I've read up on receive mods for typical radios such as cobras etc.. i see that mostly all that takes place is a diode swap after the IF amp before the actual rf receive amp, and a transistor swap that is a bit higher of HFE. I dont have this transistor available to me at the moment and im working on new mods just because the ones around are just so OLD lol.. nothing personal old timers, many of them are great but this one just doesnt seem to be worth the hassle. what im thinking is to swap the diodes with some Ge diodes and remove that whole transistor stage. what i can do is draw up a pcb using a good op amp, dual or quad (not sure what i would use yet, this is a brain storm). im thinking all i would need to use is a dual opa2134 or maybe ne5534 since its replacing a bipolar. with a little filtering between the 2 op amp stages and gain stages designed accordingly transistion freq would definitly not be an issue. maybe even trim off a little of that noise. I'd be working off a single supply unless i added a charge pump so biasing wouldn't be a big deal..
what i dont understand is that when working on cb radios do i have to set Z to 50 ohms even on the recieve amp?? or does it matter? I'd use a trim pot on the feed back stage like i did in my power mike circuit.
this seems like a good idea to me if i could get the filtering right, if not it might result in a butt load of white noise and screaming truckers in my ears.
I could build the whole thing as a band pass filter but am i just trying to get my freq between 26-29 mhz or would i trim it off the speech freq like a speech filter?
sorry if my questions seem silly, this RF thing is really new to me. but i think this might be a good idea if i can get it right? any input or ideas?
what i dont understand is that when working on cb radios do i have to set Z to 50 ohms even on the recieve amp?? or does it matter? I'd use a trim pot on the feed back stage like i did in my power mike circuit.
this seems like a good idea to me if i could get the filtering right, if not it might result in a butt load of white noise and screaming truckers in my ears.
I could build the whole thing as a band pass filter but am i just trying to get my freq between 26-29 mhz or would i trim it off the speech freq like a speech filter?
sorry if my questions seem silly, this RF thing is really new to me. but i think this might be a good idea if i can get it right? any input or ideas?
