Got my C-Band Dish up!

[bobvick]

I got my 7.5' SAMI dish up yesterday. After struggling for a few hours, I finally found my true south satellite 87W and I am getting good signals from it. I can even get the RTV S2 feeds, one of the transponders comes in sometimes, I forget which one it is, but the other one has good quality up in the 70's as is the quality on most of the transponders. I bet that with some tweaking I might could get higher. Anyway, I have a WSI DMS741 LNBF that I tried to use. I was just wanting to use the C-Band side of it, so I ran a cable just from out of the C-Band LNB. The funny thing was, with that LNBF, I could scan hardly any channels with my Manhattan, I got like 14 or 15. My Lexium 7100 meter would not lock any signals with it. I replaced that feed and LNB with an old ADL C/Ku feed that has an old 20 degree Gardiner LNB on it. The meter works fine with it, as does the Manhattan. I am using a 4DTV to move the dish, so I hooked up the servo to it to try and change polarity. My maps are corrupted in the 4DTV, so I am using "W6" on it for W3 (AMC3), it does not seem to be changing the polarity, I can only get horozontal feeds. Apparantly the servo is not hooked up correctly, or the servo is dead? Does anyone have any suggestions about how to get the DMX741 to work properly? What settings do I need to use in the Manhattan? I would like to be able to use it and not have to use a servo, but it does not appear to be reliable. Your help and suggestions will be apprecaited. Thanks

 

[FaT Air]

Remove the dielectric plate, only inserted into the throat of the feed for the circular polarized,international, satellites. (??)
The Standard DMX741 is band switched with 22khz. OFF for C, On for Ku. Select Standard LNB types with LO C-5150, Ku 10750.
The Universal DMX741U is band switched via diseqc. Port 1=C, Type=Standard,5150 LO. Port 2=Ku. Type=Universal, LO= (9750-10600) 22Khz should be automatic to select the proper LO. Although, some receivers allow you to select Standard Ku and also set 22khz to ON, with LO set to 10600. (LO at 9750 [W/ 22khz set to OFF] allows receiving those international TP's that are below 11.7Ghz. Domestic Ku it 11.7 to 12.2Ghz requiring the 10600 LO.
Being the 741 is dual band, some experimentation to determine it's optimal distance to the face of the dish may be needed. Also make sure it's centered and facing the center of the dish.
I liked my ADL feed, (Worked great on C band, not so good on Ku) and may once again use it when/if an FTA receiver with servo control arrives here. I found that my mesh is not very good at Ku though, so I replaced it with a C band only LNBF. All my Ku is done now with smaller dishes.
To test your servo, bring it right to the receiver, hook it up direct. If it only buzzes, it may be the probe in the feed is stuck. Or it may be the gears in the servo itself. Replacements are available. Red=5V, Black=GND, White is the pulse that moves it (~1ms to 2ms pulse every 50ms or so) If it works fine at the receiver, check the servo wiring to the dish. Twist the three, for the servo, together at the dish and check for continuity on all at the receiver end with an ohmmeter.

 

[bobvick]

I tried that 741 again yesterday evening. The dielectric plate is not in it, so it is not set up to be universal. I was getting great signal from the Nasa transponder on AMC3 with the old Gardiner LNB on C-Band and great signal on one of the Ku (Patient Channel) transponers on an old Astrotel Ku-LNB. I put that 741 in the scaler ring and hooked my meter up to it, it was getting nothing on the exact same transponders. I wiggled the LNB in and out of the ring to try and find an optimal focal distance, and still nothing. Also nothing when I twisted it around to skew it. I don't know if the 741 I have is bad or what. I am thinking about trying a BSC621 to see if it will work. I have a question, can the scaler ring make a big difference in signal quality. I ask because I took the old Chaparral scaler ring off and put the old ADL scaler ring I had on since it is easier to adjust the set screws. After I put that ADL ring on, the quality was cut in half. I adjusted it around to make sure it was centered and I could never get quality like I had with the Chaparral ring. Maybe I will get it all figured out. Right now, I only have H transponders, I think that the servo motor must be dead, I have not had a chance to take it inside by the 4DTV to see if it buzzes or not.

 

[FaT Air]

can the scaler ring make a big difference in signal quality.

