K40 speech processor

[Lil'Yeshua]

I would have to tap it to get the audio working but I made the mistake of taking the mic element apart and broke the little flexible piece of material that goes between the diaphragm and the hold down arm. I think this changes ground potential as the diaphragm is vibrated. Since it's part of the inverting output that goes to the IC I have to match the impedance of the new element to get the right volume level. The K40 has a 100k resistor between the op amp and the mic element.

So far I've passed up on buying a K40 speech processor mic and two K40 speech processor radios on Ebay. They wanted too much. I figured I'd try my hand at getting mine work with the knowledge I now have about the mic.

 

[camaro1]

if you ever get a chance,, try one of these,, I think you will be surprised how well it works for the price, comes with a battery, its an electret element,, steel body and button, very natural sounding and so far has worked well on any radio I have tried it on. I have a couple of them::

New Mobie Power Mic 4 Pin Black Superstar for Cobra Uniden | eBay

 

[Lil'Yeshua]

The mic area isn't to clear a picture. Do you talk into holes ?
Men's 80's Video Superstar Costume, Gold, One Size:Amazon:Clothing

 

[camaro1]

The mic area isn't to clear a picture. Do you talk into holes ?
Men's 80's Video Superstar Costume, Gold, One Size:Amazon:Clothing

I don't know what that link is,, maybe your halloween costume,,lol

the pistol grip mic fits in the palm of your hand and you squeeze the button with your finger and talk into the top of the mic

the gold color area is the element http://rover.ebay.com/rover/1/711-5...0001&campid=5336136228&icep_item=321113304572

 

[Lil'Yeshua]

I don't know what that link is,, maybe your halloween costume,,lol

the pistol grip mic fits in the palm of your hand and you squeeze the button with your finger and talk into the top of the mic

the gold color area is the element New Mobie Power Mic 4 Pin Black Superstar for Cobra Uniden | eBay

Okay. What's the other shiny metal part?
I see the element grille now.
The costume link I found while looking up that mic on Amazon. Just being funny.

 

[camaro1]

the chrome is the ptt button

 

[Lil'Yeshua]

Okay. Just got in the 25LM022 mic elements from RB Micro. I'll hook one up tomorrow and see if will match up with the 100k ohm resistor going into the op amp.
25LM022 Crystal Element - Mic Elements

 

[Onelasttime]

Just bought a NOS one and wired it to my President Lincoln! It is an Audio Demi God on SSB. Crushing Pile Up's like beer cans!!! All on it's stock MRF455. It now holds it's own on AM as well. I do wish it had more filtering though.I paid more than I wanted too but compared to other high end microphones it was still a good deal. Wish some one would remake these things.

I would rather have a electret element instead of it then the stock crystal element but nothings perfect. LOL

 

[Holydvr]

Long ago I found this thread, but I neglected to update it with information. I am only replying to put some information here that was asked by one of the others in the thread. Hopefully it helps someone someday in the future.The element used in the K 40 microphone is an Astatic MC – 564. It is a ceramic type. Depending on how the microphone was stored, they can have issues with audio output due to moisture ingress and oxidation etc. These elements can be found often with the pace 2000 series radios for a decent price if you want to get technical. They can also be found on their own with a pace model number of P5550. There were a couple other pace bottles that are easily identified by looking at them as made by Astatic. Most all of them do you have the same 564 element within.

 

[secret squirrel]

I really enjoy keeping the old tech going, best of luck. I enjoy joking around about the old ways. This is not a technical statement at all. Years ago I happened upon the K40 CB that had the speech processor installed in the CB to the board, and not the microphone. I drove out to Carlisle, PA and had Dave at DTB put the machine on it to set it up for me with my old Skythumper 65 mic from Sparky's. I liked the audio that little radio, the size of a Uniden 520, put out. Dave commented that it was worth keeping the K40 going. I ran it as my main mobile for a few years until she passed away to age related issues, and I opted not to recap and such.