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Old 11-02-2017, 3:48 PM
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Default Portable backpack type antennas?

I what to build a simple portable antenna that would work with a CB radio and could be installed on a backpack. Most of the designs seem big and not an option for walking around while using.

I know that a hand held would be more practical, but we are building this kits as a youth project and looking for DIY options.
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Old 11-02-2017, 4:56 PM
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Not gonna happen, due to basic physics. The required length of the antenna is directly proportional to the wavelength of the frequency, and shrinking the antenna below that size reduces both bandwidth and efficiency. Any practical backpackable CB antenna is going to perform horribly.

As an alternative, look into VHF twin-lead J-pole antennas and a Baofeng programmed with VHF ham, MURS, or whatever frequencies are legal in your area.
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Old 11-02-2017, 5:42 PM
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Default Bazooka antenna

https://youtu.be/KASWnflEX_0

Take a look at this roll up cb antenna for portable use
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Old 11-02-2017, 9:48 PM
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Sure you can put out a good signal from a backpack. Get the largest loaded antenna you can accommodate on a backpack like a 4ft Firestick or similar on a mirror mount clamped to the pack frame. Then use about a 9ft trailing counterpoise wire, which will become the other half of a dipole.

Trim the counterpoise length first for the best match then diddle with the main antenna tuning. You can easily put out a similar signal to the same antenna on a vehicle.
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Originally Posted by jonwienke View Post
Not gonna happen, due to basic physics. The required length of the antenna is directly proportional to the wavelength of the frequency, and shrinking the antenna below that size reduces both bandwidth and efficiency. Any practical backpackable CB antenna is going to perform horribly.

As an alternative, look into VHF twin-lead J-pole antennas and a Baofeng programmed with VHF ham, MURS, or whatever frequencies are legal in your area.
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Old 11-02-2017, 9:52 PM
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An old skit from SNL came to mind...Al Franken...


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Old 11-02-2017, 9:58 PM
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And now he is a US Senator....
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An old skit from SNL came to mind...Al Franken...


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Old 11-02-2017, 10:01 PM
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Scary isn't it!
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Old 11-03-2017, 6:29 AM
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Quote:
Originally Posted by prcguy View Post
Sure you can put out a good signal from a backpack. Get the largest loaded antenna you can accommodate on a backpack like a 4ft Firestick or similar on a mirror mount clamped to the pack frame. Then use about a 9ft trailing counterpoise wire, which will become the other half of a dipole.
I question the practicality of such a thing when the antenna is likely to be as tall as the kid packing it...
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Old 11-03-2017, 6:40 AM
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Default CB radio Portables

I have looked at the 4ft Firestick and like them, but at a $50.00 each, it's not a price point for a youth group to purchase. What we were hoping to do was find a simple antenna for simplex short range communications. Most home brew antennas.
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Old 11-03-2017, 10:08 AM
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Check out post 7 in this thread, these guys (including me) operate 80m through 6m using a back pack radio and whip while hiking and it works quite well making contacts all over the world. These antennas are a bit long being used on lower frequencies, but for CB something 4ft long is very easy to keep under control.

I see some 4ft CB antennas on Ebay including Firesticks in the $18 range including shipping, so there are lots of cheap antennas to experiment with on a backpack. Making a shortened CB antenna from scratch would be a big project in itself and I think its better to use a commercially made one then fabricate the mount and dragging counterpoise wire.
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I question the practicality of such a thing when the antenna is likely to be as tall as the kid packing it...
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Old 11-03-2017, 10:38 AM
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Default backpack antenna

Keep an eye out at garage sales, I'm regularly seeing 3-4ft CB whips for a dollar or two....

You could try winding your own helical whips on the boundary flags they use in youth soccer/football. They are about 4-5 ft, fiberglass, and reasonably durable. Wind, test, cover in heat shrink, done.

If the backpack has a metal frame, it may even work as the counterpoise/ground side of dipole.....


You may also want to look at other services (FRS/GMRS/MURS). By the time you kludge a battery, an old CB, and antennas, you are not going to have a light weight or very portable package.

Adding an external higher capacity battery and a speaker/mike to an existing portable radio may be much more practical......

$.02
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Old 11-03-2017, 2:55 PM
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jon-
I would have to disagree with you. Aeons ago, I built a custom magmount CB antenna. The stick is made from an old fiberglass fishing rod, about 1/4" in diameter, probably four and a half or five feet in length. And it breaks down in two with a metal ferrule in the middle. On that, I wound 1/4 wavelength of maybe 24g copper wire, experimenting to get the best spacing I could to fit the entire rod length. (Hey, it was what I had at hand.) The base was simply the capacitive coupling to the car roof, courtesy of some magnatron magnets, since we didn't have rare earth in those days. SWR? About 1:1.1 from the start, signal reports always were tops.

Now, what's that got to do with backpacks? Well, the same fiberglass rod could extend UP from the backpack. And a second rod could extend DOWN as the other half of a dipole, instead of the magmount base.

Ought to be a piece of cake, and an easy project for teaching kids. With CB's limited output power, proximity and rf safety should be no issue. Easy enough, cheap enough, to have a go at it. Thin wood dowels or bamboo, or old fishing poles, or those 4' long driveway marker posts, all make cheap antenna rods, and 24g wire is more than adequate for the power.

Or am I missing something here?
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Old 11-03-2017, 3:19 PM
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Default Fishing rod antenna

That is a great idea, love the idea of a fishing rod antenna. Great project for the kids! Most of our equipment has been donated free of charge or at very low rates. For the most part we have a CB for everyone and now just need antennas. Thanks Rred!
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Old 11-03-2017, 4:09 PM
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My pleasure.
Construction notes: Remove the wire bails before winding. And, when and if everything else is done, apply one or two light coats of pretty much any paint or varnish, to bind the wire down to the rod. Start, as in any antenna project, with some extra length and trim for best SWR.

Bicycle "dune buggy whip" flags are another source of thin fiberglass rods that some of the kids may have lying around, too. Putting a streamer or small flag on the top end also helps spot the radio guy in a crowd.
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