Not sure if this is the right place to ask, but here it goes.
I work in a healthcare facility that gets it's cable signal from Cablevision NY. They work in conjuction with an outside vendor who turns on and off TV service via addressable cable boxes in each patient room. We recently added some HDTV flat screens in waiting rooms and VIP rooms ( no cable box, free service) but with the cable plugged into the TV directly, it seems the HD channels of the major networks are blocked. I can't get them when I do a scan. Why they are blocked , I have no idea.
But our OTA antenna is still hooked up on the roof, and one day I tested it to see if I could get channels on one of the TV's, it worked.
So now my question is how do I combine the 2?. Do I need an ATSC to QAM converter, then feed that into the main feed where Cablevision comes in? We do a similiar setup now in which we have hospital channels with messages combined with Cablevisions signal, so I'm assuming it could be combined.

Not sure if this is the right place to ask, but here it goes.
I work in a healthcare facility that gets it's cable signal from Cablevision NY. They work in conjuction with an outside vendor who turns on and off TV service via addressable cable boxes in each patient room. We recently added some HDTV flat screens in waiting rooms and VIP rooms ( no cable box, free service) but with the cable plugged into the TV directly, it seems the HD channels of the major networks are blocked. I can't get them when I do a scan. Why they are blocked , I have no idea.
But our OTA antenna is still hooked up on the roof, and one day I tested it to see if I could get channels on one of the TV's, it worked.
So now my question is how do I combine the 2?. Do I need an ATSC to QAM converter, then feed that into the main feed where Cablevision comes in? We do a similiar setup now in which we have hospital channels with messages combined with Cablevisions signal, so I'm assuming it could be combined.
CATV and OTA can't be combined. They use many of the same frequencies.

Actually, if you blocked out everything above ~450MHz on the cable system and combined OTA UHF ONLY, it might work. You would need to put a UVSJ (http://www.cencom94.com/gpage.html) on the antenna line so that only UHF is present then combine it with the cable fed. Don't use the UVSJ to combine.

Don't know where the addressable stream is, though. Give it a try -- parts are cheap.

CATV and OTA can't be combined. They use many of the same frequencies.

I understand that. That is why I asked if I needed an OTA-QAM converter, then pump in the signal. So that the analog channels being fed by Cablevision is not affected since only QAM channels are being pumped in. And at the same time if I tune to channels 2.1,4.1,etc, I would get the HD signal.

I understand I can't just pump in the OTA signal into Cablevisions signal since for example cable Ch2 and OTA analog Ch2 will be intefering with each other.

I understand that. That is why I asked if I needed an OTA-QAM converter, then pump in the signal. So that the analog channels being fed by Cablevision is not affected since only QAM channels are being pumped in. And at the same time if I tune to channels 2.1,4.1,etc, I would get the HD signal.

I understand I can't just pump in the OTA signal into Cablevisions signal since for example cable Ch2 and OTA analog Ch2 will be intefering with each other.
With a UVSJ, only the UHF channels would be combined with the cable feed. You would be able to just press 2.1 and go to OTA channel 2. The downside is that cable channels ~61 on up would go away.

You could do an ATSC to QAM conversion, but that gets rather pricey, and you still have to make sure there is nothing on the cable system above the highest analog channel.

With a UVSJ, only the UHF channels would be combined with the cable feed. You would be able to just press 2.1 and go to OTA channel 2. The downside is that cable channels ~61 on up would go away.

You could do an ATSC to QAM conversion, but that gets rather pricey, and you still have to make sure there is nothing on the cable system above the highest analog channel.

What if after Feb 2009, after the analog channels go away, would I then be able to combine the OTA and Cablevisions feed, since there would be no more analog signal on the OTA signal?

What if after Feb 2009, after the analog channels go away, would I then be able to combine the OTA and Cablevisions feed, since there would be no more analog signal on the OTA signal?
There's no knowing what may pop up in the VHF bandwidth. Whether you do it now or later, you're going to want to make sure that only UHF gets combined with the cable feed and you're going to need to make sure that everything above ~450MHz gets blocked from the cable feed.

Don't use the UVSJ to combine.



How would I combine?

How would I combine?
Coming out of the UVSJ would be just UHF. Don't forget to terminate the VHF port. Use a 2-way splitter (5-1000MHz) to combine. You gotta make sure that there is nothing on the cable system above ~450MHz, too. An LPF-450 would take care of that (just Google it. They're ~20bux or so).

Coming out of the UVSJ would be just UHF. Don't forget to terminate the VHF port. Use a 2-way splitter (5-1000MHz) to combine. You gotta make sure that there is nothing on the cable system above ~450MHz, too. An LPF-450 would take care of that (just Google it. They're ~20bux or so).

