dish aiming (cont'd)
Bob Wier
>This ONLY holds true if you have a satellite EXACTLY due south
>AND you have adjusted the elavation adjustment with the dish
>EXACTLY at the balance point. In ALL other cases, a final tweak
For years, I've been trying to figure out HOW to determine when
you have found the maximum elevation of the dish using standard
carpentry tools (a digital level makes it easy, but they are
pricey - about $100).
If you use a carpenters level (say a 4 footer) you could lay it
across part of the dish circumference (lip to lip) and use one
of the axis to make sure you are measuring vertically. But that
does you no good because unless you are VERY far north, the
maximum elevation will be a value somewhere between 30 and 60
degrees. Basically you need a level that works in TWO axis
simultaneously, and for the elevation it needs to indicate an
arbitrary angle rather than just 0, 45, and 90 degrees.
The problem is further compounded by the fact that what you are
really looking for is a value of zero on the first derivative
of the sine function describing the elevation of the dish.
Of course, it changes very slowly as it reaches a maxima,
so you need to have an measuring instrument that is very sensitive.
Since the dish rotates as it moves thru the arc, having
a brace of something on the mount to put a level on does you
no good unless you are SURE that it hits a zero, 45, or 90
degree angle exactly at the point where maximum elevation
on the dish face is achieved.
Another way to approach this might be to suspend a plumb bob
from the center of the dish. Assuming it doesn't hit the mount,
the angle difference between the string and the center of the
mount could be adjusted for a maxima. The problem there is
how to implement this practically. I haven't figured out how
to measure such an angle accurately.
What *I* do is to use the "arc-set" which gives you a two axis
level - in my case, I rubber band the maximum elevation part of
the unit to a 4' carpenters level. I use the carpenters level
to make sure that I'm measuring vertically across the face of the
dish, and the apropriate 1/3 of the arc-set indicates when I've
hit the correct max elevation (which should then be pointed south).
(Note for the confused - the arc-set has 3 very cleverly designed
bubble levels which can be adjusted to indicate an arbitrary angle -
these will come pre-set for your location if you buy one new).
Using this method, I've successfully set c-band tracking on
poles as much as TWENTY degrees out of plumb (that's a LOT!).
But if anyone has any ideas on how to hit the max elev dead on,
another way, I'd be interested.
Please e-mail privately if you don't want to use bandwidth
here.
THANKS
wi...@bobcat.etsu.edu wi...@csn.org
===== Round Up the Usual Disclaimers! ======
Bob Wier, keeper of the Photo-3D, Icom radio (WB5KXH),
Overland Trails, and Motorola HC11 mailing lists
wi...@bobcat.etsu.edu
currently in Ouray, Co at 8,000 ft. elevation
(this is a *high level* system :-)
Bill Jones <n3jlq>
> >This ONLY holds true if you have a satellite EXACTLY due south
> >AND you have adjusted the elavation adjustment with the dish
> >EXACTLY at the balance point. In ALL other cases, a final tweak
>
> For years, I've been trying to figure out HOW to determine when
> you have found the maximum elevation of the dish using standard
> carpentry tools (a digital level makes it easy, but they are
> pricey - about $100).
>
>.......
>
> What *I* do is to use the "arc-set" which gives you a two axis
> But if anyone has any ideas on how to hit the max elev dead on,
> another way, I'd be interested.
>
the other methods, but doesn't really require accurate knowledge of
"max elev". I usually set the latitude adjustment (90-lat and the less
than a degree axis tilt) with a protractor on the mount first. The
"non infinite sat distance" declination adjustment is similarly set, if
possible (some of the mounts don't give continuous adjustment on this).
The north-south pointing of the mount is then set as close as possible
with a compass and a knowledge of the local magnetic deviation. At this
point I find the southernmost sat available and tweak the latitude
adjustment a bit, but this is usually not necessary if the protractor
measurements have been done carefully. At this point, the only thing
remaining to be tweaked is the final adjustment of the north-south pointing
angle (ie mount rotating on the pole). This part is a bit time consuming
with my method, but seems to work. Basically, I find a sat close to the
horizon, and evaluate it's signal, then make a fine adjustment to the N-S
angle then using the actuator, re-peak the sat and see if the new signal is
better or worse (ie sometimes the picture gets worse upon making the N-S
adjustment, but can be made better by moving the actuator). Usually after
3-4 small adjustments I am right on. Since using this method I have
played with computer programs to tell me more accurately what all the
various angles should be, but since it is not so easy to actually set all
these angles with any accuracy, I allways come back to the above method.
If it works well enough to get good reception on all the sats with my
"warm" approx 7 year old lnbs (I think my C-band Lnb is about 80 deg),
then it should work just fine for anyone with the newer "cool" lnb's.
