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Adjusting SWR on CB antenna?

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  #21  
Old 10-17-2007, 10:00 PM
cglofland cglofland is offline
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Default RE: Adjusting SWR on CB antenna?

Jim is right, the CB module is a TNC connector, you can buy adapters to fit your SWR meter in line with the antenna, a TNC to SO239, or TNC to PL259 with barrel connector. But bottom line is range is short with CB, don't look for distance on that frequency, you could add a linear amp to increase the 5 watt max output. I only use the loading coil on a tour pak for ground plane.
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  #22  
Old 10-17-2007, 10:56 PM
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Jim Dawson Jim Dawson is offline
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Default RE: Adjusting SWR on CB antenna?

Quote:
ORIGINAL: uweldit

I don't know why you have not switched over to FRS instead of CB. Longer range and less complicated.

FRS sets are cheap and you can have multiple radios on the same freq.


Because the truckers I listen to on the way to work to keep track of traffic delays don't use FRS. I don't talk to anyone, just listen for traffic advice.
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  #23  
Old 10-17-2007, 11:52 PM
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Default RE: Adjusting SWR on CB antenna?

Quote:
ORIGINAL: kdietz

Thanks for all the replies.....guess I'm going to go back to the stock whip for road trips, etc.

I'm still unable to check the SWR because the antenna coupler on the back of the Harley CB unit is smaller than the cable connectors on the back of my Radio Shack SWR meter....I bought the "mini couplers" and they don't fit either....I don't understand how others can check their SWR if they are using standard cable connectors

*I am definitely using the correct CB antenna lead under the fairing
*I understand that a shorter antenna will not perform like the stock whip, but I don't seem to be able to get out at all with the Freedom Cycle Reno units

Bummer
Karl:

I've had the same experience with another version of the shorty antennas -- from J & M. At the risk of him flaming me for giving my experience and opinion, I foundthe CB antennato be significantly limited inits ability to transmit and also found that the reception for the regular radio was decreased as well. Yes, there are those on this site who have had different experiences, and John also says that the J & M antennas come tuned right out of the box. But after I had them on for one long and one short trip, both with groups of riders with radios, I went back to the stock antennas and am happier with them. While the look of the shorties is better, looks isn't the main reason I have antennas on the bike!

Just my opinion and experience.......
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  #24  
Old 10-18-2007, 12:52 AM
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Default RE: Adjusting SWR on CB antenna?

Sorry to hear that. I just put my J&M cb antenna on today. Haven't had chance to check it out but will on Friday when I go to Vegas. It is a much nicer built antenna than the ones I posted about last year. That cb antenna was so limber it eventually broke the wires inside to where there was no reception. A waste of money really.
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  #25  
Old 10-18-2007, 06:50 AM
WichitaGreg WichitaGreg is offline
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Default RE: Adjusting SWR on CB antenna?

Jim, you are right. I guess I got misled by size - hard to tell in photos, and I didn't have the fairing off my bike. I'm going to install the sierra electronics splitter so I can have just one antenna. I ride a lot without my tour-pak. Will put on the antenna relocation kit, and the fiberglass antenna from sierra.

My ridding buddies all have ultra's or gold wings, CB's and range is relative to how far you want to talk. Linear amps are illegal.
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  #26  
Old 10-18-2007, 07:06 AM
swalter10 swalter10 is offline
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Default RE: Adjusting SWR on CB antenna?

You will need two adapters,a TNC male to UHF female, and a UHF male to TNC female.
I got mine from this guy. http://www.dynamicsignal.com/home.html
TNC Male to UHF Female is AT10.
UHF male to TNC female is AU08. (This item is now sold as a right angle adapter with the same function. It was not a right angle adapter when I bought it.)

Here is an alternate sight which hasboth adapters. His price is high.
http://www.pasternack.com/Default.aspx
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  #27  
Old 10-18-2007, 12:09 PM
Newhog Newhog is offline
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Default RE: Adjusting SWR on CB antenna?