Ed, forgive my ignorance. How do you terminate the VHF port.
And also , when using a 2-way splitter to combine. What goes into the "in" port? the UHF or the Cablevision feed, or it does not matter?

Ed, forgive my ignorance. How do you terminate the VHF port.
And also , when using a 2-way splitter to combine. What goes into the "in" port? the UHF or the Cablevision feed, or it does not matter?
Terminators (http://www.smarthome.com/7808/75-Ohm-Terminator-20-Pack/p.aspx). The UHF goes into an OUT port and the Cablevision feed goes into the other OUT port while the IN port goes to your distribution system.

Said slightly differently, a splitter used in reverse acts as a combiner.

So long as the frequency ranges on each cable are non-overlapping, the combiner (splitter) will, well, combine them. If they are overlapping, you need to use filters on each side to ensure there is no overlap. The LPF-450 mentioned above will block all cable channels over 62 ("ZZ"), allowing you to combine OTA UHF channels (anything 14 and higher) onto the same piece of coax.

(Note that OTA UHF 14 is above the frequency of cable channel 62, which is why this works. )

There are 8VSB decoders and QAM encoders (what you'd need to decode the ATSC digital OTA signal and re-encode as an in-the-clear digital cable channel), but they're fairly specialized and low-volume (and hence expen$ive!). You don't need or want them, assuming your TVs can be set to tune UHF ATSC digital channels and cable channels in some reasonable way.

Thanks for the info guys. I'm going to give it a shot. It would be nice if I could get some of these patient rooms and waiting rooms some HD.

One other question. When I tested the OTA antenna, our CH2 WCBS-DT (Ch 56), was the only channel that was giving me a problem as far as reception. All other channels were fine. Is it possible there is a splitter somewhere in the line that is blocking Ch2 HD? What freq would Ch 56 be?
As far as the rest of the HD channels, as well as the analog OTA, it is crystal clear. So I know I have a good signal.

A few more updates since my last post.
I traced the antenna line all the way down, and it goes into a Blonder/Tongue Apt amplifier that only goes up to 550Mhz. So maybe that was my problem. I put a 900MHZ splitter on it before it hits the amp ( the other output is needed for our radio/muzac as well) and so far Ch 2 is coming in ok). Plus I tore out a lot of old splitters and cables to clean up the signal.

But even if I tried your suggestions with the filters, how would it work? Because I have Cablevisions feed going into "Cable" input on the HDTV, how would it get the OTA signal? It would have to go into Ant1 or Ant2 since its an ATSC signal, not a qam signal ,right?

A few more updates since my last post.
I traced the antenna line all the way down, and it goes into a Blonder/Tongue Apt amplifier that only goes up to 550Mhz. So maybe that was my problem. I put a 900MHZ splitter on it before it hits the amp ( the other output is needed for our radio/muzac as well) and so far Ch 2 is coming in ok). Plus I tore out a lot of old splitters and cables to clean up the signal.

But even if I tried your suggestions with the filters, how would it work? Because I have Cablevisions feed going into "Cable" input on the HDTV, how would it get the OTA signal? It would have to go into Ant1 or Ant2 since its an ATSC signal, not a qam signal ,right?
Different TV sets do it differently. Some have you scan and they store the locked channels in memory, and as you change channels they scroll through and display ALL channels, whether they be analog (CATV or OTA) or digital (CATV or OTA). You don't even have to change inputs.

Most, though, have you scan one input for cable and then scan the other input for antenna. When you watch, you have to change inputs on the TV set to go between cable and OTA.

If there are 2 inputs, you would have to have a 2-way splitter at the TV set to feed each input.

Hi Ed,

I've been reading this thread as I'm interested in accomplishing the same thing at home. Everything seems pretty clear to me so far, however would I have to block the UHF signal from back feeding into the cable line? I'm wondering if it would interfere with my cable modem, not to mention piss off the cable company.:cool:

Thanks

Hi Ed,

I've been reading this thread as I'm interested in accomplishing the same thing at home. Everything seems pretty clear to me so far, however would I have to block the UHF signal from back feeding into the cable line? I'm wondering if it would interfere with my cable modem, not to mention piss off the cable company.:cool:

Thanks
A cable modem is a VERY different thing. Most likely, the datastream for the cable modem is in the UHF band, plus there would be a huge chance that OTA stuff would get into the return path of the cable system, which would not only cause you grief, but other subscribers as well. Not only internet, but also digital telephone, VoIP, and OnDemand users.

