TheTube Network ??

[N0QBH]

Need a sanity check.
I'm not receiving TheTube on AMC-3 C band tonite (8-7-06)
Still getting the two religous music channels (ugh!) of the same band/polarity, so I'm assuming my system is still working.

 

[photoman76]

The Tube is still there as listed on Lyngsat. The signal is strong here in California.

 

[1inabillion]

TheTube Network ??

Its still here on my setup signal quality of 80%

 

[voomvoom]

I hope I don't contribute to your Sanity Check in a bad way, but I'm getting the Tube here in Mid-Georgia.

Al

 

[N0QBH]

OK, Thanks.
Was doing some tweaking on the feedhorn...looks like I get to do some more...

 

[jjpicou]

Still viewing The Tube here. However I do notice that the transponder seems
to be weaker than others.

 

[N0QBH]

I managed to get TheTube back today although I'm tempted to name this thread "I'm shaking my feed horn in anger"
I'll attempt to describe what I did and maybe some of the old hands at satellite will be able to tell me what's going on.
My system is a Orbitron SX7 BUD C/Ku corotor feeding a Fortec Lifetime Classic receiver.
I use the old Uniden 4400 receiver as a dish mover and polarity control but due to the lack of NTSC FTA stuff to watch, don't have it connected to the LNBs.

The problem started when I decided to look into why the polar axis arrow on my Astrotel corotor feed horn was 90 degrees out of line. It had been that way from Skyvision when I bought the Ku upgrade about 3 yrs ago. I recall having problems installing it - finally going by the polarity of the pick ups when looking down the throat to get it working.
Yesterday I had the cover off of the feed horn and decided to look into why the servo was apparently off by 90 degrees. Removing the servo showed there was a square drive between the servo and the slotted plastic part that actually turns the pick up antennae which allowed me to turn the pick up 90 degrees and put everything into line. I reassembled the corotor and realigned it in the scalar ring. The pickups were in the same plane as they were before, but now the arrow on the servo was pointing through the polar axis.
Afterwards, all of my channels worked except TheTube.(go figure, my favorite) The channels on the same satellite same polarity came in fine at about the same signal level as before. The channels on the other satellites came in fine too, both polarities with both C and Ku band signals.
I tried everything I could think of with the feed horn adjustments in the scalar ring including turning slightly both ways until I'd lose signal as well as turning it 180 degrees which worked fine, but still no signal on TheTube transponder.
I strung the dish to check for warping - found none and the intersecting lines were all within 1/4" in the center. Eying through the center hole in back, and aligning the center of the feed horn using the string intersection showed everything on the money.
Used a brass rod cut to the focal length to check for proper scalar focus/alignment and that all looks good.
Finally today I decided to put the servo back the way it was and orient the feed horn as it was originally. Viola! TheTube returns and all the other channels are still there as always.
Now I want to know if someone can tell me whether there's something wrong with my feedhorn or if I need to look elsewhere for the problem.

 

[Hermitman]

I'll give it a shot. A couple of things hit me from your posting. I don't know about the Astrotel corotor but the Chaparral corotor isn't setup directly in line with the polar axis. It's offset to the 11 o'clock position. Of course, go with whatever your installation instruction say.

Next, and this may just be a terminology difference, you mentioned using the 4400 to change polarity but didn't mention adjusting skew. Using the skew adustment would be more important in getting a good picture than just switching polarity. With the skew adjustment, you don't have to twist your feedhorn at all.

And this may not have anything that affects your reception but according to Lyngsat, The Tube uses transponder 17 along with some audio stations. But it is the only program on a seperate frequency. Probably doesn't mean anything to your receiver but just interesting. Have fun.

 

[N0QBH]

Thanks for the reply Hermitman.
The former feedhorn (C band only) was a Chaparral and I even still have the cardboard offset for aiming. The Astrotel has a big arrow on the servo that points both ways and says "polar axis" on it. The instructions from Skyvision mention the difference in setting the two different brands. In the end I had to set the Astrotel as if it were a Chaparral.
As to the skew, yes, I did adjust that in both directions with no joy. As a sanity check I did the same thing on a working channel and could peak the signals. I also visually verfied it by looking down the throat.
I guess I could understand this if it were a Ku signal as in my experience, they're a little more "twitchy" but this is a relatively strong signal in the C band.
Again thanks. I hate mysteries