Major Catastrophe ...

[Vipersan]

Naa ...as Alex says ..
it has to be a miscounting issue ...on account it is repeatable within a very short time frame so no changes in geo posn's of 'birds' in orbit...
The changes/errors would hardly be noticeable in Ku ...but in Ka a couple of clicks and you're off target ..
ie ..greater pecision needed in Ka..
I'll have to learn to live with it I guess ..
..just curious that I never noticed such variation prior to the catastrophe..
maybe I just never shifted across such a large section of arc ,,,so never noticed the change ..
??
Maybe it was always there and I never spotted it until now.
rgds
VS

 

[Captain Jack]

The question is - what causes the miscounts? Is it that the pulses are coming in too fast for the VBox to keep up with? Or are they "lost" on the way?

 

[moonbase]

The question is - what causes the miscounts? Is it that the pulses are coming in too fast for the VBox to keep up with? Or are they "lost" on the way?

CJ

Just a thought, could it be due to lack of proper shielding on the sensor cables if they are too close to the voltage cables and there is some interference. In the old days of the flat ribbon cable for 36 volt motorised installations the sensor cables had additional individual shielding around them. Other than that, it could just be an artefact of a reed switch system interfacing with a 36 volt positioner.

I have some optical actuators here and some old fashioned flat ribbon cable. If I ever get a chance I will see if I can rig up a test to check how accurate the pulse counts are for individually shielded ribbon cable with an optical actuator and with a reed switch 36 volt motor.


Rgds

 

[Vipersan]

Now then ..now then ..
I'll take your ball away ...if this continues
We get along fine here without resorting to insults ...unless they are indended as a joke..
lol
Dont force me to come and hold your coats..
;)

Just a thought that occurred ..
I have had to replace the reed sensor ..
Could it be that proximity to the magnetic hotspot wheel might somehow elongate the 'on' time ie closed contacts ..and could this perhaps affect the pecision of the pulse count..??
reed closer to wheel = longer pulse ..that sort of thing ?

...conversly if the reed is too far away from the 'wheel' ie only just close enough for activation ..vital pulses could occasionally be missed ??
rgds
VS

 

[Captain Jack]

VS, if what you describe is true, then I am guessing an optical sensor would solve this?

 

[Vipersan]

VS, if what you describe is true, then I am guessing an optical sensor would solve this?

Indeed it would ..
..it could even be the lag time of the vacuum enlosed reed contacts opening and closing ..
ie new reed = different lag time.
In my case ..(old reed in new gearbox ) = problems
nuff said ....

 

[Vipersan]

I am not going to rise to your childish comments, but may I suggest you do some more studding on this matter, when a satellite moves with a slight wobble the earth does not follow it fact .

..and I'm not rising to it either ..but more ' Studding ' probably wont help buddy ??
though I could do with some ...I've run out of Stainless
;)

 

[Vipersan]

Birds in Geo definately do move ...but on a tight beamed dish of decent size ...only really noticeable in Ka ...
Both myself and Llew can vouch for this deviation as we have both witnessed it first hand ..
Top and bottom of it is ..our motors/actuators and dishes are only really designed to track within tolerance in Ku ..
C doesnt matter too much ...but Ka is a total other kettle of fish ...hence more accurate tracking needed at these frequencies..
all imo of course..

 

[Vipersan]

A little more info before I go soak in the tub ..
I can go for Ka 7E (XMW Tier 1)to Titanium C 40E Tier 2 ....backwards and forwards with minimal retweaking and signal level variation ....but noticeably more re-tweaking neccassary when going from say Ku Inverto Tier 1 24.5W to XMW 7E Tier 1 and back ...but this of course actually passes through Zero ...
Important I think as this operation falls either side of the arc ..
Obviously this is a crucial factor ..but as yet I cannot account for this oddity ....and once again I can find no slack in the system motor wise ..
If the weather plays the game tomorrow ...
I intend to get the F15 outside with a monitor and try to solve this mystery once and for all ..
There HAS to be a reason ...but not neccessarily an easy solution..
rgds and keep the peace guys..


VS

 

[Analoguesat]

Ok lads cool it please - this is a fascinating thread & we dont want any sniping at each other. We pride ourselves here on the technical content of the threads rather than bitching at each other which is why this is one of the best forums to hang out in for so many of us.

If you want to argue take it to private message. I shall be having a bit of a tidy up when Ive poured myself a beer.

Edit - beer poured & a bit of pruning has been done.

 

[scopus]

Now then ..now then ..
I'll take your ball away ...if this continues
We get along fine here without resorting to insults ...unless they are indended as a joke..
lol
Dont force me to come and hold your coats..
;)

Just a thought that occurred ..
I have had to replace the reed sensor ..
Could it be that proximity to the magnetic hotspot wheel might somehow elongate the 'on' time ie closed contacts ..and could this perhaps affect the pecision of the pulse count..??
reed closer to wheel = longer pulse ..that sort of thing ?