Yes, and no. But I wouldn't think it would cause a loss that you're experiencing. Think of it as a focusable flashlight. twist it and it becomes a flood , or the other way and it's a beam. The F/D setting of the feed and scalar is essentially doing the same. Say your dish's calculated F/D is .32. If set too wide, (.28) it will allow more earth, and possibly terrestrial, noise into the feed as it is seeing past the edge of the dish. If set too narrow,(.4) the feed sees less of the outer portion of the dish. Either of these conditions can be detrimental to Q. But just with all calculations, these can only be considered "close". Some experimentation may be necessary to get it optimized. Also, if earth or terrestrial noise is high, (Low signal to noise ratio) setting the F/D higher may cut out more noise than the resulting loss of signal(because we're not seeing all of the dish) resulting in a higher Q. (Higher signal to noise ratio)
My ADL doesn't have a removable scalar, But if your ADL is of similar construction of the Chaparral's or 741's scalar, Why the loss of signal? Many have modified their existing Chaparral scalars to 741's. This may explain it: It's the number of rings in the scalar that determines how fast the illumination diminishes towards the edge of the dish. So if its got one more or less grooves, the placement of the feed in the scalar will change, for equal F/D ratio settings, from one scalar to the other. But then again, I wouldn't expect it to produce the loss that you experienced, so I'm actually stumped. At this point I think I'd try the 741 with the scalar supplied with it. And if that doesn't perk up performance, think I'd try another LNBF. Thin strips of rubber can help that 741 scalar hold the feed better.

 

[bobvick]

I am going to try the 741 again this evening. I will use the scalar ring that came with it. I only confirmed the readings on a Lexium 7100 meter. I question how good it is sometimes. I think I need to contact them, as it seems intermittent at working, sometimes it will lock, some times it freezes up. Could be the problem. Today I am going to skip the Lexim meter. I am going to go out and move my dish down where I can get to the feed, remove the feed and scalar that is on there now and put the 741 Scalar/LNBF. I am going to measure from the outside edge of the ring to the end of the dish for each of the 3 legs and make sure the distance is equal. Then I am going to set the LNBF at a F/D of 33.75'' (I have a 7.5' SAMI and this is what the instructions say the FD is.) Then I am going to move the dish back to AMC3 (My true south satellite) and skew the LNBF to the 3 o'clock position on the dish, while the dish is set at AMC3. Maybe this will work. Perhaps I am trusting the Lexium meter too much.

 

[Scott Greczkowski]

When you try it do not put the dielectric plate in. You dont need it here in the US.

 

[bobvick]

Well, I finally got the DMX741 to work! I need some tweaking on it, and perhaps a little bit on the dish. I need to try and find some more satellites. It is a work in progress, but maybe I will get there. Thanks for everybody's help and input I am sure I will require more.

 

[Dishman Dan]

Well, I finally got the DMX741 to work! I need some tweaking on it, and perhaps a little bit on the dish. I need to try and find some more satellites. It is a work in progress, but maybe I will get there. Thanks for everybody's help and input I am sure I will require more.

What I did was aim my BUD with the old c band lnb and locked a channel on a bird.

It seems much easier to set up a "new" BUD installation with a lnb especially if it is

the original that was on the BUD. Then I replaced the lnb with my DMX741 lnbf and

set it up to receive the known channel and satellite. Afterwards it is just a matter of

tweaking to receive the rest of the arc!

 

[turbosat]

I hope you had a canopy set up over that dish today! Was so hot today down here, I had a piece of copper pipe to solder, all I had to do was leave it in the yard for about 10minutes and just stick the solder to the joint ! LOL

 

[RT-Cat]

I hope you had a canopy set up over that dish today! Was so hot today down here, I had a piece of copper pipe to solder, all I had to do was leave it in the yard for about 10minutes and just stick the solder to the joint !

turbosat,
You need to move to Michigan. It was 72 degrees at my house today. Kind of chilly if you were in the shade.
Oh, and bring the cat!

RT.

 

[bobvick]

I hope you had a canopy set up over that dish today! Was so hot today down here, I had a piece of copper pipe to solder, all I had to do was leave it in the yard for about 10minutes and just stick the solder to the joint ! LOL

It certainly was not pleasant at about 4:00, but I wanted to see if I could get it to work because it would have bugged me until I went and tried it. Now I have to try and start getting some other satellites programmed in, and that is proving to be a challenge. I am going to have to contact WSI about the Lexium meter I have, it refuses to find a signal using this LNBF (DMX741) and the damn thing is from them as well, just like the Lexium. My Manhattan receiver works fine with the 741.

 

[turbosat]

Well I'm still stuck in the past methods with aligning c-band, lol. Find one satellite, tweak, then the next ones east and west of the first, tweak and just go from there blindscanning all the while. It surely isn't as easy as it used to be without the analog channels to tune by.