Gary Albert, better known online as the HDMI Guy, is the editor of HDMI RF Modulator, a practical resource for people trying to make old-school video equipment work with modern TVs, displays, and home entertainment systems.
If you’re trying to get video from a modern HDMI device onto a TV that only has a coaxial input—or you want to send one HDMI source to several TVs using the coax wiring already in your house or building—you’ll need an HDMI-to-RF modulator.
Maybe you’re connecting a Roku or cable box to an old TV. Maybe you’re feeding a security-camera to a monitor with no HDMI input, or sending the same satellite receiver to TVs throughout a bar, hotel, school, or large home.
If picture quality isn’t your primary concern, a cheap analog modulator may be enough for a simple one-TV hookup. It converts the HDMI signal into an old-style analog TV channel, usually at standard-definition quality. For a larger system—or if you want a much better picture on newer TVs—a digital modulator such as the Thor Petit is built for the job. It creates a real digital TV channel that can travel through existing coax wiring and be tuned in by compatible televisions.
| Feature | Cheap Analog Modulator | Thor Petit |
|---|---|---|
| RF television signal | Analog NTSC | Digital ATSC/QAM |
| Picture delivered to TV | Essentially SD | HD digital video |
| Typical purpose | Get HDMI onto an old TV | Distribute HDMI through a coax network |
| Channels | Often Ch. 3/4 or limited selection | RF-agile across roughly 50–950 MHz |
| Multiple TVs | Possible, with limitations | Designed for large distribution systems |
| Output level | Consumer-level | Up to about +24 dBmV |
| Configuration | Basic switches/buttons | Ethernet/Web management |
| Encoding controls | Little or none | MPEG-2 bitrate and service parameters |
| Audio | Analog-TV quality | MPEG Layer II/AAC/AC-3 |
| Best customer | Person with one old television | Home, bar, hotel, school, commercial AV system |
What Does an Analog HDMI RF Modulator Do?
A basic analog HDMI RF modulator is mainly a compatibility device. It lets you take the HDMI output from a streaming box, DVD or Blu-ray player, cable box, computer, or other source and convert it into an analog television channel.
In the United States, that usually means an NTSC signal. Many inexpensive modulators use familiar channels such as channel 3 or 4, although some models offer additional channel choices.
For a simple home setup, that may be all you need.
If you have an older television with a coax input and no HDMI connection, a cheap analog modulator can provide an easy way to keep using the TV with newer equipment.
The tradeoff is picture quality. Even if the modulator accepts a 1080p HDMI signal, its RF output is still analog television. In practical terms, you are dropping from an HD digital source to something much closer to standard-definition TV.
That may look perfectly acceptable on an old CRT television. It will usually look much softer on a large modern HDTV.
What Does a Digital HDMI RF Modulator Do?
A digital HDMI RF modulator such as the Thor Petit takes a different approach. Rather than turning HDMI into an analog TV channel, it creates a digital television channel.
The Petit supports ATSC, QAM, DVB-T and ISDB-T modulation and allows control of things such as frequency, service name, network ID, transport-stream IDs and RF attenuation.
That’s headend equipment, albeit relatively inexpensive headend equipment.
It also produces a much stronger, controllable RF signal
Thor rates the Petit at +24 dBmV, with adjustable RF output. The company specifically designs it to distribute a channel to hundreds of televisions over an existing coax network.
That’s a very different job from running 12 feet of coax from a $50 converter to Grandma’s 1996 Magnavox.
The Petit can output ATSC or QAM, which are digital television formats commonly used for over-the-air and cable-style distribution.
That means the television receives a digital channel rather than an old analog one. The result can be a much better picture, including HD video.
This is one of the biggest reasons for the price difference.
A cheap analog unit may cost around $50 because its job is relatively simple: convert HDMI into an analog RF signal. A device such as the Thor Petit is encoding video, creating a digital television service, and producing an RF signal intended for more serious distribution systems.
One TV or Many TVs?
This is probably the easiest way to decide which type you need.
If you simply want to connect one HDMI device to one older television, an analog modulator is usually the sensible choice. There is little reason to spend several hundred dollars to solve a basic connection problem.
Digital modulators become more useful when you want to distribute one HDMI source to multiple televisions.
For example, a restaurant might want the output of one satellite receiver available on TVs throughout the building. A school might want to distribute a video feed to classrooms. A hotel or commercial facility may already have coaxial wiring running to dozens of televisions.
A digital RF modulator can turn the HDMI source into a channel that travels through that existing coax network.
More Control Over the RF Signal
Cheap analog modulators usually provide only basic controls. You plug everything in, select a channel, and perhaps adjust a few settings.
The Thor Petit provides much more control.
It can operate across a wide RF frequency range, provides adjustable output levels, and allows configuration of encoding and television-service parameters. It also supports Ethernet and web-based management.
Those features are unnecessary for most single-TV installations. They become important when you’re building or maintaining a larger coax distribution network.
Which One Should You Buy?
For most people connecting one device to one old television, buy the inexpensive analog modulator. It is cheaper, simpler, and probably does everything you need.
Choose a digital HDMI RF modulator when picture quality matters, when you need a digital ATSC or QAM channel, or when you’re distributing video to multiple TVs through an existing coax system.
The simplest way to think about the difference is this:
A cheap analog HDMI RF modulator is an adapter for getting HDMI onto an older TV.
A digital HDMI RF modulator such as the Thor Petit is a small television distribution system.
They both convert HDMI to RF, but they’re built for very different jobs.