Building an external polorizer control

[Techfizzle]

is it possible to build someting i can run a coax from the lnb input to some kind of box, then run a coax to my dish, the module would then have a 3 wire terminal to run a polorizer with a pot to control the skew

 

[Inno]

You could perhaps make something using the LNBF setting from a receiver. It changes the polarity depending on whether it gets 13V or 18V. You would not be able to adjust skew with this, just polarity.
It would likely take more time and money than a suitable 3 wire cable of appropriate length or an LNBF.
I use an LNBF for simplicity.

 

[Pismire]

Do search on the subject. Just within the last month or so someone built just that. Takes a little electrical know-how and some soldering but he said it was working great.

 

[turbosat]

I made one using a simple rocker switch and a 9volt battery, years ago, when I had a polarotor1. Just push on the switch one way to go + or the other way to go the opposite direction. Have to watch the tv though to tell what you're doing but it served the purpose.

 

[Techfizzle]

i like lnbs with polorizers, skew changes with arc travel

 

[Pismire]

I did the search for you. http://www.satelliteguys.us/c-band-...168889-polarotor-servo-controller-design.html

It was the third one down. Simple.

 

[Lak7]

i like lnbs with polorizers, skew changes with arc travel

Yes, those are much better than one that don't.




EDIT: Removed comment about "Self Leveling" Feedhorns.

 

[B.J.]

i like lnbs with polorizers, skew changes with arc travel

It shouldn't change much. If I would do an auto-tune on any sat across the arc, it would generally end up with the same result. Can't do auto-tune on many sats anymore though, since not as many analog channels up there.
It is nice to have the ability to adjust skew, but except for AMC1-Ku, it really shouldn't be an issue.

 

[Inno]

Yes, those are much better than one that don't.




EDIT: Removed comment about Self Leveling Feedhorns.

Yes..........but..........if your dish is properly tracking the arc.....yours IS properly tracking the arc, isn't it Techfizzle?.........then it should not be an issue.
I prefer a LNBF on my current setup because it's easy, there are less wires to run and it's one less thing to worry about failing. I think THE most common problem I've had in 17 years of owning and repairing C-Band systems is the polarotor.

Having said that, if you are the type who likes to tweak everything to death, then a polarotor is the right choice for you.

 

[elder]

I didn't review the data but NASA tracked C-band polarization changes due to Faraday rotation for the ATS series of satellites. The antenna was an 85' dish on an XY mount. Because of the XY mount polarization tracking was necessary. The experiment made use of the polarization tracking to follow the polarization angle with respect to time when other experimentation was not being performed. I did a quick google but found no immediate hits with data.

 

[Techfizzle]

if you have a small dish, you can adjust the skew say a 36" er, but on a 10 foot dish, moving the feedhorn everytime you move, gets a little tiresome

 

[turbosat]

Does that Drake not store each satellite in memory, including its polarization setting, H/V format, etc? These analog boxes i have will "auto-tune" the position of each sat (cool listening to the motor move east and west until it gets the best signal), and also auto-fine tune the polarity setting for each sat. Now, that part working prob is dependent on analog channels being available on the sat you're tweaking. Normally, what my Uniden or GI receivers do is set the polarity on a V channel, then automatically offset the H-channels by a certain percentage. Never had a problem with it. Or , if no analog channels to autotune with>I can set all that stuff manually and save it for each satellite. You shouldn't have to move anything or turn the lnb or change polarity each time you switch sats. (provided you have a feedhorn with a polarotor already that works)

 

[SatPhreak]

That Drake should store every sat individually. My old StarTrak C band receiver could store every sat including skew even if I set it intentionally off skew on one or more sats. My Pansat 2500a DVB receiver can also do the same ( this is based on a c band polarotor without lnb aimed at nothing but the living room floor, but I had marked the probe location at zero and 90 degrees, and if I store a sat at anything other than normal the regular sats would would go to either zero or 90, but the offset skew sats I stored would go to whatever they where set to.) If you want to just use your DVB box to store polarity then follow Pismire's link. That system has adjustable pots to enable an offset skew, but you would need to adjust on each sat unless you rewrite the code in the chip.

 

[pendragon]

if you have a small dish, you can adjust the skew say a 36" er, but on a 10 foot dish, moving the feedhorn everytime you move, gets a little tiresome

If you're having to tweak skew every time you drive the dish to a new position, something is horribly wrong. A properly adjusted C-band dish will track the Clarke belt very accurately, and since the LNB 'skew' should be in-track with the arc, there is nothing to adjust, other than for an oddball satellite like 103W on Ku. If the polar mount declination is set correctly, the skew will not vary more than a tiny fraction of a degree from perfect. You can't set it as accurately as it can be held.

