Homebrew Car Cassette Adapter

[a g chandrashekara]

4000 series ics lists

 

[modularama]

Mickey Mouse lost his fame and fortune and went into research and development and re earned a name for himself.

But he wasn't very good at it and the name he earned isn't a compliment to anyones skills.

Cheap Chinese junk is another way or putting it.
So is 'All theory no reality'.

That sucks!

I just got a Mickey Mouse mp3 player, literally! it's pretty nice too; go figure...

 

[Tipsy]

Pity we've got an ocean seperating us as I've got a cassette adapter I no longer use. Having said that, I would go for the internal modification advised earlier by Sciadwian. I've seen it done before (adding an input socket) and the modder even added an SD card reader in the form of an MP3 player.

 

[TheNewGuy]

Would it be a better to build the Mod 3/4 Schematics or a schematic with an IC in it? I don't think I've gotten to the skill of doing SMD's though.

 

[audioguru]

My Mod4 FM transmitter does not drift its frequency because It has an RF amplifier between its oscillator and the antenna and It has a low dropout voltage regulator for its oscillator and preamp.
It sounds excellent because it has the proper amount of pre-emphasis (treble boost) and because its preamp is biased properly and has negative feedback for low distortion.
But it is mono, not stereo.

 

[TheNewGuy]

Question:
1.) When I am playing music through this circuit from my music player (via a headphone jack) to my car radio, will the fact that it is mono affect the music at all?

2.) Could I use this in my car everyday w/o getting pulled over or something? (I live in the US)

3.) Would I be correct to say that the Mod.4 circuit would be efficent for this application?

 

[audioguru]

1.) When I am playing music through this circuit from my music player (via a headphone jack) to my car radio, will the fact that it is mono affect the music at all?

I made an FM tuner kit in 1960. It was mono because FM stereo was not invented yet. Stereo vinyl records were stereo and sounded much better.
A couple of years later I made a stereo multiplex adapter for the FM tuner and the stereo separation sounded fantastic.
Make or buy an FM stereo transmitter that are made for cars so the range is short which does not cause interference.

2.) Could I use this in my car everyday w/o getting pulled over or something? (I live in the US)

A guy in my city made my Mod4 FM transmitter. The next day he saw the "radio police" truck with the antennas on top go down his street. They might have been looking for me. I used my transmitter for only 1 hour because my FM dial is full of stations so I used the same frequency as a foreign language low power station on the other side of my city so I caused severe interference to it.

3.) Would I be correct to say that the Mod.4 circuit would be efficent for this application?

No.
It is mono, not stereo and its range of 2km is much too far. Because it has a high output power then its 9V battery life is short.

 

[TheNewGuy]

A guy in my city made my Mod4 FM transmitter. The next day he saw the "radio police" truck with the antennas on top go down his street. They might have been looking for me. I used my transmitter for only 1 hour because my FM dial is full of stations so I used the same frequency as a foreign language low power station on the other side of my city so I caused severe interference to it.

Can you actually get arrested for radio interference?

No.
It is mono, not stereo and its range of 2km is much too far. Because it has a high output power then its 9V battery life is short.

So I should be on the lookout for one that has shorter distance and a better battery life.

 

[audioguru]

Can you actually get arrested for radio interference?

I don't know if they shoot you or chop off your head. Maybe both.
They take away the transmitter and give you a warning to never cause interference again.

When I was a teenager I made a fan with a badly sparking old AC motor. The RC cops came and explained that it caused bad radio and TV interference to hundreds of people. They took away the motor.

 

[TheNewGuy]

I don't know if they shoot you or chop off your head. Maybe both.
They take away the transmitter and give you a warning to never cause interference again.

When I was a teenager I made a fan with a badly sparking old AC motor. The RC cops came and explained that it caused bad radio and TV interference to hundreds of people. They took away the motor.

Wow! That's really sucks! So whatever I do, I should research it thoroughly before I do it, lol.

 

[Sceadwian]

The chances of getting caught causing radio interference are pretty small unless you're putting out quiet a bit of power or affecting something important. It is possible for them to track you down if the inteference is regularly occuring, but the chances are very slim. However as a responsable person you should do everything you can to understand and minimize any interference you may cause, not for fear of being caught but just because it's good general practice.

After all, no one likes a noisey neighbor =)

 

[TheNewGuy]

The chances of getting caught causing radio interference are pretty small unless you're putting out quiet a bit of power or affecting something important. It is possible for them to track you down if the inteference is regularly occuring, but the chances are very slim. However as a responsable person you should do everything you can to understand and minimize any interference you may cause, not for fear of being caught but just because it's good general practice.

After all, no one likes a noisey neighbor =)

That makes sence

I found this FM Transmitter, another poster said it would transmit with a range of about 3 - 5 meters. I wonder if I shorten the antenna would it get a range of about 1 - 2 meters. I think that would be perfect for a car. But maby even 3 - 5 meters would be OK, except if you are at a stoplight or something. It looks pretty easy to build.

 

[Sceadwian]

Shortening the antenna will definitly reduce its range, however it could possibly shorten the life of the circuit as well. When you shorten the antenna you change it's impedance which general results in the amplifier transistor heating up as it's getting some of the energy it's tryign to send out reflected back to it. This isn't always a problem though but something you should be aware of. If you want to tune the range of the circuit optimally you'd need to put the entire circuit in a shielded box and adjust the antenna range till you get the range you want. These circuits aren't usually very stable though a lot of things can affect their stability and simply standing near them or touching them will often allow your body to act as an antenna or a tuning element. They're basically just a bit tricky.

 

[TheNewGuy]

What would the the value of C6 in the schematic?

 

[audioguru]

C6 is from 4.7pF to 10pF in most of these very simple poorly performing FM transmitters.

 

[TheNewGuy]

I need something that transmitts in short range but good quality.

That one has short range, but i don't know about quality?

 

[audioguru]

I need something that transmitts in short range but good quality.

That one has short range, but i don't know about quality?

It is a simple cheap toy with poor quality.
Its antenna connects directly to its LC tuned circuit so its frequency will change if anything moves toward or moves away from its antenna.
It doesn't have a voltage regulator so its frequency also changes as its battery voltage changes.
It doesn't have pre-emphasis (treble frequencies boost) like all FM radio stations have and it has a 0.1uf capacitor C4 that has a value 200 times too high so it will sound very muffled on an FM radio.
It is mono, not stereo.

 

[Sceadwian]

Any reason you can't use a bluetooth audio transmitter/reciever unit? You should be able to find plenty of them and they're relativly inexpensive, quality should be pretty high and the range is generally 'personal' or short range.

 

[audioguru]

Isn't Bluetooth narrow-band 300Hz to 3kHz mono for telephones?
It would sound awful with music.

 

[TheNewGuy]

The car does not have Bluetooth though?