Check SWR on CB Radio

[bobder41]

I have a 2011 STVS and would like to know if I can use another CB radio that has a built in SWR meter to adjust the antenna for SWR on my Royal Star.

 

Thanks

Bob

[Ozlander]

Should be able to. Have to take to radio to the bike and find a way to power it up.

Do it outdoors away from buildings, cars ect.

[etcswjoe]

It may get you close however each radio is different so it will not be exact.

[frankd]

It may get you close however each radio is different so it will not be exact.[/quote

 

When you adjust the SWR you are changing the frequency that the antenna works best at (or is 'resonant'), and to a lesser extent the load impedance the antenna presents to the radio. All CB radios and most other transmitters are designed to work into a 50 ohm load. What all this means is that it doesn't matter which CB radio you use, the SWR will be the same. Just make sure you optimize it to the center of the band or channel 20. That way when you go up or down the band your SWR will be the best possible.

 

Frank D.

[Guest tx2sturgis]

It may get you close however each radio is different so it will not be exact.

 

SWR meters on CB radios are never exact, but close enough to get you in the ballpark. All common CBs have a 50 ohm output impedance.

 

When you adjust the SWR you are changing the frequency that the antenna works best at (or is 'resonant'), and to a lesser extent the load impedance the antenna presents to the radio. All CB radios and most other transmitters are designed to work into a 50 ohm load. What all this means is that it doesn't matter which CB radio you use, the SWR will be the same. Just make sure you optimize it to the center of the band or channel 20. That way when you go up or down the band your SWR will be the best possible.

 

Frank D.

 

100% correct.

 

 

The only thing a common analog SWR meter measures is voltage of the reflected RF, measured as a comparison between outgoing and returning.

 

The reflected RF is greater when the antenna is out of resonance than when it is 'in resonance'. This is normally adjusted by changing the length of the antenna, a 'stinger', or adjusting a tuning stub or ring.

 

A standalone SWR meter cannot tell and does not care WHAT radio is attached, as long as the frequency is correct for the antenna being measured.

 

[etcswjoe]

Ok guess I should have been clearer, unless the SWR meter on the CB you are using is taking its reading from the antenna output it will not give you the same measurment as the external SWR meter. More than likely the SWR meter built into the CB is taking its reading before the final which will make the adjustment diffrent for the same antenna.

 

Also it may change the ground plane if you use another CB

Edited November 29, 2012 by etcswjoe

[TDunc]

I am so glad that I have never had any discussions on the therotical versus pratical experiences of whether the internal impedance of a particular transmitter can or will have any effect on the amount of forward/refected/reverse rf sent to an antenna device and whether or not you can swap radios and have the same swr on each.

I did, however, watch a ham club spend alot of time debating this and to no end.

(Kinda like the old Dan Quail thing of tomato - tomato)

 

 

 

If I may..

 

IMHO - you can not get exactly the same swr reading even on the same radio because of numerous factors that CAN change the characteristics each time you key the mic. Having said that. The difference is usually not large enough to worry about.(especially at 27Mhz)

I use one radio to check an antenna on another radio all the time. It is a good "look see" tool.

 

Would I use a radio that has a built in SWR meter? Yes if it was the only thing I could use for a look see but not if I could borrow an SWR meter that is a little better quailty from someone . Will it suffice to let me know if it is way off? Yes.

 

Again just in my humble opinion.

 

 

EDIT. See the above post too.. I was typing mine as he was doing his...Good Post.

Edited November 29, 2012 by TDunc

[etcswjoe]

I am so glad that I have never had any discussions on the therotical versus pratical experiences of whether the internal impedance of a particular transmitter can or will have any effect on the amount of forward/refected/reverse rf sent to an antenna device and whether or not you can swap radios and have the same swr on each.

I did, however, watch a ham club spend alot of time debating this and to no end.

(Kinda like the old Dan Quail thing of tomato - tomato)

 

 

 

If I may..

 

IMHO - you can not get exactly the same swr reading even on the same radio because of numerous factors that CAN change the characteristics each time you key the mic. Having said that. The difference is usually not large enough to worry about.(especially at 27Mhz)

I use one radio to check an antenna on another radio all the time. It is a good "look see" tool.

 

Would I use a radio that has a built in SWR meter? Yes if it was the only thing I could use for a look see but not if I could borrow an SWR meter that is a little better quailty from someone . Will it suffice to let me know if it is way off? Yes.

 

Again just in my humble opinion.

 

 

 

I started the debate here at work too our testing folks are split on it but we do have a lot stricter tolerances than a CB user does and put out 250 times what a CB does.

[TDunc]

The thing that is bothersome to me... On our bikes with its limited ground plane capability, what you put in the trunk has an effect. For the most part, neglagible for 27 Mhz. but for the perfectionist part of me and knowing what RF can do, It still bothers me. Had the same issue at 440Mhz on my old Surburban. Kept jumping all around and I never found out the reason. Two different antennas and two different radios.... Solved the problem by buying a new suburban.... Go figure.

[bobder41]

Thanks all for your input. I will hook up the other radio and see what I get for a reading. If it is way off I will check it with an external SWR meter.

 

Just bought the bike a week ago from the dealer and when I asked about the SWR on the radio he gave me a funny look and said they never adjust them.

 

Bob

[Guest tx2sturgis]

The best way to measure resonance, ie SWR, is with an antenna analyzer. They are independent of any radio, just a standalone measuring tool for checking SWR.

