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Why won't a diplexer work with MPEG4? It works for me


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9 replies to this topic

#1 OFFLINE   LiQiCE

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Posted 04 March 2006 - 02:41 PM

So, I've read a number of people here and elsewhere say that if you have an MPEG4 capable receiver that you can't diplex the signal with an OTA antenna and get both the local stations OTA and via satellite.

But, in practice this has worked just fine for me -- The D* installer came back yesterday and installer an OTA antenna on the roof, and ran a 3rd line for me so I could support both a D* TIVO and an H20, and he used a diplexer on both ends (at the 6x8 Multiswitch location and right before the box) ... And everything works correctly. I can watch my HD Locals OTA and I can watch them in MPEG4 off of the Satellite.

There doesn't seem to be any noticeable loss in quality either.

The antenna they installed was an Eagle Aspen UHF antenna which said it was specifically for HDTV, and they used an Eagle Aspen diplexer which reads: 950-2250 (SAT SIDE) / 40-860 (TV SIDE) Mhz...

I decided to move the line with the diplexer on it to the D* Tivo just to be safe, but there was no difference in quality.

Am I just crazy or does this work?

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#2 OFFLINE   loudo

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Posted 04 March 2006 - 03:14 PM

So, I've read a number of people here and elsewhere say that if you have an MPEG4 capable receiver that you can't diplex the signal with an OTA antenna and get both the local stations OTA and via satellite..

According to D* the new satellites that are currently carrying the MPG4 locals, not the ones found on the 80's from NY & LA that are MPG2, use the same download frequency from the LNB to the receiver, as the local OTA channels, and that is why they won't work. They will interfer with each other. It information is contained in the D* installation instructions.

There doesn't seem to be any noticeable loss in quality either.?
I decided to move the line with the diplexer on it to the D* Tivo just to be safe, but there was no difference in quality.

You may not see it with the eye, but when ever you use diplexers there is a drop in the signal level. It may not be a enough of a difference for your eye to see, but if you put a level meter or use the signal level built into the setup of your system, you will see a difference. Remember with a digital signal you either have a picture or you have "No Signal", as opposed to analog where the weaker the signal gets, the worse the picture gets.

What using diplexers results to is with a little weaker signal, meaning rain fade will probably come a little quicker with a diplexer and with a separate line, without diplexers.

I have just rewired my system from diplexers to separate wires. My local signals went for around 75% with the diplexers to about 85% to 90% with separate signals.

#3 OFFLINE   carl6

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Posted 04 March 2006 - 03:33 PM

I also believe the major conflict will come when the next satellite comes on line. At some point in time, you will probably find diplexed signals will not work properly.

Carl

#4 OFFLINE   LiQiCE

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Posted 04 March 2006 - 04:39 PM

I guess my point on not seeing a loss in quality is not only can I receive both my local stations via MPEG4, but I can also receive them via a Diplexed OTA Antenna signal ... I've read that this would either not work, or would result in a loss in quality although you're right this makes no sense considering its all digital stations. I understand what you're talking about with a decrease in signal strength, but that would happen whenever I use a diplexer, not just because I'm using it with a 5LNB dish.

And currently there doesn't seem to be a drawback to diplexing with the OTA antenna (other than a loss in signal strength). I'm in the DC Metro area and I'm receiving Washington DC local stations in HD through the satellite (the stations match the numbers for my local stations), so I'm positive I'm receiving MPEG4 stations over the satellite and not the MPEG2 NYC stations. I've also got a 5LNB dish to go with the H20 receiver and 6x8 Zimwell multiswitch.

Carl - I suppose what you're saying is probably true, there maybe additional HD stations coming online that the diplexer will interfere with ... But since I'm now using the diplexer on my good old SD D*Tivo which doesn't receive MPEG4 stations I'm hopefully OK.

#5 OFFLINE   loudo

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Posted 04 March 2006 - 05:40 PM

I guess my point on not seeing a loss in quality is not only can I receive both my local stations via MPEG4, but I can also receive them via a Diplexed OTA Antenna signal ... I've read that this would either not work, or would result in a loss in quality although you're right this makes no sense considering its all digital stations. I understand what you're talking about with a decrease in signal strength, but that would happen whenever I use a diplexer, not just because I'm using it with a 5LNB dish..

Right, you will have the signal loss from the diplexers, it doesn't matter what dish (5 LNB, 3LNB or 1LNB) you are using.

And currently there doesn't seem to be a drawback to diplexing with the OTA antenna (other than a loss in signal strength). I'm in the DC Metro area and I'm receiving Washington DC local stations in HD through the satellite (the stations match the numbers for my local stations), so I'm positive I'm receiving MPEG4 stations over the satellite and not the MPEG2 NYC stations. I've also got a 5LNB dish to go with the H20 receiver and 6x8 Zimwell multiswitch.

It is strange that it is working when they said it wouldn't. Could be that it will work as long as LNB downloads the satellite station on a different frequency than the the local OTA station is transmitting it at, and you have no local channel on the frequency that the LNB is using for that channel.
Great that it works for you, when D* said it wouldn't.

#6 OFFLINE   greywolf

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Posted 04 March 2006 - 06:15 PM

The problem will be when the 99 satellite starts up. It will use the 250-750MHz band which will get killed by a diplexer.

#7 OFFLINE   loudo

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Posted 04 March 2006 - 06:26 PM

The problem will be when the 99 satellite starts up. It will use the 250-750MHz band which will get killed by a diplexer.


Are you saying the download frequency, of the MPG4 locals, on Spaceway 1 are not using 250 to 750 and only Spaceway 2 will be use that frequency?

#8 OFFLINE   LiQiCE

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Posted 04 March 2006 - 07:20 PM

The problem will be when the 99 satellite starts up. It will use the 250-750MHz band which will get killed by a diplexer.


That makes sense. I already moved the diplexed line to my D*Tivo which doesn't need mpeg4, so it shouldn't be a problem once Sat 99 gets up and running. Its good to know though that diplexing shouldn't effect the signal for the Sat 103 HD local channels.

#9 OFFLINE   KyL416

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Posted 04 March 2006 - 07:56 PM

It will likely be a problem for you in a year or two when they begin adding national MPEG4 HD Channels to 103 and 99.

#10 OFFLINE   greywolf

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Posted 04 March 2006 - 09:46 PM

Are you saying the download frequency, of the MPG4 locals, on Spaceway 1 are not using 250 to 750 and only Spaceway 2 will be use that frequency?

Good old MPEG2 satellites are using 950-1450MHz. Satellites at 103 are using/will use 1650-2150MHz. Satellites at 99 will use 250-750MHz which overlaps the UHF band. Right now, Spaceway 1 is at 103 and Spaceway 2 is at 99. DirecTV 10 will be at 99 and DirecTV11 will be at 103. DirecTV 9S is scheduled to go up in July at 101 so there looks to be MPEG 4 programming inside 950-1450MHz before too long. If you diplex, you won't get programming from Spaceway 2 or DirecTV 10 when they start up. See http://media.corpora...VPdfVersion.pdf




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