Synchronised AM networks.

[Colly0410]

In 1967 a new AM national British radio station called BBC Radio1 started broadcasting using a 'single frequency synchronised network.' It used about 14 transmitters dotted all over the Country using one frequency 1214 Khz (247 metres) the powers went from 140 KW's down to 500 watts. It covered most of the Country, but some areas picked up a signal from from more than one transmitter, these were known as mush zones, the signal faded & speech & music was distorted in these areas. Of course I had the bad luck to live in a mush zone..

In 1978 Radio1 changed over to a duel frequency AM network, 1053 Khz & 1089 Khz, it still had a bit of a mush zone problem but nowhere near as bad as before the change, vast majority of listeners could get at least fair reception from one of the transmitters..

Were single frequency networks ever used in USA?

[Electronic M]

Not that I'm aware of. We preferred "superstations" with a "clearchannel".....Basically stick up a 100KW tower give it a station frequency no one else in the USA (or often the entire continent) could use and let that tower be heard over most of the county...WLW even had experimental license to run 500KW (there were reports of reception as far off as Australia, and your nation's Queen called in to a request show once). Some stations had and have AM/FM simulcast.

[stromberg6]

WBZ and WBZA in Mass were synchronized in the early 20th century, one in Boston and one in East Springfield in the Westinghouse plant where early radio sets were manufactured, along with other devices, now totally demolished. The Springfield Paramount Theatre still has the phone block for a line to the station that was used to do remotes of Wurlitzer organ programs from the theatre. Anyone else have more info on these stations?
Kevin

[Titan1a]

Apex anyone?

[old_tv_nut]

Stromberg, thanks for the post (and thanks to the OP), as I never heard of this. Does seem like a bad idea due to the long range coverage of AM stations, especially at night, plus no capture ratio effect like FM. No wonder there were "mush regions."

[KentTeffeteller]

Not done in the USA either. Has been discussed in the past with the FCC by some organizations.

[ChrisW6ATV]

Originally Posted by Colly0410

Were single frequency networks ever used in USA?

No, they have not been, and also RDS and its ability to automatically switch a car radio to a matching channel/station has never been used here. The main reasons are:

-The USA is a much more spread-out country than the UK or most of Europe in general.
-Radio broadcasting and station ownership here were always privately owned, and often locally owned, so there was much less centralization of programming here, no BBC equivalent. There have always been radio program networks, but they seldom or never had complete control of any stations, much less a full, wide-area set of them.

Now that a few huge media corporations own a large percentage of stations across this country, the RDS-type switching could probably be feasible here now if not soon. (Whether it is a good idea, though, is another discussion.)

[jr_tech]

Originally Posted by ChrisW6ATV

No, they have not been, and also RDS and its ability to automatically switch a car radio to a matching channel/station has never been used here.

Some classical, PBS and other stations usually originating at the educational end of the band set up small networks for increased coverage, and indeed do use automatic RDS switching. But then, these are usually FM stations.

jr

[ChrisW6ATV]

JR, that is interesting to know. I was not aware that any radios even sold in the USA had RDS switching ability. Only one station in my area even seems to use the RDS "station type" data field.

[jr_tech]

According to Wikipedia, most car stereos do support the AF (alternate frequency) field/mode.

https://en.m.wikipedia.org/wiki/Radio_Data_System

jr

[Colly0410]

Until 1967 the 1214Khz AM frequency was used by the BBC Light Program to be used by filler low power transmitters where the main Droitwich high power 200Khz long wave (long wave was never used for broadcasting in USA AFAIK, it still is in UK) transmitter didn't provide adequate signal, mostly in Scotland. The BBC until then had 3 national networks: The Light Program on 200Khz long wave with low power fillers on 1214Khz AM, Third on 693KhzAM + Low power fillers on 1593KhzAM & Home Service Regional on several AM frequencies. In 1967 the BBC introduced 4 networks, The Light became radio 2, third became radio 3 & Home Service became Radio 4. Radio 3 & 4 Frequencies remained the same as Third & Home. Radio 2 got 200khz long wave + 1484KhzAM for fillers. The new pop station Radio 1 got 1214KhzAM as a shove in & had to make do with a single frequency network. Of course it all changed again in 1978, only that was a lot more complicated, wouldn't want to bore you with that.

[zeno]

WBZ / WBZA were the most famous of the syncro AM's.
WBZ itself is a rarety. Is a clear channel BUT is allowed a
directional pattern. Clears are supposed to run 50 Kw
non directional. Argument was why put half our power into
the ocean ? The towers are in a salt marsh so it has a
fantastic ground. Thats why it used to cover most the states.
If it were ND it would be an easy catch in Europe in winter
especially on the coast.

WLLH 1400 Lowell & Lawrence Ma. were another syncro that
may still be doing it. There were others in the olden days.

BTW there are still two AM DX clubs running in the US
http://nrcdxas.org/
http://www.ircaonline.org/

73 Zeno