Wireless Microphone Systems

I like the Comtek wireless mic system I have. Of all the professional wireless mic systems I've used (over a dozen) I've had the least problems with the Comtek. Interestingly it is also one of the least expensive professional systems too (go figure). I have a lav transmitter (model M72) with a Tram 50 lav mic (great mic) & also a hand held transmitter (model M182). The transmitters have a soft compressor built in, an on/off switch, a mic mute switch, a mic sensitivity pot, a red LED for battery condition & a choice of mic connector types (choose at time of purchase).

The receiver I have (model MRC-82)(now a MRC-82C) is a non diversity (single antenna receiver) because it is VHF & meant to mount on a camera. Although it only has one antenna, I don't often notice a dropout or hit (cancelled wave), although I do occasionally get a phasing type sound in some locations. You can choose frequencies in the TV channel 7-13 range (174 - 216 megaHertz) so a portable dual diversity receiver wouldn't do much good at this frequency unless you could spread the two antennas a minimum of a 1/4 wavelength apart (about 13" - 16" apart). Be suspicious of any dual diversity systems where you can't spread the two antennas at least 1/4 wavelength apart. A UHF system at 900 MHz has a 1/4 wavelength of just over 3" so it is short enough wavelength that two antennas are practical on a portable receiver. When using a portable receiver (usually used on cameras), a dual diversity antenna would be preferable over a single antenna, which limits your choice to the 900 MHz range. The Comtek receiver comes with a rubber ducky antenna (not the type you take in the bathtub), on/off switch, output strength pot, red LED battery indicator, green LED RF detector and Velcro plate & pads for fastening to the camera. You can choose MIC or LINE level 1/8" to XLR cables (I bought both).

This Comtek wireless kit is small & nothing special to look at, but they seem to work well enough in all kinds of situations. They are very efficient with battery power & it works for a good while after the red battery LED has gone out. I have no idea who the dealers are so you will have to contact the manufacturer directly: Comtek Communications Technology Inc. 357 West 2700 South, Salt Lake City, Utah 84115 Phone (801) 466-3463. WEB SITE http://www.comtek.com

A few warnings or disclaimers: my first Comtek unit was damaged by plugging the 9 volt battery in backwards. Comtek fixed it without any charge & said that there was polarization protection built in but it failed in this unit. The output connector of the receiver is 1/8" for multipurpose use (headphone +4 dB 8 ohms, mic level balanced or unbalanced -20 dB 200 ohms, line level +10 dB 100 ohms, charging battery) but as we all know, 1/8" connections sometimes easily come unplugged, so put a piece of tape around it. Finally, wireless mic systems tend to be very much a personal taste item. One of my friendly local competitors often buys the same items I do if I recommend it. I bought a Lectrosonic 185 non diversity wireless system (now superceded by the 195 I think) & I found it to be very good in most respects but it had too many dropouts & I prefer the Comtek. My competitor bought both mic systems too but he prefers the Lectrosonic. Since I have used all 4 of them on a 2 week overseas shoot, I would have to say that our differences of opinions may have been unit to unit differences in the same model made at different times.

Over the years I have used a number of Telex brand wireless lav systems & while I didn't notice anything special about the transmitters or receivers, I have always been impressed with the tonal quality of the various lav mic capsules Telex uses. If you choose some other system than the brands I mention here, you might still consider purchasing a Telex or Tram 50 mic capsule.

Regarding choosing a frequency for the areas you intend to use your wireless mic in, the manufacture often has a list of acceptable frequencies for your area. Try to pick a frequency that others are not using in your area & in a TV channel bandwidth not used in your area. If given the choice, I have a preference to pick a frequency that is about 5.45 MHz (+- .05 MHz) above the bottom of a TV channel because that is where the guardband is between the video & audio (ie. choose 179.45 MHz for channel 7). If you chose this guardband, you can get closer to a TV transmitter before you receive interference from it. Below I have listed the VHF range for TVs in North America. The UHF TV range for channels 14 - 83 are between 470 - 890 MHz at 6 MHz intervals. If you know you will be using your wireless mic in some other country, try to find out which frequencies are acceptable. I've done field production in Israel twice & they just about went squirrelly on me when they heard which frequencies I intended to use. It caused me a lot of last minute hassle & nearly ruined our shoot. I guess we had chosen a frequency they use for the military.

Ch   7 is 174 - 180 MHz (ideal 179.45 MHz) (wavelength of 174 MHz is about 65 inches)
Ch   8 is 180 - 186 MHz (ideal 185.45 MHz)
Ch   9 is 186 - 192 MHz (ideal 191.45 MHz)
Ch 10 is 192 - 198 MHz (ideal 197.45 MHz)
Ch 11 is 198 - 204 MHz (ideal 203.45 MHz)
Ch 12 is 204 - 210 MHz (ideal 209.45 MHz)
Ch 13 is 210 - 216 MHz (ideal 215.45 MHz) (wavelength of 216 MHz is about 52 inches)

For more information on the frequency spectrum please visit http://www.rentcom.com/wpapers/telex/telex3.html

By Doug Hembruff.