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Simple AM radio that only recieves the 1,000 khz frequency.

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Electric Rain

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Hi, I need an AM radio that doesn't involve a tuning knob of any kind. Because it only needs to recieve the 1,000 khz frequency. Does anyone have any ideas as to how I could make a radio like this? It doesn't need to be very good. Any schematics? Thanks.

Rain
 
Re: Simple AM radio that only recieves the 1,000 khz frequen

Electric Rain said:
Hi, I need an AM radio that doesn't involve a tuning knob of any kind. Because it only needs to recieve the 1,000 khz frequency. Does anyone have any ideas as to how I could make a radio like this? It doesn't need to be very good. Any schematics? Thanks.

Rain
A ZN414 gives just about the simplest receiver for 1MHz reception. You can do a Google for the data sheet.
 
Thanks a lot. I'll look into it. But I can't find a datasheet for it... :?

Rain
 
Electric Rain said:
Thanks a lot. I'll look into it. But I can't find a datasheet for it... :?

Rain
I just looked up 'zn414' on Google and found 1640 references to the chip. Here is one of the circuits:

**broken link removed**
 
I think the zn414 is outdated, use the more recent version which is apparently cheaper mk484 packaged in a to-92 (looks like regular transistor.)
 
So, it looks like what I have to do is build a simple radio using the zn414 or the mk484 or whatever, and then find the right value for the cap that needs to replace the variable cap so it's fixed and not tune-able. So... what instrument do I need to measure the value of the variable cap once it's tuned for 1Mhz so I can replace it with a fixed cap of the same value? I'm on the right track right? :lol:

Rain
 
to measure capacitance, you can build/buy capacitance meter.
you can change the frequency of an LC circuit not just by
changing capacitor value, you can also use different taps on the
coil for example.
it is difficult to predict inductivity of the coil because the ferrite
cores have different shape and size for example.
btw, do you mind explaining why it has to be exactly that
frequency (is your transmitter using xtal) and why is the size
so critical that fixed capacitor is required? i mean, given the
battery and ferrite rod size, capacitor is sure not much...
 
Well, I guess it doesn't HAVE to be fixed. I wanted it to be because I'm building it for this: **broken link removed** and I wanted to be able to fit a tranceiver (the circuit show on the page and the circuit I'm requesting now) inside of a very very small box that could hang off the end of a 3" (or so) long cord coming from the DB9 hood. And I wanted to make it as simple, small, and adjustment free as I could. If you read the page you'll see that the crystal sends out 1Mhz signals. That's why it needs to be a 1Mhz radio. I just thought the fixed version would be cheaper, smaller, easier, and that it would take less current. BTW, do you think I can draw enough power from the serial port along with the power being drawn by the crystal to power the radio as well? Thanks a lot. :)

Rain
 
Just as I tought... :D

Well in that case you don't need AM radio at all, just hookup the
headphones to COM port. I would recommend adding transformer
from output stage of old transistor radios since all headphones
I've seen lately are low impedance (like for your walkman).
You might have to add capacitors in series with the primary of the transformer (like 10uF, 25V).
These transformers are really tiny https://kitsrus.com/jpg/at.jpg
and would probably be best fit for the project using as few parts as possible.
 

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I'm afraid I don't follow. How is this going to receive the signal from the other computer? I'm going to have two computers, each with a transmitter and a receiver. That way, I can send messages from one computer to the other and back. They are about 50ft apart. They are both going to be the same, therefore they will both put out 1Mhz signals. So I know they are also going to pick eachother up as well, :lol: but that's not a problem.
 
Electric Rain said:
I'm afraid I don't follow. :? How is this going to receive the signal from the other computer? I'm going to have two computers, each with a transmitter and a receiver. That way, I can send messages from one computer to the other and back. They are about 50ft apart. They are both going to be the same, therefore they will both put out 1Mhz signals. So I know they are also going to pick eachother up as well, :lol: but that's not a problem.
 
Maybe not just as I tought...
I had impression you wanted to simply learn morse code and monitor
what is being sent - on the computer you use as trainer...

:?
 
Yeah, looking at your schematic, it looks like that's what you thought. So what now? :? Thanks for your help everyone.

Rain
 
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