 

And even the least expensive analyzers will provide very accurate readings, and if a radio with a built in meter is then connected to the same antenna, you can be quite certain that if its not in agreement with the analyzer, the radio's built in meter needs to be calibrated, which is usually an internal adjustment.

 

Most consumer level digital analyzers cost between $150 to $500, depending on features, display, and frequency range.

 

Most CBers and CB shops have never heard of them.

 

However, they are used in amateur radio service and commercial radio service. They work. And they can be used with CB antennas.

 

 

 

 

 

[Cougar]

I see this is an old post from a search I did.....

 

OK gang., now that I have my new cable ran to the antenna

old one busted added a new OEM wire to the box.

 

So how do we do this tunning with the SWR Meter ?

 

Does it involve getting into the black box?

 

Or, is there tunning on the antenna near the black part

in the middle?

Or, do you screw something from the SWR into the pod were the main part screws in ?

 

The reason for asking is , I would like to put my trunk back on now

 

Thanks for your help,

Jeff

 

Adding::

 

Oh one other thing. is I did have a portable CB took it into the house and had

my wife take a listen. she said there was a lot of back ground buzzing noise

I was wondering if it was cuz the bike is enclosed in the garage with the long

10 foot tube lights causing a problem with interference?

With the old wire all it did was make a loud Squeal.

Edited February 10, 2013 by Cougar

[Cougar]

would this work?

[ame=http://www.amazon.com/METER-Radio-Antennas-Jumper-cable/dp/B002KRME3C/ref=sr_1_2?ie=UTF8&qid=1360524174&sr=8-2&keywords=cb+meter]SWR METER for CB Radio Antennas with 3' Jumper cable - Workman SWR2T & CX-3-PL-PL : Amazon.com : Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51Uqlnlu3sL.@@AMEPARAM@@51Uqlnlu3sL[/ame]

[Marcarl]

Your SWR meter should come with a short cord, so it can be plugged in where ever you have connection in the antenna lead. I usually try to undo the connection right at the antenna. You need to be outside, with the trunk in place and anything you would normally load in the trunk in the trunk. Once you have the meter hooked in, you power up the CB, key the mic, set the pointer of the meter at 'set' while the switch is in the fwrd position. Release the mic button, move the switch into the rev position and key the mic again. It should read 0, if it doesn't then you need to adjust the antenna. Do it all again and see what happened and adjust accordingly.

[Cougar]

OK thanks. was just watching some YOUTUBE and it says just what you said

so I take it that I have to un-screw at the bottom of the antenna holder put

the short cable in place, this will be pretty hard as this has a trike body on it

but think I can do get to it from under.

 

NOW.... nobody has explained how to you tune the antenna?

is it where the black cylinder is in the middle of the antenna?

 

Also, do you tune while the CB Switch is pressed?

 

Thanks!

Jeff

[ragtop69gs]

Where the black part midway up the antenna is you'll see a set screw, loosen the set screw and move the upper antenna up or down as needed. Do not make the change while keying the mic. change the adjustment ,then go through key up again.

[Marcarl]

Hope you got this right. With the meter attached, set the switch to fwd, then key the mic and set pointer at 'set'. Release the mic, set switch to ref key the mic and the pointer should read to '0', if not adjust antenna and then do this all over again, including setting the pointer to 'set' in the fwd position.

[Cougar]

OK thanks Jay.. so now as to where the split will be for the SWR

the cable is a one piece deal under the antenna. so how do

I hook up the meters cable then?

I think I am really confused now LOL

I have been looking at meters and someone said I would

need an adapter?

 

Thanks,

Jeff

[Cougar]

Yes Carl.. I have that part down now thanks.

 

I just need a diagram on how to hook the meter up

then I am good to go. I will be a pro at this soon

maybe I am just not thinking this out right yet.

[Marcarl]

OK thanks Jay.. so now as to where the split will be for the SWR

the cable is a one piece deal under the antenna. so how do

I hook up the meters cable then?

I think I am really confused now LOL

I have been looking at meters and someone said I would

need an adapter?

 

Thanks,

Jeff

There should be an extra piece of cable come with the meter. If you can't get at it at the antenna, you should be able to take the cable off the radio,,, same difference, maybe not 99% as accurate.

[ragtop69gs]

You will also need an adapter to hook up the meter because the cable style on the bike is different than what comes with most meters. I do not recall what the adapter is called though, it's mentioned in another CB thread here somewhere.

 

 

Found it, see post 21

http://www.venturerider.org/forum/showthread.php?p=693807

Edited February 10, 2013 by ragtop69gs

[Cougar]

Thanks Jay.. Motorola to RCA plug adapter I guess

so the only point to plug the RCA into is inside the BLACK

BOX ,, Darn and I just put the trunk back on And I am

supposed to be tuning this with the trunk on and full of my crap.

Umm now to figure out how I am gunna do this. maybe I can

just lay it back on there while doing it.

[Cougar]

http://www.sierra-mc.com/proddetail.asp?prod=SIE-SWR12 THIS ONE !! Need both OR

http://www.fullcompass.com/product/292075.html?utm_source=googleps&utm_medium=shopping&utm_campaign=googleps&gclid=CIPus6fqrLUCFdOHMgodR2QAjg

Edited February 10, 2013 by Cougar

[Daveand Barbie]

If you are using an SWR bridge to check you antenna, the connector on the bridge is an SO239 and and uses a PL259 connector on the cable. On the smaller cable used in mobile applications, you will need an SM58 sleeve also.

 

The UHF connector on the fullcompass website is an SO239.

[Cougar]

OMG.. now to find all of them parts. thanks