10' satellite Woes

[dedndave]

here are 9 birds i got from dishpointer, according to their "10 most popular" list
one of them was Nilesat at 7 degees W - you probably won't get that one    :P

Code Select Expand


Address: Latitude: 29.1024°, Longitude: -82.4838°

Satellite: 91.0W - Galaxy 17, Nimiq 1, Nimiq 2
Elevation: 54.8°
Azimuth (true): 197.1°
Azimuth (magn.): 202.1°
LNB skew: 14.9°
Distance: 36797km


Satellite: 119.0W - DirecTV 7S, Echostar 7
Elevation: 37.7°
Azimuth (true): 236.7°
Azimuth (magn.): 241.7°
LNB skew: 46.9°
Distance: 37961km


Satellite: 110.0W - DirecTV 5, Echostar 10, Echostar 11
Elevation: 44.6°
Azimuth (true): 226.9°
Azimuth (magn.): 231.9°
LNB skew: 39.7°
Distance: 37443km


Satellite: 97.0W - Galaxy 19
Elevation: 52.5°
Azimuth (true): 208.0°
Azimuth (magn.): 213.0°
LNB skew: 24.2°
Distance: 36930km


Satellite: 61.5W - Echostar 3, Echostar 12
Elevation: 49.0°
Azimuth (true): 141.7°
Azimuth (magn.): 146.7°
LNB skew: -32.8°
Distance: 37148km


Satellite: 82.0W - DirecTV 3, Nimiq 4
Elevation: 56.0°
Azimuth (true): 179.0°
Azimuth (magn.): 184.0°
LNB skew: -0.9°
Distance: 36727km


Satellite: 121.0W - Galaxy 23
Elevation: 36.1°
Azimuth (true): 238.6°
Azimuth (magn.): 243.6°
LNB skew: 48.2°
Distance: 38092km


Satellite: 123.0W - Galaxy 12, Galaxy 18
Elevation: 34.5°
Azimuth (true): 240.4°
Azimuth (magn.): 245.3°
LNB skew: 49.4°
Distance: 38229km


Satellite: 107.3W - Anik F1, Anik F1R
Elevation: 46.5°
Azimuth (true): 223.6°
Azimuth (magn.): 228.5°
LNB skew: 37.0°
Distance: 37312km

[dedndave]

one thing i am noticing here - they are not all on the same arc
things must have changed in the last 15 years   :P
probably got crowded
but, i am guessing your reciever takes care of all that, assuming the dish is set up correctly

the dish should point to the lower elevations at the east and west ends of the arc
for example, the elevation for Nilesat at 7 degrees W (the antenna points just S of E) was about 4 degrees - too low to work, i am sure

it should point to the highest elevation of about 56 degrees when you point it south to get Nimiq 4
if that isn't the case, then something is terribly wrong - perhaps some wires are crossed

[shankle]

I can at my latitude only get the eastern most sat called intelsat 805(55 degrees) and western echostar 9
(121) degrees.
I have also noticed that with each sat the Polarization changes. That means I have the polarization
set incorrectly for two reasons. 1. I should move the dish straight up to 82 degrees and then set
the polarization to 0.87 degrees right. 2. I set the polarization to 46.91 without knowing where I
was on the arc. HOWEVER, I can't reach the LNB when it is straight up. I don't know where the
dish is pointing when I am someplace else. Also there are no instructions on how to position
the bsc621-2d on any satellite. Is the label the pointing factor or is something inside the feed
horn the pointing factor???????
Nothing is ever easy.....

[dedndave]

well - let's start, this morning, with the documentation for the 621's
i found this page which has the basics...
http://www.dmsiusa.com/products.html#c-ku
you may want to find out which version you have:
621, 621-1, 621-2, 621-2D
although the docs for the others may be helpful

i would guess the orientation of 0 degrees skew would be where the C-band unit is at the top (this is not right - see next post)
some of the units may be electrically switched by 90 degrees
i noticed one of the units may be circularly polarized

perhaps you need to find a "best comprimise" orientation and switch it 90 degrees with the reciever
the polarization should not be nearly as critical as aiming the dish
one approach might be to tweak it for the hard-to-get birds that have content that is important to you
then, live with the results on the less important ones - the ones in between will probably be fairly good

but, if you can get one of the birds at the east or west end of the arc, you may try peaking the signal with the meter
that may verify the skew orientation

something else i noticed is the focal point is different for C and Ku bands
that could account for crappy performance reported on Ku   :P

this is the home page for that site
on the left, there are a number of interesting links that may be worth browsing
http://www.dmsiusa.com/index.html

[dedndave]

here is a pic and description of how one guy oriented his 621

On mine, the 1/4" metal rod is Horizontal, when at True South, and the "Connection Box" is on the Lower Left side when looking down at the Dish from behind the LNBF.

i don't know if he was on a step ladder, or if he dropped the dish at true south   :bg

a few other links i found:
http://www.satmancanada.com/BSC621test.htm
http://www.satelliteguys.us/c-band-satellite-discussion/184748-questions-about-dms-didital-c-ku_lnbf-2.html
http://rickcaylor.websitetoolbox.com/post?id=3760493

