Just Sharing This Something to make dish skew possible on zone 2 dishes

RustySpoons

RustySpoons

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Absolutely correct, and to be expected.


With a motorised dish it may be down to the resolution of the motor moving the dish across an arc and the accuracy of the polarity skew and declination.

For example, a v-box powering a Jaeger 1224 H-H motor generally gives just under 12 pulse counts per degree with a resolution of 1/12th of a degree per click. If a fixed dish has some type of threaded rod for adjustment of azimuth it is easily possible to get a more accurate resolution down to 1/20th of a degree depending of the TPI of the threaded rod and its securing points on a mount.

The same logic applies to azimuth and polarity skew. A fine manual adjustment mechanism should generally provide more accuracy than that automatically allocated by a dish traversing an arc powered by a motor.

I am not familiar with the resolution available using DiSEqC motors so cannot comment on their accuracy.

Does such accurate dish pointing matter, possibly not? It might only come into play when signals being received are extreme fringe and the extra accuracy might get an increase of a few tenths of a dB and achieve a lock.

Where the motorised dish comes into it's own after initial setup is the convenience, all done with a remote control or the press of a button on a receiver/controller. No messing about in the dark and rain with a spanner and a meter.
However a motorised dish can often give a better signal over most fixed dishes, provided the fixed dish has the LNB skewed, whereas the motorised dish will always skew the dish. But all things being equal a fixed dish will be better to dial in the very last drop of signal provided you can skew it.
And with motorised dishes due to resolution and calculation errors (If using USALS) some satellites might be more fine tuned than others.
I have both a HH-100 with a 1m on it and a 1.2m CM with a PM and Superjack, the HH-100 is more accurate and hits the same place from both directions, the CM1.2 PM will vary in signal slightly depending on what direction its travelled to the dish, so I set the V-Box somewhere in the middle so its roughly the same signal from both directions, although that is not wringing the last bit of signal out. I can get it very slightly higher but its so minor and lowers the signal when it approaches from the opposite direction. However I am thinking of trying different magnetic wheels with more poles on the reed sensor to see if it increases usable resolution.
 
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moonbase

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...However I am thinking of trying different magnetic wheels with more poles on the reed sensor to see if it increases usable resolution.
I think that some forum members have looked into using magnetic wheels with more poles, there should be a topic on it somewhere. I think there may also have been a forum discussion on changing the gearing of an actuator as an alternative to increasing the magnetic poles on the wheel?
 
jeallen01

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TBH, I think the thread is drifting rather too far from my original "objective" (which was a relatively simple/quick/cheap method of adjusting the skew on a Zone 2 dish!). Therefore, maybe, the above discussions should be moved to a more appropriate one, or else a new thread should be created!
 
scopus

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I really can't see the point of even trying to make a skew adjustment for a zone 2 dish. There are cheap enough solid 80-100cm dishes where it would be much easier to do....
 
jeallen01

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I really can't see the point of even trying to make a skew adjustment for a zone 2 dish. There are cheap enough solid 80-100cm dishes where it would be much easier to do....
I can see your point, except that the original concept was, as I said above, "a relatively simple/quick/cheap method of adjusting the skew on a Zone 2 dish!" - could be zero cost if you have a spare Z2 dish laying around, or fitted but not "doing as well as it could" due inadequate skew, and can lay your hands on a suitable piece of tubing.

Don't forget that the original prompt for this thread was the latter issue that had been raised by someone with pretty much that problem, and a suggestion from someone else as what to do to improve the situation but not how to do it. And then there is the situation where someone simply might not have space for a larger dish and/or the time/skills/"muscles" to fit one.
 
Channel Hopper

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The Prodelin 195X series of antennas I used to sell had the dish skew alignment on the rear, though they were very expensive for what they were.


Police surveillance/crowd control vehicles in this country would have something similar sitting on the roof.

The Surfbeam / Tooway system comes with a substantial metal Ka compatible reflector and modify the front end. A few on eBay


or

 
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moonbase

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The Prodelin 195X series of antennas I used to sell had the dish skew alignment on the rear, though they were very expensive for what they were.
...
Interesting, thank you for the links.

I think that a forum member possibly "scopus" uploaded a link to a training course covering satellite signal reception. If I remember correctly they used a similar type of dish where the dish itself could rotate around the feed assembly for fine adjustment of the polarity skew. I think the demo was done using a smallish prime focus dish?

Apexsat also offer triple axis adjustable mounts wih polarity skew adjustment.

 
jeallen01

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@Channel Hopper
Nice but somewhat expensive (and not around here) - can't quite see how the skew adjustment is done on the Tooway dish, but does it involve some form of lockable bolts through circumferential slots in the metal "bracket" immediately behind the dish face?

