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K40 speech processor
- Thread starter Robalo
- Start date
all i know..is what i have been told..they are great, but hard to get just right, never had one...but...i everybody that has them dialed in seem to love them
that is a later version of the old tone switch k40 with the astatic cartridge,
the earlier ones had a smaller cartridge and the last ones produced had no tone switch + a cheaper case that always cracked at the top,
i have all 3 versions, the ones with tone sound either too tinny or too much bass for my ears but sound ok on some radios,
the last version imho has a more ballanced tone but the case often cracks over time even on an unused mic.
the earlier ones had a smaller cartridge and the last ones produced had no tone switch + a cheaper case that always cracked at the top,
i have all 3 versions, the ones with tone sound either too tinny or too much bass for my ears but sound ok on some radios,
the last version imho has a more ballanced tone but the case often cracks over time even on an unused mic.
I need to wire this microphone to rci-2950dx and did not work
1: shield and black
2: white (audio)
3: red (xmit)
4:blue (rx)
5: n/c
6: n/c
please help me tx
This is old post but people need to know if they use Google they can find the wiring and the mod that must be done. You have to attach a diode and resistor internally from a switched supply to one of the pins. It tells you which end cathode etc... attaches to what......It is a bit more involved then just changing the pin wires since you have to supply the right voltage to the right pin for the micro processor board in the radio.
You might also need to cut a trace for impedance matching as not all radio's like the same load! It is all online though so instead of coming here and asking just use google then if you hit a snag ask for help following the mod with link to the mod you are following. This way people donot have to hand draw schematic for you and hand type instruction that are already floating around cyber space! Cool???
You might also need to cut a trace for impedance matching as not all radio's like the same load! It is all online though so instead of coming here and asking just use google then if you hit a snag ask for help following the mod with link to the mod you are following. This way people donot have to hand draw schematic for you and hand type instruction that are already floating around cyber space! Cool???
Well any mic sounds like junk on an improperly "peaked and tweaked" radio. Plenty of radio's with stock mikes, 2018 Etreme's, D104M6B that sound like the guy has either swallowed his mic or has a mouth full of cotton. That is the first symptom of a disabled limiter which in trash circles = "Loud and Proud".
No radio with only a few exceptions should ever have it's limiter's clipped or completely disabled. If the radio is so cheap to not have a pot to adjust modulation and your only option is clipping a part then it is time to buy a new radio! Plus they put an rf gain knob on many radio so if you add a compressor or amplified mic one of the two will need to be adjusted to match the rest of the system. Not every turned wide open!
So the K40 mic is fine not perfect but fine. The problem is the people trying to mod them for other radio's have no business holding a soldering iron because they do not know anything about electronics! So the bigger issue is the people trying to make them work.
I put a Corvette engine in a Toyota 4Runner once not just anyone can do that sort of mod. Today it is easier then ever since they have kits to make it easier but it is still not for everyone. Just because you have a set of craftsmen wrenches does not mean you know how to use them. Same thing goes for electronics and soldiering iron. Not all Toyota pickup's with domestic V8's in them turn out the same. Some are great and some are total hack and cut jobs and look it!
No radio with only a few exceptions should ever have it's limiter's clipped or completely disabled. If the radio is so cheap to not have a pot to adjust modulation and your only option is clipping a part then it is time to buy a new radio! Plus they put an rf gain knob on many radio so if you add a compressor or amplified mic one of the two will need to be adjusted to match the rest of the system. Not every turned wide open!
So the K40 mic is fine not perfect but fine. The problem is the people trying to mod them for other radio's have no business holding a soldering iron because they do not know anything about electronics! So the bigger issue is the people trying to make them work.
I put a Corvette engine in a Toyota 4Runner once not just anyone can do that sort of mod. Today it is easier then ever since they have kits to make it easier but it is still not for everyone. Just because you have a set of craftsmen wrenches does not mean you know how to use them. Same thing goes for electronics and soldiering iron. Not all Toyota pickup's with domestic V8's in them turn out the same. Some are great and some are total hack and cut jobs and look it!
The internal capacitor on the K40 takes its charge from inside the radio.
Use the tx wire from the mic socket and solder a 1n4001 diode in line with it with the cathode (banded end) to the pin on the socket and the wire to the other side.
Then feed 12v (from the on/off switch) through a 1k resistor to the pin on the socket where you've just soldered the diode.
Also, make sure you adjust the little trimmer on the rear of the mic.
Great mics if set-up correctly.
Since they are all old I guess it depends on how the mic element still is. I had 4 of these old magnet back K40 mics, two sounded like crap, one was not bad and one was great.
You made mention of an Astatic cartridge in these mic's. I'm looking for a replacement cartridge for my K40 speech processor mic.
Never found anybody who was able to get one of these things to work PROPERLY on anything other than a K-40 Model 7 radio (the tiny one), however, for what it was, that little rig sounded pretty good on AM.
I myself, used to own a K-40 Model 8 (rare) radio, which was pretty much like an old Uniden PC-66, only the speech processor was actually a BOARD mounted INSIDE of the radio itself. Although it came with the K-40 microphone (magnetic mount that definitely did NOT lend itself well to mobile use), the mic itself did NOT have an internal speech processor like the model 7's mic did.
After the K40 microphone came apart from constant mobile use, I replaced it with an Astatic power mic which worked much better.
Then, after I removed the radio to sell the truck, I noticed that the internal speaker began sounding crappy... as it had begun to dryrot. So, I took the speaker out and installed a 2 pill stinger board in place of the speaker. Rig would DK over 25 watts and swing to over 100. However, it was getting into my neighbor's telephones because I was using a Midland endfed halfwave vertical and no doubt getting lotsa rf in (and out of) the coax. So, I eventually sold it. Wish I hadn't, as finding a K-40 Model 8 in good condition nowadays is like finding hen's teeth.
Good luck with your project. Let us know HOW you make out with it.
I myself, used to own a K-40 Model 8 (rare) radio, which was pretty much like an old Uniden PC-66, only the speech processor was actually a BOARD mounted INSIDE of the radio itself. Although it came with the K-40 microphone (magnetic mount that definitely did NOT lend itself well to mobile use), the mic itself did NOT have an internal speech processor like the model 7's mic did.
After the K40 microphone came apart from constant mobile use, I replaced it with an Astatic power mic which worked much better.
Then, after I removed the radio to sell the truck, I noticed that the internal speaker began sounding crappy... as it had begun to dryrot. So, I took the speaker out and installed a 2 pill stinger board in place of the speaker. Rig would DK over 25 watts and swing to over 100. However, it was getting into my neighbor's telephones because I was using a Midland endfed halfwave vertical and no doubt getting lotsa rf in (and out of) the coax. So, I eventually sold it. Wish I hadn't, as finding a K-40 Model 8 in good condition nowadays is like finding hen's teeth.
Good luck with your project. Let us know HOW you make out with it.
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