Re-installing dish and tracking the arc

[Chr0nik]

Hi,

As I was missing the hobby, I've decided to put the CM 120cm on the polar mount and get it up and running. I've made sure the mount was as plumb as possible (the surface is a bit uneven) but at the moment I'm only able to get from 45e to 27.5W.

When I had it last year, I was able to get from 62e to 15w (which I knew the setup was well off) but at least now is a bit of an improvement but I would like to go further but I don't want to move anything yet without assistance.

I wonder if the declination or elevation is off.

Can you please assist?

 

[Manikm909]

mark where it is now, so u can at least go back to it - and then trial and error mate. r u setting up at 1w ?

i will have all this to do soon on my 1.8m !! never used a PM before - not looking forward to alignment time

my h-h jaegar 128G on my CM1.2 has been bloody perfect !!! always 17db on some tp's both ends 42e and 30w

 

[Captain Jack]

Have a quick look at this. Take note on what action on the dish improves the signal at the extremes. Certainly declination and elevation are prime candidates but also azimuth.. or a combination of all.

It's for Stab but the same applies to polar mount alignments as well.

 

[Mickha]

You should easily pick up 30W, providing you havened reached the set limits, of your motor, or any limits set in your receiver, or V-Box II.
Just remember the basics:
Ensure your pole is plumb, and strong enough to hold your dish, and motor, even during strong winds.
Check your Longitude, as you're probably using a 36v motor, driven by a V-Box II, so you need to align on the nearest satellite, to your Longitude location, remember negative Longitude readings = West, positive = East.
Set everything to 0, Motor, Dish and LNB.
Physically align your dish, to the chosen satellite, then peak the signal.
Next drive your dish to satellites, East, and West, peaking the signal quality, then storing their positions, noting their signal quality readings.
You can then make minor adjustments, by sending the dish back to your starting point, the satellite you first aligned your dish to, alter the bracket settings, slightly, on your motor, compensating by adjusting your dish bracket, to peak the signal, then test the quality levels once more.

Can you please post a list of satellites, that you can currently receive, along with their signal quality readings.

 

[Chr0nik]

Thanks for your replies!

I'm using a CM 1.2m with an Inverto Black LNB, 18" actuator and a SuperJack DP-6600.

Regarding the mount, it's plumb and I've tried the following sats:

27.5w​	12db​
24.5db​	10.2db​
22w​	11.4db​
15w​	14.9db​
7w​	8.0db​
5w​	16.3db​
0.8w​	15.8db​
28.2e​	18.2db​
42e​	16.8db​
45e​	12.2db​
46e​	10.6db​

Before it went dark, I've tried to move it left to right and raise/lower the latitude and managed to get 46e but not as it should be. Still unable to get 50e and anything past that (nor 30w, etc)

 

[deeptho]

There is an interesting test which I performed yesterday to check disalignment:
tune to a satellite in an inclinded orbit and observe how the snr goes up and down.

If properly aligned, the signal should peak at the time kingofsat.net reports that
the satellite has zero declination. If your dish is not properly aligned, wait until
the signal peaks, and then the sateliite's declination will tell you
if you are pointing above or below the arc and by how much. The accuracy will
be of the order of 0.4-0.7 degrees. I still need to refine this to draw conclusions on
my own dish (probably it pointed 0.4 degrees off at this position)

Of course, to know what to adjust on the dish, you would need a similar measurement on an eastern
sat....

I have found it helps a lot if you can set the rotor axis exactly right, because afterwards it becomes a lot easier to
adjust declination and azimuth

So: make your own inclinometer out of a large piece of cardboard, some thin thread and some
weight (e.g., a keychain). I have made one out of a 40cm board which shows 1, 2 ... 10 degrees from vertical. It is precise
up to less than 0.2 degree or so and much better than these electronic devixes which can be off by a degree even when
claiming 0.1 degree accuracy

The first step in the adjustment (starting from what you have now) is to rotate the dish to the exact south using the receiver
("goto 0", "reset" or add a fake satellite at zero degrees and move to that sat). Do NOT use a "close to south at". You really need
usals=0 exactly.

Then (and only then) check if the distance from the left edge of the dish to the rotor axis is exactly the same as from the right
edge to the rotor axis. Use the closest point on the rotor axis for these measurements. If the distances
are incorrect, rotate the dish around the rotor axis to make them correct. Afterwards tune to a satellite near
to south and now rotate the whole assembly around the pole to peak the signal. This is needed to compensate for the
first adjustment, which will have decreased the signal level.

Then, measure the angle on the rotor's axis with the cardboard inclinometer.
If needed adjust the elevation of the rotor to the correct value which can be computed using online calculators (modified usals angle).
This is the angle between the rotor and the vertical direction when measured between the rotor axis and the pole (so approx. in the north-south dirction. In my case this should be 3.3 degrees but it is 3 degrees. This level of accuracy is enough according to my calculations
(and I can track from 53 east until 45 west) but I would prefer to have it slightly better.

