Well, it is very obvious this post was started to make sales for the mentioned product. How do you guys think that PC is gonna run next to the Heathkit SB-220? How many keys before the mouse locks up? People, there are much easier ways that cost less if your goal is Hi-Fi AM. I work 75 meter AM all the time and you'll never hear this gadget used there.
First of all, you would never want more then 200% positive peaks for a very simple reason. The AM detectors used in every CB radio will not be able to demodulate this level of audio without distortion. Only a synchronous detector can do this. You'll notice the Mauldulator requires the use of a quality mic. You can't use your D-104 because it doesn't have Hi-Fi. The mic is 90% of Hi-Fi.
The rest is mainly making sure the coupling caps used in your radios audio chain are made larger to increase bass response. Most CB's will not have very much limitation in the high end but there may be bypassing caps in parallel that block the highs. A simple passive audio notch filter tuned around 500 Hz will give that FM sound with the right mic. This gets rid of that low end mid range that tends to sound "muddy". The filter is nothing more then a coil in series with a cap that is placed across the audio line. Many DC relay coils with 750 ohms resistance work great for this with a .1 mfd cap in series.
You can make a Hi-Fi mic out of an old Astatic 1104C or 575M6. The FET pre amp and tone control are ideal for modification. Rip out that ceramic element and replace it with any 2 wire electret condenser. These cheap mics have excellent response. The brown wire goes to the element ground. Take a .01 mfd cap and put it in series with the green wire to the element positive to block the DC. Then use a 33K resistor from the 9 volt battery + terminal directly to the positive terminal of the electret to supply bias. The mic switch disconnects the - side of the battery in RX and will shut the element off too.
If you want to take this further then use the passive notch filter I described above and place it right across the back of the electret element. Coil side to ground and cap side to hot. Even without doing any internal radio work, this mic will make a big difference in audio quality without any of the RFI problems associated with the external equipment this Mauldulator uses. If you're technical then get out your radios schematic and go after the audio coupling and bypassing caps.
Just keep your carrier around 25% (or slightly less) of your radios total PEP output and you'll be rockin loud and clear. SSB radios work best for this mod since they have carrier level control. Remember, electrets need a wind screen in front of them otherwise they become distorted from breath pops. The original Astatic foam or cotton works fine. This setup on my Kenwood TS-940SAT produces better audio quality then most AM broadcast transmitters. Yes, the Kenwood is heavily modified and no longer uses low level IF modulation in AM. The mic amps have been modified for flat response and the modulation takes place in an RF stage.
First of all, you would never want more then 200% positive peaks for a very simple reason. The AM detectors used in every CB radio will not be able to demodulate this level of audio without distortion. Only a synchronous detector can do this. You'll notice the Mauldulator requires the use of a quality mic. You can't use your D-104 because it doesn't have Hi-Fi. The mic is 90% of Hi-Fi.
The rest is mainly making sure the coupling caps used in your radios audio chain are made larger to increase bass response. Most CB's will not have very much limitation in the high end but there may be bypassing caps in parallel that block the highs. A simple passive audio notch filter tuned around 500 Hz will give that FM sound with the right mic. This gets rid of that low end mid range that tends to sound "muddy". The filter is nothing more then a coil in series with a cap that is placed across the audio line. Many DC relay coils with 750 ohms resistance work great for this with a .1 mfd cap in series.
You can make a Hi-Fi mic out of an old Astatic 1104C or 575M6. The FET pre amp and tone control are ideal for modification. Rip out that ceramic element and replace it with any 2 wire electret condenser. These cheap mics have excellent response. The brown wire goes to the element ground. Take a .01 mfd cap and put it in series with the green wire to the element positive to block the DC. Then use a 33K resistor from the 9 volt battery + terminal directly to the positive terminal of the electret to supply bias. The mic switch disconnects the - side of the battery in RX and will shut the element off too.
If you want to take this further then use the passive notch filter I described above and place it right across the back of the electret element. Coil side to ground and cap side to hot. Even without doing any internal radio work, this mic will make a big difference in audio quality without any of the RFI problems associated with the external equipment this Mauldulator uses. If you're technical then get out your radios schematic and go after the audio coupling and bypassing caps.
Just keep your carrier around 25% (or slightly less) of your radios total PEP output and you'll be rockin loud and clear. SSB radios work best for this mod since they have carrier level control. Remember, electrets need a wind screen in front of them otherwise they become distorted from breath pops. The original Astatic foam or cotton works fine. This setup on my Kenwood TS-940SAT produces better audio quality then most AM broadcast transmitters. Yes, the Kenwood is heavily modified and no longer uses low level IF modulation in AM. The mic amps have been modified for flat response and the modulation takes place in an RF stage.
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