DMX-741 problem

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markbone100

Thread Starter
SatelliteGuys Pro
Jan 15, 2011
319
8
IL
Got out and hooked it up this morning. According to the instructions, I want a separate line for ku and C. Ku is hooked into the end lnb, works fine for V and H.

C band will only work of the 22K switch is set to off. NOTE - I have the internal 22k switch bypassed on the feedhorn since I have a dedicated line to the 8x1 switch for C band.

My setup is ---- Receiver -> 22K switch outside -> ON setting goes to the 8x1 switch (OFF setting is not hooked to anything) -> port 1 for C band, port 2 for KU.

In order for these to work properly on the old system, 22K on port 1 for C and 22K on port 2 for Ku. Ku is fine, just C is not working at all. I thought the 22K internal was bypassed since the coax is hooked to RCV on the lnb, but it appears it would have to be set to off for me to pick up cband signals.

Did I do something wrong or is there something in the lnb that is messed up?
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
Got out and hooked it up this morning. According to the instructions, I want a separate line for ku and C. Ku is hooked into the end lnb, works fine for V and H.

C band will only work of the 22K switch is set to off. NOTE - I have the internal 22k switch bypassed on the feedhorn since I have a dedicated line to the 8x1 switch for C band.

My setup is ---- Receiver -> 22K switch outside -> ON setting goes to the 8x1 switch (OFF setting is not hooked to anything) -> port 1 for C band, port 2 for KU.

In order for these to work properly on the old system, 22K on port 1 for C and 22K on port 2 for Ku. Ku is fine, just C is not working at all. I thought the 22K internal was bypassed since the coax is hooked to RCV on the lnb, but it appears it would have to be set to off for me to pick up cband signals.

Did I do something wrong or is there something in the lnb that is messed up?

Mark,

I think the DMX-741 is working properly.

What I believe is that you are misunderstanding the connection of the internal 22KHz switch. You are not bypassing it with the C-band signal, you are only bypassing the switch by running the Ku LNBF signal directly to the 8x1 switch. The C band signal is still going through the 22 KHz switch. Seems to me that the 22KHz switch is hard wired to the C band LNBF internally, but the Ku band LNBF is not. That is where the jumper cable is supposed to come into play.

The DMX-741 installation was intended to utilize a jumper coax for the Ku LNBF signal to go to the other port on the 22KHz switch which is an INPUT. Then the output of both C and Ku LNBFs can be accessed from the RCVR port or the output of the 22KHz switch via one single cable routed back to the receiver. 22KHz ON directs the signal from the Ku LNBF to the receiver output and 22KHz OFF directs the signal from the C band LNBF to the receiver output.

RADAR
 

markbone100

Thread Starter
SatelliteGuys Pro
Jan 15, 2011
319
8
IL
Yep I misunderstood the directions. Ended up putting a 4x1 switch on the 22K OFF side of the external switch and its working properly on port 1 of that. May have to go out and tweak the skew a bit, first scan of 87C had the Horizontals at 70-75% where some of the verticals were only at 20-45% while some of the V were at 70%. Have to scan a few more and see if its just a particular transponder or if I need skew it a bit more

Thanks for the help :)
 
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Lone Gunman

SatelliteGuys Pro
Mar 19, 2010
3,157
827
southeast
Make sure that the little antenna wires inside that LNBF are 90* to each other!!!! I've not seen one of these yet that was correct. You can use a long pair of needle nose pliers to "gently" bend them to get them @ 90* if needed. I've also used a long screw driver on the Ku antenna. Just make sure you look at them to see where they are before you go pulling your hair out because of this.
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
Make sure that the little antenna wires inside that LNBF are 90* to each other!!!! I've not seen one of these yet that was correct. You can use a long pair of needle nose pliers to "gently" bend them to get them @ 90* if needed. I've also used a long screw driver on the Ku antenna. Just make sure you look at them to see where they are before you go pulling your hair out because of this.

Lone Gunman,

I have a tip for you. I see that you were trying to denote degrees with *. Try this... Press the ALT key on your keyboard and hold that down and then type 248. The result is °.

There are lots of other symbols that you can access this way. Like ALT 16 ? ALT 17 ? etc. or how about ALT 1 ?

Thought you would like this.

RADAR
 

markbone100

Thread Starter
SatelliteGuys Pro
Jan 15, 2011
319
8
IL
I found the problem, odd on at that......

If I am on a vertical transponder on C band, say 87W weather nation, I am at 78% strength. Switch over to RTV on the H side, in the 60's. Now go back to a V transponder, signal is 0%. I have to move the C band dish from 87 to 83/85, then move it back to 87 to get the V transponders again. Firmware bug?
 

FaT Air

HOA Free Zone
Feb 27, 2010
6,668
914
97W 48N
Try this, instead of switching satellites, go to the tune up screen And see if you notice all your H TP's working, and no Q when a V TP is selected. If so, Leave it on the V TP, change diseqc switch selection, then reselect the proper port. Does Q come up?
 

markbone100

Thread Starter
SatelliteGuys Pro
Jan 15, 2011
319
8
IL
Havent tried that yet, but this morning if I leave it on a V transponder it eventually comes in at about 77%. Now late this evening the same signal is down in the 30-40% range but on other satellites its just fine. Wonder if its just something on 87W
 

FaT Air

HOA Free Zone
Feb 27, 2010
6,668
914
97W 48N
Well then, what I was thinking, wouldn't be. Thought it was like "stuck" on H polarity. Sounds like you've got it nailed to "something on 87W". But "to rule it out" try the sat setup screen-diseqc to prove it's not a polarity switching issue. Then have to go after alignment/feed tweak I'd suppose. Think you might see Q levels vary excessively if not "right on". I'd check alignment when the Q is low, to see if it can be improved.
 

markbone100

Thread Starter
SatelliteGuys Pro
Jan 15, 2011
319
8
IL
Pulled feedhorn cover off, nothing bent in there, everything lines up with center bars inside. I can go to 99W and get V and H in the 70's no nothing too major. At least with this new feedhorn I can get the PBS on 125 plus others I couldnt get before
 

Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
7
Near Chicago, Illinois
I used a DMX741 for a long time, the ABC TPs on 99west should about max out the Receivers Meter.
On my S9, usually Q85 - which is Max., I think - with 10' Unimesh BUD.
I wonder if you need to tweak a few things.
 

Pixl

Senior Member
Pub Member / Supporter
Feb 27, 2010
1,902
66
Traverse City, Michigan
Lone Gunman,

I have a tip for you. I see that you were trying to denote degrees with *. Try this... Press the ALT key on your keyboard and hold that down and then type 248. The result is °. RADAR

I am using a netbook, no numbers key pad on it. Are there any shortcuts for using the numbers across the top row to create (deg)?
 
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