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Installed my own CB.....

TMFGO45

Seasoned Expediter
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So I installed my own CB. I used mirror mounts, then ran a 9' mini 8 (if I remember right) cable from the mounts, inside (hidden beautifully I might add), connected each end into a "T" adapter, and just hooked the male end of the adapter right into the CB. Now, the problem is I can get the left antenna tuned properly, but not the right. I'm doing them one at a time, using the built in meters of the CB. The CB is a brand new Cobra with the digital screen.

According to the meter, channel 40 is higher than channel 1, yet I can't lower the adjustable tip anymore because I started with it all the way down. These are K-40, 3' fiberglass whip antennas with the metal adjustable tip.

What's the deal here? Someone lay some knowledge on me!

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

Monty

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There was a time, when the cb band was much quieter that 2 antenna was useful. Now not so much ... may I suggest you remove that T and just use the one.

And get yourself an XM radio and leave that noise box, (the CB), turned off! ;)
 

BigCat

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Check to make sure the antenna mounts are tight everywhere. Those serve as a ground and if one isn't getting a good ground it can cause swr to be high. You say you got the digital so im guessing it is the new style cobra with the color changing face, are you getting antenna warning message when you push the mic button? Did you calibrate swr properly?
 

TMFGO45

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There was a time, when the cb band was much quieter that 2 antenna was useful. Now not so much ... may I suggest you remove that T and just use the one.

And get yourself an XM radio and leave that noise box, (the CB), turned off! ;)
I am thinking about going to one, but only if I just can't get the other to work. And I already have Sirius Premiere, so I'm good there :)

Check to make sure the antenna mounts are tight everywhere. Those serve as a ground and if one isn't getting a good ground it can cause swr to be high. You say you got the digital so im guessing it is the new style cobra with the color changing face, are you getting antenna warning message when you push the mic button? Did you calibrate swr properly?
I tightened them to where I thought the bolts were bending, but I will double check that. And yes it is the color changing face. I did calibrate properly. The only thing is that it says to hold the mic, calibrate, keep mic held and switch to the swr test mode, but mine won't switch with the mic held, so I just let go then do it. And yes I do get that warning message for the right antenna...

If I have to move the calibration, won't the calibration be off now when I put the first antenna back on? Or is that just to get them tuned in? Either way, there is still something not right on that right side. I was thinking ground, also. Is there a way to test for that even after tightening the mount again?



Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

pearlpro

Expert Expediter
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To make DUAL antennas work correctly you must use a Antenna Combiner, or a CO PHASE CABLE thats designed for MATCHING antennas, heres a link to Amazon with the Co Phase cable...or you can buy a CO PHASE Cable setup at most truck stops or CB Shops...

Amazon.com: 12' Dual Antenna Co-Phase Cable with PL-259 Conmnectors: Car Electronics

Amazon.com: 3' DUAL ANTENNA KIT BLACK 16GA.: Electronics

Several times a year we get tech calls from installers who place dual antennas on their vehicle and run RG-58 or RG-8X from each antenna to a T-connector at the back of their radio only to find that the system "doesn't get out". You should not use 50 ohm coax on a ground plane dependent dual antenna installation ... it MUST be 72 ohm RG-59 type coax. These flawed installs can be misleading because SWR tests can show exceptionally low SWR, making the installer think that all is well. However, the impedence of the antenna system does not match the requirements of the radio and therefore, the output power of the radio is greatly reduced. In several tests, we found that a 4 watt radio would only generate 1.75 watts of output power which is the equivalent of having an SWR reading that exceeds 6.0:1.

RG-59 type: This type of coax is used for dual antenna installations only. The RF resistance of this type of coax is 72-ohms. Within this group you will find coax labeled with RG-59 or RG-59/U. These cables have a solid center conductor. The second type is RG-59A/U and they have a center conductor made up of many thin wire strands (normally about 19) that are twisted together to form the center conductor. The common outer diameter for this type of cable is about 0.22".

Single antenna installations for 2-Way Radio requires 50-ohm coaxial cables such as RG-58A/U or RG-8X. Dual antenna installations require 75-ohm coaxial cable (co-phase harness) to perform properly. Note: From time to time we hear from people in the field that have made co-phase harnesses from 50-ohm coax and report better than average SWR. In tests performed at our facility we found that the lower SWR readings were a results of power losses that often exceeded 50% of the radio output when compared to RG-59A/U coax and higher SWR readings. Accordingly, do not use 50-ohm coax for co-phase antenna installations.
 

pearlpro

Expert Expediter
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I meant to include this from Firestiks website..

The quality of your communications will never be better than what the quality of your coax. FireStik's dual lead, co-phase harness assemblies are made from FireStik's RG-59A/U, Fire-Flex coaxial cable. They may be used on any dual antenna installation. Check out these features:

Stranded center conductor to maximize flexibility and prevent untimely breakage.
Shielding coverage that averages 95% to protect against RF leaks and interferrence.
Polyvinyl center insulation for ruggedness and longivity.
Performance that exceeds mil-spec requirements for 75 ohm RG-59A/U coax.

FireStik's K-9A co-phase harness is also made with two 18' (5.5m) leads. All three ends of this cable assembly is terminated with PL-259 type connectors. This cable is designed to be used with FireStik's K-4A or antenna studs and any mounts that use either of these SO-239 stud mounts.
 

TMFGO45

Seasoned Expediter
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With all of that said, which I do understand completely, shouldn't I still be able to get my right antenna tuned properly when it is hooked up by itself? Is the T adapter an issue? Or is it the fact that I have both coax cables hooked in, even though I don't have both antennas hooked in at the same time?

