Lost in the attic!!

W9CAC · #1 (**permalink**) 09-13-2011, 10:23 AM

Ok, have a little problem and am trying to figure this out. Anyone have a antenna for a 48' by 10' attic space? The antenna in the attic will be 31' above the ground. This is an HOA, no outdoor antennas except TV dish. I am going to run 100 watts with a tuner, no hy-power, would like to work multibands.
I am not trying to achieve super DXer of the year, just do some moderate radio work. Have already been fined twice for hamstick dipoles on the deck and on the driveway. So if I can put an antenna in the attic, I will be happy.
Any reasonable suggestions, other than divorce and move would be appreciated.

W2NJS · #2 (**permalink**) 09-13-2011, 04:40 PM

I believe that you will find several manufacturers of shortened dipoles for HF in current issues of QST magazine. Combined with a good automatic antenna tuner you'll be in business and able to work at least several bands. Keep the power output on the low side and no one will know what you're doing. Later on you can get on the Association Board, educate your neighbors about amateur radio, and put up some better outside antennas, or at least removable/temporary dipoles. Good luck with the project.

W9CAC · #3 (**permalink**) 09-13-2011, 05:15 PM

I became the President of the association last year! However, I cannot get either the board or the associations attorneys to see the light for amateur radio.
I have even sought help from my local amateur radio club, but to no avail.
I am trying to make a determination if I should bend a carolina windom in my attic or just stick a 66' dipole up there and hope for the best with my tuner.???

KK4DAN · #4 (**permalink**) 09-13-2011, 06:33 PM

The G5RV-jr is only 53' end to end. It leaves you coming up a bit short on space, but maybe you could angle it a bit? I have one up in my trees at the moment and its really not even that high and does fairly well. I can even tune 80m with a tuner, but I'm sure I'm not getting out well. Seems to work fine on 10-40m though and I'm certainly not going to win any prizes with it, but it gets me out.

I don't have an HOA to worry about and plane to get a better one up in the trees.

nexus · #5 (**permalink**) 09-13-2011, 07:58 PM

Quote:

Originally Posted by Bluelghtning

The G5RV-jr is only 53' end to end. It leaves you coming up a bit short on space, but maybe you could angle it a bit? I have one up in my trees at the moment and its really not even that high and does fairly well. I can even tune 80m with a tuner, but I'm sure I'm not getting out well. Seems to work fine on 10-40m though and I'm certainly not going to win any prizes with it, but it gets me out.

I don't have an HOA to worry about and plane to get a better one up in the trees.

You're forgetting to mention about the 300ohm twin-lead which is a very important part of the antenna. It can't just lay along the rafters or beams. It needs to go straight down, or at a 45 degree angle from the wire elements. So for an attic antenna, the G5RV is not very efficient.

nexus · #6 (**permalink**) 09-13-2011, 08:10 PM

David,

Have a look at this page IMHO a BTFD folded dipole would be the best solution, not only inside an attic but also for outside use too.

You can have them cut for various length, the one I linked for you is the design plans for a BTFD that is 44.5 ft over all in length. See the thing about the folded dipole is it's continuous operation from 3.7 to 30 MHz WITHOUT A TUNER. And it's rated for over 1000 watts PEP on SSB.

You can buy a complete one for around 250 bucks from Buxcomm or B&W, or buy the balun/terminated resistor from Buxcomm for 60 bucks and build the rest with your own parts (wire/spacers/insulators/etc) for much cheaper.

The formulas are on that page to help you determine the total length you'll need.

These antennas were designed specifically for government/military use and are very efficient with low noise, high reception design.

Antennas, T2FD, and termination resistors

and the B&W site:
Folded Dipole Antennas

KK4DAN · #7 (**permalink**) 09-13-2011, 08:11 PM

Quote:

Originally Posted by nexus

You're forgetting to mention about the 300ohm twin-lead which is a very important part of the antenna. It can't just lay along the rafters or beams. It needs to go straight down, or at a 45 degree angle from the wire elements. So for an attic antenna, the G5RV is not very efficient.

True, I totally forgot about that.

