Hey everyone, new to the forum and getting back in radio 11M. I am setting up a base with a mobile radio 158EDX. For the antenna, I was told that I can just take a 108" steel whip, and weld a steel mirror mount to a 108" stick of chain link top rail and basically make a vertical dipole antenna. Also was to told to make 4 coils of coax about 6" in diameter right below the feed point. Is any of this true or just a load of BS? I was always told not to roll coax up because it creates a RF Choke on transmit. Just trying to make sense of this. I know I can make a regular dipole and delta loop and various others but I have all these materials just laying around. Is McGyver a member of the forum LOL. By the way, have looked around the forum, some interesting characters and good info to be found here.
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another antenna question
- Thread starter hustlerfastrack54
- Start date
will you be isolating this dipole from it's mounting pole and if so what manner of insulator will you use?
The way it was explained to me, the mounting pole ( I guess the mast is the correct term?) was part of the antenna. The whip being the positive and the mast the ground.
B
BOOTY MONSTER
Guest
you can try it and see how it does , it wont hurt anything as long as it will tune . if you're gonna use the whole mast length as the ground element of the dipole you may want to try running the coax down the center of the mast like the starduster . it would be cheap and easy to add some ground elements like the starduster with some wire and a 30 inch pvc x as a standoff at the bottom .
One would think that if you are going to use the whip as one half of a dipole; then the mast should be the same length as the whip.
eg: a dipole is two 1/4 waves . . .
eg: a dipole is two 1/4 waves . . .
Yeah Robb that is what I was starting to think the more I thought about it. Other wise wouldn't I need a matching section since one side is longer than the other, I thinks that is what is known as electrically unbalanced right?
A dipole is a 'balanced antenna'. Coax is an unbalanced feed line. Doesn't mean that you cannot use coax to feed a dipole though.
If you use the mast as the other half of the dipole; then it will need to be insulated away from any other metal - because it is also radiating and any metal attached to that will change its tuned length. So it will need to be insulated at that point if you are going to mount it.
A 1/4 wave whip doesn't need a matching section. But it will need 1/4 wave length radials attached to the shield of the coax. It will have a ~50 ohm impedance if the radials are at a 45-50 degree down angle to the vertical. But that isn't a dipole; now that's a ground plane antenna . . .
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Welcome to the forum, hustlerfastrack54.
I have seen a whip work mounted to a pole, but I agree to actually have a common dipole each side needs to be the same length. Personally, I'd rather have a 1/4 wave groundplane using that whip as the vertical radiator like Robb described.
I have seen a whip work mounted to a pole, but I agree to actually have a common dipole each side needs to be the same length. Personally, I'd rather have a 1/4 wave groundplane using that whip as the vertical radiator like Robb described.
My point exactly and the coiled balun using the coax should be used as to not make the coax part of the antenna.
here an example minus the balun.
A Stealthy Homebrew Vertical Dipole Antenna Using Mobile CB Antennas
I played with that set up last year for fun. I like the V beam the best. I got low SWR's with it and it has a small footprint too.
B
BOOTY MONSTER
Guest
so a dipole can't be grounded to earth/dirt since the ground wire would be seen as element that radiates and changes it's tuning ???
i also got better performance with a wire starduster than a vertical dipole each 2 ft off the ground and the dipoles tip was about 2 ft higher .
Well I just got done with the antenna, I took a 10' piece of top rail and welded the mount on then cut the pipe just under the mount, but long enough to stick in a piece of pvc pipe and took that and put on the piece that I cut it from. Stuck the whip on top and ran 4 wires from the 2 bottom mounting holes of the mount at a 45 degree angle and tied the ends of the wires to mason line and ran that to some 60d nails I stuck in the ground. I haven't bought a meter to check swr yet but compared reading from the meter on the radio and I'm getting 1.3 -1.5 reading, one design I tried read 3.0, so I guess I'm getting close. The design I asked about yesterday yielded 2.1 - 2.3 on the radio meter. Waiting on the locals to start up tonight around 9:00 and see what it will do. This is the first time I actually built an antenna and have to admit I enjoyed it. I didn't roll the coil of coax like everyone is saying do because I don't have but 18'. Does the coil of coax help with swr or with feeding of the whip? I will admit I does look like crap but I am proud of my little antenna, I'll have to post a pic of it when I figure out how. Thanks for the help every one.