View Full Version : Combine two signals CATV and Air Antenna
14-Jan-2010, 9:31 AM
I want to combine two signals CATV and Air Antenna.
What I must do?
14-Jan-2010, 4:16 PM
This will generate a conflict because CATV and OTA TV share some of the same frequencies. If you put them on the same coax, you might lose some of your CATV channels. Are you sure this is what you want to do?
16-Jan-2010, 11:50 AM
Yes, I try combine the two signals by the same cable but if they (CatV and air) use the same frequency and some channels can lost, is necessary to use two lines then, If not theare another way.
Furthermore I wonder if this is really true or is another trick:
Model LPF-750 Low-Pass Filter
The Model LPF-750 Low-Pass Filter is used on systems when broadband entertainment feed
is supplied by a CATV service. The filter removes all CATV channels above the pass band,
allowing insertion of locally-generated ChannelPlus modulated channels.
* 0 to 750 MHz bandpass frequency
* Passes off-air TV channels 2 to 60
* Passes CATV channels 2 to 116
* Allows insertion of TV channels 65 to 69
* Allows insertion of CATV channels 121 to 125
* Removes cable system noise which degrades the picture quality of the locally-generated channels
This is really serious, or is another story of you accept?
16-Jan-2010, 1:18 PM
How do you use your cable TV signal now? Are you subscribed to digital cable or are you using analog cable?
Broadcast TV channels 2-69 use frequencies from 54 MHz to 806 MHz. The major US broadcasters are no longer using channels 52-69, so if you only count channels 2-51, that leaves you with frequencies from 54 MHz to 698 MHz.
Analog cable TV channels 2-125 use frequencies from 54 MHz to 804 MHz.
Digital cable TV channels 2-158 use frequencies from 54 MHz to 1002 MHz.
If you use a cable modem, then the lower frequencies below 54 MHz also need to be passed to the cable system (that's where the up-stream traffic goes).
I don't think there's any good way for both systems to share one set of coax without causing major problems. If you need both sets of signals, then you're really better off running a parallel set of coax.
Direct Broadcast Satellite (DBS) systems, on the other hand, are different because they only use higher frequencies (between 1 GHz and 2 GHz) which do not conflict with OTA frequencies. It should be possible for satellite and OTA signal to share one set of coax if they are combined through the appropriate diplexer.
22-Jun-2012, 12:42 PM
I have a similar problem. I have an antenna and also cable service. The cable service provides all channels, but only the antenna delivers my 3 local channels is good quality HD. The cable service delivers those channels in SD. My TV has only one RF input and the TV internally selects either Antenna or Cable channels. So I want to diplex the antenna signal with the cable signal into this single TV RF input. Even if I succeed at this, I will still need to switch the TV between antenna mode and cable mode, but at least I could do this via remote control without physically changing connections to the TV.
The 3 antenna frequencies for the HD locals fall on cable channels 8, 91 and 104 which would only conflict with cable channel 8 (program guide channel) since no cable channels are available on cable channels 91 and 104. Diplexers I see are always designed to combine satellite signals with lower frequency signals. But I need a diplexer that will combine the antenna signal with the cable signal. How do I solve this?
22-Jun-2012, 1:44 PM
Attempting to combine or diplex OTA and CATV signals, if done improperly, will cause harmful interference to licensed radio services such as police, fire, ambulance, rescue and aircraft communications and navigation frequencies.
CATV systems are designed as 'closed systems'. This means that no signal should be radiated over the air. Connecting an antenna to a CATV system will result in radiation of signals on frequencies that are used by legitimate licensees. You could be placing lives at risk and would certainly be at risk of civil or even criminal penalty.
Instead of trying to combine the two incompatible signal types, consider buying a tuner/converter. Some are available with high definition (HD) output.
Keeping the CATV cable completely separate from the OTA cabling, leave the CATV signal connected to the TV antenna input as it is now. Then, connect the external tuner/converter to an HDMI port or HD composite input on the TV. (The TV must have one or both, or it likely does not have HD capability.) With the OTA antenna connected to the external tuner/converter you'll have access to both CATV and OTA without risk of one causing trouble with the other.
