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Old 02-19-2020, 08:33 PM   #1
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CB/Radio Antenna

Picked up a super cheap Uniden PRO505XL CB on amazon, wanting to reuse the antenna already mounted on my bus. Issue is the antenna wire has what looks like a coaxial cable for a TV or VCR, and the CB has much larger connector.

Is the antenna on my bus a good fit for that radio? And will all I need is just adapter?
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Old 02-21-2020, 06:37 AM   #2
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Since no one answered, I went ahead and ordered the adapter, I will post back if it works!
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Old 02-21-2020, 08:13 AM   #3
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That antenna was likely for district communications. We run something similar on all of our buses. The radios they use are all custom motorola jobs that transmit on one frequency to a repeater, and the repeater broadcasts on a different frequency to all the radios.

Coax cable isn't really a complicated thing, so the ends can be changed/swapped or they have adapters too. They likely used the ends they did because they're cheaper or common.

The big thing is that the antenna is likely tuned for a specific frequency the district was communicating on. We're on a vhf band and cb radios work in the hf range, so you might have to modify it to get it to work like it should. It should be able to be used though, but I'm no expert at this stuff, so you need to talk to someone who is. But even if it isn't tuned, you still should be able to broadcast and receive a signal with it.

If it was me, and a cb radio is important to you, I'd take the bus to a radio shop and have them do it. They should have the equipment and know how to tune the whole setup, which can mean the difference between a clear signal for miles and something that's junk.
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Old 02-21-2020, 09:19 AM   #4
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Quote:
Originally Posted by bigskypc50 View Post
Picked up a super cheap Uniden PRO505XL CB on amazon, wanting to reuse the antenna already mounted on my bus. Issue is the antenna wire has what looks like a coaxial cable for a TV or VCR, and the CB has much larger connector.

Is the antenna on my bus a good fit for that radio? And will all I need is just adapter?
Different size coax cable will probably have a different "Impedance" measurement so I would be at the very least, know that all coax cable is not the same.

The cable connection itself, CB's require a PL259 connector.
2 standard coax cables are , RG-58 (standard coax) and RG-8x (premium coax).

And if your running dual antennae then you need to use an RG-59 dual antennae coax.

I wouldn't use the antenna already on the bus, it might just work but it will not work optimally. The antenna WILL need to be matched and tuned!

Do it right, go to a cb shop, most major truck stops can point you in the right direction for a CB-guru in the area or just use the web.

Here is one decent site with good basic info.
https://www.wearecb.com/how-to-tune-cb-antenna.html

https://www.wearecb.com/cb-antennas/

good luck!
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Old 02-21-2020, 09:22 AM   #5
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Dumped the original antenna and went with a 4ft ngp on mirror arm. Got 1.5 to 2 swr. 18ft coax.
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Old 02-21-2020, 02:30 PM   #6
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Like Booyah already hit on, you can't just hook up any old antenna. That goes for everything, not just CBs. All antennas are designed to work only within a given frequency range. Not only is that antenna almost certainly not a match for 11m (which is the wavelength of CB comms), it's probably WAY off. Getting it to work for CB applications shouldn't even be considered. If you do attempt to use it, on receive you'll get extremely poor performance, and on transmit you could literally damage your transceiver (unless the excessive SWR causes protective circuitry it may or may not have to shut it down before damage does occur which would be best case).

Don't use anything other than a CB-specific antenna (50 ohms impedence).

Also, like EWO said, coax impedence is a consideration. Anything made for mobile radio is going to be 50 ohms, & that's what you want. 75 ohms is cable TV, & that's what you don't. 11m generates very little coax loss, so you don't have to get fancy. RG58 is what I'd recommend, unless you're looking to upgrade sometime in the future to a ham license, in which case rg-8x would is still real easy to run & would do better at VHF/UHF frequencies.
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Old 02-21-2020, 03:17 PM   #7
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Yeah, I didn't even think about tv coax and it's impedence. I haven't messed with anything but 50 ohm in what seems like forever.

But the moral of the story is that your antenna in it's current fashion isn't going to work worth a ****.

Best bet is to visit a radio shop.
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Old 02-21-2020, 05:23 PM   #8
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Follow 2kool4skool's lead on this one ... replace the antenna with one made for the CB frequencies.
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