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

[jeallen01]

That's the question because, having now installed the "new" TD110 on a new Superior Darkmotor (metal gears but it might well be a clone version ), I think I have got the alignment pretty much correct as it does cover the arc of 52.5E to 30W with reasonable results.

However, using the TM5403 M3, I can only set the angular position to 1 decimal place - and yesterday I found that I could not really distinguish between 52E (TurkmenAlem/MonacoSat) and 52.5 (Al Yah 1 /Yahsat 1A); in fact getting stronger channels on both sats at the same angular setting (= probably "somewhere" between 52 & 52.5)

OTOH, using the Free Sat V7 “Fag packet” on which you can set the longitude to 2 decimal places, I think (it was a few days ago) I could set up both sats at different positions.

I realise that the dish beam width (as related to its size) is a significant factor but this made me ponder on what "degree of discrimination" (as opposed to "degree of longitude") you can reasonable expect from a DiSEqC motor - and is this likely to be affected by the sat positions in question being right at the extreme ends of the arc available at the dish site (which I suspect it might be because the sat-dish path distances are somewhat longer there than when the sat is directly "overhead" of the dish)?

I suppose there is a subsidiary question as well: to what level of angular degree accuracy can you really expect to set the dish mount on the mounting pole (it seems to me that to get that down to even around 1 deg is very difficult and to get it any "closer" is verging on the "impossible" unless you have some means of making micro-adjustments)?

 

[Channel Hopper]

I have Dark-ish motors with clients (and a Technomate motor here) where the accuracy is well under half a degree, though I have seen the backlash on a couple of installs has been poor out of the box, requiring removal of the paper sticker and an allen key.

Certainly I would put the issue at the door of the Freesat V7 before the motor, a client who ordered one some months ago, real as opposed to any clone, could not get a useful result from the positioning menu, even after firmware upgrades.

 

[jeallen01]

I have Dark-ish motors with clients (and a Technomate motor here) where the accuracy is well under half a degree, though I have seen the backlash on a couple of installs has been poor out of the box, requiring removal of the paper sticker and an allen key.

Certainly I would put the issue at the door of the Freesat V7 before the motor, a client who ordered one some months ago, real as opposed to any clone, could not get a useful result from the positioning menu, even after firmware upgrades.

@CH:

Many thanks for the info - judging by the way that the Free Sat has been working, I tend to agree with your statement about the motor accuracy.

OTOH, I think you misunderstood my comments about the Free Sat itself because I have little trouble in making a 0.2 (and possibly even 0.1 or less) deg change in longitudinal angle with that Rx, and the change "sticks" because the dish does appear to move a very slight amount when asked to do so and the received signal strength on a particular channel can be seen to rise/fall in a fairly predictable manner - and the new position is then locked-in.

By comparison, I can't get the TM to do that because (1) you can only change the angle by 0.1 deg at best by changing the sat longitude setting; and (2) if I use the position E or W "nudging" controls, I can maximise a signal but the "new" angle cannot be saved and so when I hit the "Exit" button the position reverts to the previously set value. Tried that approach quite a few times last night and get the same "undesirable" result:mad:.

NB: I know that the dish can be successfully "nudged" by a TM because (now having two of them - 1 indoors and 1 currently down in the garage near the dish) when doing that whilst standing near the dish I can see it move very slightly when I use the "nudge" commands . Maybe this a difference between two ostensibly identical RXs?

Therefore, if anything, the Free Sat is better than the TM for angular position adjustment, and also has a more sensitive tuner based on what I found earlier this year.

 

[Channel Hopper]

Not having had a TM receiver here for a number of years I can't comment, but I vaguely recall that on the 1500 receiver I could change the 'fine' East/West setting from on/off movement to single, dual or 3 pulse, which would nudge the dish left and right extremely well.

It might be that you are in USALs mode, whch has a different protocol to the older DiSEqC 1.2 adjustments, and is reliant primarily on the longitude/latitude settings which are entered into the motor tree above the satellite slots and the manual positioning by the user.

