I just recently bought a superstar dm-452 mic for my cobra radio and all its doing is sqealing when i key up the mic. I've tried adjusting the rf gain all the way up and down and no matter which way i adjust it it squeals when i key up the mic. I use this setup in my hunting truck. We use cb radios to communicate back and fourth while hunting, so other than using them a few weeks out of the year, im pretty green to cb radios and the ins and outs of the equipment. Any help y'all can offer would be greatly appreciated!
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superstar dm-452 mic
- Thread starter chase cooley
- Start date
like undertaker said, details please.
what cobra radio?
any mods done to it? if yes, what and by who?
did you buy the mic wired for your radio or did you wire it yourself?
are you sure the battery is good?
LC
what cobra radio?
any mods done to it? if yes, what and by who?
did you buy the mic wired for your radio or did you wire it yourself?
are you sure the battery is good?
LC
Thanks for the replies y'all. My radio is a cobra 25ltd classic with no modifications done to it. I bought the microphone new off of walcottradio.com and haven't modified it in any manner, and according to the description it works with "cobra 25, 29, and newer 148 models".
Turn the adjustment down on the microphone until the squealing goes away and problem solved. The RF gain adjustment on the radio has no relevance to your problem.
to add to what RPC is saying, the RF gain on the front of your radio could be labeled "receive gain", as it only controls the sensitivity of the receive. it does not do anything on transmit.
i believe your radio has a mic gain control on it, probably labeled "DYNAMIKE".
this is what sets the sensitivity of the mic audio.
It should be understood that none of these controls are actual "gain" controls, they are actually just attenuators that let you go down from "zero".
right now im going to assume that the mic was wired properly for the radio by walcott.
since they are the ones that put the battery in, i would try a new battery and see if that helps. a low battery can cause a power mic to squeal.
start with that "echo" slider on the front all the way down (to the left).
leave the mic gain on the radio all the way up for now.
does it squeal with a new battery and set like this?
if no, you are all set, and may just need to keep that echo level low to avoid squealing.
if yes, open the mic and look at the back of the PC board.
you will see two little trimmer resistors.
one is for the echo repeat, and one is for gain.
again, as RPC said, turn the gain down, talk into the mic, and raise it up until it squeals and then back it down a bit from there.
here is a review of the mic that may help: http://cbradiomagazine.com/Microphone Reviews/DM-452/DM-452.htm
post back with your results and we'll go from there.
LC
i believe your radio has a mic gain control on it, probably labeled "DYNAMIKE".
this is what sets the sensitivity of the mic audio.
It should be understood that none of these controls are actual "gain" controls, they are actually just attenuators that let you go down from "zero".
right now im going to assume that the mic was wired properly for the radio by walcott.
since they are the ones that put the battery in, i would try a new battery and see if that helps. a low battery can cause a power mic to squeal.
start with that "echo" slider on the front all the way down (to the left).
leave the mic gain on the radio all the way up for now.
does it squeal with a new battery and set like this?
if no, you are all set, and may just need to keep that echo level low to avoid squealing.
if yes, open the mic and look at the back of the PC board.
you will see two little trimmer resistors.
one is for the echo repeat, and one is for gain.
again, as RPC said, turn the gain down, talk into the mic, and raise it up until it squeals and then back it down a bit from there.
here is a review of the mic that may help: http://cbradiomagazine.com/Microphone Reviews/DM-452/DM-452.htm
post back with your results and we'll go from there.
LC
I replaced the battery today day and I’m still getting a squeal. I opened up the back of the mic and see the resistors you mentioned. Can these be adjusted and how? Thanks! I’m thinking I may have to send the mic back in if this doesn’t work.
yes, looking at the back of the mic with the cord facing down, the trimmer you want to adjust is the one on the right. (probably says "103" on it)
the one on the left is for the echo and you should not mess with it at this time.
(you can mess with it later if you end up using the echo function of the mic)
start by making sure the slider on the front of the mic is all the way to the left (no echo effect).
then turn that trimmer all the way one direction.
key the mic and see if it squeals.
if it does, you have that trimmer all the way up and need to turn it all the way the other direction.
key the mic and see if it squeals.
if it doesnt, start turning it up in small (1/8 turn) increments, checking the audio along the way.
you should notice a point where it starts to squeal, and you should back it down a bit from that setting and leave it there.
if this worked, you are all good!
if not, as in, if the mic squeals no matter where you set that trimmer, then you either have a miswired mic, or an antenna SWR problem
high antenna SWR can cause power mics to squeal.
if you can't get it to work, let us know what kind of antenna you have, how it's mounted, where it's mounted, and any other minor details of the antenna install even if you don't think they are important.
also, do you have a multimeter that you can use to check continuity?
good luck,
LC
the one on the left is for the echo and you should not mess with it at this time.
(you can mess with it later if you end up using the echo function of the mic)
start by making sure the slider on the front of the mic is all the way to the left (no echo effect).
then turn that trimmer all the way one direction.
key the mic and see if it squeals.
if it does, you have that trimmer all the way up and need to turn it all the way the other direction.
key the mic and see if it squeals.
if it doesnt, start turning it up in small (1/8 turn) increments, checking the audio along the way.
you should notice a point where it starts to squeal, and you should back it down a bit from that setting and leave it there.
if this worked, you are all good!
if not, as in, if the mic squeals no matter where you set that trimmer, then you either have a miswired mic, or an antenna SWR problem
high antenna SWR can cause power mics to squeal.
if you can't get it to work, let us know what kind of antenna you have, how it's mounted, where it's mounted, and any other minor details of the antenna install even if you don't think they are important.
also, do you have a multimeter that you can use to check continuity?
good luck,
LC
I have two of those. My old Cobra 148GTL has one hooked up right now. You must coordinate between any mic gain adjustment on your radio, the mic gain control on the mic itself and the echo.
I'd never run the echo higher than 1/4. I've actually got the echo set one notch below 1/4. The mic gain on my Cobra 148GTL is at 1:00 o'clock. From there, I just set the mic gain on the mic to the lowest level where it sounds good.
Good luck.
I'd never run the echo higher than 1/4. I've actually got the echo set one notch below 1/4. The mic gain on my Cobra 148GTL is at 1:00 o'clock. From there, I just set the mic gain on the mic to the lowest level where it sounds good.
Good luck.