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Difference between H-H and polar mount

kamaleon

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#1
Hi folks...

Say, please, what is the *main* difference between a horizon-to-horizon mount and a polar mount? Is there one? or is this just a way of referring to the different kind of motors? I mean, a declination is a declination, a polar axis is a polar axis, innit? can they be different in one or another way?

Sorry if this is a dumb question, but i don't seem to find any "idiot's guide to the differences between H-H and polar mounts" :D

;)
 

Topper

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#2
A polar mount is engineered to describe the Clarke curve in the sky and will do so once set up correctly with or without a motor. In other words (once set up) you could have a pulley system to move from one sat to another, you can swing it by hand and it will still track the arc. An H to H mount is a lot lighter and works in a completely different way
Below is my Polar mount
 

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kamaleon

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#3
Topper said:
An H to H mount is a lot lighter and works in a completely different way...
Ah!!! Just when you got me started, then you left me hangin...
:D please, by all means, do further explain, if you may :D
which completely different way is that? ;)
 

johnsattuk

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#5
I have myself pondered on the differences between 'Polar' & 'HH', and could essentialy see none.

To track the Clarke belt you need to,

(1) rotate the dish about an inclined axis
(2) give the right amount of declination to the dish
(3) point it south at the top of the arc

Topper said:
A polar mount is engineered to describe the Clarke curve in the sky and will do so once set up correctly with or without a motor. In other words (once set up) you could have a pulley system to move from one sat to another, you can swing it by hand and it will still track the arc. An H to H mount is a lot lighter and works in a completely different way
Below is my Polar mount
Topper's wonderfully simple setup has an inclined axis, a way of adjusting the declination, and a means of moving it. Just like any HH mount. The differences being in the different engineering design features to get to the same end result.

I don't find my Yaeger 1224 HH mount particularly light when I am up the ladder :D

On further reflection, I would suggest that any tracking mount, that is aligned to the 'polar axis', ie: north/south, is by definition a 'Polar Mount'
 

kamaleon

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#6
Spot on Old geezer, exactly what me thought too...
A polar axis is a polar axis, whether it be "driven" by a diseqc motor or an attenuator... am I wrong?
I still wonder what Topper ment by "a completely different way"... ?
On this link:
_http://www.satsig.net/polar-mount-4.htm
they clearly refer to the moteck sg2100 as a polar mount :confused
 

Lancelot

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#7
An attenuator really IS something different. :D
You mean a jack I think.

L.:)
 

johnsattuk

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#8
Or even an 'Actuator' :)
 

Topper

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#9
kamaleon said:
I still wonder what Topper ment by "a completely different way"... ?
If you analyse the forces involved when the wind blows the dish the 'feedback' to the motor has a completely different path making the actuator method of moving the dish far stronger than the alternative H - H motor. That is what I meant, if you remove the motor on an H- H mount the dish falls on the floor and cannot track the arc if you disconnect the motor on my polar mount it can still track the arc whether by hand or strings. It is a totally mechanical tracking device driven by an electric motor or other. The H - H mount does not do anything without a motor hence my statement completely different.
 

johnsattuk

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#10
Topper said:
If you analyse the forces involved when the wind blows the dish the 'feedback' to the motor has a completely different path making the actuator method of moving the dish far stronger than the alternative H - H motor. That is what I meant, if you remove the motor on an H- H mount the dish falls on the floor and cannot track the arc if you disconnect the motor on my polar mount it can still track the arc whether by hand or strings. It is a totally mechanical tracking device driven by an electric motor or other. The H - H mount does not do anything without a motor hence my statement completely different.
Wind is probably the greatest force on the dish, and is often the cause of the demise, but because of the inclined axis, the dish itself exerts a force on the drive system when off centre, and this needs to be added/subtracted to the total loading. Gregorian dishes with a second reflector outboard giving an even heavier loading.
The feedback to the driving system is torque, how you resist that torque is a matter of design.
A linear actuator driving a dish, through a lever, may well be stronger than a Motec 2100, which only has a smallish plastic gear to resist the torque.
I have however seen a faily substantial actuator coupled to a dish via a flimsy lever which would fail long before the actuator did.

A Yeager 1224 HH motor has a substantial steel gear and worm, for which you pay.
The linear actuator no doubt will give the strongest solution from a cost point of view.

I don't see them as being different, just different design concepts and solutions to give the same end result. :D
 

Topper

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#11
johnsattuk said:
I don't see them as being different, just different design concepts and solutions to give the same end result. :D
Yes exactly the end result being one snaps the teeth of the nylon crown wheel in strong winds, the other doesn't O-Ha O-Ha O-Ha
 

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#12
I think that the essential difference is that an H-H mount is directly driven off a gear and a polar mount has an actuator arm pushing the dish.

