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Re: loop yagis



For what is worth, my two 45-element loop-yagis give gain of 23 
dBi.  They are 12-foot long and spaced about 16-inches apart.  They 
are sold by Directive Systems.

A loop fed element in front of  a 32-inch BBQ dish will not have 
anywhere near this gain and have many large side lobes.  A dish needs 
to be >10 wavelength to exhibit nice clean beam pattern (23cm *10 = 
230 cm or about 7.5 feet).  I know many satellite folks are using a 
4-foot dish so on transmit only this  may be sufficient, though the 
beam will not be nice and waste much radiation in other than the 
desired direction.

I used one of the loop-yagis (20-dBi) on AO-40 with 9.5w with a 
marginal uplink signal.  Either 15w or more antenna gain was 
indicated to produce an SSB signal comparable to mode US.  of course 
P3E and Eagle requirements  may not be the same as AO-40.  This is 
the best we can do without precise knowledge of the satellite parameters.

At 03:50 PM 5/6/2007, Greg D. wrote:
>I need a good uplink antenna for the new birds, and have no real 
>space on the boom to add a yagi.  This sounds like what I need; do 
>you have any pictures?  Also, more details on how you do the 
>filtering to keep from frying the 2.4 preamp!
>
>I have a screen-lined grill dish, with a canned helix feed to a 
>Khune preamp.  See:  http://home.jps.net/~gregd/Dsc00201.jpg.  Would 
>I just put a single 1-wavelength loop around the outside of the 
>helix at about the focal point?  That would be right at the front of the can...
>
>Greg  KO6TH
>
>
>
>----Original Message Follows----
>From: "kc6uqh" <kc6uqh@cox.net>
>Reply-To: kc6uqh <kc6uqh@cox.net>
>To: <w7lrd@comcast.net>, <amsat-bb@amsat.org>
>Subject: [amsat-bb] Re: loop yagis
>Date: Sat, 5 May 2007 23:19:29 -0700
>
>Bob,
>For ATV I have used a Conifer BBQ grill type 2.4 GHz antenna with a Loop for
>1.2 GHz in front of the 2.4 GHz feed. The 1.2 side has plenty of return
>signal in the order of 18 dBi for ATV work. I haven't seen a loop yagi that
>will touch it in performance. I run full duplex with filters on both
>frequencies 1253.25 receive and 2441.5 transmit with 10 W. I am able to work
>the W6ATN repeater from 40 + miles.
>
>Art
>KC6UQH
>----- Original Message -----
>From: <w7lrd@comcast.net>
>To: <amsat-bb@amsat.org>
>Sent: Saturday, May 05, 2007 4:13 PM
>Subject: [amsat-bb] loop yagis
>
>
> > Hello
> > What is the consensus regarding loop yagi antennas for L band uplink.  I
> > have 10 watts available from an IC1271 before the coax.
> >
> > --
> > 73 Bob W7LRD
> > AMSAT member 28498
> > Seattle
> > _______________________________________________
> > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
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>
>
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>
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73,
Ed - KL7UW
======================================
  BP40IQ   50-MHz - 10-GHz   www.kl7uw.com
144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w
DUBUS Magazine USA Rep dubususa@hotmail.com
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