10 meter CB whip

[KC0ZKG]

does anyone know how to modify a CB whip to be able to use it on 10 meters? i know you have to shorten it to a certian wavelength but what all help would be great!!!!

KC0ZKG ...Signing Clear

[KE5FRF]

I am going to withhold a direct answer to this, because I know you can figure it out yourself.

Do a google search for antenna calculators. A 10 meter whip is a vertical. There are TONS of free calculators on the web. There are also formulas for you to do the math yourself.

I could just post a link for you, but I suspect you can find this on your own. It really is a simple google search!


Hint: A CB whip for 11 meters is a 1/4 wave vertical.

[WA9SVD]

Quote[/b] (KE5FRF @ May 21 2007,19:56)]I am going to withhold a direct answer to this, because I know you can figure it out yourself.


Hint: A CB whip for 11 meters is a 1/4 wave vertical.
Using the 1/4 wave formula is assuming the "CB Whip" is a full length 1/4 wave on 27.xxx MHz. If it's a shortened whip with a loading coil, the antenna calculators won't help much. (The exact type of whip wasn't specified.)

The first step would be try to borrow an antenna analyzer. If the SWR is reasonably low (less than 2.0:1) at the lower end of 10 Meters, (assuming one wants to operate on the Novice/Tech Phone portion from 28.300-28.500 MHz) the antenna may need no modification at all. (Many loaded whips will allow some slight adjustment by means of set screws holding the whip portion.) If it has a loading coil, it shouldn't be necessary to bother making any adjustments to that. If necessary, the whip may have to be shortened slightly; less than 3% shorter. that's about 4-5" for a full 1/4 wave; but much less for a shortened whip. Remembering it's easier to take off length than to make the antenna longer, you should probably trim in 1/2" increments until you achieve an acceptable SWR at the portion of the band you wish to use. (This is where an antenna analyzer can tell you if you should stop, or continue trimming.) But you don't have to (and probably won't) achieve a "perfect" match. Just keep the SWR below 2.0:1 (you probably won't get it below 1.5 or 1.6:1 no matter what) any you should be "good to go."

Good luck. Let us know how you make out.

[NN4RH]

How many times has this same question been asked since February? About a hundred?

[KC0ZKG]

it is not a full length antenna. i belive it has a coil but i am not sure. it does not have one visible and i have no way of opening it B/C the base is plastic

KC0ZKG...Signing Clear

[KE5FRF]

Quote[/b] (KC0ZKG @ May 22 2007,09:57)]it is not a full length antenna. i belive it has a coil but i am not sure. it does not have one visible and i have no way of opening it B/C the base is plastic

KC0ZKG...Signing Clear
OK, I bet there is some kind of screw holding the base together, but I imagine some don't.

Otherwise, the difference between 10 meters and 11 meters is not much, and you know the antenna needs to be a bit shorter (shorter wavelength=shorter antenna)

Bottom line is that if this is a loaded antenna, there is no "hard and fast" formula, because each antenna may be different from one design to the next.

It really is a no brainer. If you want to try to make it work on 10 meters, all you need to do is start trimming and put it on an analyzer or an SWR meter. This isn't a drastic leap, like 2 meters or 70 cm would be. It should only take a couple of inches or so to get it working.

Without the exact specs on the antenna, we can't be sure if its a 1/4 wave or a 5/8 wave design, so we can't point to a hard and fast formula or length.

I like learning about antennas as all hams should. I suggest you get a copy of the antenna handbook or some other reference material to learn more.

ke5frf...not typing on my keyboard anymore.

[W4ETE]

Quote[/b] (KC0ZKG @ May 22 2007,10:57)]it is not a full length antenna. i belive it has a coil but i am not sure. it does not have one visible and i have no way of opening it B/C the base is plastic

KC0ZKG...Signing Clear
Are there any markings that you can use to let us know what you have? If the loading coil is at the base of the whip, then it could be a K-40 or Wilson. If all else fails, maybe posting a picture would allow someone to give you some good advice...

73,
Matt W4ETE

[KC0ZKG]

you guys are great!!!!
it is a radio shack antenna.it has a screw that you can raise or l;ower. i tried using that to change swr but with the half inch movement my swr was still above 3. i also found out how hard the whip is to cut. no wire cutters can do it.

[K7KBN]

Easy way to cut those stainless whips: use a triangular file to make a good notch at the correct point, then use a pair of visegrips and a bench vise to bend the whip at that point. Smooth and round off any rough/sharp spots (to reduce corona discharge).