 

[B.J.]

That Drake should store every sat individually. ....

It will. The 1724 is pretty much similar to the 1824 I use.
One possibility is that he's not saving the polarity. If the menus are the same as my 1824, there is an easy to get at polarity page where you can temporarily change polarity, but it doesn't get saved. There is another page that requires a password to get into (should be 1724), where you actually save the polarity, along with sat positions.
Like I think I mentioned earlier, I've tuned the polarity on all the sats across the arc, and they are all the same.

Other possibility is that he doesn't have a polarotor hooked up???

 

[eurosport]

Yes..........but..........if your dish is properly tracking the arc.....yours IS properly tracking the arc, isn't it Techfizzle?.........then it should not be an issue.
I prefer a LNBF on my current setup because it's easy, there are less wires to run and it's one less thing to worry about failing. I think THE most common problem I've had in 17 years of owning and repairing C-Band systems is the polarotor.

Agree totally here. The LNBF is the best thing for me.
I get every C-band signal I've tried for and skew is a non-issue as the dish travels the arc.
And no little blue motors that always crap out at the most innapropriate times! :up

 

[melgarga]

If you're having to tweak skew every time you drive the dish to a new position, something is horribly wrong. A properly adjusted C-band dish will track the Clarke belt very accurately, and since the LNB 'skew' should be in-track with the arc, there is nothing to adjust, other than for an oddball satellite like 103W on Ku. If the polar mount declination is set correctly, the skew will not vary more than a tiny fraction of a degree from perfect. You can't set it as accurately as it can be held.

This does pretty much hold true for C band analog, but as finicky as a digital signal can be, it's been my experience that a polarity tweak to a digital tp can yield a bar or two on the graph, and might make the difference in weathering a thundershower or even getting a lock or not on a marginal signal. I dont have an S2 setup, but I suspect it would help there too. Add a dual band C/Ku feed on a Bud and a continously adjustable skew for the Ku side is definately a must for maxing the available signal. This is already presuming a correctly tracking setup, as I can see 55.5 to 137 and all points in between. (I have a line of trees ~50ft high appx 60' east and south of my BUD. I can only see 55.5 and 58 when the trees are bare in the winter.)
What is really ironic about this is that while an analog signal benifits from an adjustable skew, it really isnt a necessity, but was readily available. In this day and age, with analog all but abandoned, and the adjustable skew all but abandoned as well, a digital signal can actually benifit very nicely with this feature but essentially goes unsupported in favor of the LNBF. I wont go as far as to say the Faraday rotation comes into play here as well, but I doubt there has actually been any research into it, especially since all the non hobbyist TVRO stations have plenty of reserve capacity for signal strength and likely never notice a few percent deviation in strength.
I wonder if the guys having S2 receiption issues are running LNBFs or an adjustable skew setup. Maybe some will weigh in here and give us some reports on their experiences on the differences between fixed polarity positions and variable skew.

 

[equant]

is it possible to build someting i can run a coax from the lnb input to some kind of box, then run a coax to my dish, the module would then have a 3 wire terminal to run a polorizer with a pot to control the skew

Someone already posted a link to the forum thread, but here's a link to the website (so you don't have to read the whole thread, which is mostly me being confused about what I want to do) for what I made. It's exactly what you've described...

Polarotor Servo Controller

Now I'm working on what I call the "Priority Picking Polarity Controller" which allows the servo to be shared (good manners) among multiple receivers.

 

[melgarga]

Someone already posted a link to the forum thread, but here's a link to the website (so you don't have to read the whole thread, which is mostly me being confused about what I want to do) for what I made. It's exactly what you've described...

Polarotor Servo Controller

Now I'm working on what I call the "Priority Picking Polarity Controller" which allows the servo to be shared (good manners) among multiple receivers.

Keep it up and you might find yourself down at the Patent Office.......:.........lol
Thanks again for sharing your developments!

Now, about that 'good mannered' controller, what is your plan for the decision criteria of which rx has priority? Such an animal would definately reduce the lapfull of remotes I have when updating my scan of the arc.
One thing I do like about independent polarity control is that I can 'force' a H or V only polarity scan, saving wear and tear on the servo, and maybe even a more accurate scan due to no polarity switching settling time, though I've not documented any such results.
Sounds like another winner. Keep up posted.

 

[Techfizzle]

i wonder if they ever made a polorator that used an coax input to change polarity? if so i want one, just put it where the old one was, run a wire to the dish from it, and then from it to the receiver, then the voltages changes polarity, did they ever make such a thing