A challenge for ingenuity

Dear friends and respected colleagues!

I offer you a puzzle that is comic in form, but far from comic in content.

One elderly man, who is fond of receiving satellite signals and tunes antennas to different satellites, opened the door to the balcony one morning and saw this picture:

He remembered that he tuned the first and second antennas to satellites close in position in the Clark belt, but forgot which ones

But the third antenna has long been precisely tuned to the Hot Bird

In another corner of the balcony, he had another fixed antenna (4), which was tuned to the Yamal satellite at the 90°E position:

In front of the fourth antenna, the mount for the first antenna is rigidly fixed, precisely oriented in azimuth to the position 13°E

The balcony is oriented (as the builders did) exactly along the azimuth of 14°W of the geostationary orbit.

One floor above we see the fifth antenna, in which the satellites are tuned 13°E , 5°E (focal) and 4°W

Another photo shows the location of the antennas:

And now the question of the task:

help me remember which satellites the first (1) and second (2) antennas are tuned to

PS For Kyiv, the summit satellite has an azimuth of 30°5 E

stephan94

Yes, it's not an easy task. So far, the error is, on average, ~36°.

Try again

Good evening !

More than 60 people read my post, but only stephan94 gave the first answer.

And you can offer options as much as you like, for example, in the form

"Antenna number - Satellite position":

1 - 53E

2 - 56E

After my comments, you can pick up a couple of satellites again and give a new answer.

And now for the first hints:

1. Plot the focal axes for each of the antennas.

The focal axis passes through the center of the LNB holder ring, its projection on the horizontal plane shows the azimuth of the direction to the satellite, and the angle with this plane is the angle of elevation of the satellite above the horizon.

2. Use the program DISHPOINTER

If something is not clear - ask questions, I will try to answer.

Good luck and good mood

Zitat von bol@nov

I'll give my guess...

Antenna 1 - ABS-2 / ABS-2A @ 74.9° E

Antenna 2 - Yamal 402 @ 54.9° E

So far, the error is, on average, ~21°.

Zitat

He remembered that he tuned the first and second antennas to satellites close in position in the Clark belt, but forgot which ones

Clue:

Antennas are NOT aimed at Russian satellites

Try again

Zitat von bol@nov

Apparently antennas 1 and 2 do not seem to be pointed at nearby satellites ...

Why did you decide that the antennas are not aimed at nearby satellites? Explain, please, what arguments and facts led you to such an INCORRECT conclusion.

Moreover, in the condition of the problem it is directly indicated that the satellites are nearby ...

Zitat

... the 90E antenna, which would have been a better reference point, is upside down and completely hidden in the pictures.

Why is it completely hidden? You have determined that it is in the "inverted" position. To be precise, I note that the 4th antenna is rotated 90 ° relative to the focal axis. That is, unlike 2 and 3 antennas, which are installed on a vertical support, it is installed on a horizontal support.

In this case, the mechanisms for setting the azimuth and elevation angle change their functions.

In a "normal" setup (2 and 3 antennas) the angle between the major axis of the mirror and the focal axis is

90° - offset angle

and the perpendicular to the minor axis of the offset antenna in the horizontal plane shows the azimuth to the satellite.

When the mirror is rotated by 90° (antenna 4), the angle between the minor axis of the antenna and the vertical is equal to the elevation angle of the satellite; the angle between the major axis and the azimuth to the satellite is

90° - offset angle

Now pay attention to the fact that the shooting angle of the 4th antenna in the second picture lies in the plane of the offset mirror cut.

As for the "polar" suspension of 1 antenna, this is the most difficult case, so I will give you one more hint:

Zitat von Danny10

My guess :

1. dish AzerSpace 46E

2. dish Turksat 42E

Congratulations!

So far, your answer is the closest to the truth.

Average satellite position error is only 4°  

Unfortunately your answer is wrong.

Try again - you will definitely succeed

Zitat von femi

Ausgehend von der durchschnittlichen Abweichung 4° (Danny 10) und Antenne 1 weiter nach Osten zeigt, ergibt sich folgendes:

Assuming the average deviation is 4° (Danny 10) and the antenna 1 points further east, the following results:

And why did you decide that (1) the antenna is directed further east than (2)?

Yes, the antenna pole (1) is easterly than the antenna pole (2), but it can be adjusted from 14°W to 105°E

I have a strong suspicion that you consider the average deviation of the estimated azimuths from the true ones, taking into account the direction of the deviation, and not modulo

Your answers can be published today and tomorrow

On Wednesday, the results of this mini-competition will be summed up

Don't miss your chance to be a winner

So, let's sum up the results of the mini-competition to determine the azimuth of offset antennas from their photographs.

For a week, the topic has collected 347 views with 16 posts.

This allows us to estimate the number of people who viewed the topic at the level of 22 people, of which 5 wrote their posts. In my opinion, for a forum with a daily attendance of < 20 members, this is a good result.

I would like the activity of members of the forum to be higher, but a quarter of those who viewed the topic is a fairly good result.

On the very first day, there was a response from my faithful friend stephan94, who has known me for many years and the fact that I don’t ask questions just like that, because there’s nothing to do ...

I gave hints along the way that were supposed to guide readers in the direction of the correct answer.

After the very first (main) hint about the role of the focal axis of a parabolic mirror for determining the elevation angle and azimuth to the satellite, two more answers were received.

I was especially pleased with the answer of Danny10, who correctly guessed the azimuths of both satellites , but confused the antennas that receive them . Apparently, the stereotype that sits in our subconscious did not allow him to give an absolutely correct answer:

"The focal axis of an offset antenna begins at the lowest point of the mirror on its vertical axis and then passes through the focus"

Oddly enough, such a statement is true for a very small number of offset antennas (for example, the Russian-made SUPRAL).

In order to dissuade my colleagues in the forum from this misconception, I came up with this contest, hoping to arouse interest in the paramount issue of offset antenna orientation.

Now let's look at the correct answer : 1-42°E_2-46°E

The purple arrows are drawn from the "green" points through the "yellow" points, which coincide with the antenna foci.

The blue arrow is a copy of the vector pointing at the 42°E satellite, but shifted parallel to itself until it intersects the 46°E focal axis.

As you can see, it is visually deviated by 1°5 from the long vector, which confirms the fact that the blue arrow is directed to a satellite closer to the "southern" one.

If you are interested in how I built the "green" dots, please "like" this post. If you are not interested in this question - put any other rating, for example, "dislike".

If there are more likes, I'll create a thread about fine-tuning offset antennas with simple antenna measurements