Radio Frequency: Go Long!

So much can be said about wireless technology in location sound operations, so I'll keep this discussion fairly focused. When discussing the quality, strengths and differences between a wireless system, most make comparisons at the transmitter level, which makes sense; the transmitter is the one with the signal that needs to be sent through a field of obstacles. The transmitter is comparable to your Quarterback and one of the most important factors of that Quarterback or Transmitter is the power it can send a signal (Click here for my table of power outputs for popular wireless systems). However, what is often overlooked is the Receiver.

I used to use Sennheiser G3s as my body mics due to their value with a professional quality in an affordable price. But it was too often that I would lose a signal once someone leaves the room or turns a corner or sometimes is just surrounded by a bunch of extras. So I upgraded my wireless systems to Lectrosonics using primarily SMQv's as the transmitters and UCR411a's as the receivers. The 411a's are Lectrosonics top pride in quality receivers. They are simply bullies in the RF field. However, they do cost a pretty penny and are very bulky in an already heavy bag I lug around. So, in order to save space in my audio bag and save my back from unnecessary strain, along with relieving my bank account, I considered investing in Lectrosonics' SRb dual channel receiver. Instead of buying two more 411a's, I've got 1 SRb sitting in the bag saving more than 4x the amount of weight (~1.5lbs saved per SR) and more than double the space. But I don't like to compensate quality. Lectrosonics claims that the SRb is a comparable equivalent to the UCR411a in quality, but not equal to. The 411a has a front end filter of 11 MHz wide as compared to the SRb being a full block of 25 MHz wide (narrower is better), with no tracking filter. So I A/B compared the two in a walking test with a few sound buddies, Mike Moote and Allistair Johnson.

SMQv @100mW in car behind car,
411a on me, clear signal
We threw a DPA 4071 on Allistair connected to an SMQv in block 20 and configured an SRb and a UCR411a in the same frequency to see who would drop out first. We sent Allistair on a walk outside and down the street in Brooklyn, NY. I'd say he got about 150-200 feet before the SRb started having some bad hiss and clicks. After only a few more steps, the UCR411a would consistently have minor hissing from the weak signal. We sent him further including around the building corner and they both started having dropouts. Consistently the 411a had a stronger signal and a bit more range. In some circumstances, that hiss from the 411a may be usable if it's a crucial scene for reality or documentary as the SRb's signal may not have been usable. However, in most of my applications, once we started hearing that weak signal hiss, both were unusable in my eyes and we only started hearing that just maybe two steps further. So, already having a few 411a's in my bag, I decided to invest in an SRb, which will become more necessary when the FCC bans our use of blocks 24 and up, limiting us basically to blocks 20-22. I've been told that running wireless in the same block is better quality through an SRb rather than two 411a's as they'll play nicer when they're designed to (I hope someone can confirm this for me) and when you have 4-6 body mics, a wireless boom, 4+ monitoring IFBs, and 2+ wireless camera hops all being limited to 3 frequency blocks, everyone will need to play nice in the tiny play pin to which the FCC will be limiting us. However, there are plenty of creative ways to fight RF.

Other than setting up Shark Fins, the best ways to keep a strong signal may be the obvious methods of keeping transmitters and receiver antennas pointed up and high in the sky. It's obviously important to keep the distance of the two at a minimum but some may not realize how much getting closer helps. If I can get my receiver twice as close, i.e. from 50 feet away to 25 feet away, that does not double my signal strength; it quadruples it. So even if I can only get 5 feet closer, that's in a sense getting 10 feet closer and could certainly make the difference. Another thing many people don't realize is when setting up your transmitters at the beginning of the day, some people line them up side by side. Try to avoid doing this.
If you do this, make sure only one unit is on at a time or that the antennas are aligned head to toe, alternating; Tx 1 antenna pointed north, Tx 2 antenna pointed south, Tx 3 antenna pointed north and so on. Otherwise, the transmitters will mess each other up even when separated, sorry for a lack of technical terminology here. Turning phones off and staying away from heavy currents such as ballists are a few more obvious things to remember but when it comes to IFBs, I found a method I started using pretty regularly.

Working on a feature film, we had some locations where our video village was watching the scene from downstairs. Camera ran a boat load of BNC down the stairs but I had to send them a wireless feed for sound. I was using Comtek 216s. These only emit 10mW of power to send the audio signal. This is 1/25th of what my body mics can do. So, I took the term "wireless hop" and used it literally. Instead of sending my signal through the floor which has plenty of interfering wires and insulation in it, I sent a signal to the bottom of the staircase using a Sennheiser G2 at 20mW, and connected that receiver to a Comtek m-216 transmitter which then sent the signal from the staircase to the room next door at video village. Problem solved, and I used this method on other sets where video village was outside or at the other end of the building.

Whatever is more important in your situation, difference in size, range, or price, there are nearly endless specifications when it comes to wireless technology in this field but finding creative ways to get that signal from your Quarterback to Receiver as clean as possible is always in play.

No comments:

Post a Comment