Attic Antennas

Started by cockpitbob, January 30, 2013, 09:24:43 pm

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cockpitbob

Anyone have any experience comparing a wire antenna in the attic vs. outdoors?  Any idea how much gain/sensitivity I'll loose?

I promised my 14yo son that if he passed the 5wpm Morse test he could have a QRP rig in his 2nd story room.  It's looking like I'll have to pay up.  By far the easiest antenna for me to rig is a 1/2wave end fed wire in the attic. The attic is tall with a steep roof pitch and long enough for a 20M antenna.  Because of my situation a wire antenna outside would require a long feed line, a lot of rope, a window feed thru (not good on these 10deg New England winter days) and adding ugly to the house.  And with the wire in the attic I'll put a lightning arrestor on the coax to protect the radio's input from lightning's EMP but it won't take a direct strike so I won't have to come up with a heavy earth ground to the 2nd floor.

RadioRay

I have routinely operated with indoor , dipole type antennas.  My prime criteria in times past was top floor, attic access.  The main thing to look for is that you do NOThave metalic covering betweent he roof and the antenna, that is aluminum backed insulation and/or metalic roofing materials being the most common.  I operated this way for YEARS, with good success.

The #1 enemy will NOT be signal attenuation from the indoor antenna, but it WIL be the elecrtic al / radio frequency noise generated by home electronics, such as computers, displays, "green' lighting and. etc.  That being said, if you cannot put a wire out the window, then the roof space antenna - with no metalic barrier- is a workable solution.

Another entirely do-able solution is a magnetic loop on the balcony/backyard.  They don't even look like an antenna, but Gil and I have worked bands 80/30m with his loop and he plans a 20m and above loop for our experiments ont he 20-17m bands, when open between him and my Virginia location. I can help you quite a bit with 'ham clandestine' operations, having a looooooong history of outsmarting the eastern bloc communists, Los Angeles land lords and even the U.S. Army in keeping radio stations on the air in times past. This prepared me for dealing with covenanent communities, HOA's and nosey neighbors. 

Tell nobody that you have a ham station - nobody...  TRUST me on that last part.


73 de RadioRay ..._ ._

"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

gil

QuoteTell nobody that you have a ham station - nobody...  TRUST me on that last part.


Ah well, my friends know... But not my neighbors...

The magnetic loop indeed is great, but wouldn't work too well in an attic unless you have some way to turn the capacitor remotely.. I'm not sure I would let a teenager play with an antenna that produces 2000V even at QRP levels... And all that RF, I don't know... They work well for sure, I'll say that much. There is nothing that size that's as efficient, that I know of... A dipole might be your best best. A Buddistick might work too, set it up outside to operate, take it down when you're done..

Gil.

cockpitbob

Thanks guys.  After reading Gil's adventures with mag loop antennas I almost used this as an excuse to make one.  I've seen set-ups with a 12V gear motor to turn the capacitor and a simple on-off-on switch to control the motor for tuning, but I figure the kid will use it more if he has a no-tune antenna.  Fortunately I don't have any CC&Rs or HOA restrictions and I have lots of 75' tall trees.  I just don't feel like stringing another wire antenna and dealing with lightning protection and getting the wire into the bedroom.  I love my kid, but everything has limits.  Besides, I have a feeling it won't get used much.

The attic is standard wood construction with composite shingles so I think I'm good to go.  When I get it strung I'll post a comparison between it and my basement shack's 180' random wire up 60'. 

Geek

Sorry for reopening an old thread, but it always seems to make more sense than starting a new one on the same topic.

I have a large, open attic with very little in the way.  I am debating about where to put an antenna and I see this as one of the options.  This disadvantages seem to be limitations to power to use the attic safely, loss through the roof, and limits on the length of wire that could be run.  Advantages would be easy access and stealth.

What am I overlooking?

gil

Hello Geek,

I wouldn't worry too much about power... The biggest challenge with any HF antenna I have found is size. The bigger the better... Especially if you want to get down to 40 and 80m. My 6' loop goes down to 40m, but at the price of a very narrow bandwidth. I have worked Russia on 5W with it, so I know it works well. A 64ft. wire antenna is not easy to fit in an attic, unless you have a big house. 20m and above is much easier. I guess you could set-up a horizontal loop around the top part of the house, that's another option.. Higher is better. My loop is inside the house on the second floor, and it makes a big difference. Use a tuner if oyu have to, but try to avoid it.

Gil.

Geek

Quote from: gil on June 26, 2013, 02:20:20 pm
Hello Geek,

I wouldn't worry too much about power... The biggest challenge with any HF antenna I have found is size. The bigger the better... Especially if you want to get down to 40 and 80m. My 6' loop goes down to 40m, but at the price of a very narrow bandwidth. I have worked Russia on 5W with it, so I know it works well. A 64ft. wire antenna is not easy to fit in an attic, unless you have a big house. 20m and above is much easier. I guess you could set-up a horizontal loop around the top part of the house, that's another option.. Higher is better. My loop is inside the house on the second floor, and it makes a big difference. Use a tuner if oyu have to, but try to avoid it.

Gil.

How long a wire are you using with the horizontal loop?  I have a pretty large space, though I haven't measured it and the attic is above the second floor.

I was expecting to need a tuner.  Why do you suggest avoiding the tuner?