Mounting a CB antenna on a modern hatchback without drilling?

[drewdownkali]

Uh, I'd use the one off the website. That doesn't look entirely legit. Could be someone did their own testing and made their own chart, but the actual location of the antenna will change the length needed to make it resonate.
Also, the radiating part of the antenna is what needs to be resonate at the frequency you are using. The coil spring at the base is part of the radiating element, so that needs to be figured into the length. According to the chart I pulled off the website, the spring adds 2 inches, so it sounds like yours may be too long. I'd really use the chart off the website and make sure you use the lenghts for the whip with the spring installed. 2 inches too long is going to throw you off bad enough to keep you up all night.

This chart that you mention is off the website. The one where you enter you model. I just copied and pasted it, then wrote on it lol. It matches the bag

 

[drewdownkali]

It should still be uch lower on one end of the band then the other right? Not above 3 on both 1 and 40?

 

[mmckenna]

Nice job on the ground strap.

OK, so the SWR meter switch...
Use "Power" to set the meter to full deflection, using the calibration knob.
Then switch it back to SWR.

Not to beat the dead horse, but I think you've narrowed it down to the antenna length. From what you are saying, it's way too long. You need to cut it down to 47 inches and start there. Likely you are going to find it'll be better down around 45 or 46 inches, since the spring adds 2 inches to the length. The photocopied cutting chart doesn't sit right with me as it doesn't have anything under the "spring" column. I'd use the one from the website.

Get it cut to the correct length and it should work just fine.

At least you've run through the whole antenna system and know it's completely up to snuff. Get the SWR issue down, and you are good to go. Nice looking install, too. Much better than the mag mount.

 

[mmckenna]

It should still be uch lower on one end of the band then the other right? Not above 3 on both 1 and 40?

No, when the length is that far off, it's going to be crappy across the entire CB band. You are not even close yet. When you get it cut to something remotely close to the correct length, you'll see the effect you are looking for.

Now that you've experienced all this, keep your eyes open along the road and see all the people that seem to cut their CB antennas to random lengths, presumably based on aesthetics.

 

[mmckenna]

If you were to look at the SWR on a chart for the entire band, going up and down a few MHz, you'd see a bell curve where the SWR was good. Outside the bell curve, it just sucks. When you get within the "bell", you'll start seeing the high/low channel thing. Right now you are way out in left field where things just suck.

 

[drewdownkali]

Ok, we will see. I think I will get the other whip back from the cb guy then. Don't want to start cutting this one yet. Guessing the original one probably still has about 26.5in or more left on it. He didn't take off very much. Only difference between then and now though is the ground strap and at 47in and whatever he trimmed off he couldn't get it tuned in. But he could get it better with the 48in somehow. Was picking up truckers in that area.

 

[mmckenna]

OK, good luck. Sounds like you are on your way. Let us know how it turns out.

 

[drewdownkali]

Measuring the spring with the little hat that holds the whip is actually 2 3/4 in.

 

[drewdownkali]

Nice job on the ground strap.

OK, so the SWR meter switch...
Use "Power" to set the meter to full deflection, using the calibration knob.
Then switch it back to SWR.

Not to beat the dead horse, but I think you've narrowed it down to the antenna length. From what you are saying, it's way too long. You need to cut it down to 47 inches and start there. Likely you are going to find it'll be better down around 45 or 46 inches, since the spring adds 2 inches to the length. The photocopied cutting chart doesn't sit right with me as it doesn't have anything under the "spring" column. I'd use the one from the website.

Get it cut to the correct length and it should work just fine.

At least you've run through the whole antenna system and know it's completely up to snuff. Get the SWR issue down, and you are good to go. Nice looking install, too. Much better than the mag mount.

What are you talking about use the pwr to set the meter to full deflection? I put it on cal, then key mic and move knob to until needle is at CAL and switch to SWR.