Also make sure the angle of the rotor axis to vertical is exactly 0 when measured in the east/west direction.
This will be the case when the pole is plumb and the rotor pole attachment has not been deformed by wrong tightening

When all of this is done, the rest is very easy: point to any sat using the receiver (by setting the correct usals
value for the satellite). Use a sat close to the south. Then adjust the dish declinationto peak the signal.
After this the arc should be tracked perfectly, but some minute adjustments of elevation can help. For this,
tune to a weak sat to the east or west. It can get you another 0.5 - 1dB.

This approach is less frustrating than the trial and error approach. The procedure outlined by captain Jack
will not be needed, but it is a valid procedure.

And of course: SNRs change from transponder to transponder, so one value per sat will not tell you much...

The trick with the inclined satellite can help you to determine the maximum possible snr or signal levels.
Just observe the signal over a period of an hour or two around maximum, using the receiver to move slightly east or west
to peak the signal from time to time. Once you know the maximum value, then compare it to the value when the satellite
reaches zero declination. If the difference is very small then your dish is properly tuned....
THis assumes that the weather has not changed in the mean time...


PS. Be careful. satellite receivers sometimes decide to move the rotor and instead of the rotor pointing south it then
may point somewhere else.

 

[deeptho]

The picture shows the degree marks. The red line is the 3.4 mark, which is what I need for my dish + rotor

 

[Mickha]

Check William-1's strongest transponder list, and see which satellites you can get:

Just Sharing This - Strongest transponders

The Strongest transponders for January 4th 2021 All active Ku band satellites from 50° east to 45° west This list was compiled by William-1 $ = encrypted TM5402HD M3 +100cm Dish+Inverto Black Ultra Lnb-Signal Quality in dB Turksat 4B @ 50° east 11196 V 2222 TürkSat Tanitim==14.7 AzerSpace-1 @...

www.satellites.co.uk

can you nudge your dish any further West, to get 30W?

 

[a33]

Have a quick look at this. Take note on what action on the dish improves the signal at the extremes. Certainly declination and elevation are prime candidates but also azimuth.. or a combination of all.

It's for Stab but the same applies to polar mount alignments as well.

View attachment 140260

Well, if you take a quick look, maybe all is fine.
If you take a better look, do you still think 7.2 and 7.3 are right?

My analysis is here, in english, for instance: OTHER - Help Peaking a 1.2m on HH-120
If your actual highest point is now west of south (7.2), why in heaven's name would you rotate that highest point even more to the west?

So the STAB manual is a piece of reference that many refer to, without warning.
A good example of misinformation spreading easily via the internet, alas, I think.

Greetz,
A33

 

[moonbase]

@Chr0nik

When you previously removed the polar mount from the pole did you make a note of what satellite it was aimed at just before removal?
If the polar mount was previously tracking the arc OK then it suggests the declination and elevation angles were set correctly.

Unless you have changed these angles, placing the mount back on the pole and manually rotating the entire polar mount assembly on the pole to receive the last satellite used before dismantling should restore the arc you had before.

The main point to be respected is that when the polar mount is centred and aiming highest it should be aiming very close to the zenith satellite for your location.
For example, I am about 0.2 degrees West of the Grenwich Meridian. I use Thor 7 at 0.67 West as the zenith referential satellite and rotate the polar mount on the pole to that.

If it comes to resetting your angles, they are easily obtained from online calculators using your latitude and longitude as input parameters.

 

[Manikm909]

you say the surface is uneven, do you mean the top of the pole? doesnt the polar mount slide down and sit right on top of that "uneven surface" ? if so, that could be your issue.
is there a place you could put a small spirit level somewhere horizontal on the polar mount and maybe also against the polar mount 3 bolt sleeving to see if its dead vertical

 

[moonbase]

you say the surface is uneven, do you mean the top of the pole? doesnt the polar mount slide down and sit right on top of that "uneven surface" ? if so, that could be your issue.
is there a place you could put a small spirit level somewhere horizontal on the polar mount and maybe also against the polar mount 3 bolt sleeving to see if its dead vertical

I think a couple of pics of the mount and details of the OP's approximate latitude and longitude might help?

 

[Manikm909]

i wonder if hes out in the rain trying to sort it?

 

[Channel Hopper]

Neighbours haven't built an extension or put their washing out ?

 

[Lazarus]

I think a couple of pics of the mount and details of the OP's approximate latitude and longitude might help?

Gray's, Essex approx. 51.48N 0.32E

 

[Chr0nik]

Thanks for the replies! I haven't been able to look into this yet but I plan to do so tomorrow.

I will post pics later today

 

[Chr0nik]

I'm now able to get to 50e and 52e but the latter is very low - around 5.6db (still very low compared to being able to get it in the past around 15db).

Tried 30w but no luck.

 

[Manikm909]

i reckon your not 100% level mate...

 

[Mickha]

30 West can be received on a very small dish, in the UK, if you can get 27.5W you should be able to get 30W, unless it's being obstructed, by a tree, or building, or other.
If using a 36v motor, and V-Box II, look at the reading, when on 24.5W, then the reading when the dish is sent to 27.5W, and try to work out how far to send the dish, west, to get 30W.

 

[Channel Hopper]

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