The OIRT FM broadcast band covers 65.8 to 74 MHz. It was used in the Union of Soviet Socialist Republics and most of the other Warsaw pact member countries of the International Radio and Television Organisation in Eastern Europe (OIRT), with the exception of East Germany, which always used the 87.5 to 100 (later 104) MHz broadcast band in line with Western Europe.

The lower portion of the VHF band behaves a bit like shortwave radio in that it has a longer reach than the upper portion of the VHF band. It was ideally suited for reaching vast and remote areas, that would otherwise lack FM radio reception. In a way, FM suited this band because the capture effect of FM could mitigate interference from skywaves.

Following the collapse of the communist governments in Eastern Europe, the 87.5 to 108 MHz band began to be adopted and is now in use in all those countries. This was prompted by the expansion of broadcasting and the modernisation of existing transmission networks, using new or second-hand transmitters from western countries,[citation needed] together with a general desire for standardization with the West.

Many countries have completely ceased broadcasting on the OIRT FM band, although use continues in others, mainly the former republics of the USSR. The future of broadcasting on the OIRT FM band is limited, due to the lack of new consumer receivers for this band outside of Russia.

Countries which still use the OIRT band are Russia (including Kaliningrad), Belarus, Moldova,Ukraine and Turkmenistan.

Hungary closed down its remaining broadcast transmitters in 2007, and for thirty days in July of that year, several Hungarian amateur radio operators received a temporary experimental permit to perform propagation and interference experiments in the 70–70.5 MHz band.

Unlike Western practice, OIRT FM frequencies are based on 10 kHz rather than 50, 100 or 200 kHz multiples. This may have been to reduce co-channel interference caused by Sporadic E propagation and other atmospheric effects, which occur more often at these frequencies. However, multipath distortion effects are less annoying than on the CCIR band.

Stereo is generally achieved by sending the stereo difference signal, using a process called polar modulation.

The 4-meter band (70–70.5 MHz) amateur radio allocation used in many European countries is entirely within the OIRT FM band. Operators on this band and the 6-meter band (50–54 MHz) use the presence of broadcast stations as an indication that there is an "opening" into Eastern Europe or Russia. This can be a mixed blessing because the 4 meter amateur allocation is only 0.5 MHz or less, and a single broadcast station causes considerable interference to a large part of the band.

The System D television channels R4 and R5 lie wholly or partly within the 87.5–108 MHz FM audio broadcast band. Countries which still use System D therefore have to consider the re-organisation of TV broadcasting in order to make full use of this band for audio broadcasting.

Prev:How to Convert WMV to H.264

Next:How Does a Stereo System Work?

Leave a message

Message List

Comments Loading...

Products Category

Products Tags

Fmuser Sites

What is OIRT bandplan

Leave a message

Message List