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Amplified microphone project for the Q900

 

Since the Q900 has problem with modulation especially on FM, I looked for an amplified mic. The procomm mic that works well with, is not sold in Germany or many other countries. The mics I found where expensive.?

I decided build my own amplified microphone with parts I found online. I don't mind improvising and I have fun building stuff.
Here is what I came up with so far. I tested the mic amp module successfully NFM 2m and got a good feedback after a quick QSO. But everything still has to be put into a housing.

The mic amp module has a DC offset. I decided to use a decoupling capacitor. But what value should I take? I don't have experience with mic amps and inputs. Also the potentiometer is needed to lower the output signal. Is 10k ok? It works with the Q900 but what are usual values?

Q900 amplified microphone project.png

 

On Mon, Aug 28, 2023 at 11:44 PM, <kai@...> wrote:

Since the Q900 has problem with modulation especially on FM, I looked for an amplified mic. The procomm mic that works well with, is not sold in Germany or many other countries. The mics I found where expensive.?

I decided build my own amplified microphone with parts I found online. I don't mind improvising and I have fun building stuff.
Here is what I came up with so far. I tested the mic amp module successfully NFM 2m and got a good feedback after a quick QSO. But everything still has to be put into a housing.

The mic amp module has a DC offset. I decided to use a decoupling capacitor. But what value should I take? I don't have experience with mic amps and inputs. Also the potentiometer is needed to lower the output signal. Is 10k ok? It works with the Q900 but what are usual values?


I have a friend who noted the Q900’s poor mic quality. ?He opened up the mic and found there was no hole for sound to travel. ?He drilled a small hole in the shell in front of the microphone diaphragm. ?It sounds great now.

73,
N3CNO
 

Yes, I heard the same about drilling a hole and also maybe replacing the mic capsule.
I posted it, on my new webpage for the Q900:


For those still interested in the amplified mic, I have an updated diagram.

Q900 amplified microphone project.png

 

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And some deadening material around the pocket
?for the mic. Yep did all that. I also changed out the electret mic for a Motorola that fits the hole almost perfect. The mic sens can be farther reduced on the Pryne mic by putting a resister across the resister labeled 222 in the audio path, or a variation of that. I’m happy with the mic audio for now. It’s the lack of ALC and adjustment there of that’s got me. I’m going to go back in time and load an earlier version of firmware. Which version do you have? Thank you for the schematic! I will print and put in my binder.
Dave?

On Sep 28, 2023, at 2:16 AM, kai@... wrote:

Yes, I heard the same about drilling a hole and also maybe replacing the mic capsule.
I posted it, on my new webpage for the Q900:


For those still interested in the amplified mic, I have an updated diagram.

<Q900 amplified microphone project.png>
 

I have the Q900 V4 with firmware 3.4.1.

The MA X9814 mic amp in my project has AGC. I did not choose this one, but it was sent to me, because the other one was not available.
With the AGC there is ALC but the gain raises up to 20 dB. So everything in the room can be heard after the release time while not speaking into the mic.

Kai
 

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That’s the symptom of to much mic sensitivity. That’s adjustable in some radio’s. Mostly commercial. What I do with ham quality radios is pad down the mic. If you hold the mic at arms length it should not pic up anything. This one at arms length is just as bad as in my face. I chose their cheap little Pryne mic to modify but the procedure is the same. You can put felt or some material in front of and around the cartridge to clean up the audio a bit. I also ?turn down the mic. They multiplex the 5v a+ on the audio line with a padder resister across that line. I just add some resistance to it and voila! Mine won’t put out more than 2 watts with out flat toping and cutting the center line. (Over modulated) ?ALC problem. In my humble opinion.?
Thank you for the response. My computer guy is going to help me install an older firmware today so will know if it is a radio thing or software. Since your running the same firmware it starting to look like I got another bad radio. I will order one more if that is the case and if it is bad I’m done with Q900’s. I need a small quantity of something like this for a group I’m doing some work for and they would be perfect if they worked.
Dave

On Sep 29, 2023, at 2:44 AM, kai@... wrote:

I have the Q900 V4 with firmware 3.4.1.

The MA X9814 mic amp in my project has AGC. I did not choose this one, but it was sent to me, because the other one was not available.
With the AGC there is ALC but the gain raises up to 20 dB. So everything in the room can be heard after the release time while not speaking into the mic.

Kai

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