Just a general question, what is everyone using as a mic gain on there CDM radios? Someone on another question said the setting from the factory tend to be "hot"
Thanks
steve
CDM mic gain
Moderator: Queue Moderator
Re: CDM mic gain
STEVE W wrote:Just a general question, what is everyone using as a mic gain on there CDM radios? Someone on another question said the setting from the factory tend to be "hot"
Thanks
steve
You can go into the software and adjust both the normal mic and the aux mic gains. I have to agree that the mic gains are set from the factory a little hot.
Jim
Re: CDM mic gain
On just about every piece of fire appratus I have done I have droped the gain at least 5 to eliminate the transmission of alternator noise. Some of these trucks have 350 to 400 amp alternators and at the CDM factory setting the alternator whine would be as loud as the audio. droping the gain cut out the whine without making any change in Xmit audio.
Are they set to hot from the factory -- Yes
Are they set to hot from the factory -- Yes
Cause Motorola said so that's why
Re: CDM mic gain
Hot mic gains on any radio just add to the noise these radios transmit. A good test is to hold the mic at arms length and see just how well you can be heard while talking in a normal voice. Keep dropping the gain until you can just barely hear the voice. Now close talk the mic again. Your voice should be heard loud and clear.
The old days of leaving the mic hung up on the dash, reaching over and pressing the PTT button and talking should be gone. Train the users proper operation on how to speak into the mic.
This picking up of all the background noise is even more pronounced if your using a repeater. Reason being is that most of the radio shops don't know how to adjust the audio throughput going through the repeater. They have the audio adjusted so that it actually adds gain and compresses the audio. This just brings up all the background noise and makes it harder to hear what the users are saying.
Try this for a test. Play the normal dash FM radio on a normal station at a sound level that is able to be listened to comfortably. Then key your mobile radio mic and ask the person on the other end of the radio if they can hear your FM station in the background. If they can just maybe make out what is being said over the FM radio, your mic gain might be on the verge of being too high. If it is almost as loud as the person on the mic, then the mic gain is way too high.
Using a deviation meter or service monitor, make this test. Talk loud into the mic and measure the deviation of the transmitter. Then hold the mic about a foot away and make the same measurement. The measured deviation should have dropped off greatly. If not, get the mic gain lowered. I normally use a steady five and hold it till the deviation settles and can be measured.
So much for today's little hint on how to test a radio.
Jim
The old days of leaving the mic hung up on the dash, reaching over and pressing the PTT button and talking should be gone. Train the users proper operation on how to speak into the mic.
This picking up of all the background noise is even more pronounced if your using a repeater. Reason being is that most of the radio shops don't know how to adjust the audio throughput going through the repeater. They have the audio adjusted so that it actually adds gain and compresses the audio. This just brings up all the background noise and makes it harder to hear what the users are saying.
Try this for a test. Play the normal dash FM radio on a normal station at a sound level that is able to be listened to comfortably. Then key your mobile radio mic and ask the person on the other end of the radio if they can hear your FM station in the background. If they can just maybe make out what is being said over the FM radio, your mic gain might be on the verge of being too high. If it is almost as loud as the person on the mic, then the mic gain is way too high.
Using a deviation meter or service monitor, make this test. Talk loud into the mic and measure the deviation of the transmitter. Then hold the mic about a foot away and make the same measurement. The measured deviation should have dropped off greatly. If not, get the mic gain lowered. I normally use a steady five and hold it till the deviation settles and can be measured.
So much for today's little hint on how to test a radio.
Jim