Will it work?

[C2]

I know, TRY IT!

But maybe some ideas are just not worth trying.

A friend is restricted in his condo, but he has the end unit in a long, narrow, 3-story building (all 3 floors and the entire end is his unit).

Because he would have wife issues, he is not likely to be able to run any interior feedlines to where he is allowed to have is rig, BUT he notices that he has some RG-6 running to the roof and plans to use it! This is actually a twin cable that is exclusive for his unit that was put there for a potential sat dish, which he does have in place at the chimney, but only uses one of the feeds, which are ~ 50 feet long.

He is concerned about not having an RF ground.

Up at the roof where the RG-6 ends, he plans to connect a 1/2 wavelength wire for 80 meters and streatch that along the chimneys along the entire length of the building. The chimneys are located along the wall, but go above peak a few feet (8 feet above roof at the eve). He will use an approximate 0.05 wave length counterpoise connected to the feedline shield. All just straight connections to the F-connector, and probably 16-22 guage wire. Nobody will see that, right?

Will the RG-6 just be part of the antenna or will it act as an actual feed line? It goes into the wall and his building is stucco with that chicken wire faraday cage thing going on...

Can he use the counterpoise as one half of a 10-meter dipole and just add a second wire to the center feed to the other half?

Is there another length of wire he could add to the center feed to help on other bands?

Should he try any matching at the antenna connection or just rely on his tuner in the "shack"?

He is using an IC-718 and one of the economy MFJ manual tuners that does not have a balun, just coax connectors, that he has a F to UHF adapter to use. (btw, should he still tune for lowest SWR since he is using RG-6?)

Any other thoughts?

 

[HiDef]

The RG-6 will work fine. Use in a centerfed 468/F dipole and screwing around trying to get a good R.F. ground will be unnecessary. One half of the dipole will be the counterpoise. A second dipole can be paralled for other bands from the same feedpoint but this really only works well when the original dipole has a very poor match on the second band. Known as a fan dipole.

Some ferrite cores placed over the RG-6 just below where it feeds the wire antenna will keep R.F. offa da outside of the shield of the cable. The correct types can be found using Google.

If 1:1 SWR is a must a tuner can be used to touch things up at the shack end at the expense of a percentage of power.

Weatherproofing all outside connections is important. This type of cable can wick water just like 9913 turning it into a long dummy load.

 

[C2]

I think he will have a problem making a dipole since he has the end unit, so the dipole would have to bent around the roof making two parallel wires like a U and not spaced far apart, and one side would have to lay on the roof tiles.

I'll ask him about maybe running an extra 60 feet of coax on the roof and center feeding a dipole. What if he had one just for 80 and one for 40, then every odd 1/2 should work well...

 

[W5LZ]

Will it work? Maybe. Depends on several things. Will it work well? Still depends on several things, but probably not real well.
'HiDef' hit on a couple of those 'things', using a center fed antenna 'cures' a lot of very "iffy" things about counterpoise's. Having a tuner also takes care of a few of those 'thingys'. Being as close to his neighbors as he is, count on having a few problems there too. And as you hinted, trying it is about the only way to know for sure. Sorry 'bout that.
- 'Doc

 

[packrat]

Might work better as an inverted l, with the shield leg led down the side of the building unobtrusivly. That will be better than the u in my opinion.

 

[C2]

OK, we discussed this and he will climb up to the roof and scope out the possibility of running more coax to the center of the roof and setting up a fan dipole, one for 80, 40, and 10!

He cannot have any wires going down the exterior walls and he is just hoping that no-one notices the small guage wires up on the roof.

The big question now is those F-connectors. Can they handle 100W?

 

[Moleculo]

I don't see why it won't handle 100 watts. It's really no different than the size of a BNC connector, which will handle that much power.

 

[Beetle]

A 0.05 wavelength counterpoise (~13 feet for 80M) might just as well not be there. However, the best advice I can give for ANY antenna idea is to try it.

Actually, that's the SECOND best advice. The first best advice would be to get a copy of the ARRL Antenna Book (and all the software that comes with it). Learn enough about antennas that you feel reasonably comfortable with what you're planning.

You'll make mistakes, but so what? As long as you learn from them and can figure out what it was and how to correct it, it wasn't wasted time and/or effort.

I would point out, however, that the feedpoint impedance of this end-fed 80 meter wire with a 13 foot "counterpoise" will produce an SWR somewhere around 80:1. Even at 80 meters, this will result in almost 6dB loss (100 watts in; about 30 watts out). Coax feed line for an end fed wire is generally not a good idea.

 

[HiDef]

Eff connector will not break a sweat with 100 watts on 4 mhz as long as the when part of a flat system. Flat meaning low SWR. M Squared long boom 144 mhz antennas use a folded dipole driven element for about 300 ohms. They transform that impedance to 50 with RG-6 with F connectors. Those antennas take 1000 watts carrier power all day at VHF.

 

[hookedon6]

just an idea,...... can he put a verticle inside the chimney?

how about a "loop" on insulated stand-offs mounted on the gutters?

can he have a "real" antenna?
is this a "wife" issue or a cc&r issue. if he can have a sat dish antenna , why not an smallish amateur antenna?

 

[C2]

It's CC&R. He lives in an upscale condo complex (if that's not an oxymoron!) He's not even supposed to have his dish, but he did it anyway; fortunately, the roof side of the chimney was facing the right way, so nobody can see it unless they go on the roof, which at 3 stories and a decent tile roof pitch is not too likely.

When he goes up there, he goes out his 2nd story balcany and climbs up the overhead trellis, then gets to the roof with a ladder on top of the trellis; then another ladder to get to the 8 foot chimney.

The chimney and walls are all plastered with mud, so there is chicken wire under there, and the chimney is really a metal tube with a wood frame.

A dipole is probably his best bet, going from center of someone elses chimney to ends at the roof peak near each end of the building. He paced off the building and it is about 160' long and 50' wide.

He's just gotta find the mustard to get up there again. I bet it never happens and he just keeps using his buddy pole on his balcany, which does not work very well because he can't get it high enough above the buildings...

 

[C2]

Eff connector will not break a sweat with 100 watts on 4 mhz as long as the when part of a flat system. Flat meaning low SWR. M Squared long boom 144 mhz antennas use a folded dipole driven element for about 300 ohms. They transform that impedance to 50 with RG-6 with F connectors. Those antennas take 1000 watts carrier power all day at VHF.

F-con has the worst for me even for TV reception. It seems the center contact area is so small and the copper tends to corrode and mis-contact.

1000W?

Oh, I also suggested he use a BaLun (waiting for Molecular dude's post) or make a coax choke at the dipole feed.

I think I'm going to make a fan dipole like this too. One for 80, 40 and 10...

 

[HiDef]

F-con has the worst for me even for TV reception.
1000W?

QUOTE]

Yup. It's been in service for a year. 1000 watts. Those antennas are popular with earth/moon/earth people. Most of them use as close to 1500 watts as they can. They all use that blasted F connector.

I pulled one of these apart that had been used for several years at a few hundred watts on FM and it has zero signs of distress.

 

[Moleculo]

He's not even supposed to have his dish, but he did it anyway;

FYI, Feds (FCC) already ruled years ago that CC&R's, HOAs, etc. cannot make restrictions on preventing the use of the regular (Directv, dish, etc.) satellite dishes.

Some old CC&Rs still have the restriction in there, but it's unenforceable.