Also, I do notice I'm only getting about 2 miles range which would match what you are saying with the 1.75 watt power output. Would simply removing the T adapter and plugging that coax directly to the radio give me back the rest of my range / output power? This really would be the simplest solution....(and cheapest)

And are duals even beneficiary, or just more of a headache?



Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

Monty

Expert Expediter
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If that cb is so important to you .... stop by a quality cb shop, (like Walcott CB, on I-80), and have the pros take a look at it.
 

Moot

Veteran Expediter
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And are duals even beneficiary, or just more of a headache?
I believe dual antennas are more of a headache as you are finding out. Mount one antenna on the driver's side mirror, run 18' feet of coax, loop the excess up behind the headliner, tune the antenna and you should be good to go. If you still have problems, you may have done some damage to the radio by transmitting with only one antenna connected to a two antenna coax setup. When the antenna alert light comes on, its kinda like an oil pressure light, best to shut it down and find the problem.
 

paullud

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And are duals even beneficiary, or just more of a headache?
They are a headache, I think most dual antenna setups usually use 1 antenna for the CB and the other for the TV.

Sent from my ADR6400L using EO Forums
 

TMFGO45

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I believe dual antennas are more of a headache as you are finding out. Mount one antenna on the driver's side mirror, run 18' feet of coax, loop the excess up behind the headliner, tune the antenna and you should be good to go. If you still have problems, you may have done some damage to the radio by transmitting with only one antenna connected to a two antenna coax setup. When the antenna alert light comes on, its kinda like an oil pressure light, best to shut it down and find the problem.
There's no damage. The warning is while testing the single right antenna. The one I'm using is working properly, just not full output range.

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

BigCat

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They are a headache, I think most dual antenna setups usually use 1 antenna for the CB and the other for the TV.

Sent from my ADR6400L using EO Forums
Nah paul they are both for cb but most guys hook them up incorectly.

Now to the OP are you running cophase coax or just some single phase? If you are running single phase to a T your SWR will be through the roof. I suggest getting rid of the right antenna all together and running RG58A/U to the driver side antenna and call it a day. I was running cophase but SWR was way to high due to antenna being bad so I just slapped in 9 fot of RG58A/U and hooked my driver side antenna and right now I am at 1.5 on channel 1 and 40. On channel 19 it is right at 1.

My setup is a cobra 29,Astatic mic and Firestick tuneable tip antenna. I got a range right now of about 7 miles.
 

zorry

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Actually a lot of the newer trucks one is the CB and the other is AM/FM in disguise.
 

BigCat

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Actually a lot of the newer trucks one is the CB and the other is AM/FM in disguise.
I am just refering to when there are 2 matching antennas put there after the fact. They are T together for better performance. Problem is to the average joe doing the install it is very easy to hook them up using the wrong coax and either not get them tuned or get them tuned and not put out because the type of cables used.

When the truck leaves the dealer with 2 antennas they are infact for the tv or am/fm and cb.
 

TMFGO45

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I'm going to switch to just one. I didn't use co phase so I'm not going to spend any more money trying to go to a good dual setup.

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

BigCat

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I'm going to switch to just one. I didn't use co phase so I'm not going to spend any more money trying to go to a good dual setup.

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
That was your problem then. Rip on out and it will tune just fine.
 

TMFGO45

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That was your problem then. Rip on out and it will tune just fine.
Well wouldn't you know it. Took out the whole right side and the T adapter, now I can't get it to tune. Keep getting the antenna warning. I'm not trusting this built in meter though, it doesn't feel like it's reading properly. Always has just 3 lines lit up, implying a really low reading.
So I'm thinking of getting an swr meter and 3' jumper cable to tune it.
And wouldn't you know it again, this Loves T/S doesn't have either.

Anyway, I went through and made sure I tightened everything down real good, so hopefully there should be no ground issue. I guess I will try again when I find the meter...

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

BigCat

Expert Expediter
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Well wouldn't you know it. Took out the whole right side and the T adapter, now I can't get it to tune. Keep getting the antenna warning. I'm not trusting this built in meter though, it doesn't feel like it's reading properly. Always has just 3 lines lit up, implying a really low reading.
So I'm thinking of getting an swr meter and 3' jumper cable to tune it.
And wouldn't you know it again, this Loves T/S doesn't have either.

Anyway, I went through and made sure I tightened everything down real good, so hopefully there should be no ground issue. I guess I will try again when I find the meter...

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
I had that same radio and just returned it for that reason of the warning light. I now have the chrome 29 and it works great.

With few bars lighting up that means the swr is down which is good. You dont want to light up the whole swr bar because that means you are over the max before you damage the radio. The antenna may just need fine tuning at this point.

BTW You will get the antenna warning if either A) Antenna is too tall for your application or B) Not tall enough.
 

TMFGO45

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I had that same radio and just returned it for that reason of the warning light. I now have the chrome 29 and it works great.

With few bars lighting up that means the swr is down which is good. You dont want to light up the whole swr bar because that means you are over the max before you damage the radio. The antenna may just need fine tuning at this point.

BTW You will get the antenna warning if either A) Antenna is too tall for your application or B) Not tall enough.
Yeah I know, and according to the swr I'm good, but I'm getting the warning. Can't tell if I'm high or low on the antenna because the swr reads the same really in both channels. Maybe the external swr meter will tell me the real story.

Sent from my Galaxy Nexus! (CNA 3.2 , Popcorn 11.6, TWRP 2.2)
 

BigCat

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Those new cobras are just really sensitive. If your swr is good I'd ignore it. Most guys pop the cover off and turn the vr6 pot to adjust that warning. I haven't heard of anyone not getting that warning.
 
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