[dedndave]

here is how we adjusted ours...

don't  drop that wrench !!!

attached is an updated list of 18 birds
i added the ones from your list that my list did not have
and i re-ordered them by location
it does appear to be a single arc, afterall   :bg

[dedndave]

now for declination
it is indeed a different term - i appologize if i introduced confusion

i should have qualified my use of the term as "magnetic declination"
http://en.wikipedia.org/wiki/Magnetic_declination

for satellites (and for star-gazing), the term "declination" is used quite differently
http://en.wikipedia.org/wiki/Declination

from what i can interpolate from the tables, the "modified" declination correction angle for your latitude should be 4.23 degrees
that is even more confusing because it isn't far from the magnetic declination for your location - lol

here are a couple pics and some useful links to help understand...



http://www.geo-orbit.org/sizepgs/decchartp.html
http://www.mbcsatellites.co.uk/tag/motorised-dish/
http://www.geo-orbit.org/
http://www.geo-orbit.org/sizepgs/tuningp4.html

Magnetic Declination
here is a java script from NASA for determining the magnetic declination angle for a given location and date
http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp

for your location, it is currently 5° 2' W, changing by 0° 5' W/year
or 5.03 degrees W of true north

[shankle]

Thanks for all the pointers.
Some I've seen before and some I haven't.

I got dizzy just looking at those guys up on that tower. :bg

I doesn't do me any good at my latitude to point the dish straight up and try to get
a signal on nimik 4 (82) as it is KU as I haven't been able to get any C-band yet.
Tried the Pico there and it sat at the right.

Got to be the bloody LNB settings. I got the focal point of the lnb set to 46+ inches
from the center part of the dish. One of your references got me confused again.
They talked about f/D. In my case that's 47.36"/120" = .39. I interpreted this as
moving the lnb .40 inches past the scalar ring. Never heard of this before and I haven't
tried it yet.
As of right now I am nowhere.

[dedndave]

i don't know if you saw this or not
it shows the focal points for the 2 bands
one of the guys i saw wrapped some tape around the focal point to mark it
then aligned the tape with the scaler ring



if you can get 2 birds at the ends, but nothing in between, it might suggest a declination problem
but - that does not mean that the elevation is not also set wrong

another comment that i have seen more than once...
once they get it set up, moving the LNB in toward the dish slightly seems to help
that is probably because the aim is not quite as critical if the feedpoint is not at the focal point
moving the LNB in like that has the effect of widening the "beam" a little

[ecube]

you capable of creating a satelite that flys in space dave? :bg

[dedndave]

lol - i have worked on a few little satellite pieces here and there (microwave)
and earth-bound high-speed satellite data modems
i also did some work on the space shuttle electronics at Sperry
a box we called "SRB/MDM" - solid rocket booster multiplex-demultiplex
no - it had nothing to do with the O-rings   :P
we were sweating a little during the investigation, though
NASA design and quality specifications are far more stringent than military specifications
i don't like working on either - because of all the bureaucratic bs

[shankle]

My latest blunderings today.
Think I finally got the bsc621-2d lnb installed correctly.
Thought that would solve my problems
DMSI painted the polarization mark the same color as the rest of the lnb. Brilliant..
Very hard to see if you don't know where to look for it.
Still can't bring in a single thing.
I beginning to wonder if maybe the bsc621-2d is not compatible with the Pansat 2800a receiver.
Have no idea how to find out.

[dedndave]

with the "-2D" version, you cannot use 22 KHz to switch bands - the "D" stands for dedicated
that means you need an external coaxial switch to switch bands
on the plus side, it should provide a little better performance
it does use 13 or 18 volts to rotate polarity 90 degrees
i am going to guess your problems are still in correctly aiming the dish

[shankle]

Don't think I ever had a 22 khz switch. My previous setup had 2 norsat lnbs, c/ku and worked
but not great.
Yes, I am still having problems aiming the dish. The Pico isn't helping much.

There is a gentleman in Ca. that has an arc set he sells to put your dish on the arc.
I haven't bought one but he told me that if I went west till the face of my dish is 52.25
degrees that would put me on the arc. Trouble with western sats is there is no C band there.
And it's far to early for me to be looking for ku. I'm talking about echostar 7 at 119 degrees.

[shankle]

Two questions that might solve my problems.

1: Focal Point
dish width = 120" - D
dish depth = 19" - d
DxD= 120"x120" = 14400
16xd = 304
f = 14400/304 = 47.36"

f/D = 47.36/120 = .38"
should the lnb be set to 47.36" from the center of the dish?
OR
should the lnb be set .40" past the scalar ring?

2: elevation of the rocker arm
my latitude is 29.1024
my rocker arm is set to 29.62 (at the present time)
declination - 4.21
29.62 + 4.21 = 33.83
should it be set to 90 degrees minus 33.83 = 55.17?

I have read conflicting directions and it is very confusing.