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Author Topic: Downspout Antenna  (Read 4076 times)
KG4OLW
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Posts: 165




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« on: May 17, 2013, 08:02:02 AM »

I live in a first floor stucco apartment. My patio is covered with a stucco roof, sides, and is backed by a sliding glass door. I have tried numerous antennas on this patio including: mfj-1786 loop antenna, slinky dipoles, and screwdriver antennas. All of the antennas are just as deaf on the patio as they are inside the apartment, I think because of all the stucco.

My apartment is a 2 story building with a flat roof, there is no attic, or any stairs leading to the roof, and a policy of no personal items on shared property i.e outside of my patio.

The building however is shaped like an octagon, so every apartment is a corner apartment. I have access to a 25' metal downspout on each side of my apartment. The downspouts stop about 3 inches above the ground and they are fed by a rectangular hole cut into the cement roof. So no gutters attached.

Is there a good way to feed each downspout as a dipole leg, instead of feeding one with coax and attaching the shield to a copper ground rod? I can snake the cables out through the patio screen and there is a planter along my patio and house which should cover up any cables? I am just looking for the best possible setup. Any ideas would be appreciated.
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VA7CPC
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« Reply #1 on: May 17, 2013, 08:44:21 AM »

Three comments:

1.  Usually, stucco is laid-up on a metal-mesh lath.   So the whole outside of the building acts as a ground plane.   If you feed the downspouts, and they're close to a wall, they'll be close (inches) to a "ground", and may not be very effective as antennas.   [I'm not saying "Don't do it"; I'm saying "Don't depend on it."]

2.  The bugbear of "rain-gutter" antennas is imperfect joints between sections of downspout.  They're held together with screws, which tend to rust.  That's a recipe for "rectifying contacts", which lead to dirty signals (on the bands) and RFI (off the bands).

3.  When I was in your situation, I used a long fiberglass pole (Jackite "Windsock pole").  I taped a wire to it, and stuck it out from the balcony, at about a 30 degree angle from horizontal.  "Ground" was the metal railing around the balcony.   My autotuner was my best friend.

It wasn't perfect, but it worked decently for digital modes and CW on 20 meters.  It was _way_ better than a Hamstick.

.                  Charles
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K1PJR
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Posts: 119




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« Reply #2 on: May 17, 2013, 08:48:57 AM »

I think stucco is attached to a metal lathe that lies beneath it.  If the downspouts are attached to the stucco by a metal bracket then there is a possibility that there is continuity between all the downspouts via brackett screws ans the metal lathe. I could be wrong but I would check that first.

I would run a wire from each downspout to your coax making sure each spout/wire combination is the same length.  You can play with the length until your comfortable with its performance.  A tuner would be needed.

Good luck!
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WB2WIK
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Posts: 20542




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« Reply #3 on: May 17, 2013, 10:57:32 AM »

I'd try "valiantly" to get something above the roof.  Something low-profile that cannot be seen without flying over it in a helicopter, but something.

As for no ladder access, I'll bet there is and it can't be seen.  Or maybe something used temporarily for roof service, and then taken away; but there has to be some way to get up there, as air conditioning units, vents, chimneys and all sorts of stuff is likely up there.

I rented for 18 months a 3-story town house with stucco construction and a flat roof that was 40 feet above ground level.  Absolutely, positively no one could use any of the "common grounds" for anything not already in place and provided for residents, and that included roofs of course.

After a few months of cajoling the property management and homeowner's association, I ended up with two vertical, a 2m beam, a 6m beam, and a fan dipole for HF up there. Wink  All the cables came down through an air vent and nothing could be seen from anywhere except overhead, or using binoculars from several blocks away.  That's the nice thing about flat roofs. Smiley
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KG4OLW
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Posts: 165




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« Reply #4 on: May 17, 2013, 12:15:14 PM »

I don't think building maintenance gets on the roof, ususally they hire some type of subcontractor to do anything with the roof, or plumbing or anything else besides the basics. The building is in a gated community with big parking lots and roving security patrols on golf carts.

Here is what the building looks like, my patio is screened in like the patio on the first floor.

http://propimages.apartments.com/4607/2303523_32.jpg
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W0FM
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Posts: 2052




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« Reply #5 on: May 17, 2013, 01:18:52 PM »

First you might want to confirm that your "stucco" is, in fact, true stucco, which would have the metal lathe undercoat that supports the cement that supports the stucco.  Many new "stucco" homes here in the Midwest are not real stucco, but a Styrofoam-like faux stucco that has no metal mesh behind it.  It's just cosmetic, attached to the plywood walls with glue and roofing nails. 

If your stucco is the type without the metal mesh layer behind it then your downspouts become a better possibility for use as a vertical antenna.  I have had many years of hamming fun using downspouts on a wood frame home when all other bets were off limits.

Check it out.

Terry, WØFM
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KD8TZC
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Posts: 67




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« Reply #6 on: May 17, 2013, 01:27:30 PM »

Well, the others have posted about some of the challenges you may have, but what I would try is just run a twin lead out to the downspout.  Connect one side of the line to the one downspout and then the other to the other one.  I have no idea if it will work, but that's the fun part of the hobby... trial and error.

