Default polarity H or V

[pitman1]

Hello everyone, this may seem like a stupid question and I have gathered some info from reading other posts but I also at times have trouble getting particular sats to come in. My question is regarding the polarity of a particular sat. When I am using a particular bird I find that I don't switch off of it much and therefore I find it impossible to remember the polarity for each sat. When I stay away from a sat for a few months then come back I sometimes have to bump the dish position and skew a few clicks either way to get something to come in. Then at other times, things just won't come in at all and I start wondering if something is amiss with my setup. So the question is.... is there a default position that is easy to remember for all the sats? I mean say you're trying to get 87W and nothing is coming in when you have your IRD at channel 4 (and ref. show it is using an even numbered xponder) so you flip the polarity and go to channel 5 and still don't get anything - its frustrating at times. So I need to know how you can tell what the polarity is supposed to be for a satellite so that at least you can have that correct and rule that out when you're trying to tune something in. Man, I hope this makes some sense to someone trying to read it. Its crazy how I have been at this hobby for many yrs now and still can't figure that out. seems like I have to stumble through it everytime. If anyone has any suggestions I would appreciate. When I take the feedhorn cover off, my Ku lnb is at 1 o'clock position and the Cband lnb is at 7 o'clock position. Do I have the lnbs right? Does it matter what positions the lnb's are in? Any comments or help would be appreciated. thanks to all, great site. I can usually track between 74W and 135W. I just don't mess with it every day since I also have pay cable service. I find plenty of channels that I don't get with my cable, plus just luv surfing and searching for new stuff every couple months and trying new receivers.

My setup: C and Ku Norsat linear LNBs - Chapparal corotor 2 C/Ku feedhorn w/ chaparal servo motor - Uniden UST super 4500 IRD dish mover and servo skew control - 10ft. SAMI mesh dish - 24" SuperJack mover. - SV8KHD - Vantage 1100S - Coolsat 8100HD - ViewsatPro - Coolsat 4000 - Pansat 2500 - Fortec Lifetime Ultra.

I slave the DBS box off the Uniden feeds through a power passing splitter to 4x1 diseqc switch 1 - Cband 2 - Kuband.

 

[FaT Air]

There's either V or H transponders. Which polarity is active 24/7? Easiest way to figure that out would be TheList! I might be wrong, but I think all Chaparral feedhorns want the servo off to the 10:30-11:00 position. (with dish at Zenith) If positioned 90° off, it just reverses V and H, but may introduce some confusion. One way to check, is select a vertical polarity ch. Then look into the throat of the feed, The probe should be vertical. Again, with the dish at Zenith. Horizontal polarity would have the probe, well, horizontal.

 

[Newbie_McNoob]

Also note that adjacent satellites have the polarity reversed in order to avoid interference.

For example: if one satellite has the odd numbered transponders as H and the even numbered transponders as V, the satellite right next to it will have the odd numbered transponders as V and the even numbered transponders as H.

 

[pitman1]

I was afraid that my post might not make sense to someone reading it. I can't be the only one out there that gets tripped up with the whole polarity and skew issue. I find a way to get them in but it is mostly by trials and errors. I just cant surf over to a sat that I've never gotten anything on and know whether it's H or V. (in other words is it H on even channels or odd channels.) Thats my question in it's simplest form. But your explanation about the rotor inside the feed was very good, I never put that much together myself. I hope that I can make those observations that you talk about and that will certainly help, but it still don't tell you whether a sat is H or V. In the old days when I subscribed to the satellite tv guide ORBIT, it would have a pull out chart of the satellite arc and there would be N or and I next to each sat and that was your reference for whether it was even or odd chanels vertical but since that mag is gone now I don't have a way to ID an unknown sat to get a starting point. I hope this makes more sense, I dont know how else to explain it. thanks for the help.


@ mc-noob - yes I am aware that adjacent sat's usually have opposite polarities but thanks for your input.