Cable modem upstream frequencies (for the US DOCSIS cable modems, which is 99+% of the US market) are in the T band, well below channel 2 in frequency, so there is absolutely no concern there. Downstream (to you) is a normal cable channel, and could conflict with your UHF signal, so you do need to be sure to not interfere there (with your own or your neighborhood signal).

UHF is above the cable 62 ("ZZ") channel, so if you know your cable company transmits nothing about that, you're OK. This is very hard to know however, so if you add an LPF-450 filter to your cable line (as above), that will effectively block your own backfeed of the OTA signal into the neighborhood CATV links.

Cable phone modem, On Demand...I have that too. Probably the best/simplest thing to do is install an A-B switch in the basement and manually switch it over depending on what I want to watch. Oh well, interesting idea anyway...

Sparkatola

Okay, Sokoloff thanks. My previous post was in response to egnlsn. I didn't see your post until I replied. So you think its worth a try then? I'll see if I can gather the parts and try it.

Sparkatola

Cable modem upstream frequencies (for the US DOCSIS cable modems, which is 99+% of the US market) are in the T band, well below channel 2 in frequency, so there is absolutely no concern there.

You're suggesting that there is nothing being broadcast in the 5-42MHz bandwidth? Surely, you jest. That's 37MHz of bandwidth that is just dead space, not being used for anything. In there we have nine different Shortwave bands, seven different HAM bands, Civil Air Patrol, Land Mobile (Public Safety), and let's not forget the CB radio band (2008-2009 Frequency Allocations (http://www.cedmagazine.com/CED-Wallcharts.aspx?menuid=704) Click on 2008-2009 Frequency Allocations)

UHF is above the cable 62 ("ZZ") channel, so if you know your cable company transmits nothing about that, you're OK. This is very hard to know however, so if you add an LPF-450 filter to your cable line (as above), that will effectively block your own backfeed of the OTA signal into the neighborhood CATV links.
An LPF-450 notches above 450MHz ~50dB. A 2-way splitter has port to port isolation of 26-34dB (depends on manufacturer). Line taps have TAP to TAP and TAP to OUT isolation of ~29-35dB. OTA UHF isn't going anywhere other than his house.

You're suggesting that there is nothing being broadcast in the 5-42MHz bandwidth? Surely, you jest. That's 37MHz of bandwidth that is just dead space, not being used for anything. In there we have nine different Shortwave bands, seven different HAM bands, Civil Air Patrol, Land Mobile (Public Safety), and let's not forget the CB radio band (2008-2009 Frequency Allocations (http://www.cedmagazine.com/CED-Wallcharts.aspx?menuid=704) Click on 2008-2009 Frequency Allocations)


And exactly which of those are delivered to mikepier or sparkatola by their cable company's coax such that they would need to be concerned with "breaking" the cable company's neighborhood feed?

Oh right, none of them.

And exactly which of those are delivered to mikepier or sparkatola by their cable company's coax such that they would need to be concerned with "breaking" the cable company's neighborhood feed?

Oh right, none of them.
None of them are on the cable system at all. They are floating around in the air, though. And what, may I ask, are antennas designed to do. Oh, that's right, pick up stuff that is floating around in the air. The antenna picks it up, it makes its way down the coax, through the combiner, and on to his cable modem. What's a poor cable modem to do when it receives signals from some HAM operators on the same 21.2MHz that it is supposed to receive its datastream on?

Unstated in my recommendation was my assumption that the cable modem would be located directly on the cable company's feed, and not hooked up to his rooftop antenna nor to the combined feed. I assume most people who are doing in-house distribution with centralized equipment would have naturally hooked it up that way, but I did leave open the other possibility.

Hooked up the way I intended, the cable modem would be seeing a signal down about 80dB, which it would trivially ignore.

Unstated in my recommendation was my assumption that the cable modem would be located directly on the cable company's feed, and not hooked up to his rooftop antenna nor to the combined feed. I assume most people who are doing in-house distribution with centralized equipment would have naturally hooked it up that way, but I did leave open the other possibility.

Hooked up the way I intended, the cable modem would be seeing a signal down about 80dB, which it would trivially ignore.
Fair enough.

I always recommend having a cable modem on its own, dedicated splitter and be the first device in the line, but I also know that many people have it connected to the same splitter that the TVs are.

Another argument for having them separate. ;)

Thanks for the lively discussion guys. I've ordered the bits and will try it when they arrive and let you know the results.

Spark...

