[amsat-bb] Cuscraft 416-TB and 22XB phasing harneses???

[Chris Thompson]

Tom,

I'm also setting up some antennae and have the elements mounted in the same
position.  My understanding it that to get Circular Polarization you need
to feed one antennae quarter of a wavelength ahead of the other.  The
examples in the satellite handbook show the antennae physically mounted
quarter of a wavelength apart.  If the elements are in the same location
then the feed line to one needs to be 1/4 wavelength shorter than to the
other.  Then it will be fed first and the signal will be 1/4 wavelength
ahead of the other antenna.  Note that the elements will actually be
slightly offset and this difference should be taken into account in the
feed line length.

The two feed lines should each be 50 ohm.  You can then combine them with a
standard combiner or use a coax T and two quarter wavelength sections of 75
ohm coax, one for each feed line, as a matching section.

I don't think it is worthwhile setting up the ability to switch from LHCP
to RHCP or vice versa if the spacecraft has linear antennae, because the
difference is only 3dB, but others may disagree.  If the spacecraft has CP
antennae then its very important to match the polarization.
Good explanation here: http://www.pe0sat.vgnet.nl/antenna/polarization/

Chris

On Tue, May 24, 2016 at 1:30 AM, Richard Tejera <Saguaroastro at cox.net>
wrote:

> Tom,
>
> I have a copy of the manual for this antenna. I'd be happy to scan it and
> send it to you. It may be of some help.
>
> Rick Tejera K7TEJ
> Saguaro Astronomy Club
> www.SaguaroAstro.org
> Thunderbird Amateur Radio Club
> www.w7tbc.org
>
> On May 23, 2016, at 20:32, Tom Schuessler <tjschuessler at verizon.net>
> wrote:
>
> Hello all,
>
> I recently acquired a pair of Cushcraft Satellite antennas, the 22XB and
> the
> 416-TB.  Both are Cross fed dual polarity Yagis.  What did not come with
> either of these antennas was the phasing harnesses that were a part of the
> original contents.  The two meter 22XB is fed with crossed driven elements
> in the same location on the boom and SO239 connectors in place on the
> antenna.  The 416-TB has direct connections from coax to the driven
> elements
> and also to the coax balun on each of the driven elements.  The driven
> elements are offset fed so as to provide the natural delay in the one
> direction.
>
> Cushcraft did sell a PS-4 which I believe was a relay controlled switch for
> the 435Mhz 416-TB but if they sold a 2 meter version, I cannot tell.  I do
> have a contact at Cushcraft I was given that I will be reaching out to for
> more information
>
> The "Satellite handbook" does have some description on how to configure a
> fixed harness for the two types of feed orientations.  I am though confused
> to understand how to understand the direction of rotation but that is for
> another post.
>
> Anyway, does anyone who used to have these antennas or something similar
> have phasing harnesses, either fixed or switchable that would work with
> them
> lying around?  I would be interested in acquiring them from you.
>
> Thanks and 73.
>
> Tom Schuessler, N5HYP
> N5HYP at arrl.net
>
> PS. I just picked up a used FT-847 so am looking forward to getting these
> antennas up in the air and seeing how they perform.
>
>
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-- 
Chris E. Thompson
chrisethompson at gmail.com
g0kla at arrl.net