H or V skew (by channel)??

[esteveW]

I'm trying to program some satellites into my analog box (Toshiba 1820 with 905 side car).

I notice that when I change channels the skew changes alternately. The odd numbered channels will be Vertical and the even numbers will be Horizontal. I have the ability to change them individually from "normal" to "inverse" and in the case of one channel, it cleared up and I had a viewable picture.

Is this normal or just something my box is doing to confuse me??

Steve

 

[Corrado]

For analog it's normal to have every other TP opposite. Some satellites have the even TPs vertical and the odds horizontal like G15. Then the next satellite 2° away will be the opposite like AMC10 for example. This helps reduce adjacent satellite interference.

Digital channels are different. In this case, the TPs can carry several compressed channels grouped together.

 

[phlatwound]

Do you have an operating manual for your Toshiba? I don't see on in the manual section here on the forum but you might be able to Google one.

I think those polarity assignments were preprogrammed when the receiver was new, but you can change them, as you have discovered.

I have mine set on Channel Skip (I think it's called), it will go through all the even numbered channels, then go through all the odds.

Do you have a DVB receiver? If you did you could use the Toshiba to move the dish and the DVB receiver to locate your satellites, then save the positions into the Toshiba.

 

[Mr Tony]

If you have an old LNB with polorotor (the 3 wires) then this is very critical. But if you have a new LNB like a 621 or equivalent that has no wires then this skew adjustment is not needed.

The older LNB's had one notch in there for skew and as you flipped through channels the receiver would move that notch 90 degrees for the opposite polarity. The new voltage sensored LNB's have 2 notches in there for both H & V

 

[esteveW]

Skew and FeedHorn adj.!

I went thru the feed horn and alignment process this afternoon. I found the focal distance was off 7/8" and the horn skew was off about 10 degrees. (I used the card/arrow method) and think I got it pretty close. I measured from the rim to the center of the feedhorn throat (actually the little skew 'thingy' just inside worked fine for center.)

I tried to find a method to verify that the horn was focused on the dish center but I was getting late so I placed my digital angle gage on the dish face (center plate) and got a reading, then placed it on the scalar rings and determined it was off a few degrees (this verfied only the vertical plane). Not sure how I could horizontal plane. BTW. I had the dish lowered to it's lowest (near zero) elevation for easier access and measurements. In the end (today), I tweaked the button hook to get the feed horn centered from rim measturements. To tweak the horn face vertical plane, I would need to bend the tubing just a little. I wasn't setup to do this today.

I returned the dish to it's south facing position and raised the elevation back to the previous 43 degrees (with the declination still set from yesterday).

I'm getting much stronger signals and have identified several satalites and programed them in. Starting from south and moving west so far.

However, even with the strong signals, I'm getting a very clear picture but no color for some reason. The only place I have found to check signal strength and quality is on the 905 sidecar. This shows 99 on strength with a quality of only 1.
In all the satellite and channel scans, I have yet to see any color.

BTW. I have the manual for the Toshiba 1820 and promise to scan it for the libary as soon as I get chance. The colors have faded and some of the text that is color highlighted is hard to read. It give only a little detail about how to program in additional satellites. About half of the ones that are in factory memory are gone or changed designation or something. I have to get into that eventually.

Made some progress today but still have a little ways to go.

Thanks,

Steve

 

[phlatwound]

Sounds like you are getting closer, good job.

Do you have a corotor/polarotor-type feed...or do you have a voltage-controlled LNBF? It looks like the former in your pic in the other thread, but maybe not?

I found my original 1820 manual, a copy I made of it...and I also found a .pdf version (28 meg), but I haven't been able to zip it for some reason and I know I can't email anything that big without my mail server puking.

If you have any specific questions about anything that may be in the manual let me know...I could even mail you my copy if it would help.

 

[melgarga]

dl a proggy called MasterSplitter, they have a delayware version. It lets toy define the # of pieces/size. Zips and rars can be reassembled by winzip/winrar w/o having the MS proggy

 

[esteveW]

Skew and FeedHorn adj.!

I already have an origonal Toshiba 1480 manual. It is only 60 pages and I will scan it soon. I think the reason you .pdf file is so be is the colors that Hi lite a small portion of the text. If I don't scan in color, I'm afraid I would lost the text that is high lited.

BTW. To answer the question about my LNB. It is a Corotor II Plus and has the three wire servo. That seems to be working fine.

Steve

 

[B.J.]

I went thru the feed horn and alignment process this afternoon. I found the focal distance was off 7/8" and the horn skew was off about 10 degrees. (I used the card/arrow method) and think I got it pretty close. I measured from the rim to the center of the feedhorn throat (actually the little skew 'thingy' just inside worked fine for center.)

I'm curious what you mean by the "card/arrow method"?? Are you talking about using a little plastic or cardboard tool that comes with feedhorns that you put on the side of the polarotor, then orient it so that the arrow points up...... then this tool tends to orient the feed so that V and H polarities are at +45 and -45 (relative to the polarotor signals that the receivers send). With most old analog receivers and a polarotor, you have to calibrate the polarity with the receiver, rather than by actually orienting the feedhorn. The only reason they give you the little alignment tool is so that you'll have it close to what the receivers are expecting, and so that you won't have in in an orientation where you have to move it 180 deg to adjust it 1 degree, ie at the end of the range of adjustability.
If you're not talking about using that little alignment tool, then I'm curious just what you mean by card/arrow method???

 

[esteveW]

Skew and FeedHorn adj.!

Yes, I think we are talking about the same thing. I downloaded the image from Sattelliteguys web site. (I don't have the full link in front of me now). I had to scale it up from it's 88% size and with a little trial and error I managed to get it to the correct size. I then pasted about 4 layers of shipping labels on the back side to stiffen it up. I then cut it out. It fit fairly good over the Corotor Ku band elbow. The original set screw position was correct for the f/D ratio was correct but the orientation was off about 10 degrees. I corrected the latter.

Steve

 

[B.J.]

Yes, I think we are talking about the same thing. I downloaded the image from Sattelliteguys web site. (I don't have the full link in front of me now). I had to scale it up from it's 88% size and with a little trial and error I managed to get it to the correct size. I then pasted about 4 layers of shipping labels on the back side to stiffen it up. I then cut it out. It fit fairly good over the Corotor Ku band elbow. The original set screw position was correct for the f/D ratio was correct but the orientation was off about 10 degrees. I corrected the latter.

Steve

Yeah, that 10 deg is meaningless, assuming that you're controlling polarity via the analog receiver. And if you're not, it's still meaningless because the polarotor could have been left at any angle by the last receiver that used it, since most polarotors keep their setting after power is removed.
I have a couple of those "tools". The old ones were made out of blue plastic, but the newer ones are made out of cardboard material, like a post card.