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Re: R: Quadrifilar home brew



Agreed!  I plan to make a dual-polarity patch-feed for 1269-1296 MHz to try
on my 2.4m (8-foot) dish this summer and compare with a 1296-MHz septum
feed.  For mode-LS the dual-band patch is still probably the slickest way
to go for a medium - large dish (4 to 10 foot).

For tracking a fast moving LEO like AO-51, I suspect simpler antennas are
the best way to go for L or S-band:  small dish, helix, or loop-yagi using
a rotator that has fast slew-rate like the Yaesu-B5400/5500.  My primary
sat-ant array is such a setup: (S) 85cm-dish, (L) loop-yagi, (U) 11-element
yagi, (V) 3-element yagi...all on a B5400/Unitrac-2000.

My 2.4m dish is an oddity for such a large dish as it was designed for
shipboard use and has rapid slew-rates for compensating for ship movement
in rough seas.  Usually the drive setup with large sat-TV dishes is quite
slow and will not keep up with a LEO pass.

73's Ed - AL7EB
PS:  I will be making a septum for 2400 and 10-GHz as well.

At 10:01 PM 3/16/2005 -0800, KC6UQH wrote:
>During the life of AO-40 I made a patch antenna that worked well with my
>dish 0.3 F/D and it was easier that a QFH antenna to construct.
>
>Art , KC6UQH
>----- Original Message -----
>From: "Cliff Buttschardt" <cbuttsch@kcbx.net>
>To: "Edward R. Cole" <al7eb@acsalaska.net>
>Cc: "i8cvs" <domenico.i8cvs@tin.it>; "AMSAT-BB" <amsat-bb@amsat.org>
>Sent: Wednesday, March 16, 2005 10:15 AM
>Subject: Re: R: [amsat-bb] Quadrifilar home brew
>
>
>> Ed, your suggestion is a good one.  We should note also that the site
>> mentioned is just an all round good one to view.   Cliff K7RR
>>
>> "Edward R. Cole" wrote:
>> >
>> > >The main reason that i have experimented on 2400 MHz Quadrifilar Helix
>> > >Antennas as per AMSAT Journal May/June 2004 was to find the way to
>> > >produce a LHCP QFA to be used as a feed in a small dish having a low
>> > >F/D ratio in the order of 0.3 to 0.35
>> > >
>> > >Pulling with you for P3E to verify the results !
>> > >
>> > >73" de
>> > >
>> > >i8CVS Domenico
>> >
>> > Domenico,
>> >
>> > I have just been studying the septum feed for eme use which is very
>simple to
>> > build and provides both LHCP and RHCP.  I am giving some thought to
>building
>> > one for my 85cm offset dish on 2.4 GHz.  Have you looked at this feed?
>W1GHZ
>> > did an exhaustive analysis of it in 2002 or 2003.  I will likey make a
>plain
>> > one first, then add a sliding circular choke ring for comparison.  The
>basic
>> > feed is good for f/d 0.35 dishes.  Either a flared horn or choke is
>needed for
>> > f/d = 0.6 to 0.7.   At present I am using a 5-1/4 turn helix feed.
>> >
>> > Here is a link to the septum design:
>http://www.ok1dfc.com/EME/emeweb.htm
>> >
>> > 73's Ed - AL7EB
>> > http://www.qsl.net/al7eb
>> > ----
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