Mark V






MD 100 Sensitivity to Background Noise

Question: I hope this message will be not a little bit off topic, but, probably could be "interesting". I have a barand new FT1000 Mark V and a MD100 microphone. This microphone, unfortunately, gets a lot of background noise, I mean when a switch my home brew linear amplifier on the noise of its fan probably, a little bit noisy, "enters" in the microphone causing some troubles you can easily imagine.So my question is is there any electronic circuit to " cut " this noise ?? Is there anybody have my same problem and have already found the solution. Any suggestion will be appreciated. Andy I7DFV

Response 1: Yes Andy, there are devices to help reduce the effect of background noise (within limits). Two types of audio equipment that are designed specifically for this purpose are called "noise gates" and "expanders" (or "downward expanders"). These functions are often combined with other audio processing functions such as equalization (boosting or cutting certain audio frequencies relative to others) or compression, but are sometimes found as single purpose devices. The way a noise gate generally functions is to cut off (open) the audio path if the incoming level is below a user specified threshold and connect (close) the path for louder audio. You set a threshold control so that the audio path is open (off) when there is only background noise present, but closes (connects through) immediately when you start to speak into the microphone. Expanders are a bit different in that they simply reduce (not eliminate) the the output audio level when the input level is below a threshold, and allow it to pass unaffected when the level is above the threshold. Sometimes complaints of "lots of fan noise" are caused by having your microphone gain set too high causing excessive levels of ALC in the transmitter, which effectively reduces the level of louder audio while seemingly raising the level of softer sounds (fans?). Adjusting mic gain for ALC indications on loud voice peaks only will reduce the effect of the fan noise.

Of course, if the incoming level of your background noise is very close to the level of your voice at the microphone, no equipment (other than perhaps software noise reduction DSP techniques) can materially change that. In that case, you'll have to move the noise source (fans) farther away from the microphone or perhaps put a partition of some type between the noise and the microphone. You'll find that most of the those hams who have hi-fidelity or "broadcast" quality SSB audio on the air are using noise gates or expanders as part of their audio processing chain. [No commercials, just for information: this audio gear (new and used) is widely listed at the EBay auction site or available specifically for hams (W2IHY).] I hope this is useful. 73, John W2KI

Response 2: I have been test driving a Yaesu FT-1000 MP V which has this same microphone MD-100 and had been getting some intermittent reports of noisy transmit audio like I may have been running the processor too high or complaints of picking up background noise such as the blower in the transceiver. Well, it did it again tonight and I knew that I had not cranked up any of the controls so I noticed that this particular Yaesu desk microphone uses the cursed RJ style of mic connector in the rear of the mic. So I robbed the 8 pin to 8 pin mic cord from my own MD-1 mic and tried it. The noise was all gone! I took my RJ crimping tool and recrimped the RJ mic connector (that plugs into the back of the MD-100) and Voila! The noise is all gone. Yaesu has been have a lot of problems for many years with those RJ style of mic cords on their vhf and uhf radios as they get very noisy when transmitting and by wiggling the cord and monitoring your transmit signal you will be able to hear it all. I usually try and recrimp those mic cords and it will normally repair the problem for some time. So my suggestion is to NOT use the RJ style of mic cord on the MD-100 desk mic but rather either make your own 8 pin to 8 pin mic cord or purchase it from Yaesu.
Best of 73's from Fern VE7GZ


This site was last updated 08/27/07