve]

I understood about 1/4 of that.

 

[sLcREX]

That's alot to take in lol

I think I'll look into getting a fuse block because right now I do have several wires running to my battery terminal for a couple of switches I am running so yeah, I think that will help tidy up my engine bay lol.

 

[gijohn40]

It's been quite a while since electromagnetic field theory classes and I have little direct experience with CB's, but I'll step into this a little bit and probably will get ass handed to me:

The ground plane is very different from the DC ground to the battery measured by volt/ohm meter
(rf finds the lowest impedance path 'at it's frequency' which may not be the same as for DC)

A ground plane is an RF reflective surface that makes your 1/4 wave mono-pole antenna look like a 1/2 wave dipole and is mostly unrelated to grounding the antenna (imagine putting the base of the antenna on a mirror, what you see with your eyes (the antenna and it's reflection )is how the antenna works at radio frequencies)

Typical fiberglass antennas are top loaded and (I think) more sensitive of ground plane because most of the "length" (the coil) is farther from the ground plane and thus better DC connection helps (this is speculation)

Typical mag mount antenna is base loaded (coil at the bottom) and close to the ground plane and less sensitive to the dc connection (speculation here as well)

Both of the above are a compromise to the better 102" whip antenna since it actually matches the 1/4 wave length vs coil trickery

some/most antenna models assume an infinite ground plane in all directions

If the ground plane is not symmetric, the radiation power and reception sensitivity are biased towards over the ground plane.
Specifically, I have my antenna on the driver side of my hood, the best transmission and reception are to/from the passenger side.

SWR is a measure of the power reflected back to the radio by the antenna and cable

Changes in impedance cause reflections

Tuning the antenna changes the length/impedance of the antenna to match the radio and reduce reflections

Impedance of a cable is a function of the material used for the insulator between the center conductor and the shield and the geometry of the cable

DC shorts will definitely show a fault in a cable, absence of them does not prove a good cable

Smashing the cable may not cause a short in the cable that you can detect with an ohmmeter, but it will change the impedance and cause reflections.

These reflections will affect your SWR

Lastly, there are no fixed solutions, SWR varies with antenna, antenna placement, cable, routing, and radio. Check your SWR or the world will explode!!!! ok, maybe not, but your CB might, well not explode, but it might just poof....

Sorry, long winded post

Fire away


-Frieed

now that I had some sleep... Your dead on here....

 

[frieed]

That's alot to take in lol

I think I'll look into getting a fuse block because right now I do have several wires running to my battery terminal for a couple of switches I am running so yeah, I think that will help tidy up my engine bay lol.

Keep the ground lead short. When I installed my CB I ran both wires directly to the battery and had lots of engine noise. I tried various filters without any luck. Finally, I shortened the ground lead and the problem was solved.

 

[DAA]

I know next to nothing about any of this. But I just went through a marathon troubleshooting session trying to get the SWR of my new radio down to an acceptable level. While I may not have actually "learned" anything from the process - I certainly did make a lot of interesting observations for future reference.

Among those observations...

DC shorts will definitely show a fault in a cable, absence of them does not prove a good cable

Smashing the cable may not cause a short in the cable that you can detect with an ohmmeter, but it will change the impedance and cause reflections.

These reflections will affect your SWR

My antenna cable was a prime example of the above. It did not have a short, it tested perfectly on an ohmmeter. But it was "bad" none the less. My best guess, it got a bad pinch or crushed spot on the trail that was doing exactly what Frieed is describing above.

Check your SWR or the world will explode!!!! ok, maybe not, but your CB might, well not explode, but it might just poof....

And I think the death of my old radio was due to exactly this. I had tuned the antenna for it, years ago and SWR was well within acceptable limits. What I think happened, was my cable got damaged as described above, put my SWR through the roof without my knowing it, I continued to use the radio with those sky high SWR numbers and that killed the radio pretty quick. Then I got a new radio, hooked it all up to my old cable and when I went to tune it found the sky high SWR and had one heckuva time figuring it out from there.

Lastly, there are no fixed solutions, SWR varies with antenna, antenna placement, cable, routing, and radio.

Among the observations I made in troubleshooting my recent SWR problem, was that pretty much everything and I mean EVERYTHING in the whole system can have an effect on SWR. An example very pertinent to this thread, since power source/connection is being discussed, is that where I hooked up the power for the radio and how I routed the power wires have a large effect on SWR in my setup. Specifically, it seems that routing the power wires along the same path as the antenna cable is bad ju-ju for SWR in my Jeep. Simply separating the power wire routing from the antenna cable made a large difference in final SWR. That is to say, even after antenna tuning, SWR was a lot worse with the power wire routed alongside the antenna cable than it was with the power wire routed away from it. I discovered this by accident, using a cigarrette lighter plug-in power cable while trouble shooting and getting SWR looking real good, then hooking up my hard wired power cable and SWR suddenly going to crap.

Long winded way of totally agreeing with the notion that everytyhing in the system can have a pretty big effect on SWR.

One last thing, worth tossing in here I guess, even though I kind of don't like having to say it. But, my own experience with mag mount antennas hasn't been very good. They "work", with no muss and no fuss, but I have never been able to get one to work "very good". The K30 I have has never been able to get an SWR much less than 2.0 with any amount of tuning, on several different vehicles and two different radios. Even on the roof of my Megacab, with an hour of trying to tune it, trying every possible length adjustment in 1/8" increments, it wouldn't do any better than a 2.0 SWR. And on my Jeep, the only way to get it even that good, is to put it in the middle of the hood and even then it took a lot of tuning to get it under 2.0. I'm not sold on mag mounts, myself... But, I claim zero actual knowledge of any of this! Just a few observations of my own limited experiences only.

- DAA

 

[sixstringsteve]

my k30 antenna was aroudn 1.8-2.0. My Wilson 5000 comes in right around 1.0. I believe 2.0 or lower is safe for your radio.

 

[TROKITA]

I've got a nice cb antenna that can be had for free in Sandy.

ill take it what kind is it

 

[UNSTUCK]

My number is 8o12287952 if you still want it, or anyone else for that matter. I have a whole list of random stuff that will be going up for grabs here soon.
Josh.

 

[JL Rockies]

Magnetic fields are generated when current flows through any conductor. Since the chassis is used as the negative return to the battery, there are magnetic fields created that extend beyond the physical boundaries of the vehicle. Length of the ground wire has nothing to do if a ground will be "noisy" or not.

 

[gijohn40]

I can get my bosses dip meter and we can see what frequency that K30 is set for... and then tune it better that way if you would like... 1.5 and below is the prefered outcome.

 

[sLcREX]

I am planning on setting up my CB this weekend, from what I read a good mounting point and 50% or more above the car would be ideal. I am concerned about keeping away from harm's way though. I was thinking of mounting it an inch or two inside towards the tailgate. Is it a matter of mounting it where I choose and tuning to that location, or is it about testing different mounting locations?

 

[sixstringsteve]

ideally, you'd test different locations for the lowest SWR, but that's really not practical. I'd put it where you want it and tune it from there.