Just to update, I was still have trouble getting 2.1 (56 UHF). The existing cable was RG59 from the antenna down to the comm closet where the distribution panel is. So today I replaced it with RG6. It was approx 100 feet of cable. So far so good. I get the channel with no glitches now.
So far I have the OTA cable hooked up to 2 waiting rooms, and you have to select "air" on the remote to change inputs. I'm not sure how I can print a flyer stating how to do this for the people in the waiting room, but I'm going to give it a shot.
I already mentioned this to my co-workers, so I'm sure they will be taking an extended lunch tomorrow watching the NFL games.

Another thing. What about the CATV signals radiating out over the antenna? Is it possible? Would the signal be strong enough to interfere with someone elses OTA?

Spark...

Another thing. What about the CATV signals radiating out over the antenna? Is it possible? Would the signal be strong enough to interfere with someone elses OTA?

Spark...
With an LPF-450 on the cable line, nothing above ~450MHz would even make it to the splitter/combiner (not at a usable level, anyway). Because of the port-port isolation of the splitter/combiner, any signal that's left is knocked down by another ~30dB, then the UVSJ will pass only ~470-890MHz, which has already been reduced to next to nothing.

The answer to your question is, if done properly, "No."

Hi all,
I finally got around to trying this with the components mentioned above and it works with one small issue. The cable signal seems to interfere with OTA digital channel 14 which is broadcasting at 473MHz. So it seems that the LPF-450 is letting something through above 450MHz, most likely the cable TV frequency for channel 65 which is ~470MHz. There does not seem to be any signal leakage from cable to OTA or vice versa outside of this circuit that I set up. I took a portable TV with an antenna outside and did not see any cable channels that might be radiated from my antenna, so I think I'm OK there. The other TV sets that are on cable in my house did not show any OTA signals either. Should I try another LPF-450? I wonder what the tolerance is on the specification.

Any thoughts?

Sparkatola

Nope; replacing it with another one won't help (enough).

It's an analog filter (like all such filters). They each have a characteristic rolloff of N dB per unit of frequency, so none of them will block like a brick wall. Typically, they will pass all channels up to some freq, and then have several channels of interference (where it's neither totally blocked, nor totally clear), and then will effectively totally clear.


You could try another LP-450 in series/addition to the existing one (to further knock down CATV65 before mixing), but I don't think you're going to get totally satisfactiory performance there either.

Yeah, you could try a second LPF-450 in series, but, as Sokoloff wrote, because of the roloff characteristics, it probably wouldn't help that much.

What's the highest cable channel you really care about? You could get an LPF-XX, the XX being whatever that channel is. It would need to be in the mid-50s or below.

I thought about using a different value LPF but the only ones I could find were an LPF-230 (too low) and LPF-550 or 700 (both too high). A LPF-400 or 300 would do me fine if I could find one.

Sparkatola

I thought about using a different value LPF but the only ones I could find were an LPF-230 (too low) and LPF-550 or 700 (both too high). A LPF-400 or 300 would do me fine if I could find one.

Sparkatola
Contact these people (http://www.cencom94.com/contact.html). They should be able to help you.

Thanks for that egnlsn. However after more searching I just ordered this: http://www.hometech.com/hts/search.html?_cmd=item&itgroupno=CV-310260

We'll see how it goes....

I ended up replacing the LPF-450 from Tru-Spec with a 3102-60 low pass filter from Channel Vision. It was much better, blocking cable channels 60 and above. I am now able to receive OTA digital channel 14 perfectly.

Thanks to all...

Sparkatola

Cool!

I too am interested in doing this at home. However, AntennaWeb suggests that several of my local stations will be occupying VHF frequencies post Digital Transition. (if it EVER happens)

At that point am I just out of luck?

Just got my new HDTV connected comcast (yuck) cable, I don't subscribe to HD, to it and scanned all of the channels. When I called comcast about why sometime one of my HD channels would sometimes get choppy they asked what channel it was. I said 11-1 and there reply was they don't broadcast that channel frequency and that I must be being received from OTA being picked buy the cable wiring.
How would this be different than combining an OTA antenna to improve my reception with the comcast cable?
Everything I read says do not combine the two.

Most, though, have you scan one input for cable and then scan the other input for antenna. When you watch, you have to change inputs on the TV set to go between cable and OTA.

I've been reading this thread trying to figure out not the best way to combine OTA and cable, but a way in which I do not have to switch coax inputs on my TV's when ever I want to watch internal zeevee modulated channels I use for direct tv and surveillance cameras, vs regular HD OTA signals for local channels.

Any suggestions? Let me say I am in Mexico and therefore do not receive local channels through direct.
I guess my specific question is if I can convert HD OTA signal into a cable signal?

Thank you