Fibre is great. Fibre itself is cheap, rugged coonectors are most deifinitely not and the gear for each end is not cheap either. It's also fragile and finicky. Literally a speck of dust can kill it totally. It provides the best bandwidth and options for the future of anything.
As always, I would take cable over a wireless link.
Cable option: One of the delay towers for World Youth Day last year had a 280 metre run between
speaker processor and amps. It worked as well as any other tower. But at those sorts of lengths, you need 2 things. 1 - a
balanced line and 2 a good string
line driver feeding it. For WYD it was a Dolby Lake
Processor. For the analog backup
system for the Doha Asian Games, XTA DS800s were used at each
node (The primary was
Optocore). It's definitely possible. I know that the guys who did Athens said they could not pick the difference when they forced the
system to swap to copper and the B
console and all of that. They were slightly disappointed I think that fully digital
system didn't sound better, but it's also evidence that the analog
system was well designed.
Check the last device in your audio chain at the field end and see how it goes for output. I'd suggest an
iso transformer such as what Mike has suggested because you are very likley feeding off different
power and
ground loops could cause many headaches.
Iso transformer goes at lecture
hall end...
Adding delay is not hard, provided you have
DSP or the like available to you. I'd suggest talking to your video dude and finding out their plans. They may well have an audio in on whatever and you might just have to do some fiddling with levels and connectors.
Now wireless: Definitely doable. We did a 500m link for WYD. That was using a
beltpack. Admittedly said
beltpack had been err customised... Normal beltpacks don't have
BNC connectors for their antennas nor dual microprocessors to run multiband. We
fed that to a
paddle and then the receiver had diversity paddles. Besides a faulty preamp on one of those paddles, things were fine. Changing the transmitter battery got annoying.
From memory, UHF-R beltpacks have removable antennas and hence could be adapted to take a real antenna. You'd have to be careful of your legal maximum
power.
You can also use an
IEM system to achieve the same thing. You normally have a
connector for proper antenna already. This makes
point to multipoint links cheaper than doing it with mic receivers.
You can get RF to go a LOT longer. Add an RF amp and dependent on where in the world, a licence and you can get kilometres of range. A standard PSM700
beltpack was still locked on to the transmitter in Doha at 7km, admittedly there was an RF amp in there.
If you are looking at RF solutions that start to push the normal operational limits of systems, then you need to seek expert advice. Those results with long range RF were done with RF gurus doing frequency planning and constant monitoring.
An out there option... If you are finding loss a
bit of an issues, you could run a solution whereby you use an off the shelf paging style amp and then run your link at 100V
line and then
attenuate that down at the other end and feed it into a DI box.
Plenty of ways to skin the cat, feel free to ask for clarification if I've neglected useful details...
