[amsat-bb] Re: Arrow antenna reconfiguration results
Tim - N3TL
n3tl at bellsouth.net
Thu Sep 24 10:40:15 PDT 2009
Thank you for posting this information about the Arrow. It's very interesting, indeed. The primary reason I switched from the Arrow I used to own to the Elk dual-band log periodic was because the Elk heard so much better. Patrick, WD9EWK, and I both routinely are able to work various satellites down to the horizon, depending on the pass. I use a Diamond MX-72H duplexer here. It's about the same price as the Comet you mentioned, and its loss figures are roughly the same, maybe a bit better. I use six feet of RG-8X for feedline. I'm using a duplexer because I don't have a full-duplex-capable radio. Since the Elk is dual-band, with one feed point, I need a duplexer to connect two radios - one for transmit, one for receive. On those passes when I use just one HT in half-duplex operation, I connect the radio directly to the Elk.
Have you taken any note regarding specific times you are hearing the satellites at AOS and LOS and compared them to tracking software like Orbitron? Doing so will give you a really good idea of how low you can go with your new setup. Congratulations on the improvement you've achieved, and thanks again for sharing it with all of us who read the BB.
73 to all,
Tim - N3TL
Athens, Ga. - EM84ha
From: Jeff Yanko <wb3jfs at cox.net>
To: amsat-bb at amsat.org
Sent: Thursday, September 24, 2009 5:17:23 AM
Subject: [amsat-bb] Arrow antenna reconfiguration results
After being off the air for about a month, I recently made some changes to
the satellite setup. I upgraded from the TH-D7A(G) HT to the TM-D710A
mobile dual bander. Yes, a bit bulkier, but worth its weight. Anyhow, I
know many sat operators use the Arrow antenna setup, like what I've been
using the past 7 or so months with great results. However, I've always
known that the diplexer that comes with the unit is reather lossy. From
some reports I've read as much as 2.65dB of loss. That's almost half of
whats being received or transmitted being thrown away. When I layed out the
new portable setup I made it an issue to "lose" the diplexer and put one in
line that would perform better. I purchased the Comet CF-416. It's loss is
about .26dB. A considerably less amount by far and if needed in other
applications it can handle more power than the 10 watts alotted for the
Arrow's diplexer. I also bought some good quality RG-58 coax, only 6 feet
in length, for both 145 and 440, so there isn't much loss from this. About
.6dB according to the data sheet.
After the assembly and installation was complete, on air usage was next.
AO-27 had a fairly decent pass to the east of the QTH with a max elevation
of 24 degrees. I've remembered how the passes sounded previously at this
elevation so I could get a mental comparison. As the bird's timer turned
the digital transmission on I noticed one thing immediately, the signal was
clearer and no hiss. The analog timer swtiched on and the voices became
copiable. The signal appeared to be a bit stronger than the old setup with
the Arrow antenna but the most remarkable improvement was from the time I
started to receive the signal to near LOS, it never once dropped out! It
almost appeared as though I changed my linear antenna to a CP with a preamp.
I figured this is too good to be true. I then decided to test it with AO-51
and see how well that bodes. I noticed I was copying the signal closer to
the horizon than the previous set up and again the same results with no drop
outs, except for the one time the house blocked the signal for about 20
So if anybody is considering improving their current Arrow antenna, please
do so by getting a better diplexer. They are not expensive, $40 to $60, and
of course some decent coax, short runs are better but give yourself enough
slack so you don't cut yourself short!
See you on the birds!
Las Vegas, NV
Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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