W9CAC · #8 (**permalink**) 09-14-2011, 07:31 AM

I hadn't thought too much about either of those antennas. I had built a G5RV jr. for my son. I built it for 40 meters and it worked like a charm. I have an open chase where some of the 450 ohm window line can run from the attic to the ham shack in the lower level(my house is a trilevel), but there are three things in there that the RF from the window line may play havoc with: doorbell, fire alarm circuit and burglar alarm circuit.
I think that I am going to build a T2FD. Since I am only using 100 watts, I think a T2FD would be perfect.
I can use low loss 400 coax and I think that 2 feet between the coax and the circuits will be enough.
Thanks.

doctor795 · #9 (**permalink**) 09-16-2011, 08:07 AM

My friend in Florida lives in one of those restricted home areas..he has a long wire run around his crawl space<attic> and fed with 450 ohm ladder line to an antenna tuner, keeps the stn at 25 watts and has no problem wrking the bands, Keep the power low and shouldnt be any trouble..high power could me trouble.
DOCTOR/795

LtDoc · #10 (**permalink**) 09-16-2011, 09:24 AM

You have several choices, none of them very efficient, but workable. Since you will be using a 'shortened' antenna on some bands you have to make up for that 'shortness' by loading the antenna in some way. Or, by using a very capable tuner.
Bending a typical dipole isn't all that inefficient, sort of, and some pretty weird shapes are possible without much loss in performance. That 'loss in performance' can show up in several ways, some not bad, and some that just won't be acceptable for whatever reason.
And then you get into the RFI thingy. That can be such fun! About the 'best' advice with that is that distance is the 'best' solution, but not always very effective. Depending on what's being interfered with, I have no 'good' solutions for that. Those security devices for instance. What's the chances of just turning the thing off when operating? And remembering to turn it back on!! (Or telling the security company what you are doing?)
How about placing those 'hamstick' dipoles in the attic?
No matter what you do you will have limitations. Picking the limitations you can 'live' with is going to be your best option.
Good luck.
- 'Doc

PS - I've been the B&W 'folded dipole' route, I have to advise you not to waste your money. Mounted outside and at a respectable height, they just are not equal to what I would call a usable antenna except for short distances. YMMV, but not by much...

K9WG · #11 (**permalink**) 09-16-2011, 11:32 AM

I run a 70' longwire in my attic. Used a choke at the feedpoint with RG6 coax and a tuner. I have worked all over the world with this setup.

BUILD AN AIR WOUND 1:1 CHOKE BALUN FOR HF - THE UGLY BALUN!

Paulsan · #12 (**permalink**) 09-16-2011, 08:20 PM

Alpha Delta Communications

DX-EE

40'

40-20-15-10 w/o tuner

30-17-12 with a tuner

JnglMassiv · #13 (**permalink**) 09-18-2011, 01:10 PM

I wrote a line or two on this in the spring:
Link
I agree that you may need to dial down the power a touch. If you Association is already strict, wait till one of your neighbors complains that they can hear your transmits on their stereo.

Paulsan · #14 (**permalink**) 09-21-2011, 01:27 PM

Am I wrong, isn't it up to his neighbor to deal with that interference?

K9WG · #15 (**permalink**) 09-21-2011, 01:48 PM

Quote:

Originally Posted by Paulsan

Am I wrong, isn't it up to his neighbor to deal with that interference?

It depends. If you are running reasonable power into a well engineered system then yes. If your system is not clean then no. Also the FCC can and will restrict your operating hours if you can not work out a solution to interference.

Paulsan · #16 (**permalink**) 09-22-2011, 08:47 AM

Ahhhh...yes. Understood. I need to extend my thinking to the fact that there are poor systems out there. Thanks.

Wyandotte · #17 (**permalink**) 09-29-2011, 07:40 PM

Quote:

Originally Posted by nexus

You're forgetting to mention about the 300ohm twin-lead which is a very important part of the antenna. It can't just lay along the rafters or beams. It needs to go straight down, or at a 45 degree angle from the wire elements. So for an attic antenna, the G5RV is not very efficient.

I know someone who put a Jr in an attic and it played just fine. He bent down the ends some to fit.

I myself have had a Jr 15' off the ground, with the twin line running horizontal back to the house, and worked Ireland and France with it during a contest.

John_S · #18 (**permalink**) 10-01-2011, 11:21 AM

I've posted this one before, but it sounds like it might be right for you, so here goes again. Click on "1/4 size Cobra" to get to the particular antenna, although he also has some other neat antenna projects. I used this one for a bit and can run either as a straight dipole or an inverted vee. It will get you from 40m and up and is less than 40' total. I used a Balun Designs low power 4:1 and an LDG AT-100Pro tuner. Check it out. Frank Dörenberg's Ham & Web radio page

APTN · #19 (**permalink**) 10-01-2011, 05:29 PM

Quote:

Originally Posted by Paulsan

Alpha Delta Communications

DX-EE

40'

40-20-15-10 w/o tuner

30-17-12 with a tuner

I'll second Alpha Delta. I bought equipment from them last year and they were very helpful and pleasant to deal with.

IdenLarry · #20 (**permalink**) 01-06-2012, 11:30 AM

I bought one of those slinky dipole antennas off Ebay. Made from two slinkies and a balen so it can be fed with coax. Cheap and can be spread over a any length. It works pretty good.