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Astatic D104m6b squeal

Microphone Information Wiring etc, or if you just need help with choosing a good microphone for your radio.

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harddrive747
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Astatic D104m6b squeal

Post by harddrive747 » Wednesday, 23 September 2009, 7:40 AM

I have a Cobra 25 NW with weather that I put into my 2010 Ford Explorer (new) with the above microphone. I also have a Wilson 1000 magnet mount antenna. I had this exact setup in a 2002 Ford Explorer and didn't have any problems with it.

In my new Explorer, I mounted the radio on the right side of the console and then ran the power wire to the fuse box in the truck. I also connected the ground wire to the assembly for the parking brake. It looks like that is galvanized metal, but the radio will power up. Now, I have run the antenna wire behind the plastic and under the carpet in the truck. It is a very clean install. I have the antenna mounted on the roof in front of the luggage crossbar and behind the moon roof. I readjusted the antenna so that the magnet should be making full contact with the roof.

I have been told that when I talk into the microphone that it squeal like a pig. I have been looking for information to figure out what to do about it. I have tried the dynamic on the radio all the way turned to the left and I was told that made it worse. I also turned the microphone's level to zero, but at the time I tested it, either no one could hear me, or it was squealing so bad that no one could understand me.

I tried another microphone and it didn't even seem like it was transmitting. My one thought is to move the power ground from the parking brake assembly to the ground for one of my power points on my truck, but I don't know if that will help.

I need to know what I need to do to get rid of the squeal. It's frustrating trying to understand what the problem is when the radio works and receives nicely, but when I try to talk all I hear is that I squeal.

Thanks for the help
Terry


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Re: Astatic D104m6b squeal

Post by TheCBDoctor » Wednesday, 23 September 2009, 7:52 AM

Hi harddrive747

Is the squeal an audio feed back or a RF hum. There is a difference. If you can hear the squeal then you must have talk back. Put the talk back on a switch or remove it. I would start with that. What is your SWR? The mag mount may be too close to the luggage rack. Try moving the mount away temporarily.

As for the ground I would make it as short as possible. A long ground wire may act like an antenna. The case of the radio is not at the same DC ground as the radio chassis. It does not become the same RF ground until the point at which the antenna contacts the vehicle.

Good luck,
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Re: Astatic D104m6b squeal

Post by harddrive747 » Wednesday, 23 September 2009, 8:20 AM

TheCBDoctor, thanks for the reply. I do not have talk back. I just have the radio. The squeal is in the receivers radio. When I key up, I hear nothing on my end, but the receiver who is receiving my transmission hears the squeal in their radio.

I haven't checked the SWR as I haven't taken the time. I had a place in Wilmington, DE tune my antenna, but when I check the meter from the radio on channel 1 and channel 40, channel one is higher , but not by much. Also when I key up the meter goes right to the red and occasionally higher, but not berried to the right.

I did move the magnet mount closer to the moon roof, but the squeal for others is still there.

About the ground, you are suggesting that I move it to the ground for the power point, which I plan on doing tonight when I get home.

Thanks again.

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Re: Astatic D104m6b squeal

Post by harddrive747 » Wednesday, 23 September 2009, 17:33 PM

CBDoctor, I took time tonight to move the ground wire to ground on the power point on the console. That didn't help the squeal in others radio when I keyed up. So I went ahead and checked the SWR with the SWR meter from Radio Shack. I tested it and discovered that I was well over 3 to 1 on the meter. It was way in the red and almost where the CAL was suppose to be set. So when I tested it, I heard other mention about the squeal, which meant that the ground wasn't the problem.

So I took time to adjust the antenna and put it all the way down and still was over 3. So I cut 4 3/4" off the top of the antenna because it was bent and I was able to get it down to about 2.5. I then put the antenna all the way down and got it down to 1.5. I tried to talk, but no one was in the area to answer. I left it there and will see what happens when I head to the office on Thursday.

I looked on the web to determine what I need to adjust and tune in the antenna and will need to work on that on Saturday. I hope that I got it going in the right direction.