 

[FaT Air]

Ah hA! I used to do the same when I was using the Toshiba to run the servo and actuator. Kinda minimized the confusion by programming all sats in the toshiba so odd=vert and even=hor*. Then would select the "channel" on the FTA, look to see the TP polarity, then select the sat, then select odd or even, as necessary, on the toshiba. Completely removed the confusion by upgrading the lnb/feed to an LNBF.
*Or the other way around, it's been a while.
I then added a G-Box, and put the analog in the museum.

 

[waylew]

You could go to LyngSat and that will show what polarity scheme each sat uses.As long as you know what sat you're on ; )

 

[pitman1]

There's either V or H transponders. Which polarity is active 24/7? Easiest way to figure that out would be TheList! I might be wrong, but I think all Chaparral feedhorns want the servo off to the 10:30-11:00 position. (with dish at Zenith) If positioned 90° off, it just reverses V and H, but may introduce some confusion. One way to check, is select a vertical polarity ch. Then look into the throat of the feed, The probe should be vertical. Again, with the dish at Zenith. Horizontal polarity would have the probe, well, horizontal.

Well I did the check of looking into the throat of the feed and found that when I was in a vertical position and taking the skew to 0 on the IRD the rotor was NOT aligned vertically completely. It looked to be about 45 degrees off of that. I proceeded to rotate the entire feed 90 degrees. Now my lnb's are at the 11 o'clock position for the KU feed and 5 o'clock for the Cband LNB with the servo being at around 11 o'clock also.
Unfortunately this does not resolve the rotor orientation issue. It still appears to be about 45 degrees off. Should I be checking the orientation of the servo rotor position when the receiver has the polarity number at 0 or is it at some other number. Usually I have to have the skew at +45 or -20 to get some sort of picture. The servo is working properly as I had someone skew from 0 to +90 and then from +90 down to -90 and it did rotate about 180 degrees.

 

[Mauiguy]

Well I did the check of looking into the throat of the feed and found that when I was in a vertical position and taking the skew to 0 on the IRD the rotor was NOT aligned vertically completely. It looked to be about 45 degrees off of that. I proceeded to rotate the entire feed 90 degrees. Now my lnb's are at the 11 o'clock position for the KU feed and 5 o'clock for the Cband LNB with the servo being at around 11 o'clock also.
Unfortunately this does not resolve the rotor orientation issue. It still appears to be about 45 degrees off. Should I be checking the orientation of the servo rotor position when the receiver has the polarity number at 0 or is it at some other number. Usually I have to have the skew at +45 or -20 to get some sort of picture. The servo is working properly as I had someone skew from 0 to +90 and then from +90 down to -90 and it did rotate about 180 degrees.

The ideal solution is to have about +45 on one tp and -45 on the next. However, any position of your feed horn that allows you to adjust your polarity and receive a good strong signal without going to +90 or -90 is good. So a +70 and -20 would be ok. It sill leaves room for adjustment.

 

[FaT Air]

+70 and -20, sounds familiar. Think that's close to where my Pansats had to be set to to run the servo on my ADL feed. If you'd rather have them zeroed, could set to 0 and rotate the feed until the probe is in the proper position. Check to make sure 0 horizontal and 0 vertical are 90°, on the probe, to each other. Split the difference if needed. If servos are replaced, it is possible to get the probe off by 90° as the servo-probe drive is many times a square shaft and socket.

 

[pitman1]

fat air - you lost me on the last comment about a square and sockets. If I rotate the feedhorn again another 90 degrees I'll be right back where i started (probe orientation wise) but the feedhorn itself would just physically 180 deg. different right? Maybe I should just leave it where i have it even though the rotor is not perfectly vertical (or horizontal) when at true south. what do you think? I am able to tune in just about everything that I go for, I'm just wondering if maybe these tweaks would make a difference. I thought you said that when you're at your true south and on a vertical transponder that the rotor would be perfectly vertical in the throat of the feed.

 

[pitman1]

continuation from previous post, I guess when you mess with the skew it is perfectly vertical at some point while you are moving it. I just didn't know if it needed to be perfectly vertical when the skew is at 0 or say +55.

