[Moon-net] Jamesburg; Large Multi Dish Array

[Pat Barthelow]

Folks:

Don't sign off Jamesburg yet,  in the long term, for further EME.   There are able candidates for buying it in, or soon to be in discussions with the owner to buy, or lease-to buy options.  

The Xprize competition has given new use/importance/vitality to dishes like Jamesburg for use in high bandwidth Earth-Moon Communications.  If any of you know of a dormant large 
(>18 meters dia) dish, in reasonable (not necessarily perfect) shape, that might be available for re use, any where in the world, please contact me.

Some of the candidates, are of a nature/state of mind, to be able to allow varied uses of the dish in the future when it is not in use for "paying" projects.  That is really encouraging news.

One Xprize competitor is also looking for a location to build a very large Paul Allen Array-like Array. of 450 18 ft dishes, spaced on 50 ft centers  (roughly)   I make that out to be at least 25 acres needed.  They wanted to use Jamesburg's 160 acre land, but I know the local neighbors who are generally countrified gentlemen/Winemakers/CEOs would put up serious resistance to blanketing Jamesburg's beautiful hillsides in more dishes.  So, if anyone knows of some radio quiet, clear land that is suitable for such an array, with Fiber optic Connectivity,  I am looking.  Ideally California, (maybe Mojave Desert or similar, possibly Nevada)

Now, a technical question:

Jamesburg's two axes are driven by large 20 hp AC motors.  (approx 18" dia, by 24" in) The motors are speed controlled with variable frequency AC drives.  In the EME application, I have observed the AC Motor Shafts directly, they move at very slow RPM, with RPMs  further reduced extremely so, by large reduction gearboxes, eventually driving the ring and pinion gears on each axis.  The dish motion, even the 100 footer,  as all EME'ers know, is barely even perceptible for EME.  My question is, if you include the 20 hp motors that run lightl,  in ~10 percent opposition torque to eliminate gear backlash, there are 4 large motors driving the dish, at extremely slow speed.  On an EME weekend, this is going for hours at a time.
We have not directly measured the drive power consumption, yet, but does anyone know in a general way, if the motor electrical power consumed by the Variable frequency drive motors, is still substantial, even though lightly loaded?   At EME velocities my opinion is that the actual power/torque used to derive the dish is very low...but I may be wrong.

A reminder to Northern California folks: Check out Radiofest 2000, a two day event in Monterey,  Feb 23,24.  Great speakers, events, BBQ;  Astronauts, Hams, UC Berkeley Nanotube Radio inventors/ experts, all to be there.  This year, it is a small tight venue, so will be crowded.      see: http://www.radiofest.org for details.

All the best,
Pat Barthelow    (916) 315-9271
aa6eg at hotmail.com
http://www.jamesburgdish.org
Project Manager,  Jamesburg Moonbounce Team