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Re: Astatic D104m6b squeal

Post by 231 » Wednesday, 23 September 2009, 17:41 PM

Some radios will in fact squeal if the standing wave is too high. Sounds like you are getting a handle on that though.

Next, when you say you "checked it with another mic" did you have the factory mic that came with the radio or just some old mics you had laying around? The reason I ask is to find out if you are sure they are even wired for this radio or not?

Last but not least, change the 9v battery in the mic. If I may suggest, don't just "check it", change it. I had a newer mobile D104 that went through batteries like every month. I finally got sick of it and used the case to fix one of my old D104's...which is still in service today. All of them I've had squealed when the battery was questionable or bad.

Just another idea or two to check.

:icon_e_wink:


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Re: Astatic D104m6b squeal

Post by TheCBDoctor » Wednesday, 23 September 2009, 17:56 PM

Hi harddrive747

231 has a good point that I forgot. The battery in the power mic will cause the radio to squeal if it is almost dead. A high SWR will also cause a radio squeal. The standing wave of 3 to 1 could be at the radio case. I bet the 1.5 SWR will work. If it does I would leave it at 1.5 to 1 because that is mere 4% loss.

231, I didn't think about a weak Battery for the Astatic, but you are right I have run across that before. I must be slipping.

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Re: Astatic D104m6b squeal

Post by 231 » Wednesday, 23 September 2009, 23:27 PM

TheCBDoctor wrote: I must be slipping.
Not hardly! Heck, no way anyone could remember the characteristics of all of the mics that have been made. It just so happens I've had so may of the Astatics over the years when I hear someone say "squeal" the battery is the first thing I replace. ( I think they call that "bitter experience?" ) :confused:

My money would be on the SWR setting, with the mic battery a close second. In any event, I hope one (or both) solves the problem. Nothing worse than having that kind of thing going on. :icon_rolleyes:

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Re: Astatic D104m6b squeal

Post by harddrive747 » Thursday, 24 September 2009, 6:25 AM

231, you are so right. There is nothing worse than squeal. As I said in an earlier post, I reset the ground wire and set the antenna. I will plan on checking that this weekend, when I have a few more minutes. I tested it this morning on the way to the office and one person finally responded to me. At first things were good and he could hear me, but near the end of the conversation the squeal came back. I then keyed up a second time and the squeal got worse. So I think it is the battery. I plan on getting a new battery in the next few days and replace it this weekend.

Now, are all the Astatic microphones powered or do they have some that aren't? If not then what microphone would be good to work with and last with Cobra 25 NW WX radio?

Thanks for the information. I'm getting close to solving this.

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Re: Astatic D104m6b squeal

Post by 231 » Thursday, 24 September 2009, 6:52 AM

harddrive747 wrote: Now, are all the Astatic microphones powered or do they have some that aren't? If not then what microphone would be good to work with and last with Cobra 25 NW WX radio?

Thanks for the information. I'm getting close to solving this.
I honestly have no idea...but I'm sure CB Doctor will. Frankly, I've always used the mobile D104's. With the exception of the one I mentioned, I've never had a problem. Believe it or not, if a tune/alignment of the radio is done right, a stock mic can sound terrific. For me though, I run sideband mostly and the D104 tends to just clean up the audio and make it a little sharper and crisp. And of course, it doesn't hurt on AM either.

Without a doubt there are several mics that will work great with the Cobra 25...the D104 is just one of them. Most any amplified mic will have a battery. The question is, which type of battery? Most of the newer ones use 9v, some of the older ones use a (hard to find) 7v. I have an old Turner +3 mobile mic that is like that. I'd love to use it but the batteries were just too hard to come by and expensive. The old Cobra power mic I have doesn't sound near as good as the D104, so in a box both the Turner and Cobra mics sit. :icon_rolleyes:

I think you'd do good keeping the D104 going. They typically have great sharp, crisp, and easy to listen to audio. A 9v battery is only a couple bucks and be found at any grocery store.

