Personal analog TV station

[BigCJ]

Do you have a TV without any composite inputs? Is it too busy behind your set to add another connection? What about an old CRT with a perfectly good analog tuner that has long been dormant since the digital switchover? Do you not mind standard definition? If you answered “Yes” to any of these questions, this tutorial may be of some help.

What you will need:
Blonder Tongue AM60-550B – This agile modulator will act as your transmitter, the heart of your station. As far as I am aware, this equipment is FCC Part 15-compliant due to its low power output. This modulator is… agile… enough to broadcast on all of the frequencies that are still used for television: VHF channels 2-13 and UHF channels 14-36. eBay is your best bet for finding one.

Antenna – You can use pretty much any antenna with a standard coaxial f-type connector. I have a NOS roof antenna, so I’m going to use that.

Composite Video Source – For this demonstration, we’ll be using a Blu-Ray player with composite out.

Cables – 1 short coax cable to jumper the IF in/out together on the back of your modulator if this was not provided to you. 1 longer coax cable for your antenna if one is not built in to it. 1 short set of composite video cables to connect your video source to your transmitter.

RCA to Coax Adaptor – For some reason, the composite video in connector on Blonder Tongue modulators is an f-type antenna jack. The adaptor you need is easy to find on the sites of online retailers such as Amazon.

Small Flathead Screwdriver & Traveler’s Hook – Used for adjusting modulation levels and channel output selection DIP switches. All relevant knobs and switches are on the front of the unit.

Four Solid Blocks – Blonder Tongue modulators have a tendency to get very hot, so placing something under each of the four corners to let air circulate underneath it is essential unless you have an equipment rack in which you can mount your modulator. Video quality will drastically decrease if your modulator overheats.

First, you should pick out an open channel on which to broadcast. I wouldn’t recommend using sites like the TV Fool, as the frequency map is outdated. The FCC ordered TV stations to vacate higher UHF channels to make way for 5G cell service in 2019, so most stations changed their frequencies. I’ve found that Wikipedia is strangely the best way to find which channels are occupied. Search the callsigns of your local stations and look for a heading under the station logo listed as “Channels”.

“Virtual” is what that station shows up as on a digital TV tuner. “Digital” is the actual VHF/UHF channel you need to note. This screenshot is of the Wikipedia article for WBTV, a local TV station. You can see that they use their legacy branding and numbering of channel 3, but they actually broadcast their signal on UHF channel 23 now. After searching all local stations, any channels not used are free to broadcast on. Making a spreadsheet listing out all TV channels between 2 and 36 is a good idea. Don't set your modulator to channel 37 or higher. Channel 37 is reserved for radio astronomy, and channels 38-83 are now in use by cell phone companies.

Now that you have chosen which channel you want to broadcast on, pull the two little nubs out on the door on the front of your modulator to remove it.

There are three different styles of channel selection: the oldest one uses binary code set via DIP switches to set the channel, a newer style with two separate banks of DIP switches that use simple addition to set the channel (most common), and the newest version has a digital readout and push button selection. Pictures of the card detailing how to set the oldest modulators is common. My modulator has the newer style of DIP switches, which I will explain how to set.

Get out your Traveler’s Hook to flip the switches. The first bank of four switches from the left chooses between different cable standards or broadcast. You want to choose broadcast, first switch flipped up, the other three flipped down.
You’ll notice there are two more banks of DIP switches, each with four switches and the numbers 8, 4, 2, 1 over each of them. These will set your broadcast channel. The bank on the left sets the tens column and the right sets the ones column. Flip switches up to add up to the number desired. For example, I broadcast on channel 31 as a distant reference to the low-budget 1989 comedy flick UHF.

To get 31, flip up the 1 and 2 switch in the “tens” bank and the 1 switch in the “ones” bank. If you still don’t understand, I wrote out a spreadsheet for you to reference. Since I couldn't find a reputable file sharing site that wouldn't delete it after a month, I copied it down here. "U" and "D" refer to the position of each switch, flipped "Up" or "Down".
Channel Bank 1 Bank 2
VHF 02 DDDD DDUD
VHF 03 DDDD DDUU
VHF 04 DDDD DUDD
VHF 05 DDDD DUDU
VHF 06 DDDD DUUD
VHF 07 DDDD DUUU
VHF 08 DDDD UDDD
VHF 09 DDDD UDDU
VHF 10 DDDU DDDD
VHF 11 DDDU DDDU
VHF 12 DDDU DDUD
VHF 13 DDDU DDUU
UHF 14 DDDU DUDD
UHF 15 DDDU DUDU
UHF 16 DDDU DUUD
UHF 17 DDDU DUUU
UHF 18 DDDU UDDD
UHF 19 DDDU UDDU
UHF 20 DDUD DDDD
UHF 21 DDUD DDDU
UHF 22 DDUD DDUD
UHF 23 DDUD DDUU
UHF 24 DDUD DUDD
UHF 25 DDUD DUDU
UHF 26 DDUD DUUD
UHF 27 DDUD DUUU
UHF 28 DDUD UDDD
UHF 29 DDUD UDDU
UHF 30 DDUU DDDD
UHF 31 DDUU DDDU
UHF 32 DDUU DDUD
UHF 33 DDUU DDUU
UHF 34 DDUU DUDD
UHF 35 DDUU DUDU
UHF 36 DDUU DUUD

You may notice that the “tens” bank has the numbers 00-12 beneath it. This modulator is able to broadcast on many cable channels, even those over 100 since these cable channels strangely correspond to lower frequencies than over-the-air channels. Since we’re not using the cable encoding, 03 is the highest our first column will go.

