base ground elements revisited

[KJ4IYK]

What would be the chance of using, probably with some adjustments, an old TV antenna as ground plane radials for a verticle? If the radiation point of the verticle was mounted above the radials of the TV antenna wouldn't it work? I mounted a Wilson 2000 that I ran when driving a truck on top of my old Tv antenna for a quicky to check my old radios. It is very directional!! I am less than 2 miles from I40 and until the mobiles get east of me 5 miles I can neither talk or receive them. There are no tall buildings or towers in between us. There are a few trees. I hope to replace the Wilson soon with a Sirio 27.

 

[Moleculo]

Sure, you could do it...doesn't mean it would be the most effective thing in the world, but you could make it work. A lot depends on what type of tv antenna, how big it is, etc. If you're thinking about using one of those big log periodic type tv antennas, then expect the result to be somewhat diretional. If you can figure out a way to get it sort of centered under the vertical, that would make it less directional.

 

[Marconi]

Hey Wolf, can you post a picture of your setup?

It has been suggested here that your setup may be directional due to the shape of the TV antenna. That could be true to some very limited extent, but it shouldn't be much of an effect, at least at this close in range as described.

If the 2000 is doing what it should then a 2-5 miles range is not very good. What could be said to explain what is happening to the mobile signals that are closer to you than 5 miles and lie in the same general direction?

Try moving the direction of the TV antenna and tell us if the pattern changes.

If you can't post a picture, then maybe you can describe how and what you used to install the Wilson to the TV antenna.

 

[KJ4IYK]

I'll get a picture up as soon as the rain stops. What I meant by the distances is; when they are as close as 2miles or so I can not communicate. When they are 5 or more no problem. The TV antenna is so old I have no idea what or who it is. The elements are different sizes from front to back and of course the rotar doesn't work. There are 7 progressively longer elements with 4 short ones in front of the 1st progressive then 3 after.This is the feed for the TV. Then there are small single elements inbetween the rest. It is pointed SE, at least the smaller end is and my mod pattern seems to be more N and S. The Wilson is mounted with the coil above the TV elements on a regular mirror mount bracket and u bolted to the mast above the rotar. Using the bracket keeps the shaft from contacting the element. Swrs are 1.6:1 on AM at the radio. They're connected with 100' of grey Remeeflex miniature RG8u that I bought in '93. I'm guessing the coil of the wilson is 25' off the ground. The tip 4' from that. I'll get better pictures later.

 

[949Jake]

What is the boom length on the TV antenna? About how long is the longest element?

 

[W5LZ]

Don't expect that set up to be very directional because of the TV antenna, the TV antenna isn't furnishing any thing other than a set of radials, sort of (and only two from what I can see/guess about it). Are the 'elements' of that TV antenna shorted to the boom, or are they the typically fed 'log' thingy? The two antennas operate on different bands of frequencies so that while there may be a couple of thingys that are 'inter-usable' on 27 Mhz, there are a lot more 'thingys' that won't be usable/applicable at all.
Could a TV antenna be made to work with a CB antenna as it's radials? Sure, but I hope you don't plan to use that TV antenna as a TV antenna again. And just for 'grins', I think I'd move it's feed line well away from the TV, I'll bet it won't like it much!
- 'Doc

 

[KJ4IYK]

Hey thanks guys. I didn't really want to use it as or make a directional antenna out of it. Just wondering what the effect of the set up would be. If maybe it would eleminate or reduce some groundward radiation of signal. Keep it out of the neighbors telephones ect. Like I said, I just threw it up to test some old radios I had and tinker with repairs. Sometimes I get results from stuff like this that I don't expect or imagine. The directional properties are probably in my head anyway. Happy New Year to all!!! Wolf

 

[W5LZ]

Just a couple of thoughts, not 'great truths' by any stretch of the imagination, just things that seem to be sort of 'constant' from playing with antennas for a long time. "Your millage may vary."
About the only really effective way of stopping radiation from an antenna from going in all directions at points close to that antenna (close usually equals several wave lengths) is by electrically shielding the antenna in the undesired direction(s). Or by redirecting that radiation to some other direction that is more desirable. In other words, distance and shielding. Distance cuz that radiating field isn't always 'strong' in all directions, and cuz if you can get it far enough away from whatever is receiving that unwanted radiation, that 'whatever' thingy won't hear it anymore. Shielding cuz it blocks at least some of that radiation from getting past it. If that 'some' gets small enough the 'whatever' thingy doesn't hear it anymore. Sort of like how large the screens on your windows are, big holes let littler bugs in, smaller holes in that screen stop the little bugs too. Make that screen's holes small enough to stop all bugs and you then have to change the name of that screen to 'window' and just shut it. Which can lead to other problems. Wheeuu, sort of 'extreme' even for an exaggeration, huh? Yeah, but still true to some extent. The other side of that is don't 'shield' the antenna, shield whatever is getting 'bugged' by it, which is sometimes a lot easier, sometimes not. (And then, the whole purpose of an antenna is to radiate. Making it less efficient in what it's sole purpose in life is, is sort of non-productive, ain't it?) The simple truth is that you will never stop that radiation getting to things that don't like it. The only total solution to the neighbors not getting RFI is distance and/or a reduction in power... or just by them 'better' stuff.
Anything wrong with 'playing'/experimenting with antennas? Nope! Just don't get hung up on something to the point where you won't/can't 'accept' the results of that 'playing'. And don't assume things that you can't really substantiate/prove. It's also a good idea to sort of think about things before making an unchangeable 'modification'. But it's your wallet, right? Making mistakes is and is not a really dumb way of doing things. Mainly cuz 'foresight' ain't never as good as 'hindsight'.
Ever get the feeling that you've heard any of that before? Oh well, me too.
- 'Doc

Sorry, woke up early, can't sleep, figure this'll at least put me back to sleep...