Advice Needed DiSEqC motors - Just how much longitudinal angular position accuracy can you reasonably expect?

[jeallen01]

@CH

Having now reset the TM default sat list in USALS (thanks again - those instructions do appear to have worked) then USALS reliability seems to be quite a bit better - but I still can't distinguish between 52E, 52.5E & 53E in terms of the channels on each one. Will probably settle for the best compromise position for all of them @ 52.5E nominal.

Similarly, it can't distinguish between 30W and 31.5W and so a blind-scan on the latter throws up mainly channels on the former - but I can then find Cherifla on 31.5 if I delete all the channels found by that scan and then search on the specific frequency for that channel.

I'm guessing that I would probably never do any better unless the dish was a lot bigger (which can't/won't happen). because the lack of "selectivity" is due to that rather than the motor.

There also still seems to be some unpredictability when changing between channels, especially if they are on widely spaced sats - and I may still experiment with slightly off-setting my location longitude in the USALS set-up when I determine whether that should be E or W (currently, I'm thinking very slightly W).

Thanks again to everyone for all the help - and it's been quite an enlightening (not to say frustrating at times) exercise.

 

[a33]

I'm afraid I don't understand how to do "No 4 Execute the command: Shift "0" " on the TM because I can't see any obvious "shift" command button.
Any thoughts or suggestions?

In view of the effect in the procedure (memory erased to default, zero degrees newly set) this can only be a reset command.
Not all receivers have a command for that; in that case you'll have to find a reset button on the motor (but not al motors have that...).

Edited: Now been experimenting with switching between USALS & 1.2 - ATM it "seems" to work better in finding sats & channels on them by putting gestimates of the longitude in USALS until you get some channels on a sat, and then switch to 1.2 and fine-tune and save the longitude in that mode - finally managed to persuade the TM to then find 3.1E (it kept searching on 4.8E in USALS mode) by setting the longitude to 2.2E in USALS, and then switching to 1.2 to fine-tune and blind search .

I don't know why you would need gestimates?
With USALS you have to enter the correct site Latitude and Longitude (or modified Latitude, as I wrote earlier)

~OOOOPS! I see I wrote adjusted Longitude in my earlier post, it should be LATITUDE!
The correct text shoud be:
When you however have a setup with adjusted motor elevation (axis tilt) and adjusted declination, an adjustment for the USALS commands might be appropriate. That can be done in the USALS-input-data by setting an 'adjusted site LATITUDE', that is by adding the adjustment angle to the site LATITUDE.
The calculated Hour Angle doesn't change much by that, maximum about 0.07 degrees I believe I calculated once, but on the hard to get satellites, and when you can set Latitude with only 1 decimal precision, that just might do the job....

@Mods: Can you refer to this correction in my earlier post? I hate to be the cause of confusion!
Correction now made - Admin team

@jeallen01 , continued:
So enter the correct site Latitude and Longitude, and further you use the normal Longitude of the satellites (position on the Clarke Belt). Then USALS calculates all correct. No need to modify anything, when there is no specific problem.

When your receiver is using Goto-X instead of USALS (there is no possibility to enter your site lat and long then), you have to calculate satellite Hour Angles yourself I believe, and enter them in you receiver. But I'm not familiar with Goto-X menu structure...

Greetz,
A33

 

[jeallen01]

@a33

I don't know why you would need gestimates?

Just got home from the cinema (the latest Thor extravaganza!) and I will examine your post in detail tomorrow, but in respect of the bit I've included above, I gestimated the longitude of the actual 3.1E sat as 2.2E and then I could see the channels on it.

Of course that was before I reset the USALS table.

 

[jeallen01]

PS: FWIW, not posted in this thread recently because I had a major "meltdown" on the main laptop and have had to spend a lot of time resuscitating an old one to get online again - and so the sat system has had to take a very back seat for the foreseeable future.