12003277_10155970013860214_3415538356115695055_nI got the call to do some car rigging for a feature film last fall. They wanted me to crawl into the trunk area of a taxi to monitor the audio while the cast were doing their lines inside the moving car. This use to be standard practice but its just not safe. I knew I needed a wireless monitoring system so I could do a bag drop, let it roll, and listen in a follow car.

While in the world of location audio we have companies like Comtek, Lectrosonic, and Sennheiser who make wireless IFB/IEM systems. Knowing I couldn’t afford those products, I tried to go out and find an alternative for the rest for people who are starting out and can’t shell out a few thousand for a transmitter and a couple of receivers. That is when I came across this FM transmitter on Amazon. Now technically its a re-branded FM transmitter that goes by a few different model numbers and makers but the specs on all of these units are the same.  Here are a few different listings for the same system.



The specs they claim:

31Khnnr9ITLMode: CZH-T00
Power: BL5C Li-lon,3.7V 1000mAh
Frequency Stability: ±10PPM
Frequency Modulation: 75KHz
Transmit Distance: 10/100/300/500m
Transmit Power: 0.1/10/100/200mW
Working Hours:16/10/8/6hr
Noise Radiation:≤60dB
Input Level:≤15dBV


The Breakdown:

The specs are actually exactly what my unit preforms at. In LA the bottom of the FM band is pretty empty, especially in the hills and canyons. So the range I am getting based on the milliwatt power setting is pretty accurate. At 200mw its very possible to get the signal down a few city blocks. When I took the unit out for a test the first day I placed the transmitter with the included lav next to my TV. I than walked away from the TV, out my apartment, and around the next building. No problem picking up the signal on my digital pocket FM radio.  This signal was able to punch through several heavy 1970’s plastered walls.

51I94HqAf4L._SL1260_The battery is replaceable, which is nice and having a 5v USB input has been awesome. If you want Amazon does sell a package that includes a second battery and a external battery charger. But getting 5V USB power in a field mixer bag isn’t all that hard anymore. For my uses I just use a small 2000mAh USB cellphone battery to power my unit but the internal battery isn’t bad either if you are on a small set. Most of my testing and real world use is at power setting 3 (50mw.) Rarely do I need 200mw .

The biggest surprise about this unit is it features a mic AND stereo line input. These two can be adjusted separately and you can feed a signal into both at the same time. Sadly the two ports are not clearly marked on the unit, just the manual. I found some label maker tape fixes this issue.  In my bag I use the Zoom F8 field recorder and feed S1/S2 into my Signtek transmitter. This means submix 1 is on the right channel and submix 2 is in the left. That might sound like I’m feeding more audio into the unit than say a producer really wants or even needs, maybe. But other than being able to sending a 2-ch stereo mix to someone who’s probably not wearing his headphones on set, it really means I can use a receiver on a camera and send it 2 different scratch tracks. untitledOr with a simple modification of my IFB headphones I can make it that depending on which headphones you have will determine which sub-mix you receive. This means I can transmit a signal to my Boom Op and a different signal to camera and the director and not have to carry 2 different TX in my bag. Headphones are a lot cheaper than having to buy multiple Comtek/Lectrosonic transmitters!


In Conclusion:

Buy! This unit has been a god send product to my audio bag. It worked perfect for my needs and it was nice in that all I had to do was tune the follow cars radio to the FM signal my audio bag was pumping out.

You notice I didn’t talk about the lavalier microphone it ships with… That’s because I gave that to a friend who owns a Red Epic to use for reference audio when he shoots. I would never use this as a wireless microphone backup unit, EVER! The microphone input, to me at least, is there if I need to hook it up to a mic level signal, never to drive a microphone.


P.S. In a later review I’ll talk about the digital FM recievers I use with this unit and how to modify your headphones to let you get the most out of the stereo output.


About the Author

Andrew Jones is a location sound mixer based in Los Angeles. He started in the TV and Film industry in 2004. You can email him at  Andrew@HoldForSound.com