Re: [amsat-bb] Helix antennas

["Zachary Schrempp" <ke7eyq@xxxxxxxxx>]

Thank you all for your input. It is nice to have so many helpful
people give antenna advice.

73,
Zach KE7EYQ

On 5/12/06, Steve Holly <sgholly@optonline.net> wrote:
> Hi Zach,
>
> Take a look at Kent Britains' WA5VJB "Cheap Yagi" designs:
>
> http://www.clarc.org/Articles/uhf.htm
>
> They are very easy to construct and are much less complicated to build
> and physically support than a helical antenna at 2M and 70cm. Kent
> designed them to be very forgiving of minor construction errors without
> significant performance degradation. In other words if you are
> reasonably careful when measuring, cutting, and drilling you can be
> certain they will perform as advertised. That has been my experience for
> the dozen or so that I have built and used.
>
> In my experience the secret to success is to use mast mounted preamps.
> Using Kent's "Cheap Yagi" designs and mast mounted preamps working all
> of the currently operational analog and digital LEO's is a whole lotta
> fun! I'm a big fan of being able to actually hear the satellite that I'm
> working ;-)
>
> Note: for a great explanation of why preamps are important read David
> Bowman's G0MRF preamp article on page 24 of the July/August 2005 AMSAT
> Journal.
>
> RE: Are circularly polarized antennas required for LEO's ?
>
> As a test I ran a switchable polarity 9el x 9el commercial 70cm antenna
> on the mast for a week or so. I found that the LEO birds signal
> polarization does change during the pass and the fades can be 20dB or
> more requiring one or more flips of the polarity switch(s) during the
> pass. I went back to linear antennas for simplicity's sake. With medium
> gain linear yagi's and mast mounted preamps there is more than enough
> signal to noise ratio for armchair copy with the LEO's.
>
> 73 de Steve, WI2W FN20
>
> p.s. - thanks for the AO-51 contact on 5/9/06 !
>
>
>
> -----Original Message-----
> From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org] On
> Behalf Of Zachary Schrempp
> Sent: Wednesday, May 10, 2006 9:05 PM
> To: amsat-bb@amsat.org
> Subject: [amsat-bb] Helix antennas
>
>
> Hello folks,
>
> I am looking for advice on building helix antennas for satellite work.
> Is anybody using helices for both V and U mode to yagi-comparable
> success, and if so, how many turns are you using? I have been over the
> basic overview in the Satellite Handbook and the helix looks like an
> inexpensive, easy-to-build yagi alternative (if not capable of
> switchable polarization). In real practice, has the lack of the
> polarization switch from RHCP to LHCP really caused much difference?
>
> I have been operating FM birds with handhelds for about 6 months and I
> am getting to work on a base station that will be capable of working the
> linear satellites as well. I'm trying to avoid the extra cost and
> complexity of building circularly polarized yagis. Any suggestions would
> be appreciated.
>
> --
> Zachary Schrempp, KE7EYQ
> AMSAT #36023
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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>
>
>


-- 
Zachary Schrempp, KE7EYQ
AMSAT #36023
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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