[KC0ZKG]

thanks i will try that

KC0ZKG... Clear

[KC0ZKG]

thanks to all who left a post.!! i found a 102'' cb whip and converted it. sence it is going on my roof ,height is no problem. as for my other one it makes a great moble 2 meter whip!!!http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif http://www.qrz.com/iB_html/non-cgi/emoticons/cool.gif

[WA9SVD]

Quote[/b] (k7kbn @ May 23 2007,07:35)]Easy way to cut those stainless whips: use a triangular file to make a good notch at the correct point, then use a pair of visegrips and a bench vise to bend the whip at that point. Smooth and round off any rough/sharp spots (to reduce corona discharge).
YES, it's stainless steel, and difficult to cut.
But UNLESS the whip is tapered, (unlikely with a shortened whip) you should be cutting the BOTTOM end of the whip. Corona discharge is usually not an issue at "CB" power levels, But whips have a "knob" or some other type of attachment on the end to prevent injury. If you cut off the top end, you will have to somehow fashion a new tip that does not have a sharp point. A BIG glob of epoxy can serve as a tip; folding the wire over into a ball is usually next to impossible with Stainless steel.

Trim from the bottom, and file the burr. Trip a little at a time; maybe a half inch. TAKE YOUR TIME; it's easier to trim a "little more" than to add length if you trim too much.

Finally, be careful. If designed for "CB," the whip may not be able to handle a lot of power, and even 100 Watts Amateur power may cause component failure. Watch for signs of changing SWR during use; that usually indicates low power design unable to handle the amount of power you are using. No part of the antenna should show signs of heating after use.

Added:
Saw your last post: The CB whip won't work well "AS IS" for 2 Meter mobile work; the loading coil WILL have to be modified or removed. (Shorted would probably work, also.) Without the coil, you will have a simple 2 M quarter wave vertical antenna, meant to work against a groundplane, such as the roof of a vehicle.

Same goes with the 102" whip... you need a ground plane, of radials for it to work properly. Commonly, four radials, 1/4 wavelength (same as the whip) are used; by drooping the radials 45°, you will get a good match to 50 Ohms.

Good luck!

[w8jas]

Quote[/b] (KC0ZKG @ May 22 2007,23:42)]thanks to all who left a post.!! # # # i found a 102'' cb whip and converted it. sence it is going on my roof ,height is no problem. #as for my other one #it makes a great moble 2 meter whip!!!http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif http://www.qrz.com/iB_html/non-cgi/emoticons/cool.gif
a bolt cutter will make fast work of the steel whip. You can then file off the sharp points and round it a bit to fit the base.

Remember that a 102 inch whip IS NOT a 1/4wave on CB, 1/4 wave on CB is 108 inches!! The six inches it supposed to be added with the base spring.

[WA9SVD]

Quote[/b] (w8jas @ May 27 2007,10:35)]Remember that a 102 inch whip IS NOT a 1/4wave on CB, 1/4 wave on CB is 108 inches!! The six inches it supposed to be added with the base spring.
True, but the antenna taken as a whole (including the spring) IS a 1/4 Wave. And 102" should be just a tad longer than needed for a 1/4 wave vertical on 10 Meters. (approx. 98 inches at 28.4 MHz.) So a ltiile bit of trimming will be needed.

[AB6ND]

Try this. Place a small variable capacitor in series with the whip right at the base which will shorten it electrically. Tune the capacity for max output and save yourself the work of sawing a piece off the antenna. Short across the capacitor and you can operate it on CB again.
AB6ND

[KC7YPJ]

102" whip with 6" spring on my pickup works great fed as a longwire with a mfj-901b tuner down to 40m (performance is livable given it's 1/16 wavelength for the band), works quite effectively on 20-10m

[N4AUD]

You can get several 2m 1/4 waves from one CB whip (108 inches, I think), so to take care of the end, I round it off on the grinder then dip the tip in "Plasti-dip." You can get plasti-dip at just about any hardware store.

[ka5piu]

Quote[/b] (wa9svd @ May 27 2007,21:58)]Quote[/b] (w8jas @ May 27 2007,10:35)]Remember that a 102 inch whip IS NOT a 1/4wave on CB, 1/4 wave on CB is 108 inches!! The six inches it supposed to be added with the base spring.
True, but the antenna taken as a whole (including the spring) IS a 1/4 Wave. #And 102" should be just a tad longer than needed for a 1/4 wave vertical on 10 Meters. #(approx. 98 inches at 28.4 MHz.) #So a ltiile bit of trimming will be needed.
Hello.

