Starting to modify

[rabbiporkchop]

for those that don't want to wade through this article, i will simplify it for those that want to understand how this relates to the audio path through a two way radio such as a CB.

in your audio path you will find both series and parallel capacitors. (the parallel capacitors are used to mimic a series inductor since they are cheaper)

if you increase the value of the series capacitors, you will increase the bass response of the radio.
By the same token, if you decrease the value of the parallel capacitors, you will increase the treble response of the radio.

This goes for the mic audio path as well as the receive audio path (both become the same path at some point).

Any CB technician with an education knows how to do this, it's just that some of them really try to impress you with how difficult it is in order to place themselves above the others and in turn, get your business.

RPC, this article is not hard to understand and the math is not that complicated.
I'm sure that with a little googling while you are reading it, you would get it easily.
LC

Adjusting the width still doesn't explain how to adjust the taper or amplitude of each tone. How do we adjust the shape of the response Curve without using an equalizer? Certain frequencies are best used in moderation so how do we moderate those particular frequencies? Like I said, this gets pretty deep. Lot's of folks like to oversimplify things while saying that I overcomplicate things. Since export radios are cheap contraptions without DSP, it becomes more complicated to manually process that speech using diodes, resistors, and capacitors.

 

[QuietStorm]

I think i've heard of these types of scientific conflicts happening in the past LOL.
People with agendas tend to want to underplay any sound science that renders their arguments moot.
One particular CB shop comes to mind...


Anyway, i have helped derail this thread long enough.
Quietstorm (wooosh), if you're still reading along, have you started buying parts or equipment yet?

here is a great article on building your own dummy load, which is an absolute essential for any CB hobbyist to have. http://www.k4eaa.com/dummy.html
LC

I have not, still building a list of exactly which tools I'm going to buy at what time. It seems that I'm going to do a receive upgrade on my cobra 29 first, therefore that is where I will probably start. After that, I will get the first of Lou's books and some more tools.

-----------------

I appreciate everyone's continued assistance and I don't really mind the derailing at all. I feel it's normal for anyone with a functional brain to bounce around ideas.

 

[loosecannon]

Like I said, this gets pretty deep. Lot's of folks like to oversimplify things while saying that I overcomplicate things. Since export radios are cheap contraptions without DSP, it becomes more complicated to manually process that speech using diodes, resistors, and capacitors.

RPH, the article you posted states exactly why doing that manual processing adds unnecessary distortion to the path. and no, it doesn't matter how high quality the parts are, or where you choose to add them.
LC

 

[rabbiporkchop]

RPH, the article you posted states exactly why doing that manual processing adds unnecessary distortion to the path. and no, it doesn't matter how high quality the parts are, or where you choose to add them.
LC

Removing distortion is the whole goal. Putting limits in place is a key to eliminating distortion. Without wiring an EQ directly into the radio to do this requires a more complicated solution permanently installed in the radio.
One doesn't simply plug a Heil PR781 into an unmodified export radio and miraculously sound like this. The frequency response must be tailored within the radio itself to taper it like this. How was it done without an equalizer?

 

[loosecannon]

you can't add to the parts count of the audio path without increasing distortion.
this is one of the rules of crossover design.

It is precisely for this reason that you don't start adding little RC circuits trying to boost certain frequencies within the passband. yes, you can add a mid-boost, or whatever you want, but you WILL be increasing the distortion also.

Again, the article you posted states this if you don't believe me.

you are right that you arent going to sound like broadcast audio by simply plugging a pro mic into the radio, but by increasing the range of the passband, you allow the mic to do what it was designed to do.
basically, the well designed mic is your EQ.

trying to mystify people with CB radio magic is not a new concept.
Once the principles involved are understood, the magic fades.

I am not impressed with what he is doing in the videos because i already know what he is doing. I just don't get why he thinks he's the only one with the magic knowledge. LOL

LC

 

[rabbiporkchop]

you can't add to the parts count of the audio path without increasing distortion.
this is one of the rules of crossover design.

