How to setup a FTA (as mater) with a BUD – How to control the servo motor (skew)?

[nazareno7]

Greetings:

I’m planning to purchase a mesh C/Ku dish. I have a couple FTA receivers connected to a fixed dish. The BUD will have a servo motor (arm) and a C/Ku band feed (possibly a CoRotor). I would like to use only FTA receivers (no Analog or 4DTV). I know I can purchase a Disec positioner to control the dish motor. But I do not know how to control the servo motor (skew) with the FTA box. Below are my doubts:
1. Do I really need a servo motor? Can I get multiple satellites (with the correct skew) using a dual C/Dual Ku feed? I have heard that a servo motor is not needed for a Ku band motorized dish. Does the same principle apply to BUD systems?
2. If a servo motor is needed, can it be controlled from the FTA box?

Thank you very much.

 

[Tron]

If you are planning to use something like the G-Box 3000 to control the BUD with a FTA receiver, your best bet will be to replace the LNB/feedhorn on your BUD with a voltage-switched (13v vertical, 18v horizontal) LNBF or stacked LNBF. Some Pansat receivers can control a polarotor (servo), but most FTA receivers cannot.

 

[pcrider]

Greetings:

I’m planning to purchase a mesh C/Ku dish. I have a couple FTA receivers connected to a fixed dish. The BUD will have a servo motor (arm) and a C/Ku band feed (possibly a CoRotor). I would like to use only FTA receivers (no Analog or 4DTV). I know I can purchase a Disec positioner to control the dish motor. But I do not know how to control the servo motor (skew) with the FTA box. Below are my doubts:
1. Do I really need a servo motor? Can I get multiple satellites (with the correct skew) using a dual C/Dual Ku feed? I have heard that a servo motor is not needed for a Ku band motorized dish. Does the same principle apply to BUD systems?
2. If a servo motor is needed, can it be controlled from the FTA box?

Thank you very much.

I'm using the VBox II mover, and a Pansat 2700 reciever. on my servo feed, I'm very pleased with the setup. Its good to be able to tweak those weak sats.
I'm still waiting to see what the future holds for S2, and HDTV recievers before I upgrade. I need at least auto scan, and servo control in a stable box. How I accomplish that remains to be seen.

 

[melgarga]

1. Do I really need a servo motor? Can I get multiple satellites (with the correct skew) using a dual C/Dual Ku feed? I have heard that a servo motor is not needed for a Ku band motorized dish. Does the same principle apply to BUD systems?

If I understand your questions correctly-

The BUD will have a servo motor (arm) and a C/Ku band feed (possibly a CoRotor)............... Do I really need a servo motor?

If you mean the arm to be the positioning actuator, that motor is not a servo motor. It is a 36 (or sometimes 24) vdc motor. The servo motor is the small PWM (5v)dc motor that physically moves an element in the feed assy to select vertical or horizontal polarity on a corotor equipped prime focus C band dish (BUD)

Can I get multiple satellites (with the correct skew) using a dual C/Dual Ku feed?

If you mean getting any available C and Ku signals from a given orbital position, yes, but they are two separate outputs and require a switching scheme that allows for two (or more) satellite input signals.
If you mean puttng multiple LNBs on a fixed position BUD, prime focus dishes (BUDs) dont lend themselves well to multi-LNB applications that are not part of the prime focus feed assy. Skew (polarity offset) is the apparent change in polarity relative to your true south satellite, measured in degrees +/- from zero offset of the true south satellite for your locale. You will get all the TPs of a given (fixed) polarity of all the satellites in your tracking range from a BUD installation that is aligned to track the arc properly without any changes to the polarity settings, however you wont get the opposite polarity TPs unless you change the polarity orientation by some means by 90º. (The polarity offset is compensated for in the geometry of the tracking assy.)

I have heard that a servo motor is not needed for a Ku band motorized dish. Does the same principle apply to BUD systems?

Polarotor servo systems are exclusive to prime focus dishes AFAIK, although some people have put C band LNBs on offset dishes ("mini-BUD" projects). I do not know if polarotor switching has been used for these setups, but should work equallly as well as voltage switched LNBFs. Ku only dish installations are characteristicly offset feeds, and modern designs use the 13/18v polarity switching method. Older style setups have discrete H/V outputs or are only one polarity.

With your ideal station being one without a legacy IRD to properly control the Corotor's servo motor, you will need to purchase a 13/18 voltage switched LNBF as posted. There are many on the board with this setup, some are C/Ku too, as I recall. You should be able to find any assistance you need for that setup with any trouble.

Personally, I prefer the Corotor, but then again I also prefer my bacon cooked in a frying pan, not the microwave oven....

Another option, if you are handy on the electronic's bench, is a homebrew 13/18v to servo PWM interface designed and built around an inexpensive uC by one of the members on the board. He was generous enough to share his work. Search for the term Arduino.

 

[Cham]

I use a Pansat 3500 to control the skew for my Polarotor (Corotor III feedhorn). Works well. When I purchased the 3500 it was the only DVB receiver that had the skew output. I did try a Pansat 2700 once and didn't use it because it did not have the skew (it may have been a clone).

I use an older analog receiver to run the positioner arm and I do use it to watch the odd analog channels that are still up there. It can resolve to 1/10 of a degree which is close enough for tvro.

I wish newer HD receivers had the skew outputs for controlling the BUD polarizer motors. None have that as far as I know.

I suppose one could build something to switch polarity on corotor feedhorns using the LNB voltage (14v/18v) using a small servo, power source, and regulator to sense the voltage in the feedline, and attach it to where the original skew motor goes. It only has to turn the probe 90 degrees from verticle to horizontal, and might be manually calibrated for max signal on your favorite satellite.

Or replace the feed with a C/Ku LNBf with voltage switching built-in; or a Bullseye feedhorn using 2 C and 2 Ku LNBs and a DISEqC 4-port switch. The latter is quite expensive but best signals!

C.

 

[melgarga]

I was thinking a couple of the legacy Panny boxes did the servo out. I would like a peak at the schematic.
Equant's "interface" between 13/18v and servo out project I mentioned above is here -
http://www.satelliteguys.us/c-band-...168889-polarotor-servo-controller-design.html
With plenty units capable of servo output at my disposal, I've not vertured off into yet another project....yet, but I think it would be an interesting and realtively easy one.

 

[Tron]

I did try a Pansat 2700 once and didn't use it because it did not have the skew (it may have been a clone).

That's strange. My Pansat 2700 definitely has polarotor controls, in the form of spring-clip terminals on the back. These are much like the ones you find on the back of smaller speakers. Maybe it was a clone, or possibly they phased out polarotor control on certain revisions of the receiver.