Now that you’ve set your transmitter to a clear channel, complete the IF loop on the back of your modulator if the in/out jacks aren’t already jumpered. Screw the RCA to Coax adaptor onto the video input so it can accept a standard composite cable.



You’re nearly done! Set up your composite video source and connect it to the modulator. This modulator has the rare Stereo sound option; if you manage to get a similar modulator, be sure to connect your red cable to the jack labeled “R” and white cable to “L” and flip the switch to “STEREO”.


If you have a monoaural modulator, you’ll need either a stereo-to-mono converter or a sound mixer.


Connect your antenna to the RF Out on the back and set the modulator up on the blocks. You’re ready to broadcast!


Turn on your composite video source and plug in your modulator to begin broadcasting. Tune a nearby television to the channel you picked so you can see what you're doing and put on something with bright colors. Use your flathead screwdriver to adjust the Video Level screw on the front panel. Turn it up (tighten it) until the overmodulation warning light comes on, then turn it back down just until the light goes out.



It’s okay if the light comes on dimly when there are many vivid colors on the screen, it isn’t noticeable. If the picture is very overmodulated, it will appear distorted and far too bright.

Most of the other adjustments on the panel should be turned all the way up. Output Level, Audio Level, and Aural Carrier are usually impossible to set too high. If you have the Stereo option, Mono/Stereo Modulation may need adjustment to balance everything out. You’ll have to go by ear, mess with it until the audio sounds right.

Reception over large areas can vary based on many factors, mainly the quality of your antennae, your receiver, and whether you chose VHF or UHF. VHF has greater range, but UHF is better at passing through obstructions without getting blocked. Here’s a picture taken about 30 feet away from the transmitter, outside. Not perfect, but still watchable. Please ignore that diagonal banding effect, it’s an interaction between the camera and the CRT screen; it isn’t visible in person. Plus, the picture on this old set is always a bit soft regardless of reception. Sound comes in completely clear until you get to the very edge of the range.


Lastly, a word of warning. There are amplifier boxes such as the one shown below, originally meant to boost the signal from an antenna to the TV. DO NOT place one of these in line between the RF out of your transmitter and your antenna. While it will extend the relatively short range of your station, it more than likely boosts the power output of your station beyond FCC limits. Beware the wrath of the US government.

Also, it should go without saying, but don’t do something stupid like broadcast pornography or anything illegal. I’m just putting this here in case anyone reading gets some funny ideas and tries to blame me. Nope, not happening.

Well, that just about does it! You now know how to set up your own personal TV station at home. Any questions or comments are welcome!

[BigCJ]

I have an important addendum to add:

You can use this tutorial to operate your own radio station as well!*

*On the condition that VHF channel 6 is not being used by a commercial broadcaster (see original post for determining channel availability).

Explanation of how analog TV works and why channel 6 is important: An analog television is nothing more than an AM/FM radio receiver. The video is broadcast in AM, and the audio in FM. The full width of each channel (in the US) is 6MHz. Each channel broadcasts the video 1.25MHz from the bottom of the channel frequency and the audio 4.5MHz above that, 0.25MHz from the uppermost part of the range.
Understand? It's okay if you don't, it isn't too important for what we're doing. What is important is that VHF is split into three bands, appropriately called Band I, II, and III. Band I covers TV channels 2 through 6 (often called VHF-Lo), Band II is commercial FM radio and begins right where Band I ends, Band III (often called VHF-Hi) contains channels 7 through 13 and is located quite a bit further up the spectrum from Band II. We are going to use the adjacency of Bands I and II to our advantage. The beginning of FM radio (and Band II as a whole) officially begins at 88.0MHz, and the audio carrier for channel 6 happens to be 87.75MHz. Many older radios, especially ones tuned with a dial, can be tuned back past 88MHz just enough to pick up the audio from channel 6. Low power analog stations could seek assignment to channel 6 specifically to capitalize on the band overlap. These stations would play music and display a variety of different screens, such as test patterns, local weather, some sort of logo graphic, or an audio-based visualizer such the output of an Atari Video Music component. These were casually referred to as "Franken FM" stations, using TV equipment and licensing to operate an FM radio station. Looking it up, it turns out that the FCC actually made a partial exception for Franken FMs to continue broadcasting their analog signal, there's still 14 of them still in service!

Anyway, now for the good stuff. Simply set your transmitter to channel 6 and make sure you have some sort of video input active. It could be a video of a black screen, a slideshow, a visualizer, anything. For some reason, Blonder Tongue agile modulators won't broadcast without actively receiving video input regardless of audio input. You can use a standard "Y" cable to connect audio devices like phones/tablets, PCs/laptops, MP3 players, etc. If it has a headphone jack, you can use it as an audio source for your own personal Franken FM. Tune your radio to 87.75MHz and you should be good to go!