One can get 108" whips also, so you may want to measure.
I use a 108" whip with a spring, 114" total.
I use a bese load tuning circuit that is nothing but a bit of PVC pipe with a tapped coil and tuning cap.
I can tap off from 1.4 to 34 MHz as a quarter wave.
The neat part is that to build one is cheap, real cheap.
I can pump in well over 300 watts with no trouble.
I built this to avoid the look of a 10 meter antenna on a big truck.
By its very design and location most people, including hams, will never "see" it.
It looks like something that just belongs on the truck.

[w3bny]

http://i20.photobucket.com/albums/b220/Bunnieman/SG237-8.jpg

Now you are done.

[AB8RU]

462 divided by f in Mhz = L in Ft

or 462/f=L

Buy the Radio Amateurs Handbook lotta answers.

also good formula to memorize.

also next Q. what is Brown, Black, Brown, Silver bands represent on a 2W. Resistor ?

answer in the Handbook or the Resistor Calculator.

[KC7YPJ]

huh, formula I have for 1/2w is 468/frequency=L

[n5vog]

try 98 inches-a steel whip is 102 inches long--8 ft 2 inches #for quarter wave----divide 234 by the frequency to get the length----i use 2 steel whips on 10 and they are 102 inches--so you really dont need to cut them unless you are running lots of power and dont have a tuner------n5vog318@srcacess.net--curt

[VE9LBN]

I think n4aud said it all. If you add a 6" spring to the base of a 102" wipe it works Fine. Try it you mite like it.
73 http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

[m0dcd]

Having done this myself, it's a job for the antenna analyser and a 24tpi hacksaw. Go at it a bit at a time until you get where you want it to be. Anyone who helps themselves to my antenna might find it a bit useless for 11m, it's tuned for 29.600 for my converted 10FM rig. It only took about 60mm to bring it up band. If your antenna is a full quarter wave and you've a large vehicle beware low bridges and especially crossing electric rail lines! 16ft 6in over the rails!

[w1frh]

all this on a whip and gee I think if he had studied his book before taking his test he would have had all the info in front of him, how do u measure and cut a whip for 10 meters when its designed for 11 meters well it might just work fine on 10 meters without touching it mine does and has a good match also. No tuner necessary for the low part of the 10 meter band to 28.600 then it begins to climb.

[WA9SVD]

Quote[/b] (w1frh @ July 20 2007,21:04)]all this on a whip and gee I think if he had studied his book before taking his test he would have had all the info in front of him, how do u measure and cut a whip for 10 meters when its designed for 11 meters well it might just work fine on 10 meters without touching it mine does and has a good match also. No tuner necessary for the low part of the 10 meter band to 28.600 then it begins to climb.
Yes, if it's simply a whip, all he would have to do is trim a small amount according to the "formula."

But in his original question, he was NOT using a plain whip, it was a shortened antenna with a loading coil in the base, in which case the formulas for wavelength or wavelength fraction (1/2, or 1/4) are meaningless and worthless. The posts here that assumed or referred to a 102" or 108" whip were by those who either didn't read, or didn't understand the question. (Granted, his original post didn't specify what type of antenna, but he DID subsequently state it was a shortened whip with a loading coil.)

[KA5LQJ]

Well.....

I don't think the "loaded whip" is the problem. #The question begging to be answered at this point is: What type of vehicle do you drive, Dayton? #Compact car?, Minivan?, SUV (Hummers are bummers for fuel milage), regular car? #Large Pick-up? #Let us know.

That really is the determining factor as to where to put the 10 m antenna and type. #Today's cars come with plastic bumpers. #Never mind the safety factor, it's saving automakers billions of dollars. #http://www.qrz.com/iB_html/non-cgi/emoticons/mad.gif # #http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

If feasible, a 102", steel, tapered whip on a heavy-duty ball mount, no spring, would almost be ideal, depending on the transciever.

As for "CB"? ..... #It's a waste of radio spectrum for those who inhabit it. #

Respectfully.
73,
Don/KA5-LQJ

[w2nsf]

Yep, I'm feeding my Radio Shack 102" CB whip with an ICOM AT-4 coupler right at its base, and it tunes just about every HF band equally well. I suppose if I wanted a dedicated 10 meter antenna, I would cut it, but what the heck, I can get it all with the AT-4 so why bother? Good luck!

