[amsat-bb] Re: Looking for a G3RUH dish

5 Jan 2012

      The Balloon has APRS on it, so it is telling us where it is.  We have GPS,
so we know where we are and our heading, a PIC processor takes those two
inputs, does the 3D math and points the AZ/EL mount.  Again, the dish will
be an open-wire grid with nearly 1" spacing and have little drag.
Will have to power the Yaesu mount from a 115v AC inverter because they are
AC motors..
Bob, WB4APR
...
I'm trying to visualize you driving (bouncing) down the freeway at 70 mph
with a square yard of curved (airfoil!) metal sitting at odd angles to the
air flow, trying to aim it at a target you may not be able to see clearly,
which is also moving at some rate in another direction, with an accuracy of
+/- a half dozen degrees (which is what you get with a dish that size).  I
had a hard enough time aiming my 30 inch BBQ grill at AO-40, from my nearly
stationary house (this is California, after all), with up to date KEPS, a
rotor system calibrated earlier against the position of the Sun, NBS-sync'd
clock on a Linux PC, and so forth.
Even if you mount the dish inside a camper minivan with a fiberglass roof
(think mobile Radome), I don't see how this is going to work.  I've seen you
do amazing things, but what are you thinking?
The best use of the dish would probably be to catch the balloon payload as
it falls from the sky...
Greg  KO6TH
...
From: bruninga@usna.edu
To: k5oe@aol.com; amsat-bb@amsat.org
Date: Wed, 4 Jan 2012 17:54:02 -0500
Subject: [amsat-bb] Re: Looking for a G3RUH dish
...
Regarding your Cu wire dish... you might look at 
the Tek Sharp dishes as an easier alternative to "rolling your own."
We are after absolute minimum wind drag. I don't think the Tek dish would
survive accurate tracking while driving along the interstate at 70 PMPH to
catch a balloon. And we want it to be a good 3' by 4' dish... Need the
gain for the tiny wifi video link...
Bob
I picked one up on ebay about a year ago and put it in my attic... waiting
for amsat-dl :-)
http://www.plumdragon.com/teksharp/hr_AO-40_products.htm
Drew,
I have a spare PF dish about 60 cm, but it is steel, not aluminum like the
G3RUH. I used it on AO-40 for 24 GHz. Let me know off-list if you want it.
73,
Jerry, K5OE
---- previous message ----
You probably have one of the K5GNA "BBQ" dishes. The G3RUH is a solid
round
...
spun dish.
73, Drew
-----Original Message-----
...
From: Bob Bruninga bruninga@usna.edu
Sent: Jan 3, 2012 2:19 PM
To: 'Andrew Glasbrenner' glasbrenner@mindspring.com, 'amsat-bb'
amsat-bb@amsat.org
Subject: RE: [amsat-bb] Looking for a G3RUH dish
...
I'm looking for one of the 60cm G3RUH dishes
Got one, (but not available).
Questions: I measured reflector grid separation as .88 inches which works
out to be about 0.18 wavelength. I always thought the grid had to be
tighter than 0.1 inches to be an effective "surface".
Maybe the difference with almost double the spacing is not that
significant?
...
(especially for a steel one which would be quite heavy.
Reason I am asking is that I also need another S band dish (at 70 MPH on
the
...
roof of a tracking van) and we are thinking about building one by using
an
...
...
old solid 6' TVRO dish as a form and laying in copper wire and soldering
it
...
...
to copper straps. With all that labor, I'd not want to get the spacing
wrong.
Bob, Wb4APR

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