@moonbase
Nice but VERY big and expensive - a "little out of context" if I may say :D
 
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RustySpoons

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@jeallen01
This is how the dish skew works on my Maxview Zone 2 Clone.

126080
 
jeallen01

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Interesting! Could doable on some other dishes with some relatively simple extra metalwork and brackets.

Any idea of the radius of that slot?
 
RustySpoons

RustySpoons

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Interesting! Could doable on some other dishes with some relatively simple extra metalwork and brackets.

Any idea of the radius of that slot?
I'll get the dish out soon and check that for you and get some better photos.
 
jeallen01

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Thanks - some other people might be interested in that info as well.
 
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moonbase

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...Nice but VERY big and expensive - a "little out of context" if I may say...

The scale may be out of context but the logic of triple axis adjustment applies to smaller dishes.
 
Adam792

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Very interesting!

I may be in a position soon where I'll need to use a zone 2 for 30W (because it will have to be on the front of the house), and I'll need the signal to be as strong as possible for some of the weaker TDT Sat transponders.
 
jeallen01

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Very interesting!

I may be in a position soon where I'll need to use a zone 2 for 30W (because it will have to be on the front of the house), and I'll need the signal to be as strong as possible for some of the weaker TDT Sat transponders.
You'll get the stronger transponders quite easily with the dish in the normal orientation and the LNB slightly skewed to the "left" (edited: as viewed from behind the LNB !) but the weaker Catalan (possibly others as well) transponders will be a challenge. I couldn't get a "whiff" of those with my Z2 and standard Sky quad LNB several weeks ago, whereas they came in clear and strong on the 1.25m Giby.

Edited later on: Maybe something in this thread (like the curved tubing mentioned in my first post!) might help! :D
 
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jeallen01

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The scale may be out of context but the logic of triple axis adjustment applies to smaller dishes.
Quite so in most respects - except for the likely complexity & cost!
 
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moonbase

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... I am thinking of trying different magnetic wheels with more poles on the reed sensor to see if it increases usable resolution.

If using an actuator for motorised elevation the other option would be to source one with an optical switch instead of a reed switch. The optical switch versions have greater resolution for fine tuning but are generally a short stroke length. They are OK for azimuth motorisation on a narrow range arc.

"CH" sold a SuperJack version of one last year with the caveat that it might have a reed switch in it.


The optical switch uses a 5V source, if the actuator cable has 5 cores it probably indicates an optical switch. The LINAK optical actuators I have for sale are with 5 core cable and optical switch. Some of the older v-boxes came with the additional 5V connector for powering optical actuators.
 
Adam792

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You'll get the stronger transponders quite easily with the dish in the normal orientation and the LNB slightly skewed to the "left" (edited: as viewed from behind the LNB !) but the weaker Catalan (possibly others as well) transponders will be a challenge. I couldn't get a "whiff" of those with my Z2 and standard Sky quad LNB several weeks ago, whereas they came in clear and strong on the 1.25m Giby.

Edited later on: Maybe something in this thread (like the curved tubing mentioned in my first post!) might help! :D
I remember using a zone 2 for them briefly a few years back (without any correction for the skew), but I lived in the South West then where the 30W signal is just that little bit stronger. I definitely remember the signal on the Catalan channel (TV3) being OK, and the national commercial ones (12548V) which are two of the weaker ones here in the West Midlands even on an 80cm dish. 11653H and 11677H are the most marginal, so I'd expect to maybe struggle to get those (I never got them at all on the zone 2 or a 60cm regular dish), but they're duplicates of other available services anyway, just with some regional variations for the Canary Islands and Basque Country/Galicia.
 
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a33

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... the original concept was, as I said above, "a relatively simple/quick/cheap method of adjusting the skew on a Zone 2 dish!"
If you have a diseqc motor lying around.... you could also mount the motor to 90 degrees from the satellite direction (instead of to due south), and adjust the angle of the motor pole by setting the 'motor elevation'. You then get your skew!
(There are also brackets to do that, but I don't know the skew angle you need?)

I happen to be the happy owner of a STAB HH100 motor with a burnt-through chip ~ such a thing could easily be used for just this.
So find a broken STAB HH100, and you're happy!

Greetz,
A33
 
jeallen01

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@a33
Thanks for the suggestion,which is likely a much better overall "solution" to the skew-adjustment issue because it might also work with a streeable dish - OTOH, my suggestion for a "solution" was really only a cheap and simple (and "cheerful"!) approach to making such adjustments on a fixed one:D.
 
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