It is precisely for this reason that you don't start adding little RC circuits trying to boost certain frequencies within the passband. yes, you can add a mid-boost, or whatever you want, but you WILL be increasing the distortion also.

Again, the article you posted states this if you don't believe me.

you are right that you arent going to sound like broadcast audio by simply plugging a pro mic into the radio, but by increasing the range of the passband, you allow the mic to do what it was designed to do.
basically, the well designed mic is your EQ.

trying to mystify people with CB radio magic is not a new concept.
Once the principles involved are understood, the magic fades.

I am not impressed with what he is doing in the videos because i already know what he is doing. I just don't get why he thinks he's the only one with the magic knowledge. LOL

LC

If you know the secret why aren't you revealing it to us? I'm sure lots of people would like to know including the person who started this thread. Not telling us what the secret is means the secret isn't known.

 

[loosecannon]

i already did.

increase the value of the series capacitors, and decrease the value of the parallel caps.

the amount of increase and decrease is where the knowledge comes in, but once you've done a few you start to realize that the changes are pretty standard across chassis.

you can do little tweaks on your changes in order to tailor the sound to someone with a naturally deep voice or naturally high voice, but in general you can just do a generic expansion that will work for 90% of people.

I've been doing these types of mods for over 10 years now, and i don't generally tell people that this is the way to get the "hifi" sound from your CB, because peoples' expectations of what they are going to sound like on air vary widely.

What i tell people is that i can give your audio a fuller quality and make it sound less like two way radio audio and more like being in the room with someone.

If people want real broadcast quality audio, then direct injection is the way to go.

I install an outboard AM modulator circuit that is based on the PNP galaxy style so that people can switch between regular CB radio, and full on direct injection right to the PA stage.

for receive, the best way is to install a line level output board and then pipe that into an EQ and a home stereo receiver. I can pull in weak DX that others can't hear simply because i can boost or reduce whichever freqs i want.

my opinion is that it should all be done analog, but many others like the digital effects stuff.

Im not trying to put FTCB down as a hack. My issue is that he tries to tell everyone that he's the only one that can do that type of work.

Heck, if he wants to remove a bunch of SMT components in a stryker and replace them with different values, more power to him. I find it a pain in the butt.
Just dont try to snow people into believing that no one else has figured this all out.

LC

 

[rabbiporkchop]

i already did.

increase the value of the series capacitors, and decrease the value of the parallel caps.

the amount of increase and decrease is where the knowledge comes in, but once you've done a few you start to realize that the changes are pretty standard across chassis.

you can do little tweaks on your changes in order to tailor the sound to someone with a naturally deep voice or naturally high voice, but in general you can just do a generic expansion that will work for 90% of people.

I've been doing these types of mods for over 10 years now, and i don't generally tell people that this is the way to get the "hifi" sound from your CB, because peoples' expectations of what they are going to sound like on air vary widely.

What i tell people is that i can give your audio a fuller quality and make it sound less like two way radio audio and more like being in the room with someone.

If people want real broadcast quality audio, then direct injection is the way to go.

I install an outboard AM modulator circuit that is based on the PNP galaxy style so that people can switch between regular CB radio, and full on direct injection right to the PA stage.

for receive, the best way is to install a line level output board and then pipe that into an EQ and a home stereo receiver. I can pull in weak DX that others can't hear simply because i can boost or reduce whichever freqs i want.

my opinion is that it should all be done analog, but many others like the digital effects stuff.

Im not trying to put FTCB down as a hack. My issue is that he tries to tell everyone that he's the only one that can do that type of work.

Heck, if he wants to remove a bunch of SMT components in a stryker and replace them with different values, more power to him. I find it a pain in the butt.
Just dont try to snow people into believing that no one else has figured this all out.

