Thanks Eric Johnston for yr expert replies.
You have covered most of the points, but it seems that you may have missed commenting upon Pt 2-b of my Msg # 1 above ? - spl wrt Inline Cables, "USALS" or "DiSEqC 1.3" compliance, and how to go about for Fixed Dish etc.
************
4) I have got Google Earth (GE) in my PC.
4-a) Could you pl let me know how I can get the Blue-Green Azimuth Line in GE. Are there any settings in GE that I need to tweak ?
4-b) The Image Date in GE (at the Bottom Left) shows an Old Date for most of the points I have surfed using GE, for eg, 1st Jan, 2009. However, in yr smaller-sized Dish Pointing maps (with the Blue-Green Azimuth Line), the image date shows 2011. Could you pl let me know how I can get the Latest Image Data in GE also.
************
5) In
https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1286329665 I saw a mention of : 4 Polarisation values :
Polarisation : deg -27.66
Polar mount Main : deg 37.82
Polar mount tilt : deg 5.23
Polar mount axis rotation : deg -26.46
But now, in
https://www.satsig.net/ssazelm.htm, I can only find 3 values of Pol.
Could you pl clarify how we can obtain the 4th value : Polar mount axis rotation.
To get a hang of these values, I tried the Az-El Calculator for the same Lat / Long Loc, (let's call it say, A) with North Latitude, with 3 diff Satellites.
For this Loc A with North Latitude :
|Azimuth| + |Polarisation| ~= 180 Deg [Ave for 3 Sat values = 179.487 Deg]
Similarly, I tried to compare the Az-El Calculator for the Lat / Long Loc given in the above
https://www.satsig.net/cgi-bin/yabb/YaBB.pl?num=1286329665 Thread, (let's call it say, B) with South Latitude, with 2 diff Satellites.
For this Loc B with South Latitude :
|Azimuth| + |Polarisation| ~= 360 Deg [Ave for 2 Sat values = 355.665 Deg]
And for points exactly on the Equator, we will have :
|Azimuth = Exactly 90| + |Polarisation = Exactly -90| = 180 Deg when the site is to the West of the Sat
|Azimuth = Exactly 270| + |Polarisation = Exactly 90| = 360 Deg when the site is to the East of the Sat
I guess, this settles my previous (Pt 1) in Msg 1 - about the sum of the modulus of the 2 angles being 180 Deg - it should be correctly qualified as foll :
It is either 360 Deg exact, or 180 Deg exact, or close to 360 Deg (for S Lat), or very close to 180 Deg (for N Lat).
Do you agree ?
************
6) During the above Calcs, I also observed that :
For the Loc A with North Latitude :
Very Less Variation in Dish Azimuth Betn : Relative to True N and Relative to Mag N
Ave Diff of 3 Sat Readings = 1.4 Deg
For the Loc B with South Latitude :
Wide Variation in Dish Azimuth Betn : Relative to True N and Relative to Mag N
Ave Diff of 2 Sat Readings = 12.785 Deg
So, in general, has it been observed that the variation betn Az True N and Az Mag N is always higher for South Latitudes ?
I would guess so, since I have taken 2 arbitrary values, one with N Lat and one with S Lat, without any bias in choosing the points.
Do you agree ?
If yes, how can the Calc S/w be tweaked ?
[As explained in Pt 5 above, for N Lat, the modulus sum : |Azimuth| + |Polarisation| is closer to 180 Deg, than the corresponding sum's closeness to 360 Deg for S Lat.]
Further, after the recent Fukushima Quake, there was a mention that the Earth's Magnetic Axis has got altered. How / Has this been factored into ?
************
7) In
https://www.satsig.net/22-deg-offset-dish.htm, what is the angle of the Base Arm wrt the Diameter Line of the Dish ? Roughly, it seems to be about 80 Deg in the Diagram.
Also, the length of the Base Arm for a given Dish Dia ? ie, I would like to know the ratio of Base Arm Length / Dish Diameter. Is this ratio a certain fixed value ? If yes, how is this ratio value calculated ?
The Red Incident Input Beam Ray hits the Dish slightly above the mid-pt of the Dish.
The Base Arm Length and the above ratio, have a bearing on where this Beam Ray point will be incident on the Dish.
In this Diagram, roughly, I measured the Incident Beam Angle to be about 16 Deg wrt the Horizontal Line in the Diagram.
To put it in other words, as an example, what would be the Base Arm Length / Dish Diameter Ratio, and how would the same Diagram look like, for a 30 Deg Offset Angle Dish ?
************
8 ) I am new in this field, so I would like to understand / get confirmation of the foll :
Feed Arm Point : Pl confirm that this is the same as the (Short) Base Arm, attached to the Dish, and onto which, the Feed Horn Holder is fixed.
Which Pt is the "Feed Throat Point" ?
Cross Polarisation Perf : How is this measured ?
************
PS 1 : As I said earlier, I am new to this Satellite / Transponders / Dish / LNB subject.
So, I wish, that similar to clear replies by you in this Thread, I could also get some little more detailed replies (than the 1 line quick answers from "USN-Retired") to the 2 other Threads :
https://www.satsig.net/cgi-bin/yabb/YaBB.pl?board=point;action=display;num=13041...https://www.satsig.net/cgi-bin/yabb/YaBB.pl?board=point;action=display;num=13041...Perhaps, Eric, you may like to add some of yr own comments to those 2 Threads too ! ?
Thanks in advance.
PS 2 : In the "Post a Msg" and "Reply Msg Editor" of this website, how do we get to add Highlights, "Quotes", colors etc ?
Is there any provision to send an attachment file with Calcs or Diagrams etc ?
...
********************
Again, Thanks in advance.