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Simple Question on detecting radio wave

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Newbie level 4
Jul 5, 2011
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Hey guys..

I am fascinated by radio transmission and reception and just wanted to conduct this simple experiment..

I have successfully designed a 20 Mhz oscillator circuit and attached antenna suitably and I am sure it is transmitting signals as i heard a hissing sound when i kept it near the radio which was in SW band.. I realize that designing a transmitter (just an oscillator attached to vertical wire of 15 m in my case) is easy...

My Question is this...
How can i design a circuit which just detects the signal sent out by my oscillator and just displays it on the digital voltmeter... Like when my transmitting oscillator was off, the receiver should show 0 volts and when it was on, it should show 2-3 volts.. ( the transmitting oscillator is not modulated in any way but just sending out signals at 20 Mhz.. )

I just want basic idea to design such stuff.. like in filtering out all other radio signals from space and also amplifying the 20 Mhz signal only... Just basic idea to practically achieve this would help.. :-D

A simple absorption wavemeter may be all you need although they are only short range.

**broken link removed**


Thanx for quick replies..
I hav read about crystal sets and stuff...
But before trying to build that, few questions..

1) How to amplify the detected signal? Wil just a common emitter amplifier using bjts wil do? Should I take any other considerations like stray capacitance and stray frequencies?

2) How to make the filter part more effective... like making the bandwidth narrow and stuff like that..(Just making it little more complicated ) :wink:

I really need help on filtering and tuning... any links on this would help..

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