# Diplex OTA and BackFeed On one Cable



## lross78550 (Aug 16, 2009)

Guys I just bought a 2 story house (close to impossible to run another cable). 
I have the new dish 1000.2 dish and 2 HD 2 Tuner DVR Receivers. My wife Uses one HD Receiver In the master bedroom and I backfeed TV2 to my sons room. I watch the other HD receiver in the Living room and Backfeed TV2 to my daughters room. I built my old house and wired it myself during construction so I have always had plenty of coax runs at each location. 
The new house only has one coax cable to each drop so i need to try to do the following all on one cable if possible.

1 Use the DishPro plus seperator to provide the 2 tuner input cables from the satellite.

2 Use a Diplexer to backfeed TV2 output back to other rooms.

3 (if possible) Use a diplexer to provide OTA antenna signal from roof mounted antenna to receivers.

Please keep in mind that all 3 of these signals would be on a single cable for a short run.

Is this possible? 

If not are there any other solutions for OTA antenna signal? (wireless transceivers, etc?)

Or is an indoor antenna located close to the TV my only option?

Thanks for your time and help

Lross78550


----------



## TheSolidSignal (Feb 9, 2010)

There is no problem with combining the output of TV2 on the same cable that your using the DP Separator, but adding a TV antenna feed on top of that would most likely give you poor results

The modulated output to TV2 is on a separate frequency then the satellite so combining those works out, but because the over-the-air signal and the output to TV2 share the same frequency, it doesnt often work out. 

I have seen cases where people have made this work, but it involved channel elimination filters and combiners. Basically stripping out channel 3 from your Antenna signal, and combing in your modulated channel 3 (or 4) from the TV2 output.


----------



## MikeHou (Oct 18, 2006)

I've done this, and it was no problem for this inexperienced a/v tech. Besides the diplexors and splitters required, the only other "special" gear I used was a powered in-line amp for the 200' run from antenna to vip622.


----------



## 4HiMarks (Jan 21, 2004)

As long as the TV2 output is not set to a frequency being used by OTA stations in your area, it shouldn't be a problem. Although to be totally legal I think you need to put some sort of filter or trap on the OTA cable to keep from broadcasting your TV2 signal to your neighbors without a license.


----------



## fryguy503 (Sep 3, 2009)

I have see a single wire Plus setup, with the following running on the same cable: TV2 output, OTA diplexed signal and tv2 annt feed. Its not advised but possible.


----------



## Cap'n Preshoot (Jul 16, 2006)

4HiMarks said:


> As long as the TV2 output is not set to a frequency being used by OTA stations in your area, it shouldn't be a problem. Although to be totally legal I think you need to put some sort of filter or trap on the OTA cable to keep from broadcasting your TV2 signal to your neighbors without a license.


Bingo, give this guy a prize!
*4HiMarks* has hit the nail on the head. However, a fairly simple workaround (which you'll probably need anyway) is an amplifier on your OTA coax (recommended whether required or not). That way the backfeed signal is going to encounter at least 30db of attenuation (and no amplification) across the amplifier which should keep the FAA (and FCC) happy. We're doing the same thing and noted also that your TV2 signal may encounter some fairly steep loss in trying to make it across the two output legs of the OTA splitter. (TV2 reception in the 2nd room may become a little snowy).


----------



## destrada (Dec 23, 2005)

Any diagrams would be helpful.


----------



## Bigg (Feb 27, 2010)

I thought about this one quite a bit, since I may end up in the same situation. There are two really important things to consider:

1. The frequencies for OTA and analog cable (backfeed) are sometimes the same, and sometimes not. They did this so that 500mhz cable TV plants could use all the bandwidth, whereas there are some "gaps" that OTA has to have because that spectrum is in use by other entities. Thus, you need to actually look up all of the frequencies for your locals, neighboring locals, and cable, and pick your backfeed channels appropriately. If you split the OTA, both DVRs are going to end up joined together, and thus, both will backfeed into the same spectrum. Since each DVR uses two backfeed channels, that's 4 channels you need clear of OTA interference. There may be some "safe" channels that are not used for OTA, and thus you can use for the backfeeds universally.

2. You are going to need the best pre-amp you can get. Antennasdirect has one that's 17db I think, and even that will only just compensate for all the insertion loss of splitters and diplexers, even on a fairly short (cable length) system. First, you have to split the OTA two ways, then you have to use a splitter to inject the OTA into each backfeed, at which point it goes through the diplexer, over the cable, to another diplexer, and then to a splitter to inject the backfeed into the OTA signal, and then, and only then, to the actual DVR. At the home-run point, you may actually be better off using a 4 or 5-way splitter to join the whole system together, the antenna, the two backfeeds, and the two destinations for the backfeeds.

If you were to straight up put two diplexers inline with the satellite signal, you would probably screw the satellite signal up, although I suppose for a pair of $10 diplexers, I suppose it can't hurt to try and see what happens next time it rains.

It may not work, if your signal strength on the antenna is on the fringe in the first place. It may also require absolutely top-notch splitters and diplexers, and any new cable, and jumpers to be 3000mhz quad-shielded RG-6 with compression connectors, proper bend radius, etc etc.

A challenge with this setup is that there is no place to put an amp once you get onto the combined system, as they have insane loss going the "wrong" direction, and cable amps will only handle upstream amplification from 5-42mhz, which is the upband channel for DOCSIS, and sends commands back from SDV tuning adapters and does SDV and VOD signaling for cable boxes. Thus, you have to be all passive once you hit the bidirectional segment, so there's nothing you can do if the insertion loss goes over an acceptable range, either in degrading the receptivity of the OTA, or in putting snow in the analog backfeeds.

All that being said, if the cabling is that hard to run, give it a shot. It will probably end up costing $100-$200, but a lot of that, including the antenna pre-amp, can be re-used if you have to add the OTA coax later on.

Oh yeah, and if you're within 30 miles of the broadcast towers, and you don't have any extenuating circumstances (massive hill between you and them or something), try a good quality amplified indoor antenna before going mad-scientist on your coax setup.

Antennasdirect will allow returns, so if the antenna you get doesn't work, you can just send it back (probably $15 for shipping or something).

OR, you can wait for the gods (engineers at Dish) to add PBS to the LIL's and just go for sat LIL's.


----------

