Hi all

If I change the tank circuit components (reduce the capacitance and inductance) and change the transistors to appropriate VHF ones, will I be able to pick up ATC (Air Traffic Conversations) using this circuit ?

http://www.electronics-lab.com/proje...006/index.html

Thanks
Shelton.

 

I seriously doubt that you can adapt an AM broadcast band receiver to VHF operation. You would be better off looking for a circuit design with components that can work in that frequency range. Careful layout and construction is orders of magnitude more important at VHF than at lower frequencies.

Even if you could compute appropriate values for the L's 'n C's there is no guarantee that the transistor would operate with any gain at those frequencies.

Keep searchin' mun

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We never have time to do it right; but we always have time to do it over.

 

I googled on "aircraft receiver schematic" and got lots of hits - however only some of the hits produced designs that you might consider. A word of caution - lots of things get published via the internet and only some designs are actually proven to work. Anything that is as simple as the receiver you described it likely to be useful to demonstrate that it works. It's also likely to easily drift of frequency or have other problems. An alternative might be to purchase a kit - I've seen them in the $20 US range. The schematics suggest a bit better design but it won't perform like a commercial radio receiver.

Keep in mind that at those frequencies your construction techniques will profoundly affect things - in the sections that are operating at VHF. A simple thing like your finger in close proximity might detune it.

I don't mean to discourage you - just make you aware of some of the pitfalls.

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stevez

 

The circuit you found DOES NOT WORK!

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Uncle $crooge

 

ok thanks guys for all your responses!

 

Audio - any more input to illustrate why the circuit does not work?

Thanks

 

1) It has only a single tuned circuit. Real radios have many tuned circuits.
2) Its "regeneration" is negative DC not positive signal because the first two transistors invert and any RF is shorted to ground through the 0.1uF capacitor.
3) It has very low gain.

It would be a simple crystal radio if an AM radio station's transmitter is next door. No, then its transistors would overload because it doesn't have automatic-gain-control like real radios. It might work if an AM radio station's transmitter is not far down your street.

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Uncle $crooge