CB Tuning question.

[Paniolo]

2006 CVO Ultra with the Harmon Kardon/CB built into the head unit.

How do I tune the antenna? I plan on buying an SWR meter (if you can recommend a brand I'd be happy), removing the fairing and hooking it up to the coax cable coming out of the CB radio.

Then what?
Key the hand held microphone and watch the needle swing over and then,....?
How do I know what it's telling me, and how do I know what needs to be done?

Any help with tuning the HD CB is appreciated.

Thanks

Lastly, I was surfing the HD website. Why are there different CB antennas for bikes made before 2009? Can run I the CB antenna off my cousins 2016 on my 2006?

[carioux2008]

In my past experiences dealing with CB radios (none on a bike though) many of them have different connectors. The original connection to the antenna was with a pl-259 and so-239 connectors (plug and socket?) New semi's have sma connectors on them sometimes, as its easier to run the cable through to the cab. Ive converted all of my antennas to BNC just to make things really easy when I want to "play". Those could be the difference. As far as tuning goes, you want your meter as close to the radio as possible, then you need to adjust the meter (cal) and finally check your swr. SWR is basically the amount of feedback you recieve when you transmit, and the higher the number the more feedback you have, reducing your actual power output. 1:1 is the theoretical best you can do. Anything below 2:1 is considered acceptable. You would adjust it by using a trimmer pot (resistor/capacitor/inductor) or by trimming the physical length of the antenna wire. The owners manual should detail this...who knows. Harley specific CB stuff is where im dim, and I apologize, just thought I'd give you a brief description of the general CB stuff.

[Paniolo]

Thanks for the reply. Silly question, but does it matter which end of the antenna is trimmed? Just pop off the rubber tip, and snip away?

[Rockout Rocker Products]

The antenna may not need to be trimmed, but rather made longer. At least on cars... it can go either way.

[Coyote]

The antenna may not need to be trimmed, but rather made longer.

[FSG]

Just pop off the rubber tip, and snip away?

yes but

The antenna may not need to be trimmed, but rather made longer.

and you wont know which until you make the first snip

[Coyote]

No, you don't need to alter the antenna to find out which way it needs to go.  Just checking the vswr on more than one channel will tell you that.

[FSG]

I've cut hundreds of AE's and mostly used Bird Thruline Wattmeters not the regular $10 to $15 SWR Meter from Radio Shack.

Yes you could change channels which changes the frequency and thus the wavelength and the SWR, BUT you need to be able to see that change on the SWR Meter you have at hand and that IMO is not always possible.

It is far easier IMO for the end user to just take the first snip, which is what I do/have done in the past.

[Coyote]

Well I'm an RF Engineer with 30 years experience, I also have a Bird Thruline Wattmeter and I can tell you I've never cut the antenna first and never had any problems knowing which way the antenna needed to go.     

PS, I've been known to use my spectrum analyzer with built in tracking generator and a directional coupler to do it as well.   

[FSG]

OK you win, I'm just an Electronics Engineer with over 40 years experience, most of that time spent in the Oil Industry.

Spectrum Analyzers and similar test equipment typically remained in the various workshops although I have been known to take Oscilloscopes into the Engine Rooms of older Offshore Supply Boats, adjusting Tachometer Senders on GM V8 and V16's, making life easier for the boat drivers. 

[PoorUB]

Let us know when you two are done measuring your, well, you know what!

Can you guys explain to use simpletons how to tell is the antenna is too long or just too short y just looking at a SWR meter?

[Coyote]

All I can say is I've never had to cut an antenna to know which way it needs to be tuned. 

Can you guys explain to use simpletons how to tell is the antenna is too long or just too short y just looking at a SWR meter?

Sure. Just check the VSWR at channel 1 (low end) channel 20 (mid) and channel 40(high end). If the the vswr is lowest at channel 1, then the antenna is tuned low and will need to be shortened to bring it up to mid range. If it's lowest at channel 40, then it's tuned high and you will have to somehow tune it lower (usually by lengthening the antenna).

If it measures lowest at channel 20, then it's somewhere in between. You can further pin it down by doing the same test just using the upper or lower half of the channels.

The problem with tuning the antenna on a Harley is that there just is not enough counterpoise (ground plane) to make a stable match. You can tune and get it OK at one spot, and as soon as you put a big bag or momma on the back seat it's all gonna change.

[FSG]

OK   CB Radio is in the 11 Metre Band

CB Ch01 26.965 Mhz         1/4 wave  2.781  Metres   

CB Ch20 27.215 MHz         1/4 wave  2.755  Metres                 

CB Ch40 27.405 MHz         1/4 wave  2.736  Metres

as you go up in channel number the frequency increases and the wavelength decreases

typical CB Antennas for Motorcycles, Cars, Trucks and Boats are 1/4 Wavelength with loading coils at the base, centre or at the top of the WIP

there is some preference for one over the other but there's no point going into that

the length of the Antenna is going to be a compromise across the operating band

so check the SWR on Ch 20 then check it on Ch 40

is it going up or down  i.e. if it was perhaps 2 is it going down toward 1 or up toward 3

if it's going down then the Antenna is too short, if it's going up then it's too long but check to see where it is on Ch 1

depending on the quality of the SWR Meter you may not see any significant change to be able to make a determiniation


Below is just a SWR Meter pic found on the web





Below is a Bird Thruline WattMeter pic found on the web, they have plugin elements to suit the power and frequency to be tested as well as many input and output adapters to suit equipment cable requirements

[FurryOne]

CB Ch20 27.215 MHz

Actually, CB 20 is 27.205MHz

The OP's best bet is to find his local HAM club and ask for help tuning because they should have a decent set of antenna measurement tools (That Bird gave me flashbacks!).  My personal opinion of H-D's CB antennas is that they suck.  I added a Firestik2 to my 17SGS because it's top-loaded and easily tuned, and even cheap!  ...And here's the results...

