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Re: Gettng on AO-40 - Uplink Antenna



Well, I've tripped LEILA with 50W out and a WA5VJB Cheap Yagi (11 ele linear 
polarized), so I think you'll be fine.  True I had a VERY short cable run 
(like 10 ft at the time)...

I think RHCP is a good way to go as even though you'll do fine with a linear 
uplink antenna (I have in the past), there is occasionally some slow QSB on 
your downlink if you use a linear.  I think the QSB is somewhat minimized by 
using RHCP.

There are some cases where switchable polarization sense is a good thing, 
like when you are working off of a sidelobe of the satellite's antenna (high 
squint).. the sidelobe's polarization sense can be reversed.  It is worth 
the extra trouble?  Personally I think not, but I'm sure there are people 
out there that would disagree with me.

Fred W0FMS




>From: Mike King - KM0T <scsueepe@mtcnet.net>
>To: <amsat-bb@AMSAT.Org>
>Subject: [amsat-bb] Gettng on AO-40 - Uplink Antenna
>Date: Mon, 12 Aug 2002 23:44:13 -0500
>
>Hi all, got some equipment for getting on AO-40.  Looking at a 435 Mhz
>uplink antenna.  Hope to be on in a month or two.
>
>Question, is the circular polarization uplink antenna such as a M2 436CP30
>verses a single polarization unit a good way to go?  My research has
>indicated that there is a 3 db difference to the sat, plus possibly less
>fading?  I guess how much better is it in terms of operation?
>
>Also, I understand that the RHC polarization, just set the antenna up for
>that, no need to change polarization?  I assume that the A040 antennas
>basically allwaya point back at earth in the same polarization.  I guess
>what Im asking is if there is any reason or need for a polarization switch
>to optimize the uplink signal.
>
>In addition, any comments on this antenna verses the unit from Gulf Alpha
>antennas.  That unit is about 3/4 the boom lenght of the 117" M2 unit.  Any
>users out there with comparisons?
>
>I will be using a FT-847 with 50 watts out (or less) to one of these
>antennas.  Question is that without offending LELIA (I think thats the name
>anyway) will 50 watts do the job (assuming reasonable feedline loss of 1 to
>1.5 db) or will a brick still be required?  I really dont have a feel for
>this as all the reading I have done kind of shows guys using different 
>power
>levels across the board.  Also I imagine this has some to do with single
>verses circular polarization as well.
>
>So, sorry if this has all been covered before (I would imagine it has) and 
>I
>appreciate any info from the veterens on the bird.  Any tips appreciated,
>dont want to be a lid.
>
>73 and thank you.
>
>Mike - KM0T en13vc - NW Iowa
>www.qsl.net/km0t
>
>
>
>----
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