Induction loop & vga issue

Bobby Logan

Active Member
I have inherited a job in a large chapel, I have replaced 2x power amplifiers the induction loop amplifier and several microphones. The problem I have is that the original installers have crossed the vga cable with the induction loop cable at two points and therefore whenever the induction loop is active the vga starts to dance. Recabling is not an option due to the sheer enormity of the chapel can anyone suggest any material that would shield the vga cable at the points of crossover as a retrofit solution, I was thinking along the lines of lead flashing.
 
Another solution is to have personal Induction loops if and when required.

These consist of a FM transmitter unit linked to the output of the amplifier (like the Induction loop amplifier is now) and a number of FM receivers with Personal induction Loops that are handed out on request.
 

Bobby Logan

Active Member
Thanks that sounds like a workable solution do these induction loops require any cabling other than power to the receiver's
 
SoundFields : Digital Group Guide System - X-Tour

To keep the cost down I recommend just having a basic portable transmitter rather than the more expensive fixed base station variety. You then need to add the personal induction loop this plugs into the receiver and is worn around the neck so that the hearing aid when set to "t" can pick up the signal. This system has the added advantage over a induction loop that you can also plug in headphones so can be used by people that don't have hearing aids but are still hard of hearing
 

Bobby Logan

Active Member
I'll investigate over the weekend and present the idea to the father on Monday.
 

noiseboy72

Distinguished Member
I know you say you cannot re-cable, but a simple VGA - Cat5 set of baluns will cure the problem.

You can also try simple steel plates, as these will shield the electromagnetic radiation. Make sure you earth it however.

Personal induction loop systems are all well and good, but a major investment in one hit - No VAT reclaim on replacement AFLs. We also find the receivers tend to walk, as it is very easy to forget you have hung it around your neck.

The Transmitter also needs to be mounted quite high to get good building coverage, so you may need to add in some cabling for this as well.

Having fitted hundreds of permanent and temporary AFLs and VGA systems, I would seriously recommend the VGA - Cat5 route as the cheapest solution.
 
Re cabling and adding VGA over cat 5 I suspect is more expensive than our solution and less flexible. Though that depends that on how many receivers you would need. The count them out count them in works for most locations
 

Bobby Logan

Active Member
Good advice problem is the projector hangs from a 35ft ceiling the biggest scissor lift I can get through the doors goes to 25ft leaving the only option being scaffolding which isnt really an option as its a busy chapel also the av kit is in a lower level so placing a transmitter high would be possible but problematic if steel plates would work this would definitely be the cheapest option and at least worth a try before spending more money.
 

Bobby Logan

Active Member
I'd be guessing but I'd probably recommend 5 or 6 receivers I daresay it depends whats on in the chapel, the chapel can comfortably seat several hundred people.
 

Bobby Logan

Active Member
Agreed Joe a lift would have been better and gave better access for maintenance the building now has listed status so messing with the wooden ceiling would be out of the question.
 

avandmore

Member
I agree with Noiseboy on this, unless it's one persons job to be there every single time the receivers are used then it will be a future of lost receivers and flat batteries.
I've done plenty of induction systems over the years, it's a very dark art even with the correct test equipment and thus I'd say if you've got one that's working well then leave it and fix the vga problem.

The steel plate trick will work if they are grounded properly as will Baluns.
If you really are committed to going down the route of replacing the loop system then go IR instead of RF, we've installed plenty of the Starsound 600 systems, phenomenal coverage and noise / interference free right out of the box.

StarSound 600 infrared sound system - Phonic Ear
 

hornydragon

Well-known Member
Be aware if you start messing with induction loops (AFILS) there is a BS standard and they are part of the DDA compliance for public buildings, have you calibrated the loop? is it a perimeter loop? What sort of AMP?

Moving to IR transmitters is expensive time consuming and requires management rather than a standard loop which is fit and forget. You could try cladding the VGA cable in earthed steel or steel mesh (thicker the better) this will drop the loop power slightly but old stone and wood structures like chapels and churches there will be minimal loss in the building so should be ok.
 

avandmore

Member
I respectfully disagree on one of your points Mr Dragon, my experience of IR loops is fit and forget - they aren't cheap however.
 

hornydragon

Well-known Member
I respectfully disagree on one of your points Mr Dragon, my experience of IR loops is fit and forget - they aren't cheap however.
Lost receivers, dead batteries, muppets that don't turn them on/off.. Fit and forget for installer but not the staff onsite... The number of faults than turned out to be battery/power switch related is nuts... Never underestimate the stupidity of the user or the the ability of one member of a congregation to make a fuss! And "know their rights!"! Especially if it is suggested they "could just sit in a different place" and all is well.....
 

avandmore

Member
Ah, totally agree with you there, it's just like when a client insists they want to use radio mics in meeting rooms, every time I visit they are either lost or the batteries are flat, hence -
I agree with Noiseboy on this, unless it's one persons job to be there every single time the receivers are used then it will be a future of lost receivers and flat batteries.
The best way advice I can give from afar is, fix the vga, the induction loop isn't broken.
 
I think we all agree that fixing the VGA is the answer but if recabling isn't feasible, as the OP said, then we can only suggest alternatives.

Our Soundfields division use FM personal loops in locations as diverse as University's, village halls, museums, guided walks and find them very cost effective. We also provide IR based systems however these aren't so cost effective and need more careful positioning of the IR radiators so may involve more cabling.

We are happy to provide quotations on any system from fixing the VGA with VGA over Cat5 senders/receivers (£99+VAT) to FM Transmitter and Receivers (1 to 5 approx. £836+VAT) through to IR Radiators and personal receivers (£1700+VAt plus based on 5 receivers but very dependent on size and layout of the chapel).

Hope that helps
 

Bobby Logan

Active Member
Thanks for all the replies guys as avandmore highlighted budget is a consideration I will attempt the steel plate route first hopefully that will do the trick as for calibration the amp has been configured and tested as per manufacturers instructions and tested with a basic induction loop tester.
 

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