[amsat-bb] Re: Antenna Opinions?
ko6th_greg at hotmail.com
Wed Sep 22 22:21:41 PDT 2010
The length sounds about right (I didn't measure it, but it's longer than my garage 8 foot ceiling is high). But searching for pictures of the Tonna antenna, I'm not seeing one that matches. The Tonna antennas have a different mounting (a parallel bar below the boom), and elements above the boom, or so it seems. I have put some pictures of the mounting for this antenna, and the overall "array":
http://home.wavecable.com/~ko6th/dsc00319-800.jpg shows the mounting, and element style. There is another similar block of metal at the rear of the antenna; slightly smaller, but with the same type of pipe fittings going up and down. The PVC pipe mounting is mine. 1/2" pipe elbow, slathered with glue and tapped into place with a hammer. Seems to work.
http://home.wavecable.com/~ko6th/dsc00320-1024.jpg for the whole thing. You can barely see the back of the antenna in this image, with the split reflector. The coax cable is hooked to a 90-degree elbow, so that it hangs down without kinking (and so it can reach!). Left to right are a 2x15 element 70cm antenna (also unknown pedigree), 13cm BBQ dish, 23cm antenna, tower camera in box, and 8 element 2m antenna. The cross boom is a wooden closet pole, and yes, the weight of the dish is causing a bit of a sag... Hence my earlier thread about replacing it with a pair of flat panel Wi-Fi antennas. I haven't finished that project yet.
If the gain is more like 20dBi (the seller claims 23), then the difference between my 18 turn helix and the 35 element yagi is even less. For satellite use, the helix probably wins because of the circular polarization. In terrestrial work, I lose 3db going circular to linear, so the net difference is going to be about 6dB. Not trivial, but not "wow" either. The helix is a lot smaller of an antenna, too, thinking of wind load and such.
> From: domenico.i8cvs at tin.it
> To: ko6th_greg at hotmail.com; amsat-bb at amsat.org
> Subject: Re: [amsat-bb] Antenna Opinions?
> Date: Wed, 22 Sep 2010 15:17:15 +0200
> ----- Original Message -----
> From: "Greg D." <ko6th_greg at hotmail.com>
> To: <amsat-bb at amsat.org>
> Sent: Wednesday, September 22, 2010 7:03 AM
> Subject: [amsat-bb] Antenna Opinions?
> > Hi folks,
> > The Find was a 35 element 1296mHz antenna, well built and in excellent
> condition. Linearly polarized, horizontal; supposed to be 23dBi gain.
> Manufacturer, of course, is unknown. No markings, but it does not look
> home-built. By the mounting hardware, it looks like it was part of some
> sort of stacked array.
> > Thanks,
> > Greg KO6TH
> Hi Greg, KO6TH
> If your antenna is from Tonna it must be 3,07 meters long.
> Tonna make two models one for DX and SAT and the other one for ATV
> By the way the gain is 20 dB isotropic.
> 20635 35 ELEMENTI 1260/1300 MHz dx,sat 20 dB 3,07 meters long
> 20636 35 ELEMENTI 1250/1260 MHz ATV 20 dB 3,07 meters long
> 73" de
> i8CVS Domenico
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