Some of the MFJ Tuners have a twin lead or a single wire post on the back of the tuner, so you would just hook that up to there.  Or you can get a balun like the LDG RBA-1:1 that can convert the coax to the twin lead.

I've been thinking of playing around with a downspout antenna as well and have also thought of using it like a dipole.  One on the front of the house and one on the rear.  I have everything I need to try it, just need to find the time to do it.
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John - KD8TZC
KE3WD
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Posts: 5694




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« Reply #7 on: May 17, 2013, 04:32:52 PM »

Is your car driveway in close proximity to the apartment? 

I know one young fellow who installed a Screwdriver antenna on his SUV, but rarely puts the radio inside the car. 

In the evenings, he snakes a coax with control wiring attached out to the car from his apartment and operates fairly well that way. 


73
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WB2WIK
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Posts: 20542




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« Reply #8 on: May 17, 2013, 06:28:21 PM »

I don't think building maintenance gets on the roof, ususally they hire some type of subcontractor to do anything with the roof, or plumbing or anything else besides the basics. The building is in a gated community with big parking lots and roving security patrols on golf carts.

Here is what the building looks like, my patio is screened in like the patio on the first floor.

http://propimages.apartments.com/4607/2303523_32.jpg

"Anything's possible," but if the property owners use contracted management and they can't access roofs, I think they're crazy.

I'd be tempted to wait until 2 AM, lean a 40' extension ladder against the building, and just go up there myself.  What could they do?  Arrest you?

Probably "nothing," if they're too lazy to go up there, themselves. Wink

I'm different, I guess: I think life's too short to be worried about somebody else's rules if what I do can't hurt anybody.

The other suggestion about parking a vehicle nearby and using a good mobile antenna is very good; I've done that, also, and it works a lot better than highly compromised "home" antennas.
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KB3MDT
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Posts: 193




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« Reply #9 on: May 17, 2013, 07:02:26 PM »

Hi,
    The picture of your apartment complex shows some Palm Trees.  If one is near your apartment, try running a small gauge wire out to one of the trees.  You could use it as an end fed antenna.   Folks may never see it.    Good luck.


KB3MDT
Ken
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NO2A
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Posts: 754




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« Reply #10 on: May 17, 2013, 09:50:21 PM »

Well, the others have posted about some of the challenges you may have, but what I would try is just run a twin lead out to the downspout.  Connect one side of the line to the one downspout and then the other to the other one.  I have no idea if it will work, but that's the fun part of the hobby... trial and error.

Some of the MFJ Tuners have a twin lead or a single wire post on the back of the tuner, so you would just hook that up to there.  Or you can get a balun like the LDG RBA-1:1 that can convert the coax to the twin lead.

I've been thinking of playing around with a downspout antenna as well and have also thought of using it like a dipole.  One on the front of the house and one on the rear.  I have everything I need to try it, just need to find the time to do it.
I would try that myself,with an excellent tuner. Or run some very light gauge wire out to one of the palm trees.
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KG4OLW
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Posts: 165




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« Reply #11 on: May 17, 2013, 10:56:59 PM »

Thanks everyone for the suggestions!!!

Tonight I went outside, scraped some paint off of the downspout about 2 inches off the ground, towards the building so as to be less noticeable. I drilled a small hole. and attached the coax with a sheet metal screw. I brought the coax around under the cover of bushes and poked a small hole in my screen right next to the floor. I attached this to the random wire terminal on my mfj-971 tuner. As soon as I turned on the radio, I heard a Wyoming station on 7.189 come booming in completely off the range of my meter on my ft-817. The downspout picked up many QSO's all through the band. The amount of noise that gets picked up also seems low.

My only question now is the mfj-971 requires a ground connection when using it in a random wire configuration, I am not sure what would be the best ground to use for transmitting, short of buying a grounding rod and using that, however that may be harder to hide.

Any suggestions?
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GW3OQK
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Posts: 133




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« Reply #12 on: May 18, 2013, 05:38:29 AM »

Yes, my first thought was like NO2A, connect the other downspout to the tuner using its balanced terminals so it becomes a centre fed U antenna.
Maybe the metal lath will give some screening of local noise and weird directional properties. Looking forward to your results whatever you do. I have heard of people using counterpoises of resonant length.
73
Andrew
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K8AXW
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Posts: 3651




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« Reply #13 on: May 18, 2013, 08:23:38 AM »

Looks to me like it's time to start experimenting with some kind of antenna that can be clamped to the handrail....maybe with a counterpoise...... Personally I'd forget the downspout.  Too many ifs or whatifs involved. 
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KA4NMA
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Posts: 317




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« Reply #14 on: May 18, 2013, 02:16:03 PM »

I am also thinking of using a rain gutter and downspout for an antenna.  If I go with the gutters and downspout, I would have 2 downspouts about 8-10 feet high.   Both stop several inches about a concrete splash guard. The horizontal section would be about 25-35 ft.  I have not measured, but am not good at estimating.  The single wire feed would be about 1/3 or so along the horizontal section.  I do not have eznec nor how to use it.  Any ideas on performance? I live in a single story fourplex.  The horizontal section has a break and downspout, so it does not run the entire length of the building.  It only covers 2 apartments.

If I keep power to 50 watts or less, will I be within RF safety exposure guidelines for 75m-6m? What about 100 watts?

Randy ka4nma
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