AM/FM Radio Stompbox

[SeneX225]

The idea:
I want to build a stompbox that will get an AM/FM Radio signal and inject it into the output feed. The final effect should be something like this .

First attempt:
I got a few of these pocket radios at a local garage sale. Main feature is that they use headphones as both output and antenna. So, I wonder if I can use the guitar pickups themselves as signal receiver and already existing output as it is.


To do that I tried daisy chaining the radio output to a female guitar jack, intending to use it as input. This, however, didn't work at all. There wasn't any clean bypass either, with the radio both on and off.




What have I done wrong and is there any way at all to make this idea work?

[idy]

Surely it can be made to work. Funny how we just had a long thread about a guy who couldn't get rid of radio signals...

You didn't tell us if the idea of using the guitar as antenna worked.
You are hearing the radio?
How are you bypassing? I don't see any switch.

I would think you would want to still hear the guitar, but mix in some radio sound, no?

If so you will need some kind of simple mixer circuit, the one I've used is:
https://tagboardeffects.blogspot.com/2012/02/split-n-blend.html

then you would use a common 3pdt bypass for the splitter/blender. That is a super handy utility box to have if you like to experiment....

[SeneX225]

How are you bypassing? I don't see any switch.
I would think you would want to still hear the guitar, but mix in some radio sound, no?

I, the idiot, for some reason thought I don't need one and just daised the output straight into the radio. My bad, sorry!

So, to fix this, I made a simple DPDT true bypass and connected the radio to it as such:



Bypass now, unsurprisingly, works and it even gets the radio signal! However, it is very quiet and can be barely heard even on maximum DAW/Amp volume.
Is it a wiring issue or maybe I need to fit it with some kind of amplifier?

[idy]

So the output is less than a guitar?
The output jack for the radio was probably 1/8" stereo?
And before you started this the level was greater?
You want mono. That is not your problem, but something to consider.

I would use a 1/8' stereo plug and (confirm for yourself) there is probably audio on the tip and ring, and ground on the "sleeve." Since we are cavemen, you can just twist those two conductors on the cable you have sacrificed for this project and solder them to the tip of a normal 1/4" jack or plug. And ground to the sleeve.

I can't tell from the pic what is what with the radio output jack. Or why you have arrows to "input" marked.

[Kevin Mitchell]

I can loan you my old Frontman amp that often brings mariachi music to the mix.
I don't know why it's always mariachi. But it is. 

Interested to see where this goes!

[SeneX225]

So the output is less than a guitar?
The output jack for the radio was probably 1/8" stereo?
And before you started this the level was greater?
You want mono. That is not your problem, but something to consider.

It does indeed, however I don't use it as the output but as the "effect" input/output (I failed to clarify that, sorry!). The schematic goes like this, if you'll excuse my caveman drawings:



Where the radio jack pins are as such:

So the output is less than a guitar?

Guitar level stays the same with the radio both on and off.

[FiveseveN]

I don't use it as the output but as the "effect" input/output

No you're not. The radio does not have an audio input.
Both an input and an output exist in reference to "ground". Which one is your ground connection?

the radio jack pins are as such

Also wrong. You have your tips and sleeves mixed up, for starters.

they use headphones as both output and antenna. So, I wonder if I can use the guitar pickups themselves as signal receiver

Headphones don't have a LRC lowpass in the kilohertz, tone controls and other dangling bits. Sometimes pickups/guitars have active electronics.

[SeneX225]

Also wrong. You have your tips and sleeves mixed up, for starters.

I am not, actually. Pins closest to the sleeve connect to the tip:



I also did a continuity check using a jack-jack cable and a multimeter before drawing the pin diagram.

Which one is your ground connection?

I'm not sure, quite honestly. Ground connection leads to an LED on one end and to turn-off mechanism on the other.

[SeneX225]

A small update:
In another very old thread on this very forum I've found this video:

This is exactly what I have in mind! The author, as far as I can gather, uses a bigger radio with AM/FM switch and better antennas. Maybe that's the reason my one sounds so quiet?

[SeneX225]

Small update №2:

On realizing the possibility that my pocket radios might just be not enough, I looked in DIY FM Receivers. I found a bunch of them and most don't look too hard (except I'll have to convert the schematic into veroboard and I'm very not good at that), but I'm not sure about where exactly should I sent the guitar signal in. Speaker should be the output and If I insert input jack like that (red is + and black is -), will it work?





Also, what would be the best alternative for BF494's used here?

[SeneX225]

Major update!

It took me a few days of racking my brain around to realize the mistake I made in wiring. The ground on the radio output was going into the hot and that's (probably) why it was so quiet.

Now, I present the updated schematic:



The best part? It works!

I've recorded a small (and very weak-played) demo. Now the stompbox properly uses guitar pickup as antenna (I think it does, at least). Also, It does an interesting sound when you turn the volume knob on the guitar back and forth (at the very end of the demo).

[idy]

Congrats. Can't hear the demo, but good.

[johngreene]

Major update!

It took me a few days of racking my brain around to realize the mistake I made in wiring. The ground on the radio output was going into the hot and that's (probably) why it was so quiet.

Now, I present the updated schematic:


I'm a little late to your thread but I've designed several of these "pocket radios" years back as well as FM transmitters that you used to need to listen to your iPod in your car. One of my designs even got the highest rating for quality over major competitors such as Belkin! Good old days. Lol.
If you need any additional help let me know.

The best part? It works!

I've recorded a small (and very weak-played) demo. Now the stompbox properly uses guitar pickup as antenna (I think it does, at least). Also, It does an interesting sound when you turn the volume knob on the guitar back and forth (at the very end of the demo).

[SeneX225]

I'm a little late to your thread but I've designed several of these "pocket radios" years back as well as FM transmitters that you used to need to listen to your iPod in your car. One of my designs even got the highest rating for quality over major competitors such as Belkin! Good old days. Lol.
If you need any additional help let me know.

Actually, there is another thing I could use help with. I want to replace this on/volume wheel with a knob I can mount on the case, but I've no idea what type of wheel it is and if more knob-like replacement even exists.






Update: Could it be a potentiometer? At first I thought it's not because 5 pins and an on-off mechanism, but while researching I've found this and now I'm not very sure.



Update 2: I think it actually is a potentiometer. However, It reads value of 32k, which is quite unusual. Would it be okay if I replace it with 50k?

[johngreene]

Looks like a pot with a switch. The outer two lugs are the switch. The middle three are the pot lugs. Did you measure it while it was still in circuit? If so, your measurement will likely change as you turn it. Meaning you will need to unsolder it to get an accurate reading.

[SeneX225]

Update:
In an embarrassing amount of time I've managed to unsolder the pot. On off-board measurement it read 50k as before, so that's exactly what I've got from a local radioshack (this is the first time I've ever encountered and used a pot with a switch. They're pretty cool!), except the one I can actually mount on.
So, this is pre-final design on the stompbox on a testing case:



Button under the footswitch is an Off-(On) and changes the station when pressed.
The pot is used both to turn the radio on and adjust the volume (which is kind of inconvenient but I am yet to figure out how to make it better).