...and do I win the length game with 50 years? (Including managing an RF Technology section in a Govt. Research Lab?)   

[FSG]

Actually, CB 20 is 27.205MHz

Yes you're correct, my bad I had meant to type Ch 21 but really Ch 19 is the center of the band.

[Paniolo]

I'm not being a samartass, but now I'm more confused than ever. I didn't know  I had to tune at multiple channels, 1, 20 and 40. I never thought about having to lengthen the antenna, don't even know how I'm going to do that.

[PoorUB]

You don't tune for each channel, but you should check each end and the mid channels. You can tune the SWR to the channel you use most.

[FurryOne]

As far as tuning goes, you want your meter as close to the radio as possible,...

Actually, this is not true.  You want the SWR reading as close to the base of the antenna as possible.  Why?  The cable will throw off the SWR readings because few, if any, manufacturers supply the actual correct length (1/2 wavelength) of cable to match the antenna. (No, I have no idea why.)

[Rockout Rocker Products]

I'm guessing it's because a 1/2 wavelength is about 18 feet.

[Coyote]

The length of the cable makes no difference (other than add some loss which will make the SWR read lower at the radio end of the cable). For tuning, it won't matter where you put the meter but it's best to put it near the radio so you are farther from the antenna while tuning. Anything in and around the tour pack will pull the antenna tuning.

Every HD I've tuned, the antennas have always been long. I always recommend tuning to a low channel and just using that one. The reason has to due with how much of the antenna needs to be trimmed. I've found that if you tune them mid band (which would be preferred) you have to cut enough off the antenna that it's noticeably shorter than the FM antenna.

[Paniolo]

So am I hooking the SWR up at the radio in the front of the bike, or at the antenna at the rear of the bike?

[FurryOne]

The length of the cable makes no difference (other than add some loss which will make the SWR read lower at the radio end of the cable). For tuning, it won't matter where you put the meter but it's best to put it near the radio so you are farther from the antenna while tuning.

Say Whaaatt?  Sorry, but not in this reality.

Every HD I've tuned, the antennas have always been long. I always recommend tuning to a low channel and just using that one. The reason has to due with how much of the antenna needs to be trimmed. I've found that if you tune them mid band (which would be preferred) you have to cut enough off the antenna that it's noticeably shorter than the FM antenna.

That's why I'd recommend using an antenna from a Company that actually knows what they're doing, not one from a Company (H-D) who's main "competence" is something else.  And buy one that actually allows you to correctly tune it, not have to cut pieces off.

[FurryOne]

So am I hooking the SWR up at the radio in the front of the bike, or at the antenna at the rear of the bike?

If you can get to where the cable attaches to the antenna, it's the best place.  I believe the tour packs have a built-in antenna loading system that the short antenna screws into.  If you can get to where the cable connects to that, it's the best place for that type.  If you can't, then you can fall back to using the connection to the radio - your SWR will just be a bit off due to the cable, but better than not doing it at all.

[Coyote]

Say Whaaatt?  Sorry, but not in this reality.

It is most certainly reality. Changing the cable length on a matched antenna does nothing to what the radio sees. Changing it on a slightly mis-matched antenna will alter the phase and change the reactance (rotates you around the Smith Chart). Changing the cable length on an extremely mis-matched load (open or short) may alter the reading but that's not what we're discussing here.

I'm not saying you are wrong on measuring near the antenna if possible but there are good reasons not to do so on a Harley as I stated above.

In the end, most of all of this is picking nits. Pick whatever spot you want to insert your meter and tune it for lowest SWR and be done with it. It's not rocket science.

[FurryOne]

Let us know when you two are done measuring your, well, you know what!

Did I win?   

Can you guys explain to use simpletons how to tell is the antenna is too long or just too short just looking at a SWR meter?

Yes.  As you go from channel 1 to 40, the frequency increases.  As the frequency increases, the wavelength becomes shorter, so the required antenna length becomes shorter.  When you go from Chan 1 to channel 40, the required antenna length becomes shorter - thus going from chan 40 to chan 1, the required antenna length becomes longer.

So if your SWR is higher on chan 40 than on chan 1, your antenna is too long.  If it's higher on chan 1 than on chan 40, your antenna is too short.  If it's the same on chan 1 as on channel 40, your antenna is in tune - give yourself a pat on the back! 

Cheap SWR meters, like those $20 specials, are notoriously crappy.  That's why I suggest finding a HAM radio guy who'd be willing to lend you a hand. 

I use a RigExpert AA-30 Antenna Analyzer for CB antenna setup.  Here's a picture of the SWR showing that my antenna was too long before adjusting.  The best SWR (1.2:1) was at a channel lower than chan 20, which is where the center marker was.