LC

It would be cool to let us hear some over-the-air recordings of some of the modifications you've done. Without direct injection it seems kind of tricky. Keeping a wider signal from splattering seems kind of tricky also.

 

[loosecannon]

ok i'm game.

it'll have to wait though. (trust me i realize this sounds like a cop out)
The only radio i have that has these features is my Madison, and i am currently replacing the encoder with a higher quality unit and it has been sitting half assembled for two weeks now. I have lots of time to be on the forums due to my job, but actually sitting down at the bench for something that isn't bringing in any money is proving tough at the moment.

I'm willing to make a contact with someone that can record a watergate if that can be arranged. Not too many locals around here that even understand what that is all about.

I can do a quick video on the circuits that i built into the madison, but you won't get to hear it. none of the stuff in this radio is store-bought except for the components. all add ons were built by me. (can't take credit for original designs though! those things were figured out long ago)

My setup may impress you, but it may not. I have different goals than many others.
for example, i set my station up in such a way that i can pipe a CD or MP3 player into the radio through a mixing board, as well as play my guitar over the air if i want.
I like to have fun LOL.
LC

 

[rabbiporkchop]

ok i'm game.

it'll have to wait though. (trust me i realize this sounds like a cop out)
The only radio i have that has these features is my Madison, and i am currently replacing the encoder with a higher quality unit and it has been sitting half assembled for two weeks now. I have lots of time to be on the forums due to my job, but actually sitting down at the bench for something that isn't bringing in any money is proving tough at the moment.

I'm willing to make a contact with someone that can record a watergate if that can be arranged. Not too many locals around here that even understand what that is all about.

I can do a quick video on the circuits that i built into the madison, but you won't get to hear it. none of the stuff in this radio is store-bought except for the components. all add ons were built by me. (can't take credit for original designs though! those things were figured out long ago)

My setup may impress you, but it may not. I have different goals than many others.
for example, i set my station up in such a way that i can pipe a CD or MP3 player into the radio through a mixing board, as well as play my guitar over the air if i want.
I like to have fun LOL.
LC

I really enjoy listening to quality audio. Unfortunately, I don't get many opportunities.

 

[QuietStorm]

I really enjoy listening to quality audio. Unfortunately, I don't get many opportunities.

Tell me about it, had a convo with someone 10 miles away that came in Crystal clear like they were in the truck with me, had the range and clarity without being "loud". I was pretty envious of his mobile. During that time someone passed me and came in really "loud" but had a weak signal that didn't make it 4 miles and sounded flat as a pancake.

 

[bob85]

I'm with LC, there's no secrets to changing audio, even using the same value caps but changing the type effects the sound,
all components cause distortion, the less of them the better,
finding a distortion that pleases your ears is the trick.

The typical audio path could be described as a series of frequency variable potential dividers,

my first audio mod was on audio based speech processors as a school project when the other kids were building door bells,
I also modded the "practical wireless" design processors to sound much better than stock when I was a kid with zero help from anybody, just a basic understanding of electronics and good ears,

I modded dozens of amplified mics, turned £5 shitters into something that sounded on par with a £30 turner,

I started modding the audio path in cb's in 1981 when UK legal FM came out and uniden/audioline rigs sounded muffled, I was still a kid, I did my own thing changing cap values to widen the response increase trebble reduce bass

Then I came across another guy who wrote an article in a magazine, he was changing more than caps to not only widen the response but add some pre emphasis to the uniden muffleboxes,
just a couple of components more than I used around the opamp but to me it added articulation to the the flat sounding TX audio I had so I started using his mod combined with my own,

by the mid 80's I was doing the same thing with some HF sets, swapping cheap caps for better quality of a different value or the same value, just getting rid of electrolytics & tantalum is a plus,

I still mod things but I'm not using cheap wima polycaps for anything but LOWFI cb radio,

these youtube techs modding for monetary gain have jumped on the cb audio bandwagon 30 years late as if its something new.

 

[Robb]