See the following thread for a diagram and some possible tuner/converter options: http://forum.tvfool.com/showthread.php?t=2882
22-Jun-2012, 2:03 PM
I agree. I would then like to locate an inexpensive HD capable OTA tuner (probably not so cheap) since it is only for 3 local HD channels. My TV does have HDMI and component inputs.
The other complication, or maybe solution, is desired DVR capability. If I could find a DVR that has a cable RF input and OTA RF input (maybe doesn't exist), I could solve the problem, plus give record capability for each of those sources.
22-Jun-2012, 2:26 PM
Please read the thread referred to in post 6 (http://forum.tvfool.com/showpost.php?p=26026&postcount=6) of this thread. Links to several STB tuner/converters are cited.
Re. PVR/DVR functions... http://forum.tvfool.com/showthread.php?t=820. Also, http://www.silicondust.com/products/hdhomerun/prime/
Also, take a look at the Channel Master CM-7000PAL (http://www.channelmasterstore.com/HD_DVR_receiver_for_antenna_p/cm-7000pal.htm)
23-Jun-2012, 1:54 AM
In the middle of the CM-7000PAL webpage, ChannelMaster says that this model has been discontinued. If you can locate a model in the inventory of Crutchfield or some other consumer electronics store, either brick-and-mortar or online, then my recommendation is to buy it--quickly. If not, then give careful consideration to the ChannelMaster TV CM 7400R HD DVR (http://www.channelmasterstore.com/HD_DVR_with_no_subscription_p/cm7400r.htm). The older CM-7000PAL is my preferred DVR because it features the TVGuide On Screen guide, which is completely free of charge. TVGoS downloads data from your PBS and CBS stations. The CM 7400R features as variety of Internet-based media services. It supports ClearQAM cable as well as ATSC for OTA digital reception. It has much more storage than the CM-7000PAL. However, its Internet-based guide is not free. Although ChannelMaster advertises the CM 7400R as subscription-free, the user cannot take advantage of all features of the DVR without paying a subscription fee.
23-Jun-2012, 3:00 AM
This is all good advice. If I refuse to pay for TV from companies like Bell and Shaw (in Canada), I can guarantee you I will never pay somebody to tell me what's on my free OTA. There are many free sources for channel information on the Internet. If I can't use the DVR without paying somebody every month, then I wouldn't buy the DVR.
24-Jun-2012, 5:30 PM
hey guys just a thought but if you only have one cable to tv could you not use a simple a/b switch wherever you signals come into the main run to the tv.
they even make ones with remote control for like 30ish bucks ... i've thought about doing this because i have kept cable service for internet only but some of the chs are still there ... now it may or may not be hd and i'm not sure how much the cable company would like anyone viewing the channels but it can be done much easier this way than trying to combine them on one coax.
24-Jun-2012, 7:00 PM
We have identical situations. I continue to be a paying customer for their Internet service via cable. There continue to be lots of QAM unscrambled signals on the cable though. Although the remote control A/B switch would work, paying $30~$40 dollars for one remote control switch seems excessive.
24-Jun-2012, 7:13 PM
With an A/B switch, using only the built-in tuner of the TV, you'll need to go through the process of reconfiguring the tuner each time you want to switch from OTA (ATSC coded signals) to CATV (QAM coded signals) and vica versa.
On the up side, the A/B switch is less expensive than adding an external tuner.
Any attempt to diplex the CATV and OTA signals short of converting the ATSC format to QAM (build the equivalent of a CATV head-end... $$$$$$$$$$$$$$) will leave you with the same problem of reconfiguring the tuner via the TV's setup menu. To make it even less convenient, you may find a channel scan is required each time you switch modes.
24-Jun-2012, 7:19 PM
"Reconfiguring the tuner" on my Sony TV means simply switching between Cable mode (QAM channels) and Antenna mode (OTA channels). This takes a couple of quick button pushes via remote control. Scans for each mode are saved so there is no reason to rescan when switching between the modes. I have my 3 local OTA channels saved in Antenna mode. And my many QAM cable channels are saved in Cable mode. I do have to rescan the QAM channels regularly since they change.
26-Jun-2012, 8:26 PM
http://www.tinlee.com , has coax switches that can be at a remote location and the remote control at your location.
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