Mobile homebrew

[Bandit1]

Ok guys I'm not the smartest.
And I know it would be easier to buy one.

I've seen ham articles talking about making your own mobile cb antenna

Like a fishing rod cut to 102" 1/4 wave
Has anyone got a way to make a mobile antenna?

I love making things and I wanna try it

 

[Captain Kilowatt]

You definitely need to be creative and handy. You need to realize just what a mobile antenna has to put up with in regards to vibrations and wind loading at highway speeds. I made a mobile antenna for the 15m band that was 10 feet long. The bottom half was a 3/8 inch diameter fibreglass blank that was originally a quad spreader from a Wilson Shooting Star . It was wound tightly with the outer braid from some old RG-8 coaxial cable and covered with heat shrink tubing. I fitted a standard 3/8-24 stud on the bottom and a 3/8-24 female stud on top. I made a short coil form from a piece of fibreglass rod with a 3/8-24 male stud on bottom and a whip ferrule on top. The coil was about three inches in diameter and located on this short piece so I could eventually make more coils for different bands and just swap them out. The top part is a 60 inch stainless whip. It works great as is on 15m and I have used it on other bands with a remote mobile auto-tuner.

 

[Bandit1]

I guess I should have specified I need it
for 11m.
I'm studying my ham material right now
So I can't talk on other bands
I do know what home brew 1/4 wave dipoles are.
I was just trying to figure out
A way to maybe use a dipole vertical
With 108" stranded wire
And mast it with a pole of some kind
And ground it to truck
Thanks

 

[rabbiporkchop]

Ok guys I'm not the smartest.
And I know it would be easier to buy one.

I've seen ham articles talking about making your own mobile cb antenna

Like a fishing rod cut to 102" 1/4 wave
Has anyone got a way to make a mobile antenna?

I love making things and I wanna try it

With access to a machine shop, anything is possible.
[photo=medium]5105[/photo][photo=medium]5104[/photo]

 

[Captain Kilowatt]

First of all there is no such thing as a 1/4 wave dipole. It is a half wave dipole and second if you use a 1/4 wave vertical (approx 108 inches for 11m) on a vehicle the vehicle body becomes the ground plane and you need only to ground the coax shield to the vehicle at the antenna feedpoint. Using stranded wire and a pole however is pretty crude and will be hard to manage while moving and will not likely survive many whacks from low tree branches. Perhaps you wanted it to use while stationary I don't know as you did not mention that.

 

[Robb]

Go for it.

You are going to need a test bed: vehicle mount, vehicle, antenna analyzer, and materials.
Some guidelines of commercial made units ('dimensions')
Might be best to start out copying an antenna that is already in production; then reverse engineer.
Lotsa antenna gurus on the forum that can help you thru the tough parts, and there will be that.
Think those are good starting points . . .

 

[Bandit1]

Ty guys ya I didn't know if I could use solid copper 108" long wire and tie it to a pole of some kind then ground it

 

[nomadradio]

Three or four 108-inch wires attached to the ground side of the coax, angled down at 45 degrees will get you a proper ground plane, all of them spaced evenly around the feedpoint.

A single 108-inch wire hooked to the ground side of the coax connection that points straight down will get you a 75-ohm antenna, a vertical dipole.

SWR won't be perfect, but should not be much above 1.5 or so.

73

 

[Bandit1]

So I could use 108" solid wire one piece
Like a 102" whip with the 6 spring

I wonder if I ziptied the wire to a sturdy mast and grounded that element
If it would be a good antenna

 

[Bandit1]

https://www.qsl.net/n2ffl/220antenna.jpg


Would that work

 

[Bow]

https://www.qsl.net/n2ffl/220antenna.jpg


Would that work

you would have to scale it up... a LOT..

That is for 220 MHz
You need something for 27 MHz

But the principle is correct.

 

[Bandit1]

Ok ya I appreciate the comback

 

[BJ radionut]

 

[Bandit1]

That 2nd video is one I was looking at doing also doesn't look too hard

 

[Robb]

If you don't have a clue; then say so.
Are you going to build a mobile antenna - or a base antenna?
You started out saying a mobile antenna.

Yes; having a tuned coil on the base is one way of building a mobile antenna. But unless you know how many coil turns you need, where the tap point needs to be, and the length of the whip you want to use - you are going nowhere - fast.

What materials do you have to work with now?
How far along with a design have you gone?