 

[Channel Hopper]

By comparison, I can't get the TM to do that because (1) you can only change the angle by 0.1 deg at best by changing the sat longitude setting; and (2) if I use the position E or W "nudging" controls, I can maximise a signal but the "new" angle cannot be saved and so when I hit the "Exit" button the position reverts to the previously set value. Tried that approach quite a few times last night and get the same "undesirable" result:mad:.

NB: I know that the dish can be successfully "nudged" by a TM because (now having two of them - 1 indoors and 1 currently down in the garage near the dish) when doing that whilst standing near the dish I can see it move very slightly when I use the "nudge" commands . Maybe this a difference between two ostensibly identical RXs?

Ah, dejavu.

If you are using a second (and different ) receiver with different protocol, you may have to reset the motor zero position. It is not absolutely clear if this can be done by using the remote control alone.

Instructions

HARDWARE RESET BY RECEIVER
1. Execute the command: Go To Reference (Go To “0”).
2. Cut off the power by disconnecting the coaxial cable.
3. Reconnect the coaxial cable.
4. Execute the command: Shift “0”.
5. Then, its memory erased, the receiver rewrites the satellite table to initial one and corrects the “0”

HARDWARE RESET BY DiSEqC MOTOR
1. Cut off the power by disconnecting the coaxial cable.
2. Press and hold both EAST / WEST buttons for 5 seconds.
3. Reconnect the coaxial cable.
4. LED1 and LED2 blink for 5 seconds.
5. Then, its memory erased, the receiver rewrites the satellite table to initial one and corrects the “0”

BUILT-IN SATELLITE TABLE RESET
1. Press and hold both EAST / WEST buttons for 5 seconds.
2. LED1 and LED2 blink for 5 seconds.
3. Then, its memory erased and rewrites the built-in Satellite table to initial one.

 

[jeallen01]

Not having had a TM receiver here for a number of years I can't comment, but I vaguely recall that on the 1500 receiver I could change the 'fine' East/West setting from on/off movement to single, dual or 3 pulse, which would nudge the dish left and right extremely well.

It might be that you are in USALs mode, whch has a different protocol to the older DiSEqC 1.2 adjustments, and is reliant primarily on the longitude/latitude settings which are entered into the motor tree above the satellite slots and the manual positioning by the user.

@CH

Thanks again, and Yes the TM is in USALS mode - but I will try it in DiSEqC 1.2 mode this evening and see if that makes a difference to whether the position found using the nudge function can be stored.

Could I ask again about the subsidiary question that I asked in the last paragraph of my first post, i.e. "... to what level of angular degree accuracy can you really expect to set the dish mount on the mounting pole (it seems to me that to get that down to even around 1 deg is very difficult and to get it any "closer" is verging on the "impossible" unless you have some means of making micro-adjustments)?
So, what do you think is a "reasonable" accuracy to look for in the angle when I set up the "reference satellite" which is Thor @ 0.8W whereas our house is at 0.41W, and any tips/ideas on how to best align dish & mount (which probably weigh a total of around 20kg when mounted on the mast) because it is very difficult to turn the whole lot by minute amounts by hand (although I think I haven't done too bad a job so far)?

 

[Channel Hopper]

According to Powertech specification for the DG240

Smart Software Achieves very High Positioning Resolution of 0.1 Degree

I would assume therefore that the pulsecount within the motor is beyond ten pulses per degree, which would be within reason. You would have to try running a receiver in DiSEqC 1.2 mode to check though.

 

[jeallen01]

Ah, dejavu.

If you are using a second (and different ) receiver with different protocol, you may have to reset the motor zero position. It is not absolutely clear if this can be done by using the remote control alone.

Instructions .......

Thanks also for those instructions - I'll study them carefully!

BTW: I didn't seem to have any trouble switching between the Free Sat and the TM - but, after a time (several evenings ago) and a lot of dish movement over several hours the motor appeared to move erratically and then stopped responding at all. Just left it all overnight and then it seemed to work OK until, on Wednesday evening, it stopped moving beyond 19E, but all the supplier then told me to do was to, with the power ON to the motor, press and hold the E&W buttons on the motor for 20s. I did that and then the dish did/now does move all the way to 52/53E - that sounds similar to your last set of instructions "BUILT-IN SATELLITE TABLE RESET"

 

[a33]

OTOH, using the Free Sat V7 “Fag packet” on which you can set the longitude to 2 decimal places, I think (it was a few days ago) I could set up both sats at different positions.