...conversly if the reed is too far away from the 'wheel' ie only just close enough for activation ..vital pulses could occasionally be missed ??
rgds
VS

Could be VS. I replaced the reed sensor on my 1224 and had to resync the whole arc on mine, easy though as the V Box can do this. But I would make sure the sensor is as close the the magnetic wheel as possible.

 

[Vipersan]

Ok ..
This much I can tell you for definite ..
Positioning of the reed IS very critical when the mag wheel geared down to such an extension..
I'll tell you what I found ...
I hads 16E Ka and 30W set as my references ..
and swung Carl between these 2 points ..
I then lifted and slid a piece of plastic cut from a plasic bubble pack ...the kind of thing most blister packaged items come in these days ..
probably about 0.2 mm thick ...under the reed thus lifting it o.2mm closer to the wheel ...
Then retraced these 2 reference points ..
Finding neither ??
Obviously the ref points had to be re-set which I did ..
32 Clicks ....yes you heard me right ...
32 clicks out ..
As to improving or worstening the count inaccuracy I have yet to decide but what I can say is ...
Thats Huge ...and to me proves that solid and critical positioning of the reed IS crucial..
rgds
VS
Further investigation will have to wait ..as the CH9 coverage of the Ashes 24.5W is about to restart..
;)

 

[Mickha]

My old Echostar 3600 used to have the option of automatically fine tuning, to get the strongest signal possible, when moving between satellites, perhaps that could be your next project;)

 

[Vipersan]

My old Echostar 3600 used to have the option of automatically fine tuning, to get the strongest signal possible, when moving between satellites, perhaps that could be your next project;)

Sadly not easy any longer as that used the agc levels generated from an analogue tuner ..
Digital tuners are much trickier to interogate ...
I've no doubt it can be done ..but doubt it will be me who does it ..
;)

 

[Vipersan]

The mental picture of whats going on in my head ..is this ..
The closer the reed is to the wheel the bigger the problem ..
It works like this imo..
If the reed is closer to the wheel then the magnetic hotspot can activate the reed sooner from either direction E or W ...therefore a longer /wider pulse ..and thus the Vbox will stop the motor within a much wider range ...
thus the error intoroduced when approaching from the E or W is greater ..
A shorter/sharper pulse is needed for greater accuracy ..
Therefore the reed needs moving further away from the Mag wheel ...but not so far that it is borderline activated as this may then introduce 'missed pulse' errors ..
There is therfore and optimum distance where accuracy and activation trade off ..for an almost perfect track of the arc ..
It will NEVER be be perfect ..but will be the best compromise achievable using this method ...
rgds
VS

 

[scopus]

Strange that VS, I have always found the closer the reed to the wheel on my 1224 the better the accuracy...nowt is black and white.

 

[Vipersan]

Strange that VS, I have always found the closer the reed to the wheel on my 1224 the better the accuracy...nowt is black and white.

Agreed buddy ..
nowt is black and white ...but do you agree with my logic ..?
I cannot denitively say it's true ..but makes sense in my head ..
rgds
VS

...and the same would be true of a pulse generated by spinning a slotted disc in front of a opto sensor ..
Meaning the wider the slot ..the less accurate the stopping point of the motor on the arc...
Narrow slots = greater accuracy but not so narrow as to occasionally skip a slot at speed..

 

[scopus]

Agreed buddy ..
nowt is black and white ...but do you agree with my logic ..?
I cannot denitively say it's true ..but makes sense in my head ..
rgds
VS

...and the same would be true of a pulse generated by spinning a slotted disc in front of a opto sensor ..
Meaning the wider the slot ..the less accurate the stopping point of the motor on the arc...
Narrow slots = greater accuracy but not so narrow as to occasionally skip a slot at speed..

Sure do agree VS, makes sense in my head too...

 

[Vipersan]

So ..
put my money where my mouth is ...
ordered 10x reed switches from China on ebay ..for a couple of quid ..
These are 14mm long x 2 mm thick ...
When I get em I'll fit one as close to the side plate as possible replacing the original ..
The theory being I should be able to mount it a couple of mm further from the mag wheel ..
Thus increase the accuracy yet hopefully still be able to influence the reeds with the magnetic hot spots ..
...
we shall see if this provides a solution in due course..

 

[moonbase]

Sadly not easy any longer as that used the agc levels generated from an analogue tuner ..
Digital tuners are much trickier to interogate ...
I've no doubt it can be done ..but doubt it will be me who does it ..
;)

VS,

That's an interesting point re the EchoStar 3600 taking the agc levels from the analogue tuner. I did not know that, I had assumed it was interrogating the digital tuner when autofocusing on a satellite. It explains why my AD3600 often places the dish a few units off the maximum signal point when moving to another satellite. Its given me very good service over the years but perhaps its time to replace it with a Titanium ASC1.

Rgds