 

[drewdownkali]

If I can't get it below 2 I think I am going to have to look at a different setup. If I can't get at least a couple miles I should have just got the motorola gmrs radios, lol. Owner of the antenna farm said I am lucky to get my SWR below 3 with this setup and I should use the Maxrad MLBDC2700, but it seems the same as mine. He said the Laird needed a good ground plane. They both say they need less ground plane than others. LOL.

Maxrad MLBDC2700 [MLBDC2700] - $39.95 : The Antenna Farm, Your two way radio source

Laird Tech CB27S - $59.95 : The Antenna Farm, Your two way radio source

 

[drewdownkali]

Thank you. Will let you know if there is any difference or a good outcome. I always have this kinda luck with things. And now days everything is on the internet. Can't buy hardly anything or get any help in person.

 

[drewdownkali]

What do you think about this mini RG-174A/U or mini RG-188A/U type cable that is used for the first 18"? I thought they would use some form of rg-8.

 

[jhooten]

If I may interject. If I read right you are using a 10 foot jumper between the radio and the meter. If so replace it with one as short as possible. Preferably a double male connector.

 

[nonperson]

LOL. What do you mean thats it? Base loaded just meas the coil is in the base. It's not the wrong antenna for the band. it covers 27 to 31 Mhz. This already is an NMO setup. I based this off someone else who used same materials on a later model of the same vehicle. And if I drill and it still don't work then I have a hole with nothing to put in it. Lol.

I mean that's exactly what I was talking about. Check that spot to make sure it was the correct one. I don't know how much you know about antennas and two way radios so I tried to be more descriptive in what I was talking about. I can look at and see you have an NMO mount. Other than the drill and bit to make the hole you have everything you need to make it a permanent mount. That is if you ever decide to go that route.


Before cutting the whip, using the chart, I would wait and try the mag mount out first. I cut my Laird VHF antenna according to their chart and when I did get it test it was to short. But if you want to try it get the original and experiment on that one like you are talking about doing.

Any ways, try the mag mount before cutting any on that antenna. When you get the mag mount try it in the dead center of the roof and on the corner where you have the mount and see if anything changes. As for running the coax stick it through the window and test the mount on different areas of the roof. When you find the ideal spot then worry about routing the coax to the radio.

RF ground is different than DC ground but they can be one in the same. For example The mount on the hatch back door may give you a good DC ground but it's probably a horrible RF ground. The middle of the roof will give you a much better RF ground and an excellent DC ground.

If I had to guess, I suspect the lip mount bracket and the hatch back door is giving you a poor impedance mismatch and poor RF ground. If you could find some one with an antenna analyzer could make things a little easier.

 

[mmckenna]

If I can't get it below 2 I think I am going to have to look at a different setup. If I can't get at least a couple miles I should have just got the motorola gmrs radios, lol. Owner of the antenna farm said I am lucky to get my SWR below 3 with this setup and I should use the Maxrad MLBDC2700, but it seems the same as mine. He said the Laird needed a good ground plane. They both say they need less ground plane than others. LOL.

Maxrad MLBDC2700 [MLBDC2700] - $39.95 : The Antenna Farm, Your two way radio source

Laird Tech CB27S - $59.95 : The Antenna Farm, Your two way radio source

Not sure what he's thinking. They are both base loaded 1/4 wave antennas. Antennas and RF are governed by the laws of physics, and no manufacturer has anyway around those laws. Other than making your wallet lighter, you won't see a difference. What he is probably running off of is what his customers report. I wouldn't waste the $40 on another antenna.

 

[mmckenna]

What do you think about this mini RG-174A/U or mini RG-188A/U type cable that is used for the first 18"? I thought they would use some form of rg-8.

Short runs of it isn't going to be noticeable. RG-174 is a 50 ohm cable, so thats the correct stuff. The difference between that and the bigger stuff is the amount of signal loss. You'll lose slightly more signal in the 174, but you gain easier cable routing. The cable itself won't cause this issue. The area of question would be where the two cables join. If you are getting continuity through it, it's probably fine. I wouldn't go replacing anything else until you get your whip trimmed to something remotely close to being resonate. We've run through everything else and it's OK. A mag mount isn't going to fix the whip length issue. You -really- need to cut the whip to what the manufacturers chart says before anything else.

