[amsat-bb] Re: Fixed antenna for ISS reception?
ko6th_greg at hotmail.com
Wed Oct 22 20:34:43 PDT 2008
Don't rule out putting up a rotor and some moderate sized beams, even on a rental...
What kind of roof do you have? I built a small "tower" from some scrap lumber and metal bracing, and it's been serving me very well for nearly 10 years now. See http://home.wavecable.com/~ko6th/DSC00031.JPG for an old picture of it (ca 2001).
The design is a 3-dimensional "T", built from 2x4 lumber. 8 feet wide at the base, which goes horizontally across the roof with some rubber pads at the tips, and 4 feet up the roof to a vent pipe. There's a 4 foot 2x2 vertical piece that rises from the junction of the two pieces, and is braced to the base on 3 sides. The whole contraption basically just sits on the roof, and is kept from sliding off by lashing it to the vent pipe. My roof has a relatively mild pitch (4 inches per foot, I think), so there's not too much of a tug on the pipe. There's a 5 foot piece of steel mast pipe (Radio Shack, I think) lashed to the vertical wooden part, and the rotor sits on top of that. None of this is permanent; it can be unlashed from the pipe and dismantled, with no trace.
I've had no problems with stability or wind, and it hasn't even broken any of the roof tiles (cement shingles). Since the picture was taken, I have upgraded the BBQ grill (for AO-40 13cm) to 30 inches, added a 23cm helix (AO-51), and upgraded the 70cm beam antenna to 2x15. The 2m beam remains at 8 elements. The biggest problem is keeping the steel mast from spinning when the wind blows hard, but I think I've got that fixed now too. We'll see what happens this winter :-).
We own our house, so the last part of the puzzle may be a problem for you. Getting the wires into the house. I mounted a power utility box (the kind you put circuit breakers in) outside the room where my Shack is located, and drilled a 2 inch hole in the wall to feed the wires through. Lightning arrestors go in the box. There's a 2 inch conduit running from the box, up the side of the house to the underside of the roof overhang, so water can't get in. Perhaps you have some other means to snake the wires inside?
The whole setup is controlled by my computer in the shack, and I've gotten some beautiful pictures from the ISS this past week. I also worked Richard over the weekend. The ISS has been full quieting, from horizon to horizon.
The other antennas in the picture, by the way, are a 2 meter J-pole, and my 10/15/20/40 meter HF dipole strung over the wooden supports along the ridge.
> From: gordonjcp at gjcp.net
> To: amsat-bb at amsat.org
> Date: Wed, 22 Oct 2008 09:43:01 +0100
> Subject: [amsat-bb] Fixed antenna for ISS reception?
> At the moment I've been receiving the SSTV and voice signals from the
> ISS with a homebrew omni on a pole in my back garden. I don't really
> have the room to put up a tower, and since the house is rented I suspect
> the landlord would have some pithy words to say about digging up a chunk
> of the garden and pouring a plinth.
> How well would an aerial with a cardioid pattern such as an HB9CV work?
> Since the ISS is never much above 30 degrees this far north (IO75) I
> doubt I'd need to worry about elevation.
> How well would just adding a 144MHz preamp to the omni work?
> How have other people solved this, without recourse to big rotators and
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