- Posted by Simon Byrne
- On May 1, 2016
Getting wireless microphones to work reliably is getting more challenging and will continue to be so.
The simple fact of the matter is that productions demand more and more channels of a spectrum resource that is increasingly becoming incredibly crowded. Our thirst for mobile internet needs spectrum, lot’s of it. If we look to the to developments in the US and Europe, it is clear that available spectrum will get more scarce.
Politics of spectrum allocation aside, a battle in my view that the production industry is unlikely to win, we as audio professionals need to have the tools and skills to reliably deliver wireless audio in this increasingly hostile environment.
Operators need to have a full understanding of the RF environment that we work in. To help with this, the major wireless manufacturers have excellent scanning and coordination capabilities in most of their upper end equipment so we have the ability to do a spectrum scan, but they are usually slow and tie up a receiver channel.
The solution is a stand alone RF spectrum analyser which gives you the ability to conduct close to real time scans during setup, rehearsals and show. This gives you a picture of the landscape that you are operating within.
The RF Explorer is a handheld spectrum analyser that comes in various configurations. It is affordable…really affordable, starting at about $225 for an entry level model which covers 240 Mhz to 960 Mhz which easily covers the range that most of us are interested in. Several other models are available, giving the user the ability to scan right up to 6 Ghz as well as some 2/5 Ghz wifi diagnostics.
It has an internal battery charged via USB, a 128 by 64 pixel mono screen, an antenna connection with an antenna (or 2 depending on model) and all functions are controlled by 7 push buttons on the front.
As a standalone unit it is quite limited, mainly because of the low resolution LCD screen. It is hard to get really useful information out of it for this reason.
However, the RF Explorer really starts to excel when connected to your laptop with one of the cheap or even free analysis programs. I’m aware of 4 different software solutions that are tightly integrated with the RF Explorer. There are even some options for users of Android based phones which I won’t go into here
There is RF Explorer’s own quite usable software (free), Touchstone (free) and Touchstone PRO ($49 USD), ClearWaves ($295 USD) and for Mac users, Vantage ($99 USD).
Each piece of software has different features so it is a case finding what works for you, however, they all fundamentally do the same thing. They give you a close to real time depiction of the RF environment that you are operating within.
Best practice is to insert the RF Explorer into your receiver’s antenna system somehow. Many receivers have a loop output or hopefully you have a spare output on your RF splitter. That way, you can visualise the signal that your wireless receivers are seeing. Then simply connect the RF Explorer via USB to your laptop and launch your scanning software.
So, what questions can you answer with your spectrum analyser? Heaps.
- What is the RF noise floor in my venue? The greater the noise, the less range you are going to get out of your microphones.
- Am I getting full RF strength from this microphone? Most problems with microphones are related to the antenna connection to the transmitter. You can easily compare your suspect unit with a known working unit.
- How much loss am I getting through that RF cable? All cables have loss but you can quickly determine whether or not it is within acceptable parameters.
- Am I getting signal from the wireless in nearby rooms? In major convention centres, there is going to be wireless used in other rooms. This may, or may not be a problem but you will easily be able to tell.
- Can I use the old aerial from my now illegal receiver in the 700 Mhz range? Sometimes the loss from slightly wrong antennas is well within acceptable limits.
- If I move my antennas, can I lower the noise floor from that LED screen? A lot of (cheaper and larger) LED screens are wideband noise generators. The bigger the screen, the bigger the potential problem. Quite often moving your receiver’s directional antennas so that they are not picking up the screen as much, but are picking up the talent well, can mitigate this.
- Can I get away with running my wireless indoors within this venue even though I am squarely in a local TV channel frequency? Quite often the answer is yes provided you are operating indoors with a low power transmitter (10mw).
- That TV news crew that just walked in. Is their wireless gear going to cause problems? You will quickly spot any new transmitters giving the time to deal with any issues that may arise.
Apart from greatly increasing your capacity to plan your RF and fault finding, the ability to monitor your wireless throughout the show gives you piece of mind that things are operating as planned and you can spot problems early.
For example, I’ve done multi day shows where a nearby TV Station started test broadcasting on the 3rd day and it was not in the local database. It should not have been there. This reduced the usable range of my microphones in that block and I wouldn’t have known unless I was monitoring the spectrum before walkin and could take steps to reallocate channels to my backup frequencies outside that block.
There are certainly more capable and expensive RF Scanners out there, however the RF Explorer combined with some software is very workable for most users.
http://j3.rf-explorer.com Price depends on model. Starts at about $225.
RF Explorer for Window – Free
Vantage – $99USD
Clearwaves – $299USD
Touchstone (Free) and Touchstone PRO ($49 USD)
This article first appeared in CX Monthly Tech News May 2016
I am a contributing writer to CX Magazine. CX Network is the voice of technicians in entertainment and audio visual across Australasia.
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