Diseqc-USALS-protocol translates that into an accuracy of 1/16 of a degree, I believe. So with the ability of setting two decimals, you are a bit better off.

When you have greatest difficulties at the ends of the arc when using USALS commands, another thought comes to my mind.
USALS algoritm usually calculates Motor Hour Angle, assuming mount axis being parallel to polar axis, I've read.
Never seen that confirmed by comparing the sent diseqc commands, though. (I don't have a diseqc reader, alas. I'd be interested to know...)

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....

Of the motor precision itself, I don't know much, I'm afraid.

Greetz,
A33

Added/edited:

So, what do you think is a "reasonable" accuracy to look for in the angle when I set up the "reference satellite" which is Thor @ 0.8W whereas our house is at 0.41W, and any tips/ideas on how to best align dish & mount

When, after perfect aligning of motor and dish at perfect goto-0 position, you give USALS command goto 0.8W, it will be 100% accurate. That is the beauty of USALS: You don't need a due south satellite....

ADMIN NOTE
Paragraph with incorrect information has been corrected as requested.

 

[jeallen01]

@a33

Many thanks for all that info:

...
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 longitude', that is by adding the adjustment angle to the site longitude.
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 longitude with only 1 decimal precision, that just might do the job....

On a previous occasion some months ago I did actually do something like that (without realising what I had effectively done ref the USALS input data) - can't remember exactly what happened, but I think I concluded at the time that it would be better to do a bit more alignment of the dish mount on the mast and then reverted back to the nominally correct long & lat settings in the receiver.

That said, that was when I was using the smaller TD88, and I think things become more critical with the TD110 due to the narrower beam width - however, I will experiment with such changes over the next day or so and see what happens (got to go shopping now ). That might help deal with any slight misalignment of the mount on the mast.

 

[Channel Hopper]

At positions closer to the ends of the arc, one degree of movement at the motor will translate to increasing fractions of a degree when looking at the satellite observation angles. If the degree per pulse count is around 16 though you should still have the ability to get a minimum of 0.1 degree accuracy wherever the dish is pointing.

 

[Channel Hopper]

I've just seen your moniker

Several receivers and a few dishes - the steerable Triax TD88 got about 53E to 31.5W, but the "new" TD110 seems to be having problems at the extreme ends of the same arc, even though it seems to be tracking pretty well inside that arc???


and you might be suffering from low elevation droop (ooer) with the larger reflector, which will be further compromised with a Quad/Octo LNB hanging off the end (double ooer) . Does the 110 dessign still have that hinged bracket for the boom arm ?

 

[jeallen01]

At positions closer to the ends of the arc, one degree of movement at the motor will translate to increasing fractions of a degree when looking at the satellite observation angles. If the degree per pulse count is around 16 though you should still have the ability to get a minimum of 0.1 degree accuracy wherever the dish is pointing.

@CH +A33
Thanks again guys - That's what I am now thinking/hoping and it looks like the TM will probably need that sort of adjustment rather more than the Free Sat.

This is all very enlightening and I am sure that I will learn a lot from sorting it out - as I hope will any others who may be experiencing similar issues.

 

[Trust]

I worked around with a lot of diseqc rotors , almost all of them calculating with ± 38 pulses /º rotation .
At the bench in the loft I use a Maxplus 2100 receiver to test them .
Right this moment I'm testing with a Hengstler electronic counter connected to the pulser (HS connection on the SG2100 circuitboard )
All tests are done at a Vert. TP , the counter could not hold up at Hor. TP
With a short command MOVE in the 1.2 diseqc menu there is a counting of ± 60 pulses , the same happens in USALS mode , thats about 1.6º movement .
CORRECTION with both receivers ± 52 pulses with Usals ( ± 1.4º movement)
Connected to a CT5000+ , action with USALS is equal , but with diseqc 1.2 there is the option to choose STEP 1 to 5 .
With Step 1 , movement of 6 pulses ( 0.16º movement ) Step 2 , 11 pulses but with 3 , 4 and 5 every time 12 pulses .
Changing the sat position number in USALS with 0.1º and then press GO TO , does not work , movement starts only wenn changing with 0.2º.
But first change with 0.3 and push GO TO and than 0.2 back , will bring you fine movement of 0.16º .

