Worldwide DX Amateur Radio Forums - Ham - CB - HF - VHF - UHF

Don't get too worried about a dipole being directional. That depends a lot on how high the thing is. Until it get's above about 1/2 wave length above ground, it isn't all that directional at all. Even if it's very high, that directional thingy is never a 'spot light', more like a 'flood light', pointed in two directions.
Inverted 'Vee's.
There are a lot of antennas called inverted 'V's, but are really 'droopy' dipoles instead. An inverted 'V' has an angle between it's legs of 45 degrees, and a feed point impedance other than 50 ohms. They are typically fed with ladder line and a tuner, not coax. They cetainly do work, but there's really not all that much going for them.
The 'typical' inverted 'V', or that 'droopy' thingy, is actually what you see most of the time. That angle between it's legs is whatever it takes to get the input impedance close to 50 ohms. It isn't difficult to do at all, just takes a little time to find the right 'angle of the dangle'. They are also typically horizontally polarized so might not be your best bet for what you want to do. Most CB antennas are vertically polarized, that's because of there being a lot of mobiles which are also vertically polarized. Want both polarizations? Easy! Just make two of the things. (I said make them, not buy them. If you can't find enough wire for a bunch of dipoles for less than you'd give for one bought one, you just ain't trying.)
The hardest thing about using dipoles is finding a place to hang them. Got trees??
- 'Doc

102 in. each side works perfect for me as an inverted v on 11 meter. Use a 1:1 balun as the feedpoint and you will be good. This comes from experience AND the 1999 ARRL handbook.

I don't know why I'm worrying about polarization...its easy enough to change this setup, so I can take a previous suggestion, and experiment. I figure I'll try vertical, then switch things up once I get talking with the locals.

I had some questions related to this install.

The first is the coax...I'll be buying new. This setup will be used with a barefoot (tuned/aligned) Grant XL. So power handling isn't really an issue, but I'm not sure attenuation will be with the lower power? I have two placement options, one (the preferred) would be to the adjacent shed and the other would be the house eave. Obviously the house would have the length around 25 feet, the shed will be between 75 and 100 feet (will be cut to length). While LMR-400 Ultra seems to have the best number, it just looks BIG at nearly 1/2 inch...I'm thinking LMR-240 Ultra at 1/4 inch?

The second is lightning/surge protection...is it worth looking into, besides grounding the mast and radio? I was looking at a cheap air core suppression deal that went in the feed line. I know nothing (cheap) will stop a direct lightning strike.

Lastly, relating to the first question, if I mount the antenna to the shed all of the antenna will be above any close obstructions. If I mount the antenna to the house, only the top section of the dipole will extend past the side of the house. Both setups will net about the same overall height above ground surface (around 18 feet). How would that affect the performance, having the lower section below the roof line?

What coax to use? The 'best' that you can afford within rea$on. Nothing wrong with using LMR-400, or the '240, but there are others to pick from. There is going to be some losses no matter what you select. The 'trick' is to minimize those losses as much as -practical-. Larger sized coax tends to lessen the resistive losses, doesn't necessarily mean a lessening of other kinds of losses. Take a look at the loss per 100 feet of coax, use the one with the least amount of loss. Pay attention to your wallet, it'll make about as much difference as anything will, and you'll feel it a lot more than some undetermined amount of loss that you don't even know was there.

Safety, lightning etc. Nothing wrong with minimizing that as much as possible. A dipole antenna requires no grounding for radio purposes. For safety purposes, the simplest solution is to disconnect the antenna and ground it, or just throw the end of the feed line outside. Considering the height you will be putting it, does your house, trees, etc, ever get hit by lightning? Maybe something 'close' at one time or another? If your answer to either of those is 'no', then I wouldn't waste a lot of good worry on it. I'd still disconnect when applicable though.

