European FM channel allocation
I'm working on a project that contains a digital FM receiver and I'm writing code to interface it to an analog tuning front-end, basically recreating an "analog feel" to a digital receiver. Since the software controls everything from the tuned frequency to the AFC behavior I have a question about FM radio in Europe that I haven't been able to find online.
In North America each FM channel occupies 200kHz and our receivers only tune to 200kHz channels on 100kHz boundaries, i.e. 88.1MHz, 88.3MHz and so on.
In Europe I know the radios tune to 100kHz boundaries (except in Italy and the former Eastern Bloc with OIRT at 50kHz but I am not intending to support this). I have read that parts of Europe are standardizing on using 200kHz channels on even 100kHz boundaries but this is not widely accepted so all receivers need to support 100kHz channel allocation.
Would I be correct in assuming that FM stations in Europe occupy 200kHz just as here with the only difference being they can be allocated on any 100kHz boundary? I assume this is the case since the content of the FM modulation is the same (audio bandwidth and sub-carriers) so the AFC routines can be the same for all regions.
RDS is similar between US and UK/Ireland. I have used PIC based RDS decoding to an LCD in Ireland and added our own User data fields to a PIC based RDS encoder.
In theory the pre-emphasis is the only difference. It's a pity that most FM stations are processed to hell. Only one here in Ireland is "decent" (Lyric FM). But Irish DAB is worse, we have lower bit rates than the too low UK bitrates and less choice as only the national PSB is on it (RTE with a bunch of extra semi-automated niche stations).
I looked at Raspberry PI so as to have 320 x 240 colour touch screen, but I think too power hungry, so I will use my Pi for something else.
I also have a USB DTT stick that uses DSP for DAB and FM. Works about 45MHz to 1.7GHz I think. But for low power consumption I think I will go DDS + mixer and analogue and PIC and only use "Digital" to simulate a tuning scale on the colour Touch screen (The main issue with PIC and Colour 320x240 touch screen is RAM, but it does work).
I've looked at Spartan 3E for a full DSP radio, but power consumption is just stupid. Spent most of the evening listening to R. Scotland on MW on RCA 8BX6, lower power consumption on its 9V 50mA LT + 9mA 90V HT than a DAB Radio or any DSP based AM/FM! (No I don't know how a 1948 battery/117VAC US set got here).
So I'm safe in assuming that other than the pre-emphesis and 100 versus 200kHz channel boundaries, most other important aspects are the same. That will definitely ease the requirements on the software.
Amateur uses 12.5kHz steps on 50 to 52, 70 to 70.125 and 144 to 146 (148 USA), but only for NBFM, if you are making something that wide.
The OIRT band in Eastern Europe is from 65 to 74 MHz approx and might be 50 kHz steps. Still used Though quite a few have changed over. Japan is 76 to 90 (or 92? I forget) Still.
What sort of "Engine" are you using?
For this project I'm only concerned with the world wide broadcast FM bands. From what I've read the 50kHz spacing in Eastern Europe is quickly going away and the ITU recommended discontinuing 50kHz in all of Europe back in 1984 so I don't think it's worth supporting this. (Italy still has some stations that use 50kHz) This makes most of the world uniform with a 87.5 to 108MHz band and 200kHz wide channels. Japan is the only deviation with their band ranging from 76-90MHz.
The engine in this project is an Atmel ATTiny micro. It requires only 2ma running at 8MHz so it's very efficient.