[WA9SVD]

Quote[/b] (w2nsf @ July 21 2007,13:00)]Yep, I'm feeding my Radio Shack 102" CB whip with an ICOM AT-4 coupler right at its base, and it tunes just about every HF band equally well. I suppose if I wanted a dedicated 10 meter antenna, I would cut it, but what the heck, I can get it all with the AT-4 so why bother? Good luck!
Again, that's fine IF the person has a multi-band transceiver and tuner, not just a 10 Meter radio. Without the added expense of a tuner, a plain whip WILL have to be trimmed for best performance.

The point's really moot; the original question was about a loaded whip, and that seems to be applied to a dead horse by now in this thread. Not sure how many people have to tell him th either "get a book and figure out how to cut an antenna he didn't ask about" or to "get a different antenna."

[ke5pcv]

Quote[/b] (KC0ZKG @ May 21 2007,19:45)]does anyone know how to modify a CB whip to be able to use it on 10 meters? i know you have to shorten it to a certian wavelength but what all help would be great!!!!

KC0ZKG ...Signing Clear
take off a foot of wire off the antenna http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[W4INF]

Number 397, the number of post lately that has used the letters C and B together on this forum. http://www.qrz.com/iB_html/non-cgi/emoticons/laugh.gif

[ki4agd]

i have a 102 inch whip with a ball mount and spring with 18 feet of coax and my tool box.i put my analyzer to it and i found out that i had to do nothing to my whip.the swr,s were very low from 26.965 to 29.700. mike (ki4agd)

[W0LPQ]

swr's?

What's that..?

[ka5piu]

Hello.

Standing Wave Ratio.
This term is somewhat correct, perhaps he ment the readings?
Thus SWRs might be a bit more correct.
This is kind of like whan the internet got started.
Some purists insisted that is was period or comma or who knows what.
In the end, dot won out, now it is dot com, not period com.
Must drive the english teachers insane.

[W0LPQ]

SWR is a ratio ... the answer is a number that is singular.

[K7KBN]

Quote[/b] (ka5piu @ Aug. 05 2007,20:49)]Standing Wave Ratio.
I notice you said "Ratio", not "Ratios" or "Ratio's".

That's the point: it's not "SWRs" or "SWR's". Just "SWR".

[KC0TPI]

102" whip works fine throughout the band

[WA9SVD]

I've been thinking about the subject now for a while.

MAYBE it's time for ALL of us to get off our white horses, or albino donkeys (or donkeys of any color) and think back, look back, at some of the "newbie" questions and types of materials that USED to appear in QST.


this EXACT same subject was addressed in QST for June 1972, in a QST (construction) article by none other than one of the TRUE gurus of the time, Lew McCoy, W1ICP.
In those days, rather than taking questions from the "Peanut Gallery," QST took a proactive role, and offered solutions and ideas BEFORE they were even asked.

In this article, Lew outlined how to take a then typical "CB" short whip, disasemble it, add an appropriate matching coil, and capacitor, and a guide to the proper adjustment to use the antenna on 2 Meters.
But there was no grumbling about "newbies," no complaints ahout those "*(*(#$#" CB'ers, toss the junk; just straight forward "let's use this to our advantage, make something WE can use on OUR bands."

Other QST articles of the day described what capacitors (nee condensors) were, what they did, and how to use them properly.

IMHO, THAT is true Elmering, and perhaps the ARRL needs to return to some roots, lest the tree they are now nurturing eventually fall down fron lack therof. REAL explanations of the basics.

Many of us are fortunate enough to live in a city, town, etc. where their public library has an archive of QST and some old ARRL publications. Many of the older publications are tremendously more informative than current publications. We should take advantage of those resources while they still exist; many libraries WILL eliminate such archives (due to budget cuts and lack of space) if they are not accessed or requested often enough. THAT would be a tragic loss.

[MrGoodwreck]

WOW!...

Just wow...

I honestly expected people to know how to read a post, and be helpfull to new guys...

It must be great being perfect.

To those of you that were willing to help him, this is not pointed at you. I have been on the air for 8 years now, and have never had people act on the air the way they do on this board to people.

Sad really.

[WA9SVD]

Quote[/b] (MrGoodwreck @ Aug. 29 2007,11:38)]WOW!...

Just wow...

I honestly expected people to know how to read a post, and be helpfull to new guys...

It must be great being perfect.

To those of you that were willing to help him, this is not pointed at you. I have been on the air for 8 years now, and have never had people act on the air the way they do on this board to people.

Sad really.
There is some truth to your comment. but also remember this is the Internet, and NOT Amateur Radio on the air. At times, some people, even the apparently best behaved, do blow off a little steam or display some annoyance. It IS better here than on the air.
Of course, truly rude comments or posts are not really appropriate even here, even if they are made. They become a reflection upon the person making such comments.