Drive In Movie Sound - Quick and legal ? ????

[henny]

Morning All - Ideas, please

If got a UK based client that wants to go live with a 250 car drive-in move 3-month project within the next two weeks...

The big stumbling block is the Audio

The options I've come up with so far are:

 

1) FM transmission to cars - Can't be done legally in the time as it is up to a 10 week lead on getting a temporary licence if they give you one at all, Not worth the risk doing it without a licence as our friends at Ofcom will be pouncing on popup drive-in movies as an easy target.

 

2)Silent disco beltpacks connected to rechargeable speakers, no one in UK has stock and china are saying 6 weeks to manufacture and import.

 

3)Streaming to an app - Can be done there is low latency kit out there aimed at the US sports bar market but relies on people to bring their own device ......

 

Does anyone else have any other ideas on what will work?

[bruce]

Ofcom announced some changes a couple of weeks ago - they have removed the “got to give 10 weeks notice” rule for drive-in movies and church services, and say they will process applications within 2 weeks.

 

https://www.ofcom.org.uk/about-ofcom/latest/features-and-news/licensing-drive-in-services

 

I can point you towards some companies who can supply/hire the necessary transmission equipment.

 

Edit: Ofcom are also waiving the Broadcasting Act fee, so the license cost is just the Wireless Telegraphy Act cost, which for less than 1 watt is £25/day

[sunray]

Ofcom announced some changes a couple of weeks ago - they have removed the “got to give 10 weeks notice” rule for drive-in movies and church services, and say they will process applications within 2 weeks.

 

https://www.ofcom.or...ive-in-services

 

I can point you towards some companies who can supply/hire the necessary transmission equipment.

 

Edit: Ofcom are also waiving the Broadcasting Act fee, so the license cost is just the Wireless Telegraphy Act cost, which for less than 1 watt is £25/day

That's terriffic, big up to them for making such a brilliant decision.

I will repeat my suggestion to another similar thread recently. It was suggested to me by a previous licensing agent to get a link license for band 1 [48-53MHz] and tune to the second harmonic as it's easier to get a link license than a broadcast license. However looking at the current system that may not be so relevant.

 

[Brian]

...get a link license for band 1 [48-53MHz] and tune to the second harmonic...

 

Surely any transmitter that puts out so much spurious harmonic energy as to be receivable would fall foul of the regulations anyways. And shouldn't be CE marked.

[sunray]

...get a link license for band 1 [48-53MHz] and tune to the second harmonic...

 

Surely any transmitter that puts out so much spurious harmonic energy as to be receivable would fall foul of the regulations anyways. And shouldn't be CE marked.

For a start Broadcast kit does not have to be type approved and can be built to order, therefore not requiring a CE mark in those situations.

We have done this with SBS TX400 running a measured 18W at 52.4 and successfully used it at 104.8 at about 400m, as it happened this was for a proper link of some 6 miles with 3 element yagis each end and the Band 2 RX [portable superbass with CD player type of thing with a telescopic whip] was used to feed into another PA system about 120 degrees off axis.

When we used it for a general broadcast I think it was a STL and getting 200m with ease into car radios but less so with portable radios.

Have you ever listened to radio mics at double or triple frequency?

Never heard a taxi break into UHF radio mics?

 

[Alec]

Or just put in a big-ass PA?

 

Interesting that the barriers to FM transmission for this kind of event appear to be easing. One sanity check question, however, does every car still have an FM radio? I know that most/all now come with DAB units - do all of these also do FM? (Mine is too old to count, by the way)

[pscandrett]

I know that most/all now come with DAB units - do all of these also do FM?

Asking for interest, through ignorance, and it's probably irrelevant to this discussion, but... is it possible to do a 'popup' low powered DAB MUX for this sort of thing, so you can indeed broadcast to the DAB radios in the viscinity?

[ImagineerTom]

I don’t know the broader technical implications but I do know that the bbc time code pips on the hour are only accurate on FM broadcast because when transmitted over DAB the lag can be seconds in some case and varies because of different receiver decoding processes.

 

Since shifting audio 1/4 of a second out sync can make something unwatchable I would expect that trying to encode, transmit and decode through DAB is a non starter for a paid drive in movie experience

[bruce]

Technically, small scale DAB is very do-able. There are a number of pilots running around the UK at the moment (I”m involved in one), and OFCOM are inviting bids for a longer term service.

 

Cost to do it is affordable, using SDR and (relatively) commodity hardware, the cost to set up a small scale DAB mux is probably about double the equivalent FM rig. But of course you can run multiple channels down the mux.

 

As Tom says, there’s a substantial delay in the encoding.

 

There’s no licensing provision for a “pop-up” mux.

[bruce]

There’s lots of stuff in a post above which aint exactly professional, and remember the original poster was asking for a “quick and legal” solution.

 

 

]For a start Broadcast kit does not have to be type approved and can be built to order, therefore not requiring a CE mark in those situations.

 

That’s true - but when you come to commission such equipment, the first thing an OFCOM commissioning engineer will ask you for is the CE statement. If you don’t have it, they’ll ask for evidence that the equipment meets the appropriate emissions regulations, and at that point you’ll wish you’d just bought some CE-marked stuff. I have done this for a RF transmitter which was built in the pre-CE days, and if I was to cost my time it’d have been easier and cheaper buying a new unit off the shelf.

