pondering motor upgrade

[hairybadger]

Hi,

I have a Moteck SG-2100 driving a Gibi XP 1m. I'm not convinced it performs particularly well at the extremities of its range; as described in other threads I'm pretty sure that everything is vertical and set correctly and yet I still can't everything that I should be able to. I'm considering replacing the motor with a better model, but I'm not sure if I should jump to an actuator or not. I'm aware that the dish is small and light enough to be driven by a DiSEqC motor. Questions:-

* would there be any advantage in going for an actuator setup?
* what would I need? Polar mount, actuator and positioner?
* if I stay with a DiSEqC motor, any recommendations? Noise isn't an issue - the dish is on a pole at the end of the garden and the cows that are in the adjacent field aren't likely to complain.

thanks again!

 

[Captain Jack]

I hate actuators. They are not linear and introduce a fair amount of play when extended at the end of the arc.

I would stick with a DiSEqC motor for simplicity - a TM-2600 motor should suffice your needs.

However, when I get the opportunity, I'll be putting a 1m Channel Master dish on a 36V H-to-H motor, like this one, which is also an option for you. You'll need a VBox type positioner so you can drive it directly from your receiver.

 

[sonnetpete]

I've got a Clarke Tech motor driving my Laminas 1.2M. It was used with the Gibi 1M prior to that. It's not missed a beat up to now and even in the strongest storms, it's the dish assembly which has moved on the mast, not the motor. However, it looks from this like it's undergone a name change....

http://www.hm-sat-shop.de/en/motoren-positionierer/powertech-dg-380-high-end-diseqc-motor.html

 

[satelliteman]

The 2600 motor will be fine. In saying that, I did fit an 18 inch actuator on my own Gib 1.04m and it was spot on. Mainly because it was exposed high on a TK arrangement and didn't want to keep setting it up after high winds.

 

[hairybadger]

Thanks for the suggestions. I guess I'll be avoiding actuators since performance at the extremities is what I'm after. If I can find a 36V motor I'll be going down that route, but I'm a bit confused as to what cabling I'd need. Some 36V motors say they are driven off ordinary coax, and others require 5 separate wires (two of which need to support 6A - will probably use 1.5mm^2 cable for that, have plenty of it lying around). Fortunately I put spare conduits in the ground when I dug the trench to run the coax!

 

[Captain Jack]

You'll need a separate 4 core cable (I use an 8 core alarm cable with pairs twisted together) for the motor. One pair for 36v motor and the other for the reed sensor/pulse counter. This will connect to a Vbox positioner, which will in turn connect to receiver via coax.

 

[Huevos]

I've got a Clarke Tech motor [...] However, it looks from this like it's undergone a name change....

Variants of that motor are sold under all different names. Alsat, Clarke-Tech, etc. Nice motor, but some British installers don't like them because the cable comes out inside the bracket, but down here that doesn't matter because elevation is a bit higher. In my opinion better than the 2600 because the cable is well away from the moving parts.

On USALS-v-actuator I'd always pick USALS, and that is from the perspective of a person that has both. My actuator setup nails the satellites every time but setting up is a lot of work. I've got 63 positions set up on that dish and the only practical way is to have a spreadsheet to keep track. To find and store all those satellites takes days. Best thing about the actuator is you can tell when the dish is moving because the counter on the V-box is spinning.

USALS on the other hand is a luxury because one the dish is aligned there is no more work to do. It's just a pity they don't make something like that for bigger dishes. And unlike an actuator it is a lot easier to get from horizon to horizon.

 

[hairybadger]

On USALS-v-actuator I'd always pick USALS, and that is from the perspective of a person that has both. My actuator setup nails the satellites every time but setting up is a lot of work. I've got 63 positions set up on that dish and the only practical way is to have a spreadsheet to keep track. To find and store all those satellites takes days. Best thing about the actuator is you can tell when the dish is moving because the counter on the V-box is spinning.
USALS on the other hand is a luxury because one the dish is aligned there is no more work to do. It's just a pity they don't make something like that for bigger dishes. And unlike an actuator it is a lot easier to get from horizon to horizon.

Thanks for your reply Huevos - I have a question. You have 63 sats dialled in - your profile says 57E to 58W, so 115° - and you say that the actuator "nails the satellites every time", but then you go on to say that it's easier to get from horizon to horizon with USALS.

Could you explain what you mean, please? How is it easier with USALS if the actuator does the job as well? Do you just mean setting it up is easier?

Captain Jack says

I hate actuators. They are not linear and introduce a fair amount of play when extended at the end of the arc.

So for Huevos the actuator is fine across the range, although H-H is easier with USALS (unless I've misunderstood), but for Captain Jack an actuator is flakey at the edges.

I'm not fussed about the work taken to set it up - I just want something that works wherever I point it!

 

[Huevos]

1) DiSEqC motor is just a form of polar mount where the mount, bearings and motor are all contained in a neat package.

2) DiSEqC motor and actuator can both be set up as DiSEqC 1.2 (i.e. find positions and save) but only a DiSEqC motor can be set up as USALS. USALS means you enter your coordinates and the motor does the maths and automatically points the dish in the right direction without having to do the find/save procedure for each satellite.

3) Horizon-to-horizon means 75º in either direction.

4) A DiSEqC or H2H motor scans across the arc at a constant speed. An actuator doesn't. That means at 50E you might have 10 counts per degree while at 50W you might only have 3 counts per degree. This makes setting up harder work because it is more difficult to predict where each satellite is during the set up procedure.

5) IIRC, CJ's setup doesn't nail the satellites every time. I had the same trouble when I was using the Gibertini dish. Always had to fiddle with the V-box remote to get signal lock on weak channels. This situation is worse as the actuator is near full extension as less counts move the dish faster and faster, and the dish starts to feel 'loose' along the direction of the arc, i.e. it has lash.

 

[BlindFaith]

4) A DiSEqC or H2H motor scans across the arc at a constant speed. An actuator doesn't. That means at 50E you might have 10 counts per degree while at 50W you might only have 3 counts per degree. This makes setting up harder work because it is more difficult to predict where each satellite is during the set up procedure.

..or vice versa depending on whether the actuator's eye is fixed at the left or on the right side of the mount ;)

 

[hairybadger]

5) IIRC, CJ's setup doesn't nail the satellites every time. I had the same trouble when I was using the Gibertini dish. Always had to fiddle with the V-box remote to get signal lock on weak channels. This situation is worse as the actuator is near full extension as less counts move the dish faster and faster, and the dish starts to feel 'loose' along the direction of the arc, i.e. it has lash.

Thanks again for your answers - I already have USALS up and running, just with a motor I don't like OK - as far as the looseness problem goes, could that be obviated with a larger jack so that in effect I'm using less of its movement range? Hmm - would this lose me accuracy *across* the range? Am having trouble getting my head around the practicalities of using an actuator since I have no experience of them.

 

[Huevos]

as far as the looseness problem goes, could that be obviated with a larger jack so that in effect I'm using less of its movement range?

No. The looseness problem occurs when side 'A' of the triangle (actuator) approaches the combined length of sides 'B' and 'C' of the triangle. The 3 points of the triangle are the polar axis and the 2 spherical joints of the actuator. Having a longer actuator does not change the fact that the longest side of a triangle must always be shorter than the combined lengths of the 2 other sides.

 

[hairybadger]

Thanks for all your advice guys - have ordered the DG-380. Was tempted by the actuator route for the technical challenge as much as anything else but finally can't really be bothered with it (for now!).