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+--- Thread: FM broadcast band (/thread-1463.html)
FM broadcast band - VK1DJA - 09-10-2024
I am playing with a homebrew FM broadcast band (88-108 MHz) receiver to use the band as an indicator for 2M DX.
There are a couple of puzzles. Can anyone help, please?
Is RDS used in Australia? I can find only one oldish claim that RDS is used by only one Sydney station and only for traffic reports.
How is a signal including a pilot tone generated? A straight FM modulation with only the pilot tone (i.e. during a period of silence in speech or audio) should place all the transmitted power in the pilot tone. This commentary,
ham.stackexchange.com/questions/7517/what-are-the-3-or-5-peaks-in-an-fm-broadcast-during-silence
suggests something different.
Thanks in advance.
Dave VK1DJA
RE: FM broadcast band - VK5TM - 09-10-2024
Here's a list of RDS enabled and active stations (from January this year) https://www.tvchannellists.com/w/List_of_RDS-enabled_radio_stations_in_Australia exactly how accurate it is, who knows.
Pilot tone and RDS carrier insertion is continuous, stopping and starting the carriers would cause problems with receivers locking to it.
RE: FM broadcast band - VK3RX - 09-10-2024
Some stations send RDS, but as far as I am aware, the ABC doesn't.
Those that do, some fields are populated e.g. track playing, weather, program/announcer etc. and some fields aren't.
I've used SDR# with an SDR add-on to tune FM signals to see if the fields populate or not.
Around here the only Bendigo station sending RDS is Triple M on 93.5MHz.
By looking at the signal with a spectrum scope you can see the RDS carrier if present.
1st pix is the ABC (no RDS) and the second is MMM (RDS).
RE: FM broadcast band - VK6CPU - 09-10-2024
Both ABC FM and JJJ send RDS here in Perth - current music/track etc,
There is only SBS and some community stations that do not.
RE: FM broadcast band - VK3RX - 10-10-2024
Seems more around than I thought.
We have a bedsiide DAB/FM clock radio that has no battery backup but does have the facility to update the time via FM station RDS or DAB (no reception of the latter here without an outside antenna).
Initially I set it to update via the only station with RDS Triple M, but that proved unreliable because after a power failure sometimes it would work but occasionally their date & time would reset to 1 January 2000.
It seems they may not pay a lot of attention to keeping the date & time current .....