Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Attic antenna farm  (Read 1270 times)
N0JY
Member

Posts: 7


WWW

Ignore
« on: March 09, 2007, 08:19:20 PM »

I've looked through a lot of the topics here but don't see where this thought was addressed.  Please point me there if it was!
In planning for the design of a new home in an area where there are no specific words in the CC&R regarding towers, with the architectural committee indicating that a 50 foot tower would not pass the design approval, I'm thinking about building the antennas into the house.  More specifically, over the garage (because the garage attic doesn't have a/c ducts and a you could even eliminate any ceiling electrical wiring).
You could fit a reasonable multi-band HF yagi in a 30x30 foot "second story" or attic over a garage.  The wall material could be of wood or even possibly better, fiberglass.  Such a 30x30 foot area could also house other VHF/UHF verticals or yagis.
So what does the ham community think about this idea?  If the antenna were say, 25 feet above ground, you are at >1/4 wavelength for 20 meters.  If there is no metal radiant barrier stuff in the roof or ceiling of the garage (because I don't mind if the garage gets kinda warm or cold here in north Texas) you shouldn't have any big losses or variances to the radiation pattern?  Please air your thoughts about whether this would give a reasonable facsimile to the same antenna on a 25 foot tower just outside the house.  Understanding that a wet roof from rain could distort things a bit, would there be much influence outside that?
Logged
K7JQ
Member

Posts: 286




Ignore
« Reply #1 on: March 09, 2007, 09:08:17 PM »

I live in a CC&R neighborhood and have mono-band dipoles for 10, 12, 15, 17, 20, and 40 meters in my attic over the garage. They are remotely switched with an Ameritron RCS-10, with one coax to the shack. and all have a 1:1 balun to reduce feedline radiation. The only wiring there is for the garage door opener and garage light...no HVAC ducts or anything. They are only max 15 feet above ground, concrete tile roof...no metal to distort the radiation pattern. They work just OK, but most of the time are plagued with noise from all of the electrical and electronic crap in the rest of the house...not good for picking out weak signals. They're cut for low SWR at resonance, but the SWR varies depending on if the metal garage door is up or down. I do get some TVI on certain bands, and on 40 meters my subwoofer thumps.

Bottom line...I have found that attic antennas are marginal at best, but do perform depending on propagation. I have worked my share of DX with them. Get them outside, if possible, and higher than 25 feet for 20 meters...should be at least 1/2 wave up (approx 33 feet) for best results. I also have a ground-mounted screwdriver with 40 radials that resonates 1:1 on all bands 10-80 meters. It's away from the house...no RFI, very low noise level, and, on A-B tests, outperforms the dipoles 90% of the time, both transmit and receive. It's completely hidden from neighbors and HOA eyes. I also run it with 500 watts, no problem...just keep kids, etc away from it!

Remember, any antenna is better than no antenna at all, even with compromises. Do what you can and have fun. hope this gives you a little insight.
73, Bob, K7JQ...Arizona.  
Logged
W2RDD
Member

Posts: 191




Ignore
« Reply #2 on: March 13, 2007, 04:02:11 AM »

In another QTH, I had a 20M bazooka dipole in the attic which worked quite well. Some of the bazooka characteristics makes this an interesting antenna under difficult configuration circumstances. Is mono-band and coax fed so don't try to make into something it isn't.
Logged
KC8VWM
Member

Posts: 3124




Ignore
« Reply #3 on: March 14, 2007, 11:19:23 AM »

As others have said attic antennas are marginal at best.

I would much rather prefer to install an outdoor  stealth antenna over an attic antenna anyday.

One idea is to install a TV antenna tripod on the roof and make an inverted V antenna to appear as fake supports for the mast.

The fact that you have cable installed or if the TV antenna is functional or not isn't important. Everyone is allowed to install and have one on thier roof.

Outdoor TV antennas seem to be gaining popularity since HDTV has come along.

I suppose you can just call it your new HDTV antenna.

73
Logged
KC9KRF
Member

Posts: 5




Ignore
« Reply #4 on: March 15, 2007, 10:35:26 AM »

I concur with the other comments here...outside is much better, but if it is not an option, indoor is still better than nothing.

I had posted a similar question some time back and I was able to do some tests. The thread is at http://www.eham.net/forums/AntennaRestrictions/3099.

73's
Logged
N0JY
Member

Posts: 7


WWW

Ignore
« Reply #5 on: March 15, 2007, 11:51:56 AM »

Thanks for the comments.  Given that most of the replies are in regard to noise generated from within the house, if all of the electrical wiring was in conduit, do you think that the noise would be all but eliminated by that?  Would it be any worse than to a yagi on a tower right next to the house, or a yagi on the roof?  I read the other subject regarding losses, but don't see enough to have a definitive answer as to whether the lumber and shingles actually attenuate the signal that much?  The yagi could be up 33 feet above ground (1/2 wavelength on 20 and greater on the higher bands).
Logged
K7JQ
Member

Posts: 286




Ignore
« Reply #6 on: March 16, 2007, 08:38:13 AM »

I'd give my right arm (well, not really) to have approval for a yagi mounted on a 33 foot tower bolted to my house, or on a roof mount. You might still get some household electrical noise, but certainly not as much as attic antennas, and you would greatly lessen the chances of RFI. Also, the ability to rotate the yagi is invaluable (I don't think you could do that in the attic). No contest here, my friend. If the CC&R's permit, do the tower. Although they work, my attic antennas and ground-mounted screwdriver (mentioned in a post above) are compromises at best, but I don't have a choice.
Logged
N0GBR
Member

Posts: 24




Ignore
« Reply #7 on: April 06, 2007, 02:18:34 PM »

I use a Sigma 5 vertical dipole (11 ft tall, 10-20 m coverage)from Force 12 and am happier with this than the multiband dipole I had strung up in the attic.  161 countries during the past 4 yrs.
Logged
K7KBN
Member

Posts: 2754




Ignore
« Reply #8 on: April 07, 2007, 08:50:50 AM »

Conduit generally serves as physical protection for electrical cables, not as RF shielding.  It might help to some degree, but you'd have to make sure that it was all properly bonded (which generally means "welded" at junction boxes and such.

But then you have the unshielded motors of the vacuum cleaners, microwave ovens, coffee grinders, etc.

Then you can worry about the computer control centers of the laundry machines, dishwasher, and so forth.

I'm slanting this reply to some of the same problems that we encounter on Navy ships with new equipment that hasn't been completely RFI tested before it's installed.
Logged

73
Pat K7KBN
CWO4 USNR Ret.
W2DIP
Member

Posts: 17




Ignore
« Reply #9 on: April 19, 2007, 09:18:57 AM »

I found a small opening where one of my vent pipes exits my attic and slipped out about 45 feet of wire. The wire lays on my roof. I attached it to a 4:1 balun and cut about 5 counterpoises for various bands. Works great and I can tune it from 160m to 6m with a 1:1 SWR. There is definately a difference between that an my attic dipoles but we are talking about going from a 57 to 54 at worse but mostly it is just one or two S meter segment difference when propagation is good.
Logged
KC9JYB
Member

Posts: 9




Ignore
« Reply #10 on: May 09, 2007, 12:06:12 PM »

W2DIP,

I like your idea of the balun attached wire up on the roof. Quick question, where do you put the counterpoise wires? Do you run them in the attic itself? Also do they need to be at 180 angles to the center wire outside in order to properly work?

Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!