Can my house's coax cable wiring share an indoor antenna across rooms?

August 1, 2023 7:59 PM

Moving into a newly built house next week, and trying to decide what to do TV-antenna-wise. The living room is on the second floor and my office is on the third floor, and both have coax cable plugs in the walls. Could I buy an indoor TV antenna and plug it into the wall in my third-floor office (for higher-up reception and less of an eyesore in the living room) and then use it with the TV on the second floor by plugging that into the wall? Or is there something I'm missing?

BONUS QUESTION: If anyone has any recommendations for a way to (relatively easily) watch broadcast TV on my Apple TV, via the home wifi network, that are also compatible with the Japanese market, I'm all ears.

posted by DoctorFedora to Technology (16 answers total)

Unsure if they work in Japan, But the HDHomeRun series of devices let you share a broadcast antenna with any number of internet connected devices including an Apple TV.
posted by AaRdVarK at 8:51 PM on August 1, 2023

What's the norm for TV antenna installation where you live - are you sure that the coax sockets aren't already connected to an antenna in the attic or on the roof (or to a point there where you're expected to install one)?
posted by offog at 9:17 PM on August 1, 2023

Response by poster: ah, unfortunately it looks like the HDHomeRun probably won't work here, if only because Japanese broadcasts are encrypted and need a BCAS card to decrypt them
posted by DoctorFedora at 9:18 PM on August 1, 2023

I believe the Japanese equivalent to HDHomerun is called a Nasne.
posted by kschang at 10:11 PM on August 1, 2023

Response by poster: offog, the norm for TV antennas is an exterior antenna, but the house we bought does not have one. The main options there are UHF aerial antenna on the rooftop, or rectangular panel-shaped antenna on the exterior wall, but we're looking at probably something like ¥50,000+ including installation for those.

kschang, I'll have to look into whether the Nasne is one of the tuners that has an Apple TV app or not. It seems to have an iOS app, but that's honestly probably not adequate I think
posted by DoctorFedora at 10:25 PM on August 1, 2023

It works best with a PS5.
posted by kschang at 10:28 PM on August 1, 2023

Response by poster: yeah, that makes sense. I have a PS4 but not a PS5. Ideally any sort of home-wifi-based tuner situation would work with the Apple TV, for sound output through Homepods (and just general convenience of use compared to the Playstation).
posted by DoctorFedora at 10:43 PM on August 1, 2023

Assuming that the house doesn't have cable TV already hooked up and the coax is just for an antenna, you can use it.

Find the terminal point of the coax. All the runs should meet somewhere like a utility closet or basement/attic. In North America coax cables sometimes meet at a box on the outside of the house near the telephone drop. Hook your antenna there. That way if there's any kind of one way device on the circuit you'll be on the right side of the signal path.

You might need an RF amplifier if there isn't enough gain coming off the antenna. Having a bunch of cable in the house and multiple outlets will cause some signal loss. Try without an amp before you spend the money. Make sure the amp will pass digital signals!
posted by Zedcaster at 11:10 PM on August 1, 2023 [1 favorite]

Response by poster: I want to say there's a sort of conduit that opens to the outside of the house, for an external antenna to be mounted on the wall or roof, but it's basically at third-floor level above the second-floor balcony. The idea here would be to have an indoor antenna instead of that outdoor antenna, but I don't know if it'd be viable.

I suppose there's also the factor where it is, structurally, pretty different from an American house. I do not actually know where the coaxial terminal point would be, especially since we don't really have a utility closet and certainly not a basement or attic!
posted by DoctorFedora at 11:21 PM on August 1, 2023

I want to say there's a sort of conduit that opens to the outside of the house,

If there's no basement/attic/utility closet then I'd bet the cables start outside. That conduit might be where the coax starts. Having said that there's no harm in hooking the antenna to one of the wall connections, the signal will appear at any connected wall jacks.

The idea here would be to have an indoor antenna instead of that outdoor antenna, but I don't know if it'd be viable.

It could be possible. Antennas like to be high and outside, but depending on the amount of shielding that the house provides you might get some signal. Have it as high up in the house as possible and near or against a window.

There are a lot of factors regarding antenna placement, but digital radio frequency signals work even at low levels so there's a chance you'll have success.
posted by Zedcaster at 12:44 AM on August 2, 2023

Response by poster: Hmm, it does seem fairly likely that the interior cabling situation probably involves splitters with diodes that would prevent an antenna in one room from providing a signal back upstream on the cable. Well, I guess that likely settles that.
posted by DoctorFedora at 4:05 AM on August 2, 2023

If you can find the splitters, you can remove or reconfigure them to support your intended use. They make inline couplers for coax if you want a direct connection, or put the run with the antenna on the input side of any splitter. Note that a splitter will cause some signal loss, so generally should be avoided unless you have a need for it.
posted by yuwtze at 5:40 AM on August 2, 2023

Yes, you can. You need to connect the end of the second-floor cable to the end of the third-floor cable with an F-F F coupler, wherever they may be found. It's not likely to be configured like that right now.
posted by flimflam at 9:36 AM on August 2, 2023

Response by poster: Interesting! I'll have to look into my options.

There is a very real possibility that "just pay someone to install an antenna on the exterior wall" might actually be not expensive enough to be worth going all this stuff with indoor antennas, too, heh
posted by DoctorFedora at 10:03 PM on August 2, 2023

With UHF signals, at least in the US, there's a lot of attenuation that can cause issues with reception. Having the antenna outside is going to make your reception far more reliable.

Maybe mentally prepare to spend that money if you'll be at the place for a while. I think 50000 JPY seems cheap to have someone go up on a ladder and install an antenna you provide. That's about what I'd expect an electrician to charge to install an antenna in the US. Maybe an hour's worth of two people's labor.

Even so, a TV panel antenna is pretty good, acting as a "magnetic loop antenna," which is excellent for rejecting RF noise in urban areas. Your plan will probably work well enough to justify trying before hiring someone.

I'm not sure if "Cable TV" is a thing in Japan, but if it is, make sure that any connection from your house to the Cable TV network via coax is terminated (like, not just unplugged, but there's a terminator on the end). As long as your house's coax is isolated, you can use the rest of the coax network however you like, including distributing the signal from the antenna feeding from the 3rd floor.

Get a decent amplified flat antenna with a built-in amplifier and tape it to the window in the 3rd floor room. Connect it to your coax jack. If Japan is anything like the US, that should only cost you a few bucks from a junk store. Suppose it works well, sweet! If not, experiment with orientation. If that still stinks, you may want to hire someone.
posted by Geckwoistmeinauto at 4:02 AM on August 3, 2023

Response by poster: Thanks for all the info, everybody!
posted by DoctorFedora at 3:30 PM on August 3, 2023