[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Automatic AMSAT Antenna Rotators


WB4APR writes:
> It is crazy that more software doesnt support the ubiquitous 24 VAC garden
>  variety TV rotators.  I know this is apples and oranges, (AO-40 precision
>  pointing versus the other 20 LEO amateur satellites), but it is SO easy to
>  control a standard TV rotator...

I think you underestimate how practical your software (and rotor interface 
circuit) could be for an AO-40 system.  The need for high-precision in 
pointing is driven by high-gain antennas.  AO-40 can be worked with 
reasonably low-gain antennas as long as you make up for the low gain with a 
top-end receiving system and a little bit of power on the uplink.  

I know from experience a 65 cm dish has about a 10-12 degree 3 dB beamwidth 
(in azimuth).  A typical 2 foot solid dish with a good patch feed and a 0.6 
dB NF preamp will easily work 95% of the signals on the satellite.  Been 
there, done that.

A 10-13 dB uplink antenna on 70 cm, such as the nifty new dual-70 Arrow, or a 
homebrew 10-el beam such as the popular WA5VJB "cheap Yagi" has an even wider 
beamwidth than the dish.  50 W to that antenna should prove adequate for most 
circumstances, except QSO Parties, FD, and rare DX when both NA and EU are in 
the window :-)

Now about elevation control...  not that big a deal to use two RS actuators 
(been done by many people over the years--see the AG5RS pic in the 2002 FD 
issue of AJ), but a polar mount with a manual elevation adjustment for the 
"drift" of AO-40 around the equator would be simple and effective.  How many 
people don't even have that sophisticated a setup?  You hear ops all the time 
who work AO-40 without even a rotor!

I don't think you have to apologize for your software/hardware innovations:  
they are perfectly usable for AO-40 if people would just think outside the 
Yaesu box.
Jerry, K5OE
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org