Jim Roberts
WOW !!! I have just found this/your July 11 Posting and feel like I
have missed The Parade. There are no "threads" attached, which I can
find to trace back to what you have partially quoted from some prior
Posting(s), and if you can/will be kind enough to share the background
with me, I'd really be grateful !!
I see my ARC SET mentioned, with some cut-off words about "gives you a
two axis", which really peaks my curiosity !!
Anyway, picking up where I now find the discussion: The top (toward the
Equator) look angle of a "Polar" Mounted Dish is the combined total of
"normal" (perpendicular) to the AXIS inclination, minus (more toward the
horizon/Equator, by) the Declination adjustment. The proportioning of
the total, between these two component parts, is the key to being able
to actuate through the Birds to either side (East, and/or West).
Forgive me if I seem to be careful of my wording, but I set ARC SETs for
folk in the Southern Hemisphere, and they get a bit hurt in the feelings
when we/I always talk about "South" (as if the only direction toward the
Equator).
In either Hemisphere, the AXIS inclination is basic (#1 in my ARC SET,
and the central section where there are two screws to hold that bubble
extra tight). Any as-built compensation needed (as for an
unintentionally off-center Feed, a warped Dish--or a by-design Off-set
"Spoon", as we used to call 'em Dish) should be in the Declination
(above the AXIS). The adjustment mechanisim(s) which controle the Axial
inclination are more convenient/conspicious than the Declination
adjusting mechanisim(s)--but they should not be diddled, once the Axial
inclination is properly set for your Latitude (about half, to
two-thirds, of a degree more than your Latitude's angle).
Please go browse the www Site, which my son Kris has created for my
Tools (have your mouse bight the purple address in my signature bar).
You do not have to buy anything (my Tools are really for the
Professional/Multi-use Installers) but there is a table in the first
page which gives the AXIS and ZENITH angle values, by Latitude, FREE !!
For those who are really interested/curious/open-minded, going further
into the Site (to the extended infromation on ARC SETs) will bring you
to information on how these angular values are to be used (even by those
using protractors).
I will refrain from further lecturing (it is in me, by habit, however)
at this point--but will truly like to hear when/where/who the threads of
this discussion may be found/re-traced.
The Bubble & Squeak Man.
--------------------------------------------------------------------
Jim Roberts gou...@caprica.com
Gourmet... ENTERTAINING http://www.gourmet-ent.com
3915 Carnavon Way, LA, CA 90027 Ph:(213)666-2728 FAX:-2442
Vidiot
In article <950711114...@bobcat.etsu.edu>, wi...@BOBCAT.ETSU.EDU (Bob Wier) writes:
<>In article <3tkv28$9...@roch3.eznet.net>, stev...@eznet.net says...
<
<>AND you have adjusted the elavation adjustment with the dish
<>EXACTLY at the balance point. In ALL other cases, a final tweak
<
<For years, I've been trying to figure out HOW to determine when
<you have found the maximum elevation of the dish using standard
<carpentry tools (a digital level makes it easy, but they are
<pricey - about $100).
It is interesting to read all of these postings about how to get the dish
aligned.
I too was worried about aligning the used 10.5' dish that I obtained. Since
it was working once, I figured that it would be a lot easier than starting
from scratch. I didn't know how easy until I mounted it.
Right now the dish is mounted on a 5' pole that is built into a wooden base.
Yep, that is right, a wooden base. I have an 8x8' base (using 4x4 wood),
with 2x4s going to the center to hold the botton of the pole. I used very
large bolts to mount the wood to the pole. There are two bolts, each holding
two pieces of wood, which help remove the twisting effect of the wind.
The base is bolted together is angle braces, no nails at all. The top of
the pole is held vertical is wooden angle braces, though the actual piece
mounted to the pole is metal, i.e., there is a wood to metal interface.
I made the pole vertical by using a large carpenter's level. I then bolted
everything into place.
This arrangement has been working since March of this year and has been
through a few wind storms already, with ZERO readjustment so far.
As for the north alignment, I knew that the property was East/West (at least
that is what I remembered from the lot drawing :-), so I just did an eye-ball
and said that this looks like North/South and tightened the mounting bolts.
I hit the arc with NO READJUSTMENT. I even did a test elevation adjustment
on T1 and ended up right where I started.
This past weekend Mike Kohl (Global Communications) stopped by to look at
my site to see about permanent placement and determined that may not need
to move it at all. Maybe just 4-8 feet west from current location. It
looks like I may just poring concrete over the current wooden base (making it
larger) and replacing the wooden braces with metal.
Needless to say, it isn't as hard as it seems :-)
--
System Administrator - Extrel FTMS - Madison WI.
e-mail: br...@ftms.com
phone: (608) 273-8262 fax: (608) 273-8719 voice-mail: (800) 426-6488 ext 6293
Visit - http://www.cdsnet.net/vidiot/ (Your link to the world of Star Trek)