AM receiver

[k7elp60]

I once heard of a fellow that could hear the sounds of AM radio stations when he got close to the transmitters, seemed like the cause was a filling in one of his teeth was a good detector.

I sure do remember the galena crystal and the cat whisker for the detector.
I also remember when the CK722 transistor was available commercially. As I recall one cost me about $4.00. To a teenager in the early 50's that was a lot of money.

 

[audioguru]

I saw the CK722 transistor used in the projects in the electronics magazines of times gone by.
Since you were a teenager in the 50's and i was just a kid then you are a little older than me.

 

[Roff]

I once heard of a fellow that could hear the sounds of AM radio stations when he got close to the transmitters, seemed like the cause was a filling in one of his teeth was a good detector.

I sure do remember the galena crystal and the cat whisker for the detector.
I also remember when the CK722 transistor was available commercially. As I recall one cost me about $4.00. To a teenager in the early 50's that was a lot of money.

I had two CK722's. i think I waited until they were US $0.99. One of them I used to make a regenerative AM radio that worked great. The other one never worked well, but I may have damaged it shortly after I got it.
I bought a few of them on Ebay about 9 or 10 years ago, but I'm danged if I know where they are now.

 

[Gaston]

how can a detector alone make sound without a transducer?

 

[Roff]

how can a detector alone make sound without a transducer?

Are you referring to a particular post?

 

[audioguru]

When the tooth filling is the detector then no sound is produced by a transducer. The detected signal goes along a nerve and into the big empty space in the head.

 

[Gaston]

Are you referring to a particular post?

yes. the airstream and the tooth

 

[HerbertMunch]

**broken link removed**

Nice one bill

 

[raj_404]

hey guys my apologies for being a jerk before and taking your jokes seriously.Well I am doing trade certificate in electronics and this year is my final stage where i have to do a project and i will be assessed on it. I don't wana fail thats why i asked for your guys help. The thing is that we have to follow some protocols regarding this project. As mentioned by kchriste that " Why should we help you steal someone else's design?" . The thing is we can use someone else's design but we have to make some modifications on the cct by ourselves so that we get an idea how that certain cct operates and how we can modify it when the need arises. I have got one AM receiver cct that i wana work on but i don't know what i can modify in the cct. I have found a cct diagram and it looks something like this

**broken link removed**

I have shown the cct to my lecturer and he thinks i should go forward with the cct but also do some modifications to it. The reason we are doing this project is just to prove that how are our soldering skill, implementing a cct on a PCB etching techniques and testing all the parameters in a cct.So guys will i get some help now. The point is how i do the modifications to the cct that i have chosen and building a prototype. I will be waiting for post replies

P.S. Mr torben i think i have fixed my keyboard....just kidding mate

Thanks

 

[Torben]

hey guys my apologies for being a jerk before and taking your jokes seriously.Well I am doing trade certificate in electronics and this year is my final stage where i have to do a project and i will be assessed on it. I don't wana fail thats why i asked for your guys help. The thing is that we have to follow some protocols regarding this project. As mentioned by kchriste that " Why should we help you steal someone else's design?" . The thing is we can use someone else's design but we have to make some modifications on the cct by ourselves so that we get an idea how that certain cct operates and how we can modify it when the need arises. I have got one AM receiver cct that i wana work on but i don't know what i can modify in the cct. I have found a cct diagram and it looks something like this

**broken link removed**

I have shown the cct to my lecturer and he thinks i should go forward with the cct but also do some modifications to it. The reason we are doing this project is just to prove that how are our soldering skill, implementing a cct on a PCB etching techniques and testing all the parameters in a cct.So guys will i get some help now. The point is how i do the modifications to the cct that i have chosen and building a prototype. I will be waiting for post replies

P.S. Mr torben i think i have fixed my keyboard....just kidding mate

Thanks

Hey Raj,

It's cool that you came back and explained the situation. Not everyone does after the first round of "hey, that's not how we do it here!" posts.