 

 

We have done this with SBS TX400 running a measured 18W at 52.4 and successfully used it at 104.8 at about 400m, as it happened this was for a proper link of some 6 miles with 3 element yagis each end and the Band 2 RX [portable superbass with CD player type of thing with a telescopic whip] was used to feed into another PA system about 120 degrees off axis.

 

So the regs say that for a TX of up to 25W, you can put a max of 25 microwatts into the first harmonic, and for higher powers it needs to be more than 60dB down. Are you honestly suggesting that using that harmonic, while splattering the surrounding area with spurious RF, is a sensible and professional way to deliver an advertised production service?

 

 

I do feel that I’m troll-feeding here...

[sunray]

There's lots of stuff in a post above which aint exactly professional, and remember the original poster was asking for a "quick and legal" solution.

 

]For a start Broadcast kit does not have to be type approved and can be built to order, therefore not requiring a CE mark in those situations.

 

That's true - but when you come to commission such equipment, the first thing an OFCOM commissioning engineer will ask you for is the CE statement. If you don't have it, they'll ask for evidence that the equipment meets the appropriate emissions regulations, and at that point you'll wish you'd just bought some CE-marked stuff. I have done this for a RF transmitter which was built in the pre-CE days, and if I was to cost my time it'd have been easier and cheaper buying a new unit off the shelf.

 

 

We have done this with SBS TX400 running a measured 18W at 52.4 and successfully used it at 104.8 at about 400m, as it happened this was for a proper link of some 6 miles with 3 element yagis each end and the Band 2 RX [portable superbass with CD player type of thing with a telescopic whip] was used to feed into another PA system about 120 degrees off axis.

 

So the regs say that for a TX of up to 25W, you can put a max of 25 microwatts into the first harmonic, and for higher powers it needs to be more than 60dB down. Are you honestly suggesting that using that harmonic, while splattering the surrounding area with spurious RF, is a sensible and professional way to deliver an advertised production service?

 

 

I do feel that I'm troll-feeding here...

Nothing spurious about it, proper links set up with proper aerials etc, it just happens that a bi-product it very useable. And as I mentioned before it was a system recommended to me by a licensing authority, they even allocated a 'non standard' link frequency so it came up in a blank spot of band2 in the geographical area.

My 'broadcast work' is limited to about a dozen RSL's, of which the last was 2008, and 2 drive-in style events, the last of which was 2014. the kit used has been an ecclectic mix of spectrum to SBS/STL and homebrew, the amount of official involvement has been vanishingly small and when there was I've found the technical expertise of some of their inspectors appeared to be even vanishingly smaller. I've found those that know what they're doing get on with it and test but those out of their depth ask for bits of paper, pretty much like many trades.

 

Example: one of the TX sites had a run of 130m of RG213 and our license was for 14dBW, the transmitter rated to 120W. Complaints started about excess coverage [common scenario by other RSL providers] and the inspector finding we were running the full 120W had no clue about feeder losses or ERP and insisted we turned the power down to 25W [using his Bird throughline and a 400-500MHz slug! but the front panel meter was showing <20W] a few days later another inspector turned up as the complaints continued, did the calcs and asked why we were running low power and measured with a proper slug as we turned it back up to full, he fed it into his SA, gave it a clean bill of health and left a copy of his lovely report with us which has stayed with the Veronica transmitter ever since.

 

Then last year I assisted with setting up a community radio station, my main input was the mechanical side but being a long term station we had a number of OfCom inspections and testing during the trials, one of which he was using a Marconi 2945. They asked us to alter the aerial arrangements but I don't think there was ever a mention about CE on the home brew kit.

 

However all of this aside now that the application for a Band2 service has been simplified there is probably no need to circumnavigate the process.

 

 

EDIT:It's simple, OP asked for advice.Knowing how much effort used to be required for a Band2 license I offered the solution I've used in the past which was legal and worked adequately well.

 

[djw1981]

One minor issue if using car stereos - my radio shuts down after 20min parked to save battery.

Is this running risk of car engines running during movie - noise / air pollution - or needing to jump start many cars at the end!

[Andyb]

How about sennheiser mobile connect?

 

WiFi to app. Can even have a choice of channel and eq your own feed! Latency is lower on iOS devices but good enough on Android too.

 

Sales@enlx.co.uk would be able to help you out with a quote and availability.

[richardash1981]

Interesting that the barriers to FM transmission for this kind of event appear to be easing. One sanity check question, however, does every car still have an FM radio? I know that most/all now come with DAB units - do all of these also do FM? (Mine is too old to count, by the way)

 

My parents <1yr old Hyundai still has FM as well as DAB on the head unit, it treats them as a "combined" band in that it can work out which are the same program on DAB and FM and switch to the other if you loose signal (with a rather obvious delay effect!). There is only one preset group as a result.

I think it would be a brave move to not have FM for the UK market, given how many commercial stations are not on DAB, but this is quite regional - I'm sure there is much more FM use in north west England (where I am, and where pirate/breakthrough is rare) than in London and the home counties (where friends tell me FM is rarely usable).

[sandall]

I think it would be a brave move to not have FM for the UK market, given how many commercial stations are not on DAB, but this is quite regional - I'm sure there is much more FM use in north west England (where I am, and where pirate/breakthrough is rare) than in London and the home counties (where friends tell me FM is rarely usable).

In my part of London the main problem with FM is the number of (probably illegal) "music" stations crowding the band, particularly around Radio 4. On the other hand good old 198kHz Droitwich gives a strong signal, though "compatible" laptop power supplies can generate pretty wide no-listen zones.