nesdev.org

I hate the auto-scanning feature. Fortunately my TVs will let me add channels manually without weirdness. So I typically have Channels 2, 3, 4 & 95, 96 added manually. Atari was partial to allowing the user to select between 2 & 3 via RF, Nintendo preferred selecting between 3 & 4.

Over the Air and Cable-ready channels 2-13 used identical frequencies in North America. It's the UHF channels from 14 on upwards where the channel assignments used by OTA and Cable differ. OTA never went above 83 and was restricted to 69 by 1983. Cable squeezed in channels in all bands up to 1.02GHz to provide up to 158 channels selectable through Cable-ready TVs See here for more info : https://en.wikipedia.org/wiki/Pan-Ameri ... requencies

If you had a cable box, typically you would set it to "broadcast" a seldom-used OTA channel, such as 3, and use the cable remote to change channels on the box instead of the TV. The TV's channel would remain at 3.

With the thanks of r0ni / Jay Lanagan, who I gave my Famicom to years ago, and was kind enough to send it back for me to test on, I can happily state that I was incorrect in my insistence that using an NES RF adapter (NES-003) worked on channels 3/4 with my NTSC Sony Wega KV-13FS100. I have to use channel 95 or 96. Details on how to get that to work on this TV:

* Famicom: Adjust TV/Game switch to Game -- if Famicom is missing labels, this switch is the one closest to the AC adapter jack -- left = TV, right = Game
* Famicom: Adjust CH1/CH2 switch to CH1 (95) or CH2 (96) -- if Famicom is missing labels, this switch is the one closest to the RF jack -- left = CH1, right = CH2
* Famicom: power on with a valid/known working game installed
* TV: Set Input to Cable (i.e. coaxial jack)
* TV: Channel Setup menu: set Channel Fix to Off -- important!
* TV: Channel Setup menu: set Cable to On -- important!
* At this point you can either input channel 95 + Enter or channel 96 + Enter on the remote, depending on what you picked for CH1/CH2, or you can select Auto Program from the Channel Setup menu. The latter will let the TV scan through channels 1-125. It will eventually find the Famicom and that channel will be auto-added to your selectable channel list. Else see the user manual for details on how to add channels by hand.

What the important steps are about: if Channel Fix is set to anything other than Off, you can't use the Cable option. Likewise, failure to set Cable to On will limit the channel range to 1-69. The user manual describes these as follows:
I will state that channels 4-6 or thereabouts (hard to pinpoint) and something like 27-28, do briefly see a picture, but the signal won't stay stable (read: it's unusable).

Also, if you're not also attaching a cable TV to the other end of it, I think probably any RF adapter will work?

A schematic of it that I found, I think is designed to block out the interfering signal on channels 3 and 4, while more or less connecting the NES RF jack's output directly to the coaxial input on your TV. The blocking should switch on only when power is present from the NES' incoming signal. (RL filter network covering the range of channels 3-4?)

So... a Famicom one I assume would do the same, just blocking Japanese channels 1 & 2 instead... unless there's something different about it. (What does that TV/Game switch do?)

If you don't have the problem of trying to combine NES / Famicom with incoming cable television, I think you can use something much simpler that just directly connects the RF RCA to your TV's coaxial input. One of these?

koitsu wrote:I will state that channels 4-6 or thereabouts (hard to pinpoint) and something like 27-28, do briefly see a picture, but the signal won't stay stable (read: it's unusable).

Japanese 95 is adjacent to 6 in frequency, according to this table. I think there's a lot of crosstalk between channels, but normally it's too weak to interfere with a signal already present on that channel, at least with cable channels. With antenna television that was a bit of a different story, where there were often very mismatched amplitudes.

@rainwarrior To clarify a bit about the RF adapters -- I suspect you know all of this, but some of the questions and "what does that tv/game switch do?" prompted me write this. Apologies if I'm adding confusion.

