Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

A Dipole for your CB Base Station?

As any dipole for any frequency requires, each leg should be 1/4 wavelength. The height above ground should also be 1/4 wavelength - or more.
That is - if my memory is correct...

A balun is required IF you are going to use coax to the antenna feedpoint. If you are going to use 'ladder line'; then you won't need a balun.
 
Last edited:
The Jerk said:
So they should be 1/4 wave? That definitely makes them smaller...

So I would need a balun, but which one for an inverted-V?
Click to expand...


Any 1:1 current balun, or just make a coax choke. BTW, it will work without the balun, too.
 
OK, the way someone indicated that for a "beam" (horizontal or vertical) it wasn't needed, but for an inverted-V a balun was needed. That's the reason I asked the question.

I see what my project next week might be...
 
A current balun is often necessary to insure keeping the TX on the dipole - and off of the coax. The choke -as mentioned by Mole- is probably the 'better' way to do it right.

More importantly, the antenna match can be made by making your won balun. You will probably need a 1:1 current balun. But by some chance if you match is wrong, you may need a 2:1 balun if the antenna match isn't correct. Go with the choke first, as this will be the first 'natural' way to go with your project...
 
Last edited:
Don't get too hung up with baluns. They can be nice to use, but they are just not absolutely necessary.
A typical balun has two functions, makes the change from an unbalanced feed line to a balanced antenna less 'disruptive', and handles large impedance changes. Both of those functions are very dependent on the particular situation/circumstance. Coax is an unbalanced feed line. Some directional antennas use a matching device which makes them unbalanced antennas. In such a case, a balun is not called for, does no particular good at all. For particular 'large' impedance changes, a balun makes for a really nice impedance transformer. Feed line is 50 ohms, antenna is 100 ohms? Very nice place for a 2:1 balun. Feed line 50 ohms and antenna 150 ohms? Use a 3:1 balun. But if the two mismatched impedances are not 'on the money' at 2:1, or 3:1, or 6:1, but something sort of inbetween, then that impedance transforming balun just ain't doing you much good, is it?
If a balun 'fits' the situation, fine, use it. If it doesn't, or you don't happen to have one, most times that just fine too. Just wanna use one? Have at it! Don't wanna use one? Don't, there's a bunch of us who don't.
- 'Doc
 
Dipole

OK,
this is only my second post. I used a 1:1 balun and cut both ends to 102 in.(i should say that the lenght started at 112 in.)
Strung it up on 9 four ft. poles i got from ebay at a cost of about 25$ for 12, 4 ft. lenghts. I used a 102 in. piece of #12 wire off each side, and a 3/4 in. piece of pvc across the bottom (1.37 @ home depot). I used a 100 ft. rg8 coax, and right from the start i get a 1:1 on channel 1, 11 meter. A 1.3:1 on channel 40, 11 meter. My elmer, thogh gone now, taught me this. It works well. The pvc (102 in.) across the bottom of the wire keeps the wire at the same angle. I used 110 in. and wrapped it at the 102 mark. This works for me always. Use as an inverted V it will work for you without much or ANY tuning on 11 meter. Oh yeah; i use 100 ft. of coax to get from my apartment to the nearest trees. This was only my third attempt at a dipole, but use two legs at 102 in. you will not be off by much. I actually cut my legs at 112 in. this time to allow for adjustment. I didn,t need to. I twisted both legs off back upward at 102 in. and havent had to adjust SWR yet. Please let me know how this works for you if you try it. Oh Yeah, I have talked on this from cincy to you won,t believe where. This is only my 2 cents worth of dipole knowledge. By the way, i made my first the same way with no balun, and never got better than a 2:1 SWR. Go figure that out.
 
RE:

If a balun 'fits' the situation, fine, use it. If it doesn't, or you don't happen to have one, most times that just fine too. Just wanna use one? Have at it! Don't wanna use one? Don't, there's a bunch of us who don't.
- 'Doc

Nice explaination DOC


In my situation the 1:1 balun actually stopped the rf i was experiencing on all my neighbors electronics. Excuse me, i should say on SOME of my neighbors, including my wifes bedroom electronics. Once i installed the balun at a 45 degree angle( inverted V) i have been free of the interference. Though my dipole is about 60 ft. from a power line, i AM experiencing distortion from the line. Not sure about that yet.
 
RE

It was as much as 2.7:1 on channel 1 to 3.5:1 0n 40+. For 11 meter keep those legs at 102 in. an you won,t go wrong.
Someone correct me if you have better information.
What i am posting is tried and true by me as taught to me by by Bob Hegwood, Xenia Ohio. Thanks Bob
 
A properly installed dipole (horizontal) will have a feedpoint impedance somewhere close to 70 ohms. By gradually turning it into an inverted vee, you'll notice the impedance drop closer to 50 ohms. Either one is fine.

I've built and used dozens of dipoles, vees and other wire antennas in the past half century (!) and I've NEVER had to use a balun. The antenna pattern might have been skewed on some of these antennas, but I was able to make all the contacts I could handle.
 
i had a dipole up about 6 months ago after my imax 2000 fell down i duck taped a piece of bamboo to the top of my mast at a 90 degree angle and hung it vertical with a small plant hook and some fishing line at the bottom to keep it straight.it was about 35-40 ft up and worked very well i was able to make skip contacts and regular non skip contacts to about 60-70 miles.this dipole i tuned for 27.385 and it was 1.1.i hung this in a tree 2 summers ago with a fishing pole,swivel and sinker and was talking 30 miles plugged into a realistic trc-209 walkie talkie.i think i will try a bazooka for the next one.
 
I'm also running a dipole on 11 meters. Mine is in the attic as a temporary set up until the fall. I run an MFJ line isolator just off the transmitter, and it helps a ton. It has eliminated all of my RF problems. I was coupling RF into everything in the house. The same on the receive end too, very noisy before the line isolator. I'm sure most of my RF was because of the attic location. As far as performance, it works very well for what it is. It's not as directional as I thought it would be. I want to use it on 10 meters also, but need a tuner. I want to trim it for the upper end of 11-the lower end of 10 , but It's too hot up in the attic to go up there and mess with all that. I wish the receive was better, but again I think the location has much to do with that. I'm hopefully going to put a vertical up in the fall, and chop this one for 6 meters.
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ Wildcat27:
    Hello I have a old school 2950 receives great on all modes and transmits great on AM but no transmit on SSB. Does anyone have any idea?
  • @ BJ radionut:
  • @ ButtFuzz:
    Good evening from Sunny Salem! What’s shaking?
  • dxBot:
    63Sprint has left the room.
  • dxBot:
    kennyjames 0151 has left the room.


      Top Bottom
      Back