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Re: Eggbeaters



Robert,
A QFH antenna using 1 wavelength per side gives you the following pattern.
Assuming that the antenna mast is perpendicular to the earth and the pattern
is
related to a  balloon The balloon has a 25 dB dent on the bottom with a -7
dB dent on  the top. A bulge of max gain occures at 20 dergees. The whole
envlope of a QFH antenna is circluar polorized.
 You get to add 3 dB for matching circular polorization .The 1 wave length
per side QFH antenna Has its best gain at 20 degrees above the horizon and a
25 dB front to back ( top to bottom ) ratio helping to cancel out the 3 dB
of ground noisefound in vertical antennas that go to the horizon.  I can
copy down to 3 degrees on most passes, and below that elevation the signal
path is into trees and houses anyway.

Art, KC6UQH

----- Original Message -----
From: "Robert Bruninga" <bruninga@usna.edu>
To: <daleh@alaska.net>; <kc6uqh@cox.net>
Cc: <amsat-bb@amsat.org>
Sent: Friday, June 17, 2005 5:56 AM
Subject: Re: [amsat-bb] Eggbeaters


> There are 3 things to think about when using OMNI
> antennas for Satellites.
> 1) Satellites spend 67% of all in-view times below 20 deg
> 2) Satellites below 20 deg are 6 to 10 dB further away
> 3) You cannot afford ANY coax loss (use a preamp)
>
> Thus, assuming you have a preamp,  a good base
> station antenna will work well for about 50% of the
> time when the satellite is  below about 15 deg IF THE
> SATELLITE IS STRONG ENOUGH  TO BE HEARD IN THE
> FIRST PLACE.  But the main lobe of such antennas
> is only on the horizon and there is a big null from about
> 15 deg up to about 45 deg.   Thus if the signal
> is too weak on the horizon to be heard anyway,
> then no only do you not hear it there, but now you
> have null higher up, where it is closer in and you
> would be able to hear it on a 1/4 wave low gain
> whip.
>
> Conversly, a hemispherical antenna has equal
> gain everywhere (usually inadequate on low
> elevations where the bird is 6 to 10 dB farther
> away and also where it spends 67% of its time.
> But when the bird gets closer (higher) then
> this antenna gives solid performance (but for
> less than 1/3rd of the pass.
>
> So it all goes back to one thing.  You cannot have
> high gain on the horizon witout having a null higher
> up, and if you have gain higher up, then you miss
> most of the time on the horizon.  BUT IF THE
> SATELLITE IS SUCH THAT IT CANNOT BE HEARD
> ON THE HORIZON ANYWAY without gain, then
> dont bother.  Go with a omni such as a 1/4 whip
> over a gorund plane and just plan on only hearing
> the 30% of all pass times when the satellite is
> closer in (and above the trees) and hear it well.
>
> But always use a preamp.
>
> I dont think there are any amateur satellites other
> than the ISS that fall into the category of workable
> at the horizon on an omni.
>
> de WB4APR, Bob
>
>
> >>> "Dale - KL7XJ" <daleh@alaska.net> 06/17/05 1:39 AM >>>
> Art,
>
> I agree with what you stated.  Another thing about EB ant is
> that you need the radials below the antenna.  The EB was one of
> my first satellite antennas.  I improved the reception with the preamp.
> It is now my back up antenna system.  I have both 2m and 70cm
> EB's mounted on my tower at about 40 '.  I use crossed yagis for both
> bands on a separate tower for satellite work now.  I am also mounting
> S band and L band antennas with G5500 rotors after field day.
>
> Happy Fathers Day!
>
> 73's
> Dale/KL7XJ
> ----- Original Message -----
> From: "KC6UQH" <kc6uqh@cox.net>
> To: "Dale - KL7XJ" <daleh@alaska.net>
> Sent: Thursday, June 16, 2005 7:45 PM
> Subject: Re: [amsat-bb] Eggbeaters
>
>
> > Dale,
> > I suggest that a 1 wave per side QFH is better than a egg beater,
circular
> > polarized and will work to a few degrees above the horizon.
> >
> > Art, KC6UQH
> > ----- Original Message -----
> > From: "Dale - KL7XJ" <daleh@alaska.net>
> > To: "John Henderson" <jah@ec.rr.com>
> > Cc: <amsat-bb@amsat.org>
> > Sent: Thursday, June 16, 2005 7:40 PM
> > Subject: Re: [amsat-bb] Eggbeaters
> >
> >
> >> A preamp will definitely help.  I have one at about 40' using 9913
coax.
> >> I do have a preamp mounted right below the antenna.  I used  the
antenna
> >> without preamp for a long time when UO14 was alive.  But they sure do
> >> make
> > a
> >> differance on the recieve end.
> >>
> >> Dale/KL7XJ
> >> #30600
> >> ----- Original Message -----
> >> From: "John Henderson" <jah@ec.rr.com>
> >> To: "AMSAT-BB" <amsat-bb@amsat.org>
> >> Sent: Thursday, June 16, 2005 5:56 PM
> >> Subject: [amsat-bb] Eggbeaters
> >>
> >>
> >> >I have constructed, very carefully I might add, a 70cm eggbeater II,
got
> >> > the swr down to 1.1/1 at 435-438 .Stone deaf at 25' height and 40
foot
> >> > run of 9913.
> >> > I must have too much attenuation in the line into the shack. I don't
> >> > have any N connectors on hand so there are a couple of 259's in the
> >> > line.
> >> >
> >> > Am I wasting my time and $$ or will a mast preamp help?
> >> >
> >> > 73,  John
> >> > N4NAB/ FM14lq
> >> > AMSAT # 32411
> >> > ----
> >> > Sent via amsat-bb@amsat.org. Opinions expressed are those of the
> >> > author.
> >> > Not an AMSAT member? Join now to support the amateur satellite
program!
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> >> ----
> >> Sent via amsat-bb@amsat.org. Opinions expressed are those of the
author.
> >> Not an AMSAT member? Join now to support the amateur satellite program!
> >> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
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