Quote:
ORIGINAL: WichitaGreg

Jim, you are right. I guess I got misled by size - hard to tell in photos, and I didn't have the fairing off my bike. I'm going to install the sierra electronics splitter so I can have just one antenna. I ride a lot without my tour-pak. Will put on the antenna relocation kit, and the fiberglass antenna from sierra.

My ridding buddies all have ultra's or gold wings, CB's and range is relative to how far you want to talk. Linear amps are illegal.
The Harley relocation kit comes with a very nice black antenna whip a little over 3' long and it works very well. You don't need to buy a seperate antenna, I also don't believe the fiberglass would serve you any better. I've done all of this, as above, used the J&M shorties (which work very well), the Harley shorties (don't work well at all), and experminted with other brands. You are on the right track, getting a good ground and setting the SWR correctly is the key.

[IMG]local://upfiles/8807/49AF75DCE3E4483C8D609088BF8A6775.jpg[/IMG]
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  #28  
Old 10-18-2007, 01:06 PM
Dr.Hess Dr.Hess is offline
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Default RE: Adjusting SWR on CB antenna?

Yes, an amplifier is illegal. Yes, lower SWR is better. Yes, antenna length is very important, even in a system with a 1:1 SWR. Yes, coils at the base of an antenna or in line with the coax increase the electrical length of the antenna. Yes, a motorcycle has crap for a ground plane.

You can purchase antennas designed specifically for vehicles with no ground plane, like fiberglass cars and snow mobiles. They won't look "cool" but they will work better than just a standard antenna on a bike. Do they still have CB shops? They might have them, or search online for the CB antenna makers. If you're getting a couple mile range with what you have stock, that's probably about as good as you're going to get without going to a much better antenna or more power (illegal).

You can also purchase a small tuning circuit to tune your antenna system for a lower SWR. I don't know how well it would work (retain settings) on something that vibrates as much as our bikes, but if your SWR is way off, like 2:1 or moreand you don't want to change your antenna, that might be something to look into.

Dr.Hess
NG6Y
Radio Electronics Officer, USMM (Ret.)
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  #29  
Old 10-18-2007, 02:17 PM
NCCopBikeRider NCCopBikeRider is offline
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Default RE: Adjusting SWR on CB antenna?

You can also mount a 4" circle of thin brass sheet stock under the base of the CB antenna to create the necesssary ground plane.

We doit all the time with fibergalss bodies sports/racing cars for improved radio reception/transmission.

YRMV
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  #30  
Old 10-18-2007, 03:12 PM
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Default RE: Adjusting SWR on CB antenna?

Quote:
ORIGINAL: Panhead_1_9_4_8

Sounds good. What's it mean?
what that means is for an antenna to transmit properly it should be resonant to the operating frequency. Meaning the physical length of the antenna should match the electrical length of the frequency. For a CB freq, depending whether its a 1/4 or 1/8 wave antenna it needs to be aorund 104" (give or take, depending wht formula you use) as stated which is usually not practical for a bike. So, a matching unit is usually used or a loading coil, something to electricaly match the antenna length to the operating frequency. The whole idea is to minimize your Standing Wave Ratio (SWR) which allows more radiated energy off your antenna. Higher SWR means you have an antenna which is either to long or to short, leaving "standing waves" on your antenna, unwanted energy, since it can't get off your antenna travels back down to your xmitter and could burn it up.

I've seen people physical cut their antenna in 1/2 inch increments while checking their SWR to trim the antenna to the lowest SWR. Providing you start with a to long antenna first.

Also limit the length of the xmission cable/coax, having it all bundled up interferes with the transfer of RF energy to the antenna and could create an inductive coil also increasing SWR. xmission line should go right from point "A" to point "B"

That about sums it up.
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adjusting, antenna, antennas, cb, davidson, dont, fit, ground, harley, instructions, jmcb2003, meter, no, plane, radio, shack, shorty, swr

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