My first thought about the circuit is that I don't know what its characteristics are, so I'd build up a quick prototype (with solder on stripboard, not a breadboard) so I could get an idea of how the thing behaves. Should take an evening, assuming that I had the parts and got it close to right. I'd take notes, because I *don't* want any surprises once I start trying to make changes. Once I know that the base circuit works I can start messing around with it.


Torben

P.S. You haven't filled in the location information in your personal profile so we don't know where you are--different places in the world have different access to parts. The board has members in many countries so if you fill that in, someone local may be able to help direct you to good places to get things you need.

 

[JimB]

Raj
When someone comes onto the board and announces:

I am building am AM receiver for my final project in uni....

we make the assumption that they are in the last year of a four year degree course at university, and should not be asking for a circuit, but should be able to design their own from scratch.

However, when the true story emerges:

Well I am doing trade certificate in electronics...
...The thing is we can use someone else's design but we have to make some modifications on the cct by ourselves so that we get an idea how that certain cct operates and how we can modify it when the need arises.

If you had told us the full story straight off, you are doing a basic technicians course, you would not have been ripped up and told not to cheat, but been helped as required.

So many times on here we get just half the story, it does not help, tell everything and the problem is usually easily solved.

JimB

 

[Roff]

I don't see any regenerative feedback in this circuit. The 120k resistor is negative feedback. It stabilizes the bias. If you want to make some mods, do some research on regenerative receivers. You can easily add some regen feedback to this circuit.

 

[Hero999]

It's cool that you came back and explained the situation. Not everyone does after the first round of "hey, that's not how we do it here!" posts.

I agree.

Before I was close to red squaring him but now I've green sqared him.

 

[raj_404]

I agree.

Before I was close to red squaring him but now I've green sqared him.

Thanks hero

 

[raj_404]

Mr torben i am having some problem now when i am trying to build this circuit. i cant find any 500 pF variable capacitor....can I use some other value capacitor....have you built that circuit and simulated it.....pliz help

 

[raj_404]

sorry forgot to give you the link to the circuit....

**broken link removed**

 

[Torben]

Mr torben i am having some problem now when i am trying to build this circuit. i cant find any 500 pF variable capacitor....can I use some other value capacitor....have you built that circuit and simulated it.....pliz help

Hi Raj!

First off, you don't have to call me 'Mr.'

I'm afraid I'm hardly a radio expert--but I'll try to help. I haven't built or simulated this circuit, but in your situation I'd try to find an old radio and tear out the variable cap and ferrite rod and use that for the tank in your circuit. That's what the circuit's author says he did, too. You might not have exactly the values given in the schematic, but if it's just a normal old radio then I would think it would at least be close enough to let you know if the whole circuit was going to work.

Sorry I can't help too much more than that. Perhaps you can find something on eBay or an online mail-order company like Digi-Key, Mouser, or similar. I'm not sure which of them might ship to Fiji, though.


Good luck,

Torben

 

[audioguru]

I haven't seen an AM radio for many years. My grandmother had one but I don't know where it is now. Maybe an antique store will have one that you can take apart to re-use its old parts.

 

[mvs sarma]

Mr torben i am having some problem now when i am trying to build this circuit. i cant find any 500 pF variable capacitor....can I use some other value capacitor....have you built that circuit and simulated it.....pliz help

Perhaps YES. You may get PVC gang condenser as used in modern radios. it may have 2 sections with 180 pF each or 180+90 . the lower pF is used for Oscillator section. If you parallel them you would get upto 270pF.

But it would be better to have a ready radio if it is for actual use. If for experience, you may try other RF projects or analog projects.

If making a radio is the only motive, then it could be three of 4 transistor multi-band superhet tuner followed by and Audio amplifier using some audio IC.

we Find some aM /FM kits in the Indian kit shops, Raj.

 

[ashfaqueahmadbari]

**broken link removed**

could you please tell me which components can be used in this. I'd like some suggestions even if these can use general components(Coz i'm pretty much a noob here).

Thanks