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Re: Starting up



On Fri, Mar 28, 2008 at 7:55 PM, Alberto Mart <iz0fma@yahoo.it> wrote:
> I do belong a TS-2000k and i'd experience some traffic over satellite. I did attempt using my vertical but results did not make me happy (very limited, in time, footprint and fading). I was recommended to check Gulf Antenna but they have jsu drop satellite's solutions (in term of antennas).
>
>   I would buy a pair of 2 mts and 70 cms antenna and phasing them. Where could I find more infos ? i did "google" as well but did not find usefull infos (from my point of needs).
>
>   I do hope some "guru" here could forward me to the right antenna's manufacturer.
>
>   73s de Alberto, iz0fma
>

Alberto:

I'm by no means a guru, but I'm happy I followed the advice of the
gurus who recommended me to build my own antennas for LEO
communications. In truth, the LEOs do not require very high-gain
antenna systems.

One approach which has please many of us is to use a simple TV-type
rotor to rotate two yagis which are pointed at an elevation somewhat
above horizontal, say around 20 deg. If you keep the gain of the yagis
low, you can adjust the rotor manually a couple of times during a
pass.

I have built four antennas using the Kent Britain 'Cheap Yagis' design
in single polarization. I used bronze welding rods, not aluminum, as
elements. My 435 MHz antenna is an 8 element design, and the 144 was
three. I'd be inclined to go for 4 elements on 144, but with that
combo you can work all the LEOs with great style. I built these
without an antenna analyzer, using a VHF/UHF SWR meter. You don't need
to get the SWR perfect for satellite work.

Please note, though, that there is pretty broad consensus that for any
antenna design you should have a mast-mounted low noise preamp
installed, especially on 435 MHz. In my experience everyone's advice
is based on the assumption that you have one of those. In your case,
with the 100 and 50w available on transmit, the uplink power will
never be a problem with working receiving antennas.

I'm slowly upgrading all this to a full az-el arrangement with higher
gain antennas. This is a considerably greater engineering challenge,
and means that, in the Winter, if anything goes wrong I'm off the air
for quite a while. I'm enjoying trying to meet the challenge, but my
struggles make me all the more certain that a simple, low gain, design
is ideal.

73, Bruce
VE9QRP
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