 

[FaT Air]

You're actually safe as long as the skew does not have to be adjusted to + or - 90, or whatever the limit is on your particular receiver. You are then not driving the servo to it's mechanical limits.
>>If servos are replaced, it is possible to get the probe off by 90° as the servo-probe drive is many times a square shaft and socket.<< The output shaft of the servo is a square shaft. It mates with the probe mechanism via an adapter that will allow for some axial misalignment of the shaft and probe mechanism. Square pegs fit square holes 4 different ways. 0-90-180-270

>>I thought you said that when you're at your true south and on a vertical transponder that the rotor would be perfectly vertical in the throat of the feed.<< Yes,(assuming rotor=probe) the probe in the feeds throat will be vertical, with vertical selected and at true south. This is the result that is aimed for.
Ideally, this is accomplished with the receivers skew adjustment as close to the receivers default skew setting as possible. This affords the greatest range of adjustment without fear of running the servo into its mechanical limit. This will also afford less "fiddling" while trying to acquire a new satellite. To see, set the skew to default for both V and H, watch the probe move 90° when changing channels, odd- even.
What I'd do, and did many times BITD, is set the skew to default, select Vertical, and put a hash mark on the exterior of the feed where the probe points to. Mark it V. Then select Horizontal, skew set to default, and put another mark. H, on the feed. Then reinstall it, aligning the V mark with the top of the dish. If the marks are not perfectly 90° from one another, I'd split the difference while reinstalling it. Then only +- 10, or so, for V or H is needed to peak the skew perfectly.
And if the setting is left at default, The probe is most likely close enough, to perfect, to get signal on a new satellite.
Some receivers used 0 as default skew setting for V and H, while others used +45 for one polarity, and -45 for the other.
But I'll repeat: You're actually safe as long as the skew does not have to be adjusted to + or - 90, or whatever the limit is on your particular receiver. You are then not driving the servo to it's mechanical limits.

 

[pitman1]

good stuff fat air and thanks for that instruction. I need to get back out there and see if my feeedhorn has other holes for mounting that are not the same 4 being used now. because I am about 45 deg. off, rotating the entire assembly 90 degrees is never going to put that rotor in the correct position with the (default polarity as you call it) on mine i guess default is 0. I have never heard that term, ive only heard of Hor. or Ver. and Normal or INverted. thanks, I'll post back what I find and if I'm gonna consider moving the feed again.

 

[pitman1]

after I read your post again, maybe I don't have the 0 default skew. would a 0 default skew system go +/ - 45 or 90? My skew settings go 0 to + 90 or 0 to - 90. Is there any way to tell. I'm rarely at 0. LIke i said before I usually have to be + (pick a number 20 - 60 ) and - (pick a number 20 - 60) when switching channels.

 

[FaT Air]

It's been eons since I've played with that receiver, and feed horn. But looking over all that's here, and seeing you're at -20 and +70 leads me to believe that receiver uses +45 and -45 as the two polarity defaults. TTBOMK- On that feed assembly, the feed throat should be able to be spun in the scalar, to afford something less than a 90° rotation. If not, I'd leave well enough alone, and just remember your defaults of -20 and +70 will have to be entered first when chasing after a new sat.

 

[pitman1]

again great feedback. now that you have given me that idea, I do believe that I can spin the feed around without having to unbolt the scaler from the feed support arms which is what I did last friday. I believe that there is a small allen screw which secures the feed to the scaler. again, not positive but I think so. I will probably get out there again on friday and make these adjustments. thanks fat-air, you have been a GREAT HELP!!!

 

[N0QBH]

Here's a couple of pictures showing a Chaparral C band feed horn being operated by my own design servo controller.
The knob is to adjust the skew, if needed.

 

[pitman1]

pretty cool. but do you have to change the knob when you switch polarities. seems like using an IrD would be less cumbersome

 

[N0QBH]

No, the knob is just for adjusting skew. The unit is in line to sense the DC voltage on the coax and switches polarity automatically.
I added the voltage display for troubleshooting. First time I used it, I found a loose coax because the voltage would jump around when a wind gust hit the dish. Turned out I'd forgotten to tighten a connector at the grounding block.

 

[FaT Air]

Your own design or ?? Info?? Inquiring minds want to know. Maybe it deserves it's own thread??