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Discussion Starter · #1 ·
I currently have D*tivo which has a dual tuner. I would like to mount my new squareshooter on the same post as our D* dish. What would I need to combine the 3 wires (one from squareshooter and two from D* dish) into two before entering the home and then, once inside, open them up to three wires? There are currently two entering the home from the dish (one for each tuner in the d*tivo). Thanks!


Tom
 

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greywolf, I need to ask you a question about exactly how multiswitches and LNBs work. Also, about adding OTA to a multiswitch. Does it degrade the signal? Can I email you? If so, give me your email address in a PM. If not I'll just open a thread but I think I have most of the answer but I just wanted to run it by your astute and learned mind because I have followed your posts for some time and you are very knowledgeable when it comes to multiswitches etc. Thanks.
 

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purduealum you would need two diplexers one to combine the signals at the dish/antenna and one to seperate them for the receiver. The only exception being that some models like the Hughes E86 have internal diplexers to seperate the signal. The DTivo will need an external diplexer. I assume you are just wanting to pass the OTA signal through the DTivo as it doesn't have an internal NTSC tuner.


plasma

Adding OTA to a multiswitch does degrade the signal in the form of db loss. The amount of loss depends on the size of the multiswitch a x4 multi will have signigicantly less loss than a x8 as the signal isn't split as many times. Just diplexing into one line doesn't result in as much loss as diplexing and splitting the OTA into multiple outputs. In most cases you uses a pre amp to compensate for the signal loss caused by the split and diplexing.
 

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Quote:
Originally posted by plasmamaniac
greywolf, I need to ask you a question about exactly how multiswitches and LNBs work. Also, about adding OTA to a multiswitch. Does it degrade the signal?
Start a thread. Anybody can help then and more people can benefit from the exchange. I have PM turned off to keep exhanges of information public. For now, DrDon's explanation of how multiswitches work is a favorite of mine and follows.


Polarization is used to double the number of transponders on a satellite. You can have two different transponders sharing the same frequency by polarizing the signal. Your STB works like this: You tune a DirecTV channel. Your box knows what transponder that channel is on. If it's on transponder one, your STB sends out 13v which tells the LNB to select the LH (left-hand) polarization and, hence, the odd numbered transponders. The LNB sends ALL of the odd-numbered transponders down to the STB which then tunes out all but transponder one. It then passes that digital stream on to the digital processor, which extracts the information necessary for the channel you selected.


Now, if you then select a DirecTV channel that's on transponder 8, your STB will send out 18v, telling the LNB to select the RH (right-hand) polarization and, hence, the even numberd transponders. You know the rest.


In a multi-satellite situation, you have a new problem in that the STB must be able to request the correct polarization, but the correct satellite. Transponder one on the 101 is the same frequency as Transponder one on the 119. So, obviously, you can't have send both sets of signals down the pipe at the same time... they'd interfere with each other. So, they devised a switch that uses an audio trigger. When you select a DirecTV channel from the 119 bird, your STB sends out the proper voltage for odd or even transponders ..PLUS, it sends a 22khz audio tone The switch hears the tone and switches from one satellite's LNB to the other. The switch passes the voltage to the appropriate LNB which does the rest.


A "multiswitch" Works like a telephone operator. The input lines to the multiswitch send a constant voltage to each of the 4 LNBs (2 for 101 and 2 for 119.. remember, they're DUAL LNBs) and receives back the transponders associated with that voltage. The multiswitch then senses what the STB wants (by looking at the voltage and tone combination) and connects the STB to the proper line. The line going from the multiswitch to the STB never has more than one half of the transponders from either satellite on it at any given time.


The Sat-C arrangement uses a special trick to take some transponders off of the 110 bird and place them into unused slots on the 119. (The slots aren't really unused. Dish transmits programming on them). Since the original transponders on 110 are different from the slots on 119, a special LNB is required that will shift the frequencies to the slots. Then, a special combiner is used that strips out three of the Dish transponders from 119 and inserts the DirecTV transponders from 110 in their place.


And that, in a nutshell, is how the whole thing works. Again, this is a nutshell and not a perfectly technically accurate representation.


Doc


There is some loss when any item is added to a line but it's rare that diplexing a signal is a deal breaker.
 

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Discussion Starter · #11 ·
Thanks for your help. Perhaps I am not explaining my situation correctly so I will give you a revised and more detailed description:


We currently have a D* dish with a dual LNB mounted on a pole outside of our townhome. There are two wires from the dish that enter our townhome. The two wires, once inside, are fed directly into our D*tivo. There are two wires entering it because it has dual tuners inside of it.


We are taking delivery of a Sony widescreen TV that has a built in OTA tuner.


Yesterday, I decided to order the Winegaard squareshooter. I am going to mount it on the same pole that our exisitng D* dish sits on. Naturally, by installing the squareshooter, i will now have three wires exterior to the townhouse.


What I would like to do is route all three wires into our townhome using the two existing wires from the dish. Once inside, I would like to split the signals apart so that the two exisitng wires from the dish go to the d*tivo and a new single wire goes to the built-in OTA tuner on our new TV.


I am new to this so please explain how this can be done. To me, it seems like a diplexer will not work. I would need a set of two dual diplexers or the like.


Thanks for your help!


Tom
 

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Diplexers will work for that scenario. Since you are mounting the Squareshooter on the same pole you will use one diplexer to put the OTA feed inte one of the feeds for the DTivo. Inside the house you will connect the second diplexer to other end of the sat cable. The sat feed on the diplexer will of course go to the DTivo while the Ant feed will go to the TV, VCR, etc.
 

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Discussion Starter · #13 ·
By jove, I think I got it. So any diplexer will work regardless of brand?


Also, since I do not have crimping tools, etc. where can I get 3ft lenths of RG-6 already assembled? Home Depot?
 

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Thanks greywolf, that's exactly the info that I needed. Appreciate your wonderful and timely response. I'm thinking of adding a cascadeable multiswitch 5 X 8 and adding OTA so that I can get the HD channels upstairs. Someone else a while back said that it will degrade the signal and not to do it but maybe that's for long runs over 100 feet, I dont know why his experience was so negative towards diplexing the OTA. Thanks again for allowing me to tap into your wonderful expertise in this area, you help alot of people out with their dish, multiswitch, antenna problems.
 
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