This difference is important in traditional motor drives where the H-H motor has a fixed number of pulses per degree moved and, because the actuator is pushing at a tangent, the number of pulses increases (or decreases - can't remember) as you move from maximum to minimum.

As Topper says, the biggest problem with H-H motors is broken gear teeth after high winds.
 

johnsattuk

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#13
_http://www.satsig.net/polar-mount-4.htm :confused
 

Channel Hopper

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#14
PaulR said:
I think that the essential difference is that an H-H mount is directly driven off a gear and a polar mount has an actuator arm pushing the dish.

This difference is important in traditional motor drives where the H-H motor has a fixed number of pulses per degree moved and, because the actuator is pushing at a tangent, the number of pulses increases (or decreases - can't remember) as you move from maximum to minimum.

As Topper says, the biggest problem with H-H motors is broken gear teeth after high winds.
Almost, the price of a decent polarmount system (including actuator drive)is usually far less than an Horizon to Horizon mount with similar accuracy.

H-H mounts do become far cheaper to manufacture when you are only dealing with 1m antennas, average weather, and dubious online guarantees. But they are almost unique in having the ability to move dishes using the LNB drive circuit and DiSEqC protocol.
 

johnsattuk

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#15
Channel Hopper said:
Almost, the price of a decent polarmount system (including actuator drive)is usually far less than an Horizon to Horizon mount with similar accuracy.

H-H mounts do become far cheaper to manufacture when you are only dealing with 1m antennas, average weather, and dubious online guarantees. But they are almost unique in having the ability to move dishes using the LNB drive circuit and DiSEqC protocol.
.

I'm sure cost is one of the biggest factors, if a manufacturer thought that enough people would pay a high enough price, we would have very robust Diseqc HH mounts. There are no technical or engineering difficulties.

There are also some Diseqc actuators appearing, best of both perhaps :D

Topper's mount with a Diseqc linear actuator, the ultimate :cool:
 

kamaleon

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#16
Jeezus, how many posts since me went to bed yesterday!:eek:
Yes, i actually ment a jack/actuator :-doh2

i'll read the rest of it now :)

edit: ok have read :D
Right on fellas,
So, basically, to sum up, technically speaking, a H-H mount tracks the Clarke belt using the same type of declinations/elevations than a polar mount, and a polar mount is a more full-on setup being able to cope with higher loads, heavier dishes and stronger winds;
I'm sorry if this sounds stupid, but the reason for my thread on the first place was that i didn't understand the difference between the way the 2 different mounts tracked the clarke belt, but i've now realised: it's exactly the same :D
Actually, thinkin of it, "polar mount" vs "horizon-to-horizon" seems like a quite daft designation, as both setups seem to be polar mounted (ie used the polar axis) and track one horizon to the other - or is the jack/actuator system more limited in ° scope?
 

kamaleon

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#17
johnsattuk said:
.There are also some Diseqc actuators appearing, best of both perhaps :D
Topper's mount with a Diseqc linear actuator, the ultimate :cool:
Are you talkin' about let's say a Vbox positioner?
 

Lancelot

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#18
I think what he's saying is that there are/wiil be, jacks/actuators that are diseqc controlled like the SG2100 et al. As opposed to the current crop which are 36V controlled and require a VBox to run them on most modern recievers.


L.:)
 

johnsattuk

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#19
Lancelot said:
I think what he's saying is that there are/wiil be, jacks/actuators that are diseqc controlled like the SG2100 et al. As opposed to the current crop which are 36V controlled and require a VBox to run them on most modern recievers.


L.:)
I do have a SuperJack DiseqC 1.2 actuator that I was going to play with, but went a different route. It works directly off the reciever, no V-Box required. :D

SuperJack DiSEqC 1.2 actuator, 12v motor 8inch stroke. DARL-1208+
 

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#20
kamaleon said:
or is the jack/actuator system more limited in ° scope?
Unless the actuator is matched perfectly to the polarmount, there will be a limitation on one (or both sides ) of true South.
One problem of standard polarmount designs on walls is that the actuator will stick out the back of the system, and may run into the wall if the bracketry is too small.

Many of the cheaper polarmount designs also restrict the distance of the actuator from the main point of rotation and then accuracy of tracking and positioning is affected, and leads to premature wear of all parts.

I would be very wary of any polarmount that can only use the mini jacks, though I do have one prototype in the garage somewhere that did look the business - will try to get some photos later.