Analogue morse with dmr ???

[timberwolf]

I'm hoping someone can help me puzzle this out ! I narrowed down an Edinburgh Shopping Centre's DMR to 453.150MHz. When they're not chatting about who's turn it is to collect the trolleys from the car park, there are regular bursts of short 'carrier' Mototrbo dmr (one second of TX at regular intervals of 30 seconds.) I guess that this is just a channel idle signal that keeps base / mobile RX 'awake'. However, every thirty minutes there is an analogue transmission that immediately follows the channel idle signal. It's a morse TX which spells FORBO. Now it could be that the channel idle & morse are co-habit the same frequency as the Shopping Centre. Maybe I'm picking up a signal from the Forbo-Nairn factory over in Kirkcaldy (seems unlikely though ; the channel idle signal is strong and can be heard in the Shopping Centre's car park which is in a valley surrounded by tall buildings. If I'm being stupid and missing something obvious, feel free to slate my ignorance !

[MrWeetabix]

Do both the DMR and CW have the same signal strength? Maybe an easy way to determine if its related

Unsure if DMR regs state idents need to be made in-the-clear or not, may be similar to 15min idents from HAM repeaters and hams themselves actually, its a requirement of the license (or at least it used to be, havent checked tonsee if that particular reg has changed recently)

[timberwolf]

Thank you Mr W. Think the regs still insist on regular morse id for commercial repeaters. S6 for DMR & Morse. And it's definitely not coming from the Shopping Centre. The Forbo-Nairn site in Kirkcaldy has a large footprint ; perhaps they do need a repeater. If that's the case, it seems odd that they're allowed to come up with their own call-sign. Either that or my two-word per minute prowess in Morse Code was just a fluke during my Ham training!!

[paulears]

The current licence doesn't require CW ID, mine certainly doesn't but I have an analogue ident - it uses the abbreviation of my business name - as it's not a licence requirement, it's just useful.

[jhampton2000]

WTR lists Forbo Florring [sic] UK Limited license 0871570/1 on 453.1500 at that Kirkcaldy site. I think that's your morse carrier. S6 for both repeaters is, I suspect, simply a coincidence.

All that huge spectrum and OFCOM still stick them both on the same frequencies. And to think people pay their hard earned cash on this for so called 'co-ordination'.

[MrWeetabix]

Thanks for info everyone. Hopefully mystery solved

[bigpimp347]

maybe the company who set up the repeater are using something like a Zetron multi-user CBS control panel to allow DMR and Analogue users to use the same system.

[paulears]

Doesn’t coordination just mean they don’t interfere and happily can co-exist? Repeaters on the same channel are fine, it’s where the outstations are that make it work. I bet both users are totally unaware of each other. It’s a great example of coordination and efficient band management.

[jhampton2000]

Perhaps I mis-read the OP's post, but it sounded like he was picking up both signals when close to one of the sites (the shopping centre). I agree it is very efficient use of the spectrum: frankly you can't get much more efficient if you just stick everyone on the same frequencies. The sites can't be more than about 10 or 12miles from each other. Without digging into all the details, that sounds like they might have overlapping blocking signal areas which ofcom should avoid for a tech assigned freq.

[MrWeetabix]

Perhaps OFCOM only care about operations within a specified footprint for each user, so if you happen to hear both outside of either and are in a zone where they overlap, then maybe OFCOM simply don't care about that or factor it into their allocation decision making because neither users should be affected within their respective geographic locations.

[Metradio]

Perhaps OFCOM only care about operations within a specified footprint for each user.....

Think you are quite correct there.

Mike

[paulears]

My technically assigned repeater can be heard quite strongly around ten miles from its location, but all the users are on handhelds making the service area probably 3-4 miles reliably. If one was on the same frequency ten miles away, with them also using handhelds I doubt that with CTCSS we'd even be aware of each other.

[jhampton2000]

Perhaps OFCOM only care about operations within a specified footprint for each user.....

That's spot on, they do. These footprints are what are known as DSA and BSA's. You can read about them here:

https://www.fcs.org.uk/image_upload/pdf ... dorsed.pdf

Again, to quote from this - Ofcom's own guidance - page 13 "Ofcom will not assign a neighbour with a DSA within this BSA for exclusive channels".

The inference from the example quoted by the OP was that the BSA of the Forbo-Nairn repeater could be heard in the car park of the shopping centre. The 'collecting trolleys' comment indicates the DSA of the shopping centre system is meant to include that car park. Thus the potential of the BSA of Forbo-Nairn overlapping with the DSA of the shopping centre.

[timberwolf]

Thanks to all. You guys are amazing. I've learned a great deal about DSAs & BSAs. It's a pretty efficient system where two co-operational frequencies can TX & RX in harmony with both licence users completely oblivious to the existence of each other ! You can't fault OFCOM's co-ordination there ! I'm still impressed that I was able to read 'FORBO' in Morse after all these years.