The native Famicom RF adapter (HVC-003) looks like this (higher res). The long spooled up cable plugs into the Famicom. The top-right connector plugs into your TV. The left-bottom terminal is intended for you to insert a raw coaxial antenna for broadcast television. The left-upper-two terminals I'm not sure about -- the Japanese talks about a VTR (video tape recorder), but maybe it's just an additional pair of terminals for older TVs that have classic pair of U-terminals on the them that can't use the top-right connector? I don't know. I also don't know what "U-V" refers to, but possibly UHF/VHF (the Japanese comes out to be "U-V duplexer").

We had more or less the same thing in North America a la Game/Computer and TV RF switches. The difference is that the physical switch to move between Game/Computer and TV was on the box itself; with the Famicom the switch/slider is on the console, along with the channel switch. I suspect this may answer some questions about what the actual HVC-003 is doing compared to what we're used to in North America.

The NES RF adapter (NES-003) is, I think, the exact same thing -- RF/RCA plus into the NES, other coaxial end plugs into the TV, and there's a coaxial plug for an antenna -- just that there is no physical Game/TV switch any more. I think the adapter just figures it out automatically based on signal strength or voltage or something from the RF/RCA end. (The NES was the first system I saw that had one of these; I was used to the aforementioned ones with the physical Game/TV switch on them. Not having to reach behind your TV to switch between things any more was convenient)

I've never seen a Famicom RF adapter actually, so that was cool to get a picture.

I had an Atari 2600 with one of those RF switches that has an actual switch on it. That one's easy to understand though, it's a literal SPDT switch.

The NES RF adapter eliminates the need for the switch by actively filtering out the corresponding channels (I think) whenever it is receiving a signal.

The Famicom RF adapter... as far as I can tell externally it should work more or less the same as the NES RF adapter, except those other terminals are weird. The diagram seems to suggest that you should bridge them together with another wire...? That can't be right. Maybe I'm interpreting that diagram wrong though, and it is like the old two-terminal connection we also used to have. Though that leaves me with the question of how the alternate connection works. You have a bare coax wire core going to the shared terminal, and the metal clamp should connect with the outer shielding? That seems really complicated for people to set up, but maybe that's how it was in Japan. ...except on the other end of the adapter is a regular coaxial connector?? Why didn't it have an input like that too instead of something that seems to require you to strip the cable yourself?

So that still leaves the question of why there's a TV / Game switch? Maybe it's just a way to turn off the RF output without powering off the Famicom, in case you need to leave it on, but want to watch TV, and don't want to pull out the cable? Though I guess if that's all it does, I can see why they just dropped the feature with the NES.

I didn't check when I had my TV set up, and I've since re-scanned it back to channel 3 so I can't really test anymore without doing the whole scan thing, but if you've got it going, does the TV / Game switch just make it stop outputting its RF signal without affecting anything else?

Found some diagrams in the Famicom manual:0
https://archive.org/details/Family_Comp ... _4/page/n5
(Extends for several pages.)

The pictures are interesting, it seems like there was a common Japanese coaxial cable ending type that didn't have a screw end but instead the inner wire extended out to be wrapped around a terminal, and the shielding had a big connecting surface below that, which would be clamped to the device? I'm trying to find a picture of this that isn't a diagram, but my knowledge of Japanese isn't good enough to find it so far.

The screw type ending that comes out of the RF adapter appears to have been a separate snap-on adapter that may have been provided with the Famicom? An emerging standard, but not the norm at the time?

Edit: Wow, this looks like instructions for stripping your own coaxial cable at the back of the manual:
https://archive.org/details/Family_Comp ... 4/page/n17

So that answers my question about that part. Yes, you really were expected to strip wires to hook up your Famicom.

Japan, like the US, used the standard 300 Ohm twin lead balanced connectors for connecting VHF antennas. However, for 75 Ohm coaxial connections, they did not adopt the screw connector as we did, at least not until later. The connection is the same, the center wire would be wrapped around a screw-type connector like speaker wire and the shield would be held down by a metal clamp. The adapters they show at pages 6 & 7 of the Family Computer manual are just wiring adapters. Everything about that RF box is 300 Ohm it appears. Page 8 shows the adapter for balanced leads and what appears to be a 300-to-75 Ohm Balun. Page 5 shows the stripped wire connected directly to the terminal on the back of the TV, but I think the manual is indicating that these TVs should have a switch to select 300 Ohm or 75 Ohm connections.