Dipole- In attic or garage roof?

[kc0jez]

Well, while I continue to ponder the possibilities for a big vertical vs dipole, vs a bunch of other choices (see my other thread) I've decided to put up a "quick" 20 meter dipole, and I have two options.

The easiest is a dipole in the attic, as I already have a presently unused inverted V for 6 meters up there, so I already have a run of coax to the attic.  the attic is a third story pyramid style walk up, and our house is nearly 100 years old, so we have 10 foot ceilings, so the attic is in the ball park of 30 feet up. I can run a north/south dipole up there quite easy (I'm located in northern Minnesota) and get it hooked up quite easy. Drawbacks are -- it would be quite close to the wooden attic roof structure, and of course it's indoors.  But, EASY to get it going, and there's a virtually straight shot of coax from the attic to the shack in the basement, right down the middle of the house.

But, if performance would suffer too much being inside and near structure, my second choice would be a 20 meter dipole on the garage roof.  It's a single car garage with the roof about 12 feet off the ground.  I can get away with a dipole on this roof that is physically about 5-6 feet from the roof itself, one end supported by stringing it right to the house, the other end going to an antenna tripod at the far end of the garage. So, it's about 17 total feet from the ground, 5 from the roof.  Dis-advantages of course are that there's been no antenna there so no existing coax.  And the coax run from there to the shack will be long and contrived.  Also, it would be near (about 8 feet away and below the antenna) power lines, that would be not quite parallel to it -- they would not actually cross over each other.

Question is, is the advantage of being outdoors but lower and near power lines going to trump easy to put up, higher, but indoors?

Sorry so many antenna questions, but my HF experience goes back to Novice days in 1970, and all I did then was a 40 meter dipole!  I am having great fun getting my vintage Heathkit gear put together, tweaked out, and ready to go and accumulating various doodads I'll need once again, that I've either lost or sold since my childhood days on the air!  So, I'm kinda just hoping to brainstorm with those more experienced than I.

Tim in Bovey

[W1GFH]

I notice there's a lot more line noise and man-made hash on the HF bands than there was years ago when I first began putting up antennas. If you can contrive the space for a loop, I'd go for that and its associated low noise benefits. The second option is a 5 to 10 ft. PVC mast atop the roof peak of the house that would give an inverted vee a high center point. That's my 2 cents FWIW.

[KD6VXI]

I notice there's a lot more line noise and man-made hash on the HF bands than there was years ago when I first began putting up antennas. If you can contrive the space for a loop, I'd go for that and its associated low noise benefits.

Here's a question for ya...

Would a folded dipole have the same low noise bennies?  I think so, as it's basically a quad.

How about a standard dipole, shortened a bit...  Then short it with a hairpin, like the hairpin matches on yagis.  Seems that would give the same effect?

Thanks, in advance.  I have a full size 160 dipole at one house, and have been pondering the above.  I'd assume that a ladder line fed dipole wouldn't matter, as the tuna is shorted in the matchbox.

--Shane

[W1GFH]

Don't know the answer to that one, Shane, but from what I recall reading from R. L. Cebik, folded dipoles do have some low noise benefits but they are mostly used to give added bandwidth on the frequency range of interest.

*And I just noticed that the Cebik files are no longer free, you have to sign up or buy a CD ROM or something. Too bad.

[KD6VXI]

Don't know the answer to that one, Shane, but from what I recall reading from R. L. Cebik, folded dipoles do have some low noise benefits but they are mostly used to give added bandwidth on the frequency range of interest.

*And I just noticed that the Cebik files are no longer free, you have to sign up or buy a CD ROM or something. Too bad.

I'll go through some of his stuff I have archived...  And I also have a Username / Pass to get on his site, if I can find it.

I <<think>> Cebik's stuff is still free, they make their $$$'s by selling off your info, or some such noise.

It would be a good thing to try, though....  I've never had one that I could do...  Maybe I'll build a decent 2 mtr dipole and test it...  The MFJ goes high enough to test for match, and I can shove a DMM on to the Yeasu for pretty precise measurement of antenna stuff.... 

Nice to find a way to get noise level's down, while still being able to use our existing antennas.

I also was pondering hooking the ends of the inverted V together, and making a delta out of it.  If fed with ladder line, it should be low loss enough to where it could multi-band, AS WELL AS give the bennies of a quad (noise).

Too bad antennas are so much cheaper than everything else.  Makes my excuses for not trying something by the end of the day pretty flimsy..  UNLIKE my antennas

--Shane

[K1JJ]

I'd agree with Joe/GFH.   Put a mast on the garage as high as possible with an inverted vee at the top. Pull the legs out as far as possible for max height. Keep it as straight as possible too.


A dipole is the attic is going to be down from the outside one due to attenuation from surrounding materials. Remember that the house contains electrical wiring, metal plumbing, radiators/covers, appliances, computer noise, etc.  Generally an outside antenna is better.  The question is, can you get that mast up on the garage to increase the height to approach the height of the attic ant?  Hopefully the garage antenna will be farther away from the house objects mentioned above too.

T

[kc0jez]

I'm doubting I can get away with enough masting on the garage to get the antenna nearly as high as I can in the attic. The attic antenna would be a good two floors taller than the garage roof.  There are very minimal materials in the attic except wood. In this old house, wiring to the attic pretty much amounts to one lightbulb.  There is no heat, etc in the attic so nearest radiators, etc are at floor level of the floor below, probably 20 feet down from the antenna location.

Also feedline to the attic is a straight shot to the shack, from the garage would be quite a bit longer and would have to cross over power lines coming into the house, OR be considerably longer and winding to get to the shack.

I'm thinking it's going to turn out being a wash between the options.

 Tim in Bovey

[w4bfs]

do both and check em out ...73...John

[Opcom]

My boss, in Boston, runs a dipole in the attic and a 100W radio. He gets very fine results, but does not use AM, mostly PSK31, some CW, and a little SSB. He says it works great and since it is above the 2nd story, the height is good and it is away from ductwork and electrical wiring.

[WU2D]

What about a 20M thinwall steel tubing rotatable dipole on the garage? 20 bucks worth of materials and an old TV rotor.

Tom's favorite antenna manufacturer MFJ has a simple 49 buck solution that looks like they just put two hamsticks back to back. www.mfjenterprises.com/pictures/MFJ-2220.jpg

Mike WU2D

[WBear2GCR]

Outside, outside, outside.

Inside sucks. Period.

It might help to post a jpeg of your place, so that ideas can be suggested?
That and/or a simple diagram of the lot with some dimensions shown...

Anything up and outside is superior.

The horizontal loop idea has merit too. Small on 20m!!

Higher is better. Top of the house roof is better than top of the garage.

Just the driven element of a trap yagi, like a TA-33 will play very well just stuck 10 ft above the roof off a simple TV antenna mast and side mount or chimney mount, or roof tripod mount. Probably 20dB better than an attic dipole.

Outside. 

                     _-_-bear

[KB2WIG]

  ' I <<think>> Cebik's stuff is still free, they make their $$$'s by selling off your info, or some such noise.
"

you think correctly....... just gotta sign up. I saved most of it on the hard drive...
klc

[flintstone mop]

I know your pain with the easiest way and the "higher" antenna, but being cooped up inside a structure is not a very good way of life for an antenna.
Nails holding down roofing, building materials, etc.


Fred