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Easiest way to achieve hi fi?
- Thread starter Bearcat
- Start date
That's the cheaper way but adjusting it all and making it work is much harder than the MMM board or Asymod . You either have to learn or pay. No free rides.
The most important piece of rack gear is a peak limiter when you do the direct inject thing. Basically an external modulation limiter.
I don't think you are going to direct inject a 29 with any measure of the term "easy".
You could inject audio through the audio wire on the mic input, it will pass through the amplification stage, and to the TA7222 (depends how old/new the 29 is..)
If you inject audio at the TA7222 you still face the limitations of that device.
And the modulation transformer itself will ultimately act as a bottleneck...
Other Audio Amp IC's found in the 29 are YD1022 which came after the TA7222, & then they switched to the TDA2003 (newest one used I think)
But maybe i'm way off base and have not a clue what i'm saying...
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Top shelf choice for CB would be a Cobra 2000 GTL, or a Cobra 148 GTL.
If you don't mind export rigs.. R.C.I.
(Galaxy, Connex, Ranger)
I don't have experience In doing direct inject, all my thoughts and ideas come from theory and info I read online. On an Export you would use a wider filter as discussed earlier in this thread, and then pipe audio directly into the balanced modulator?
Someone else with experience is going to have to chime in.. Also the resultant radio may or may not be okay to use on SSB after modification, but I simply do not know.
Stock mod
The 148 chassis is a good choice. A low level modulated rig that uses a balanced modulator like most ham rigs will work on AM and SSB. The exports that I'm familiar with will work similar to the 148, no filters to change, AM only and no SSB unless you use the stock mic. You can inject further upstream and have ssb but sacrifice bandwidth.
Another limitation of the 29 in addition to what you mentioned earlier is the modulation transformer. Have to use a bigger one or lighten the load on the stocker. You can get a respectable sound by piping the audio gear straight to the audio chip.
Most people that start these threads don't want to hear what the guys that have done this have to say. Their answers aren't what they want to hear. Easy costs money, cheap will take effort.
The 148 chassis is a good choice. A low level modulated rig that uses a balanced modulator like most ham rigs will work on AM and SSB. The exports that I'm familiar with will work similar to the 148, no filters to change, AM only and no SSB unless you use the stock mic. You can inject further upstream and have ssb but sacrifice bandwidth.
Another limitation of the 29 in addition to what you mentioned earlier is the modulation transformer. Have to use a bigger one or lighten the load on the stocker. You can get a respectable sound by piping the audio gear straight to the audio chip.
Most people that start these threads don't want to hear what the guys that have done this have to say. Their answers aren't what they want to hear. Easy costs money, cheap will take effort.
543 you are right, also I mentioned the transformer two posts back about the 29.
So I can direct inject a Galaxy radio without even changing the filter good to know, after all I won't be running rack gear any time soon, I may play with the Galaxy.
I am going to experiment with a "noise toy" (door bell) at the audio I.C. on a 29.
To get the concept down.
I am going to use a current limiting 1/2 watt resistor @ BLANK ohms in an effort to not blow up the weak TA7222 in my 29 LTD Classic.
-Leap
So I can direct inject a Galaxy radio without even changing the filter good to know, after all I won't be running rack gear any time soon, I may play with the Galaxy.
I am going to experiment with a "noise toy" (door bell) at the audio I.C. on a 29.
To get the concept down.
I am going to use a current limiting 1/2 watt resistor @ BLANK ohms in an effort to not blow up the weak TA7222 in my 29 LTD Classic.
-Leap
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@LeapFrog
It may be prudent to use some kind of buffer circuit between your audio source and the high level audio amp. I mean more than just a cap. The MPF102 is a cost friendly and very warm sounding FET.
Cheers
CBPhreaker
It may be prudent to use some kind of buffer circuit between your audio source and the high level audio amp. I mean more than just a cap. The MPF102 is a cost friendly and very warm sounding FET.
Cheers
CBPhreaker
Thank You CBPhreaker.
I will use a buffer inbetween the audio source and the TA7222
I don't want Hi-Fi or Direct Inject on the 29, first I want to tackle the simple concept of injecting audio into the already present circuit on the radio, that's the purpose of the blasted noise toy experiment. lol
The door bell tone board has an amplified output, so now that my scope probes are compensated I will poke about the board and sniff out the signal before it gets amplified.
I was going to "rig it" that's why I mentioned a current limiting resistor, you have presented a superior route to go with a buffer.
-LeapFrog
Galaxy DX 2547 + Deez Modz = HiFi CB :
Start off by changing the response of the mic pre-amp (IC 7). In order to do this, I changed the operation from a low pass filtered non-inverting input to a flat response inverted input. To do that, I removed C153. I changed R178 from a 12K to a 10K. R176 was changed from a 270K to a 470K (a little more gain).
C154 was removed and replaced with a 4.7uF cap. The negative lead of the new C154 cap was placed in its regular hole. The positive side of the cap was moved from its original hole to pin 2 of IC7. (Move the input coupling cap (C154) lead from where it was previously on pin 3 to pin 2. Pin 2 is now the input pin. Solder the cap lead directly to the IC's pin 2) C171 and C235 were changed to 4.7 uF caps as well.
And finally, C238 was changed from a 100 uF to a 2200 uF cap (this was the final piece that brought the low end response down from 120 hz to about 40 hz).
I also inserted a 7 band EQ at R262. I lifted one end of the resistor, and added another 10K to the hole just vacated by the lifting of R262. The two free ends of the 10K resistors I connected to shielded audio leads to the input and output of the EQ
Much Thanks to Sandbagger in S.E. PA for the mod info. I get to hear this great sounding setup about once a week on air
Start off by changing the response of the mic pre-amp (IC 7). In order to do this, I changed the operation from a low pass filtered non-inverting input to a flat response inverted input. To do that, I removed C153. I changed R178 from a 12K to a 10K. R176 was changed from a 270K to a 470K (a little more gain).
C154 was removed and replaced with a 4.7uF cap. The negative lead of the new C154 cap was placed in its regular hole. The positive side of the cap was moved from its original hole to pin 2 of IC7. (Move the input coupling cap (C154) lead from where it was previously on pin 3 to pin 2. Pin 2 is now the input pin. Solder the cap lead directly to the IC's pin 2) C171 and C235 were changed to 4.7 uF caps as well.
And finally, C238 was changed from a 100 uF to a 2200 uF cap (this was the final piece that brought the low end response down from 120 hz to about 40 hz).
I also inserted a 7 band EQ at R262. I lifted one end of the resistor, and added another 10K to the hole just vacated by the lifting of R262. The two free ends of the 10K resistors I connected to shielded audio leads to the input and output of the EQ
Much Thanks to Sandbagger in S.E. PA for the mod info. I get to hear this great sounding setup about once a week on air
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