How close is too close? Uh... good question. Wish there was a good answer. Best is when an antenna is not close to anything (good luck!), close defined as in miles? From there, it's a compromise to some degree. 'Further' away is almost always better. Do what you can, then live with it. 'Above' stuff is better than 'beside' stuff. It's a good idea to think of an antenna as one lump, not in pieces. Getting the whole thing away from stuff is better than just part of it away from stuff. But, sometimes getting just a part of it away from stuff is more practical. Which of the two locations you gave would be 'best'? Beats me! Try them both, see for your self.

Nothing very specific in all that, huh? Sorry 'bout that, any more specific and it turns into an opinion, which isn't all that good, sort of. Good luck.
- 'Doc


Oh, one 'opinion' that I will 'share' is that 'spark-gap' type lightning arrestors are totally worthless. Don't waste your money. Why? Cuz by the time the voltage is strong enough to jump that gap, it's already inside the equipment you wanted to protect.

Using cheap coax is false economy (IMHO). Get the best and you can use it forever (almost) on all your future antennas. Get 100' and you can use it at any height (up to 100'). Coil the unused part on the ground (etc)

"The chain is only as strong as it's weakest link."

What are other options for cable...I was mainly looking at lower attenuation numbers. What would you recommend for a run of 100 feet?

I have some new RG-6 quad shield, actually a lot of it (as in around 1500 feet). I know we discussed the 75ohm feed line and 50ohm transmitter / feed point. I guess my main issue running RG-6 QS would be getting a PL259 on it...unless they make an adapter from cable to a PL259. (ON EDIT: I found a "F" to PL259 adapter, so I'm covered there) Would this require an antenna tuner down the road?

Thanks for that info about the spark-gap deal, that's what I was wondering.

I use this stuff
K1CRA Radio Store - Davis RF "BURY-FLEX tm" Low-Loss RG-8 - EST TO SHIP 6/5/09 Details

but there are others.
Just to give you an idea

Coaxial Cable by the Foot : The Antenna Farm :: , Your Two Way Radio Source!

One of the things I look at when buying coax is price. No electrical significance with that, but there is an economical one! [It ain't easy being this cheap, you know. A lot of times it just depends on what I happen to have in my pocket at that particular time.] I also look at (or try to) how easy the stuff is to work with. I think you've seen at least one aspect of that with that RG-6. Another part of that sort of thing is the aluminum that's used for shielding in some coax. That stuff is just difficult to solder to, most of the time I'm not going to bother with it. Then again, if I happen to have a few hundred/thousand feet of it, I just might! The non-50 ohm impedance can be dealt with, the aluminum soldering is a bit harder.
It isn't as much a problem as it used to be, but I hate paying for a "name". If there's something else around that has the same characteristics as that 'name brand' stuff, I don't mind using it. The biggy is paying attention to those characteristics. 'Loss' is just one of them, there are others such as power handling ability (take a real close look at that one, in some cases, that 'name brand' comes out on the short end), size (as in connectors), if it's locally available or do I have to pay to get it here, and so on. Same sort of things you do when shopping for anything! Would I tell you to run right out and buy RG-6? No, I don't think I would. But... uh... What do those adapters cost? Also keeping in mind that they are not going to be the absolute most bestest way of doing things. (I haven't done the "F" to PL-259 thingy, but I have done some things like that. It filled the need I had so it's just dandy. Not the best way, but it works.)
So what do you think? Is it feasible for you to use the RG-6? Or not?
- 'Doc

The RG-6 "Quad Shield" has two aluminum foil and two braid shields...should be easy enough to solder the shield braid. I already have the weatherproof F connectors for the cable...I just rewired my entire house using this RG-6QS, Thomas-Betts connectors, and a single splitter...the increased picture quality is simply undescribeable.

The adapter runs less than $3, probably less than $10 shipped.

How is the mismatch dealt with? I assume a tuner is required?

Another question I had, would a low-pass filter be a good investment (to prevent any possibility of TVI)??

I bet this would be easy with an antenna analyzer?? Like an MFJ-259B?