 

[jeallen01]

I've just seen your moniker
Several receivers and a few dishes - the steerable Triax TD88 got about 53E to 31.5W, but the "new" TD110 seems to be having problems at the extreme ends of the same arc, even though it seems to be tracking pretty well inside that arc???

and you might be suffering from low elevation droop (ooer) with the larger reflector, which will be further compromised with a Quad/Octo LNB hanging off the end (double ooer) . Does the 110 dessign still have that hinged bracket for the boom arm ?

I've "only" got an Inverto Black Twin on the boom arm (same LNB as was on the TD88) and it's not very heavy so I don't think that would contribute to drooping

Also the arm:

- Doesn't have the hinge as on the TD88 because the arm slides through a rectangular tube attached to the dish and is held in place by 2 bolts - one goes through it laterally to control the position that the arm is in the tube, and the other one (with a wing nut in this case) vertically upwards into a fixed nut on top of the tube. If you take the latter out you can swing the arm slightly upwards, and I did that as part of the setup to see if that made a difference to signal level/quality. If so, then I adjusted the dish elevation so that the improved signals were present when the wing nutted bolt was fitted and tightened (as it normally should be);

- Is fitted now with metal braces from either edge of the dish to a position just short of the LNB holder to make sure the arm does not droop/sway in the wind. These, of course, were not connected until I completed the adjustments as above.

PS: got to go shopping now and so I will reply to the further comments - including that from Trust1 - in a couple of hours or so.

 

[jeallen01]

@Trust1
Many thanks, and so there is a notable difference in which the ways in which USALS & DiSEqC 1.2 work in this particular context, as you described above - will aim to try that out on the TM.

And a general thanks to all who have been providing information - as I said earlier, this thread is becoming more and more informative and interesting .

Cheers

John

 

[jeallen01]

@CH

Sorry to bother you again, but the dish motor is not responding again this morning (it seemed to be working OK when I switched the system off yesterday afternoon).

Therefore I have been trying some of the Instructions, and specifically the one below (before I go down the garden to the dish) - and 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?

Ah, dejavu.
If you are using a second (and different ) receiver with different protocol, you may have to reset the motor zero position. It is not absolutely clear if this can be done by using the remote control alone.

Instructions

HARDWARE RESET BY RECEIVER
1. Execute the command: Go To Reference (Go To “0”).
2. Cut off the power by disconnecting the coaxial cable.
3. Reconnect the coaxial cable.
4. Execute the command: Shift “0”.
5. Then, its memory erased, the receiver rewrites the satellite table to initial one and corrects the “0”
.....

I suspect that this motor will be going back anytime soon

 

[Channel Hopper]

I believe that is a command to 'go to -X' or go to reference/zero. I think the original manual was written inTaiwanese.

Where did you get the motor from ?

 

[jeallen01]

@CH

Many thanks again.

I believe that is a command to 'go to -X' or go to reference/zero. I think the original manual was written in Taiwanese.

Sounds about the most credible interpretation

Where did you get the motor from ?

VU+Plus UK in North London (Colindeep Lane)

Also, I did another reset with the power on via the E/W buttons on the motor (it's a bit difficult to remove the cable from the motor right now (and a long way down the garden from the house!) and it now seems, after a few false starts, to be working reasonably predictably again.

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 .

Looks to me like I do need to do what you explained above and reset the TM default Sat list in USALS - though probably not today (cinema tonight if all is well with my wife).

 

[Channel Hopper]

Rather than disconnect cables, you can turn the LNB voltage off /0n via the remote, you might even get it to work down the length of the garden