Copper Talk » Ask The Tech » Microphone Wiring » Lon, need help with DM 452 « Previous Next »

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Dwd
Junior Member
Username: Dwd

Post Number: 14
Registered: 7-2004
Posted on Sunday, October 03, 2004 - 8:32 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Lon, I am having trouble out of the 452 again. I am running a Galaxy 55V with the swing mod in it and a Texas Star 667V. When I first added the 452 I was getting a squeel when I key down, but I found a bad ground wire on antenna. At that time swr went to 1.8 . Bad wire was changed went back to 1.2 The 452 sounded good. After a few 4 wheeling trips, mic started to squeel. The first thing I did was check swr.,it was still 1.2. Next I changed mics to stock mic. Squeel went away. I check all wiring. Looked good. On meter it even shows that the variable power knob is not working most of the time with 452 squeeling. It is pushing high power no mater what the knob setting is. When I can get the radio to tune down to low power which is 2 watts, the mic sounds fine. When I turn variable power up again, it squeels. Then sometimes I cant get the radio to turn back down and it stays on max power which is 8 watts. And the 452 squeels. I dont understand how this mic could be effecting all of this but it is. And also this happens even if 667v is not in the settup. With stock mic, the variable power always works and mic never squeels. Could this mic just not work very well with this settup or is there a problem I am not seeing. Could I send the mic to you to check out?
DW
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Tech808
Moderator
Username: Tech808

Post Number: 3748
Registered: 8-2002


Posted on Tuesday, October 05, 2004 - 9:59 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

My guess would be with the Swing Mod and Modulation in your radio as you are throwing RF right back into the radio when you key up.

Try streaching the Mic outside of the vehicle and see if you still get feedback?

If they have added a 1N4001 or higher diode this can also be the problem.

It is not the Mic that is causing your problems.

It can be your Ground on the Radio or the Amp or your Antenna or a combination of any of them together and the DM452 is a POWER Mic where your Stock mic is not.

I have used the DM452 mics on maybe 100 or more radios and never had a problem when using them on stock / Non Clipped or Super Swung radios and I have NEVER had to make any adjustments on the inside controls.

I would suggest trying it on another radio without a swing mod or one of your friends and see what happens.

You just list so many different things that can cause the problems you are having that it is hard to try and single any one out.

Lon
Tech808
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Dwd
Junior Member
Username: Dwd

Post Number: 15
Registered: 7-2004
Posted on Wednesday, October 06, 2004 - 7:09 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Ye s I added the 1N4001 diode in line . Does this make it hard to run a power mic?
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Tech808
Moderator
Username: Tech808

Post Number: 3757
Registered: 8-2002


Posted on Thursday, October 07, 2004 - 6:48 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Dwd,

Yes, by adding a 1N4001 it can cause problems when using a Power Mic with some radios.

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Dwd
Junior Member
Username: Dwd

Post Number: 16
Registered: 7-2004
Posted on Thursday, October 07, 2004 - 9:29 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I added an extra ground wire to the radio and it got the squeel out of the 452, it sounds great , but when I talk on it a few minutes and I am watching the meter, My variable knob wont cut the power down. I am dead keying 6 watts on high and 2 watts on low, but after I have talked on the 452 for a few keydowns, the variable when it is turned down , doesnt always take the radio to 2 watts. As a matter of fact, it only takes it down to 2 watts about 3 out of 10 times trying it. This is important because 6 watts is too much for the Texas Star 667v I run. I Talk barefoot at 6 watts then when I want the amp on I use the variable knob to go down to a 2 watt dead key. I guess it is the 1n4001 diode causing feedback from the power mic. Any sugestions? I like the way the 452 sounds and would like to figure out how to run it, but I dont want to give up my swing mod because it added alot to driving the amp. When I am running the stock Galaxy mike, I have no problems at all. The variable always turns the power down every time. It is a strange problem.
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Mike0228
Junior Member
Username: Mike0228

Post Number: 18
Registered: 6-2004
Posted on Friday, November 26, 2004 - 9:21 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I recently diagnosed a problem a friend was having with his 2950 and amp. Power level was inconsistent and sometimes nonexistant. Came down to a poor connection between ground of the rig and the cheap SO-239 manufacturers use. The quick fix was to loosen the nut and clean up the area with a ScotchBrite pad and retighten the nut on the SO-239. The long range fix will be to replace the SO-239 with a quality flange type using screws, internal tooth lockwashers and nuts.

Mac

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