Back in the 1960’s - with a good rooftop antenna (or if the moon and stars aligned), we (living in Montreal) could get a passable over-the-air analog signal from (then) channel 8, WMTW (Poland Spring ME). The studios were well over 200 miles (350 km) away. However - the transmitter was on the top of Mt. Washington NH (still about 180 miles or over 300 km away).
I was always amazed that we could pull in a TV signal from that far away. Of course - Mt Washington is the highest point for hundreds of miles around, but you would think that the signal would fade before it went all that distance. (some years ago, the station went digital, removed the Mt. Washington tower, and now uses one nearer to its studios and aims its signals primarily at Portland ME).
I can still easily get over-the-air signals from VT and NY - up to about 100 miles away. Most seem to have their transmitters on Mt Mansfield VT (4,393 ft) compared to Mt Washington (6,288 ft) - probably due to cheaper maintenance costs.
What is the range of an over-the-air TV signal? Does it depend on the power of the transmitter (as well as its height and any obstructions)? Is a 200+ mile range unusual?
Since TV went digital, almost all the stations have switched to the UHF band. While VHF and UHF signals are both “line of sight” UHF signals are more sensitive to atmospheric conditions.
Also, digital transmission at any frequency is a much more all-or-nothing proposition. In the good old days, your TV signal might have had a lot of snow, but you could still make out the picture. Today, a digital signal will drop entirely.
In Toronto, we could get signals 60 miles from Buffalo (Ch 2 and 4) but Barrie, even closer, was iffy. This was because the antennas were tuned to the lower channels and pointed to Buffalo, Also likely that Buffalo knew its market and beamed a signal deliberately to Toronto with more power than a minor local TV channel up north. Rich people had multiple antennas pointed multiple directions.
My grandparents had a rotator on their TV antenna with a control box on top of their TV. Not sure why, there was only one station in their area (rural central MN) they could get (or at least that they watched). Possibly the salesman from Second Hand Lions stopped by at some point.
I don’t feel like getting into the calculations, but basically, the range of any radio signal is related to the transmitter power, the receiver sensitivity, and the gain of their antennas. 200 miles is pretty far for TV, since those signals will not bounce over the horizon, but as you note, having the transmitter on a mountain can increase the range by a lot. To give you some idea of what can be done with a sensitive receiver, a record for LoRA radio was recently set, where a transmission was received over 475 miles away - from a transmitter with as much power as a garage door opener.
I could occasionally pick up French TV from Plymouth UK, which is at least 115 miles, albeit mostly over open water. This was a UHF signal to a crappy set-top antenna, and though the luminance information was OK there was no colour due to the UK using PAL and France using SECAM, which processes the colour information differently.
When I was a kid living east of Rochester, NY, at home we could get channel 6 CJOH from across Lake Ontario. Our reception was consistently pretty good, but most other kids in my school could not tune it in at all. Their studios are in Ottawa, about 170 miles away. I’m not sure where their transmitter was at that time, but apparently at one time it was in Deseronto, which at only 65 miles away seems a lot less impressive. My fifth-grade teacher who lived about two miles east of us claimed that he once tuned in a station from Montreal, about 240 miles away. By his own admission, he liked to tell stories that were improved in the telling, so I don’t know if I believe that one.
I remember those days in Montreal, and channel 8 was the hardest one to get among the three major US network affiliates. You needed a really good rooftop antenna, which to my disappointment my parents never got, though we did eventually get cable when the then-newfangled technology finally came to our neighborhood. The easiest US channel to get from Montreal was WPTZ, channel 5 from Plattsburgh, NY, an NBC affiliate. The second easiest was WCAX channel 3 from Burlington, VT, a CBS station. As a kid I learned to manipulate the rabbit ears to a fully extended horizontal position to get channel 5 quite reliably with a passable image that was sometimes surprisingly clear, and channel 3 more often than not depending on weather. VHF is not strictly line-of-sight but does produce some scatter over the horizon. Otherwise the only available TV station in the area for a while was the CBC station CBMT channel 6 (and a French equivalent), until CTV launched a network and opened up CFCF-TV channel 12. Still remember the excitement of having a brand new TV channel, and watching The Andy Griffith Show for the first time.
When I lived in the north part of Toronto and got my first digital HDTV, I tried it out initially by putting a small outdoor UHF antenna (the flat kind, with “bowtie” elements in front of a rear reflector) in my living room window behind a curtain, and the results were amazing. The front of the house was south-facing and quite well aimed at both the CN tower and the Buffalo area across Lake Ontario. There was a park across the street, so no building obstructions nearby. The result was that I was reliably able to get not just all Canadian networks and nearby independent stations, but all four major US broadcast networks. I never bothered mounting the antenna on the roof, and eventually cancelled my TV cable.
There are various websites that give you an approximation of the OTA TV stations you can expect to receive with any given antenna, which depends mainly on:
[ul]
[li]Transmitter power[/li][li]Height above average area ground level of transmission antenna[/li][li]Height above average area ground level of receiving antenna[/li][li]Gain of receiving antenna[/li][li]Intervening terrain[/li][/ul]
IIRC, some local Toronto TV stations were required by government edict to reduce their transmitter power when they relocated their antennas to the top of the newly built CN Tower, because of the extra range that the height alone would provide.
I remember reading some 50 years ago that UHF curved a bit and the signal could travel about 30% further than line-of-sight.
Our local PBS station has two transmitters. One of the transmitters switched back to VHF about six months ago. (I’m guessing they sold their UHF frequency) At my house 48 miles away, I can no longer receive the VHF signal although I could receive their VHF signal back when they were analog. I have no trouble receiving the UHF signals from the other 4 stations that share the same tower.
As others have said the nature of digital broadcasting makes it very difficult to pick up distant signals (and I don’t think signal boosters will help much) but it does mean that you can pick up strong transmissions from a variety of satellites that are floating above your local horizon.
In most cases you might need a suitable box or a decoder card but it’s not impossible to pick up signals from foreign stations with some basic equipment. And those satellites are not always stationed above the countries they are beaming to so could be closer than you think.
Many Brits living in Europe use a UK address to have a box sent to and use it in their European homes in order to receive British TV.
The difference in reception between digital vs. analog modulation is (heh) analogous to the difference between AM (amplitude modulation) and FM (frequency modulation) radio: AM reception falls off gracefully, which is why you can sometimes hear AM stations much further away than any FM station. This is more common at night, when atmospheric conditions are more amenable.
We had a rotating antenna on our roof in Morgantown, WV, in the early 1960s. It allowed us to choose between TV stations in Pittsburgh (to the north) and stations in Clarksburg/Bridgeport WV (to the southwest). Dial it in, and you could hear it through the celing: ka-thunk, ka-thunk, ka-thunk…
