Monday, August 18, 2008

OIRT FM

The International Radio and Television Organisation or OIRT was known before 1960 as Organisation Internationale de Radiodiffusion or OIR I wanted to get the Esperanto out of the way first. It was a network of Eastern European radio stations established in 1946 for the express purpose of sharing content to reduce operating costs. The original member stations were in Bulgaria, Finland, Hungary, Poland, and Romania.The first FM station in the U.S. was only constructed in 1937, so this was very forward-thinking.

But this is Arcane Radio Trivia, and we arbitrarily disregard radio outside the 50 states. What makes OIRT matter domestically, is the scope of the FM band. In most of the world, the portion fo the radio band used for FM radio is 87.5 Mhz to 108 Mhz. In the U.S. It begins at 88.1, with a scant half dozen FMs on 87.9. On 87.5 is VHF TV channel 6, of course that frequency can be tuned on some radios as the audio is carried by an FM wave.

The original plan for FM in North America was 42-50 MHz but this was changed in 1945. (
Sorry Mr. Armstrong.) At that time under intense pressure from a bastard at RCA the FCC moved it to it's current position with one slight difference.

The
OIRT FM broadcast band covers 65.8 to 74 MHz. This was the preference of the USSR, and they pushed it onto the Eastern European nations they'd been occupying since the end of WWII. (See OIRT membership first paragraph.) Following the fall of the Berlin wall and the collapse of Russia, these nations all adopted the 87.5 to 108 MHz band. This wasn't as political as it sounds. It was just easier to get used hardware configured that way. Only 4 nations still use the old OIRT band Russia, Belarus, Moldova, and Ukraine. Hungary was the most recent to convert, only making the change final in 2007. (also interesting to note that Japan uses 76-90 MHz, beginning just above OIRT and ending shortly into the American band.

While it's interesting that FM has occupied three non-contiguous segments of the VHF band, it's more interesting how spacing was handled. In the US we consistently apply a
200 kHz offset. OIRT FM frequencies are based on 10 kHz rather than 50 or 100 kHz multiples. Wilder still is that the FCC originally originally envisioned a play with an 800 kHz separation for each metropolitan area. More ridig still, the FCC reserved 20 FM frequencies for Class A liscenses only. That plan lasted until 1987, when they relaxed the rules to allow more powerful Class A staitons. Then in 2004 they tossed those rules entirely for a "whatever fits" policy. Fits being as defined under 47 CFR Section 73.207 Separation requirements. OIRT's spacing originally seems too narrow, but over time we've drifted toward their 60-year-old standards.