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Re: Astatic D104m6b squeal

Post by OneEyedJack » Thursday, 24 September 2009, 8:13 AM

I'd have to agree with 231. The D-104 mobile mic is very good. Has great quality audio. With heavy use, any battery I've put in these mics have lasted 6-12 months. My radio is pretty loud and I've been told that even with the stock mic it is loud, I just like the difference in the audio quality that I get with the D-104.

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Re: Astatic D104m6b squeal

Post by harddrive747 » Thursday, 24 September 2009, 18:41 PM

You guys are right about the Astatic mic. It is a good mic. I was on the way home and I caught up with a friend of mine, who I thought I would sell my radio to. In a way, I'm glad that I didn't. Well I was able to get the mic working and if I didn't stay on long the squeal wouldn't be there. So I thought that I would change the battery, but haven't.

My friend wanted to see how I put the radio in and how clean the install was. I told him that I changed the ground to the power point on the truck and that makes it much quieter. Well the squeal was still there near the end. I could use the mic. So we tried one of his stock mic and that squeal terrible. I mean the second I keyed up, nothing but squeal. At least the Astatic mic gave me a few seconds. He decided it was a grounding problem. So he told me to get an RF choke, which I did. I put two of them on the microphone cord, one near the mic and the other at the radio. I tried it out and everything seems fine.

I asked for a radio check and it was clean, but according to the guy who talked back to me said that there was a bit of background noise from the FM radio, which I had on. I turned it off and he said it cleared up. However, I will not turn my FM off as it has too many other good things to go with it. One thing on there is the SYNC, which allows me to pair up my phone that has bluetooth on it and to play songs from many different sources. I don't know if that is causing an issue. So it looked like a grounding issue and with the two chokes on there, that apparently has taken care of my squeal issue.

The next thing that I need to do is to recheck the antenna and make sure that SWR is low and I should be good to go.

Thanks for all the help.

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Re: Astatic D104m6b squeal

Post by SKYHAWK0115 » Monday, 16 November 2009, 21:39 PM

harddrive747 wrote:I have a Cobra 25 NW with weather that I put into my 2010 Ford Explorer (new) with the above microphone. I also have a Wilson 1000 magnet mount antenna. I had this exact setup in a 2002 Ford Explorer and didn't have any problems with it.

In my new Explorer, I mounted the radio on the right side of the console and then ran the power wire to the fuse box in the truck. I also connected the ground wire to the assembly for the parking brake. It looks like that is galvanized metal, but the radio will power up. Now, I have run the antenna wire behind the plastic and under the carpet in the truck. It is a very clean install. I have the antenna mounted on the roof in front of the luggage crossbar and behind the moon roof. I readjusted the antenna so that the magnet should be making full contact with the roof.

I have been told that when I talk into the microphone that it squeal like a pig. I have been looking for information to figure out what to do about it. I have tried the dynamic on the radio all the way turned to the left and I was told that made it worse. I also turned the microphone's level to zero, but at the time I tested it, either no one could hear me, or it was squealing so bad that no one could understand me.

I tried another microphone and it didn't even seem like it was transmitting. My one thought is to move the power ground from the parking brake assembly to the ground for one of my power points on my truck, but I don't know if that will help.

I need to know what I need to do to get rid of the squeal. It's frustrating trying to understand what the problem is when the radio works and receives nicely, but when I try to talk all I hear is that I squeal.

Thanks for the help
Terry
HARDDRIVE,

IN YOUR D104M6B MIC, JUST CUT YOUR WHITE AUDIO WIRE OR DISCONNECT IT AND PLACE A 4700 OHM INLINE AND A .001 CAP TO SHIELD ON EACH SIDE OF THE RESISTOR. THIS WILL CUT OUT YOUR SQUEAL ! SKYHAWK0115

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Re: Astatic D104m6b squeal

Post by harddrive747 » Tuesday, 17 November 2009, 6:47 AM

Thanks for the suggestion, but I discovered that the Antenna was the issue and I have ordered and put in place a brand new Wilson 1000 and the squeal went away. I now have a range of 15 miles when no "big" radios are broadcasting.

Again, everything is ok.


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