 

[nonperson]

Short runs of it isn't going to be noticeable. RG-174 is a 50 ohm cable, so thats the correct stuff. The difference between that and the bigger stuff is the amount of signal loss. You'll lose slightly more signal in the 174, but you gain easier cable routing. The cable itself won't cause this issue. The area of question would be where the two cables join. If you are getting continuity through it, it's probably fine. I wouldn't go replacing anything else until you get your whip trimmed to something remotely close to being resonate. We've run through everything else and it's OK. A mag mount isn't going to fix the whip length issue. You -really- need to cut the whip to what the manufacturers chart says before anything else.

The mag mount certainly won't fix the whip length issue but if there is something else mucking it up, it may help identify that.

I tried cutting mine according to their chart and the whip ended up being to short. Once he cuts it, he can't re-attach it so easily.

But it's his setup I'm just throwing in my two cents.

 

[drewdownkali]

If I may interject. If I read right you are using a 10 foot jumper between the radio and the meter. If so replace it with one as short as possible. Preferably a double male connector.

Yeah, The other option was a 2ft at radio shack. Nothing in 3ft lengths which was wierd to the cb guy, he said "why would they even sell an off length like 10ft"? Umm it has to have a male on both ends to plug into the meter and radio.

 

[drewdownkali]

I mean that's exactly what I was talking about. Check that spot to make sure it was the correct one. I don't know how much you know about antennas and two way radios so I tried to be more descriptive in what I was talking about. I can look at and see you have an NMO mount. Other than the drill and bit to make the hole you have everything you need to make it a permanent mount. That is if you ever decide to go that route.


Before cutting the whip, using the chart, I would wait and try the mag mount out first. I cut my Laird VHF antenna according to their chart and when I did get it test it was to short. But if you want to try it get the original and experiment on that one like you are talking about doing.

Any ways, try the mag mount before cutting any on that antenna. When you get the mag mount try it in the dead center of the roof and on the corner where you have the mount and see if anything changes. As for running the coax stick it through the window and test the mount on different areas of the roof. When you find the ideal spot then worry about routing the coax to the radio.

RF ground is different than DC ground but they can be one in the same. For example The mount on the hatch back door may give you a good DC ground but it's probably a horrible RF ground. The middle of the roof will give you a much better RF ground and an excellent DC ground.

If I had to guess, I suspect the lip mount bracket and the hatch back door is giving you a poor impedance mismatch and poor RF ground. If you could find some one with an antenna analyzer could make things a little easier.

Antenna analyser huh? Doubt theres any of those around here. I know I am getting continuity! Thats that little greek symbol right? lol.

 

[drewdownkali]

Umm, yeah, sure, if I want to drill a hole and take apart this mount (hich has some kind of silicone or something holding part of it together) I don't want to drill a hole if I don't have to. Knowing my luck I would have rust and or leaking issues. The fact that I am having this many issues with this might imply that, lol.

Put it this way. I had some front end work done, so I needed an alignment. Went to LesSchwab, and it still pulled to the right. (Stock height) Took it back, guy did nothing but switch front tires, said I can't do anything now it pulls to the left. Nope still to the right. Take back and says he can't do anything. Take to another one, aligns it and same problem. Get a refund. Taje somewhere else and they tell me they have to alighn the rear or I will keep having the problem. I told them it's a solid rear cant align, can only equalize. They insist they have to align so left and Took it to VW. Vw guy tells me I need 4 wheel alignment. LOL I laugh and say no I don't. He says its a gti right? I say yes, but its a MKIV (4th gen) not an MKV(5th gen.). It has a solid rear not an independent. Their mechanics finally fixed it though.

This is what I have to go through it seems for just about everything. I feel like its just this area I live in though. Miss L.A. Everything was within reach.