Question about Ortho on the 4DTV

[linuxman]

In light of the fact that I am about to lose my sub from NPS on October 25th, I got on my roof today, and replaced my Co-Rotor with a C-Band only orthomode feed I had setting here gathering dust.

My question is concerning the setup in the 4DTV. I have it set on "dual c-band lnbs" with no polarotor, but I have the off-set set to standard.

I have always heard that when using that kind of setup, that the off-set needed to be set at 90 degrees. Is that true?

I ran the dish over to 135, and QVC comes in fine on TP 9, and HSN comes in fine on TP 10, so I think I have the polarity set correctly.

Can someone clue me in?

Thanks!

 

[pendragon]

It sounds like you have everything set correctly if you can select both polarizations appropriately. I'm not using it at the moment, but my (very old) 920 would output the opposite voltages for H & V compared to the normal FTA convention. While I don't recall the menu exactly, I know I had to set the 920 to use reversed polarization voltages. It's possible this depends on the model or vintage of the 4DTV receiver.

 

[linuxman]

Thanks Pendragon!

I think it is set correctly too, but just wanted to make sure.

I did this in preparation for my sub running out, so I can add this dish to the rest of my system, and park it on a satellite just like all the others.

Thanks for your help.

It sounds like you have everything set correctly if you can select both polarizations appropriately. I'm not using it at the moment, but my (very old) 920 would output the opposite voltages for H & V compared to the normal FTA convention. While I don't recall the menu exactly, I know I had to set the 920 to use reversed polarization voltages. It's possible this depends on the model or vintage of the 4DTV receiver.

 

[crackt]

it really depends on how you have your feedhorn orientated and which lnbs you have connected to which inputs. if you are using a multiswitch then select cband lnbf. in this case you may need to have to set the rotated 90 option. the 4d units do seem to output voltage opposite dvb recievers. if you connect both lnbs to the h / v inputs of your 4dtv then may have to swap cables and you would want to select dual cband lnbs.

crackt out,.

 

[Corrado]

With my 905 running a LNBF on the BUD in the proper orientation, it has always required the rotated 90 deg setting. Polarity reads normal on the analog Uniden Ultra, Diamond 9000HD and all other FTA receivers I've had attached over time.

Now that I think of it, my 922 on 105W on the Prodelin is set that way also.

 

[linuxman]

Well I guess I'll find out on the 26th after my sub runs out.

I got up on the roof this morning and ran the cables from a vacant side of a 4X4 switch to this dish, so all I have to do on the 26th, is switch out the cables at the pole and park this dish where I want it to be, and have another dish in my "farm" for all my other receivers to access.

That will tell me if the polarity is correct or not.

 

[pendragon]

Do you have two separate coax lines, one for each LNB, running into the C and Ku inputs on your 4DTV? In that case your results make perfect sense. If you have a switch with a single line running to the 4DTV, then the polarization switching may or may not require reversing the selection voltage.

 

[linuxman]

All I did was to run the former Ku cable to one LNB, and the C-Band cable to the other LNB which runs all the way into the 4DTV receiver with separate inputs and no switch involved.

On the 26th, those two cables will be re-routed to the 4X4 switch that I spoke about above, and made available to my 3 FTA receivers on the "system".

For those that never saw the original monster thread, after the 26th, I will have 11 C-Band LNBs/LNBFs on 10 - 6 foot or larger dishes, and a total of at least 12 - 15 Ku LNBFs on Ku sized dishes. I've forgotten how many Ku LNBs I actually have in operation, but I need to make a few changes in the line up, but will probably wait until Spring for that project.

Who knows, it depends on how I feel in the next 2 or 3 weeks, how much else I get done. It's been a long year since last October.

Do you have two separate coax lines, one for each LNB, running into the C and Ku inputs on your 4DTV? In that case your results make perfect sense. If you have a switch with a single line running to the 4DTV, then the polarization switching may or may not require reversing the selection voltage.

 

[crackt]

beautiful thread linuxman. i get to chat with two of my mentors. thanks for the 920 linuxman. a great way to archive old maps. i hope that batt job you did holds till we see some new 4play action. the vid caps are shot and im leary to change them till i dump the 12 month old maps. haha.

pendragon, your also a super smart person who inpsired many of my buying sprees. haha. orthos rock but a proper prime focus tuning method will always outperform good hardware. you can get by with some really bent s@#$ in my field exprience (without an S/A), if properly measured and installed. between me you and updatelee we should have the prof smoking on the linux side. did i mention i got my first t90 ? haha.

crackt out,.

 

[pendragon]

orthos rock but a proper prime focus tuning method will always outperform good hardware. you can get by with some really bent s@#$ in my field exprience (without an S/A), if properly measured and installed. between me you and updatelee we should have the prof smoking on the linux side. did i mention i got my first t90 ? haha.

I hear what you're saying about alignment and it's music to my ears. I was helping a buddy tweak his new 2.3m (with single ortho of course) yesterday and we had gone from one extreme of the arc to the other seemingly a hundred times. I finally came to the conclusion there was no way we could get the thing mechanically closer, but my buddy knew we were a tad low on the far east end. He's got the right idea as I then measured we within 0.03 dB of the peak. Why stop when you can measure a difference?

Glad to hear you've been infected by a toroid. I love 'em as much as I hate 'em, but I wouldn't want to live without the three T90s on my roof. The neighbors don't quite see this the same way, even when I try to explain the next best alternative would be 35 x 90cm fixed dishes. Sheesh! By the way I've had a little time to work on the Prof Linux driver and it's working much more smoothly, now that a few bugs bit the dust. But I've made so many changes I need to hand check each one, because testing some of them would require resources I don't have.

Sorry to be so OT.

 

[truckracer]

I have a bullseye II c/ku dual orthomode...love it!!

 

[meinename]

Linuxman, for what it's worth when I got the DSR-922 I did a little testing of my own.

The goal was trying to get a BSC-621 to work.
So this was a single wire solution.

I hooked up my analog sqealer meter with it's "V/H" and "22kHz (tone)" LED's to the appropriate port.

I power-cycled the 922 every time I needed to move the meter or the LNB cable.

Setting | rotation | C-H port | Ku-V port
 C-band LNB | normal | 18V Vertical, 13V Horizontal | 0V Vertical, 0V Horizontal
 C-band LNB | 90 deg | 13V Vertical, 18V Horizontal | 0V Vertical, 0V Horizontal
Ku-band LNB | normal | 0V Vertical, 0V Horizontal | 13V Vertical, 18V Horizontal