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CB Transceiver Antenna Dilemma

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telly123

New Member
Hello:
I bought a CB transceiver and I bought a stainless steel "whip" antenna that is 102 inches in length. Then I read many things about the importance of a good antenna and then I began to worry. My antenna is a well crafted piece of stainless steel with a 3/8 inch male threaded stud at one end. I intend to use my CB transceiver in my house only. So I cannot receive the advantages of the "ground" effect of an automobile frame. I intend to pound a pipe into the ground and apply some sort of flange to receive the 102 inch antenna. I have two questions. How may I create this "ground" everyone talks about and how can I create the connection for a coaxial cable since the aforementioned antenna has no type of connection junction whatsoever? Thank you for any information that you may be able to give me.
 

Sceadwian

Banned
"Ground effect" Isn't an effect, it's simply saying that the car body is being used for the ground plane reference of the whip, it's not optional it's required for the antenna to function. Obviously you don't need a car though =) Hopefully someone here knows more about antenna's than I do cause I'm not sure what you do for a ground plane on a mast mounted whip. I know it's not a problem though, just not sure how to do it. The center conductor of the coax cable would be wired to the actual antenna, and the shield of coax would be attached to the ground plane. BNC connectors are used quiet extensively for antenna connectors, but if you don't want to bother and don't mind having to solder to remove the antenna you can solder the conductor and shield directly to their needed connections.

Hopefully someone else here will be able to help you with the ground plane. Keep in mind however you're going to need some kind of lightning arrester on this, a 9 foot long heavy duty stainless steel rod stuck up in the air is a mighty attractive target for mother nature. While not technically needed for the antenna to function if your house catches on fire because your unprotected antenna let a lightning bolt into the house your insurances company is gonna tell you to take a hike.
 
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telly123

New Member
Thanks

Well that basically explains it. Thanks. I read something about using ceramic "donuts" on the guy wires. I don't know if the guy wires are supposed to be isolated from the whip antenna/whip antenna support pole. Someone was explaining a home-made antenna made from aluminum or electrical conduit and #16 a.w.g.. I was even thinking of clamping the antenna to the backyard hose bib. Thanks for reminding me about my fire/earthquake insurance! I was going to pound a 3/4" galvanized pipe into the ground and at about 3 feet from the ground I intended to clamp the 106inch whip antenna with my home-made flange. Well at least I know where the two poles from the CB transceiver antenna input go!
 

Sceadwian

Banned
You should be able to pick up ceramic standoffs at a local hardware store in the electrical department. Maybe even a lightning arrestor, tell them it's for a cable TV line, you'll get a clue for what you're looking for by looking at the cable TV lines going into your house (if you have cable)

I'm used to antenna's that have counterpoise elements as part of the antenna so I get a little lost when I see whip's, RF is still a bit of a black art to me. As far as I know all you have to do is run that shielding to the pipe you're going to mount the antenna on, but don't blame me if a black hole forms on the spot if you do it =)
 
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Sceadwian

Banned
Just as a quick example, to turn your whip into a dipole you would get another antenna just like the one you have, mount it upside down directly underneath the other one (not connected) and connect the conductor to one side, and the shield to the other. As you can see for CB frequencies that would make for a very large antenna =)
 

stevez

Active Member
Telly - if you intend to mount the antenna close to the ground, the ideal ground plane would consist of 100 or more wires about 0.4 wavelengths long that run outward from the mounting point in a radial pattern. That's pretty extreme though broadcasters and serious hobbyists do precisely that.

Unfortunately most of us have to make do with less than ideal situations. Driving a ground rod at the mounting point is a start. A counterpoise is certainly going to be a help - a counterpoise being a length of wire run along the ground. A few radials of any length are going to improve things too. All of these things will change the feedpoint impedance -and you'll see that as you attempt to match your antenna to the transceiver.

It is my understanding that if you were to mount the whip at some elevation above the ground, that you would need less radials to get improved performance. Take a look at ground plane antennas and you'll see what I mean.

Amateur radio literature contains a lot of good information for the do-it-yourselfer. The literature will also show some of the things required for your installation to meet the electric codes. My budget/low cost way of dealing with lightning is to have a connector outside the house and a companion connector solidly grounded. I leave the line connected to ground - making the change only when I use my system (which isn't all that often).

There are lots of other antenna configurations but the whip is a good place to start. If you can take care of matching the antenna to the transmission line right at the antenna you will get all of the power to the antenna. A matching unit closer to your transceiver will work but the losses in your line will increase.

With CB there will be days when nothing works - then other days when the worst of installations go halfway around the world. The sunspot cycle is supposed to be on the way up so conditions should improve in the next few years.

QRP is hamspeak for low power and lots of low power amateur radio enthusiasts operate on the 10 meter band. CB is 11 meters - you can get a lot of good information by googling on QRP.

Have fun.
 

MikeMl

Well-Known Member
Most Helpful Member
As others have posted, a 1/4 wave whip needs a counterpoise (ground plane), consisting of a minimum of three radials, which are approximately 1/4 wavelength long, which radiate outwards from the base of the vertical whip. The radials are electrically connected to the shield on the coax cable; the center conductor is connected to the vertical whip.

Most CB base station antennas are either 5/8 or 1/2 wave verticals which require a complex matching section to be fed with 50 Ohm coax; but they require less in the way of a ground plane. You might also look at a 3/4 wave length antenna called a J-Pole, which doesn't need radials at all.

btw: a quarter wavelength at CB frequencies is more like 108". Your 102" whip normally sits on a 6" spring which is part of the antenna when figuring resonance.

Mike ML Amateur Extra (ps if you could see it in my profile picture, I have a 1/4 19" wave whip for 2m (146Mhz) mounted on the airplane. It relies on the airframe as the counterpoise)
 
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microtexan

New Member
Go to your nearest "Truck Stop" and you will find a mirror mount and several similar arrangements for mounting the whip and connecting with the coax to the radio. I think you'll see how several of the suggestions will work.
 

telly123

New Member
A belated thank you to you all. It was also suggested to mount the 102" whip antenna on the highest portion of my 2" copper DWV on my house. (I did all my DWV plumbing in 2" and 4" copper DWV) The whip will not touch the copper pipe through the judicious use of thick neoprene with strong clamps with the central conductor from the RG-58 coax cable @ 20 feet in length soldered to the whip and the shield from same will be soldered to the copper DWV. Will it work?
 

MikeMl

Well-Known Member
Most Helpful Member
You will still be missing about 6" in the overall length of the antenna, and it will resonate in the 10m Amateur Band; not in the CB Band. As I stated earlier, to be resonant in the CB band, the overall vertical element length needs to be 108". The whip is intended to be used on a ball mount with spring, which adds about 6" to the overall lenght.
 

bomberlouis

New Member
Hi i have just put a silver rod 1/2 on to a pole with a braket attached to the house , the higher i put the pole the harder it is to get the swr reading down, infact it goes up to 2.5 and i cant get it down at all the silver rod has 3 short ground planes , can any one help me realy getting me down now
 
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