[amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE

Jeff Yanko wb3jfs at cox.net
Sat Sep 26 04:48:23 PDT 2009

Hi Bruce and all,

No problem.  Actually, I wouldn't call it research as much as curiosity. 
Maybe the research will come later when developing something better. :)  I 
know the antenna "works" but can it be made to perform better?  The antenna 
itself is of great quality and workmanship, it's the diplexer that has been 
making me wonder if that is the weak spot.  The Achilles heel of the system.

OK on setting up the FT-817 using two coaxes.  I've heard a number of others 
doing the same thing with great results.  I would suggest doing what best 
suits the individuals needs and affordability.  You be surprised what one 
can dream up when you plan it out and follow through with the design.


Jeff  WB3JFS

----- Original Message ----- 
From: "Bruce Robertson" <ve9qrp at gmail.com>
To: "Jeff Yanko" <wb3jfs at cox.net>
Cc: "AMSAT-BB" <amsat-bb at amsat.org>
Sent: Friday, September 25, 2009 6:53 AM
Subject: Re: [amsat-bb] Arrow antenna reconfiguration results - UPDATE

Jeff --

I really appreciate you doing this research for us. Two additional
ideas come to mind:

1. Those of us with FT-817s could configure its two RF ports to use
different bands and connect the rig directly to the beam's antenna
connectors, bypassing the duplexer. For this purpose, higher-quality
bnc terminated cable would be useful.

2. If I'm correct, your replacement duplexer is rather larger than the
one it is replacing. It would be a great topic for a Journal article
if someone with the necessary equipment and expertise were to design a
replacement with less loss.

73, Bruce

On Fri, Sep 25, 2009 at 6:10 AM, Jeff Yanko <wb3jfs at cox.net> wrote:
> Hi all,
> A quick update to my new project to improving the Arrow antenna, 
> efficiency
> wise. I wanted to see how well it would perform on gaining and losing
> access during AOS and LOS. AO-27 is not a good choice since the timer is
> turned on when it is well above the AOS horizon and it is switched off
> before it reaches its LOS horizon. That leaves a dependable AO-51 to test
> it out.
> With the last setup, the OEM diplexer provided by Arrow Antenna, I would
> copy AO-51 about 3 minutes after AOS and lose it about 3 to 4 minutes 
> before
> LOS. Not bad, but people were saying they worked the birds when they were 
> 1
> degree off of the horizon. I have some pine trees that could be an issue
> but they are spaced far enough apart that I can work between them and I 
> also
> have to deal with the McCollough Range to the SSE of me here in Las Vegas,
> NV. Today, there were 2 passes of AO-51, one at 12 degrees elevation, the
> other at 74 degrees. During both passes, I began to copy the downlink 
> about
> a 1.25 minute after AOS. A considerable difference from 3 minutes. The
> downlink also improved down to about minute before LOS. On the last pass I
> worked KG6NUB at 0124z and LOS was 0125z and my downlink sounded fairly
> good, though I was fighting desense. (That's another issue I need to
> resolve.) Also, on both passes, I never once lost the downlink. No
> dropouts or fades. I'm still amazed.
> Another issue I came across was how wide the beamwidth is of the Arrow
> Antenna between the Arrow diplexer and the new diplexer. I was wondering 
> if
> this was going to happen and it did. The reason that this happened was 
> with
> the old diplexer, the signal attenuated so much that you had to be pointed
> right smack dab on the bird, a few degrees off and you lost the signal.
> Now, with the new diplexer, you can point the beam in the general 
> direction
> and still copy the bird. In most cases I had to turn the beam 90 degrees
> before I completely lost the downlink! Twisting the antenna to make
> polarization changes makes absolutely no difference now. This also
> attributes to the fact that now I'm copying the entire pass without 
> dropouts
> or fades. Makes sense. What I've regained over the lossy diplexer makes up
> for any polarization differences, etc. for a better copiable signal.
> Next weekend I will have to try more passes and get a feel of how much 
> this
> system has changed.
> 73,
> Jeff WB3JFS
> Las Vegas, NV
> DM26
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