Crystal driven receiver.

yes receiver with a crystal oscillator and preferably without an inductor.

Direct conversion CW (morse code) receivers are indeed popular and easy and often done with crystals, but they do not make good AM receivers. It's not that they're completely unusable but the beating of the receiver crystal with the transmitter's carrier is really irritating, and the AVC features of regular superhet AM receivers are not present either. (Some direct conversion receivers do have their own way of doing AVC but it doesn't work well for AM. It's mainly to prevent blowing the ears off the poor guy listening to a weak CW signal when an adjacent powerhouse keys up.)

Superhet crystal-controlled receivers were popular for fixed-frequency AM use (think CB transceivers back when each was filled with 23*2=46 crystals), but the crystal frequency for receive is different than the one for transmit by the IF frequency.

There's been some discussion here about fixed-frequency AM receivers using a crystal filter not in the IF, but basically just hooked to the antenna.

Tim.

I want a fixed freq. CW type receiver. I only need to ditect the precense of the carrier. What I exactly want is a cct diagram with 1 or

Look at the receiver used in the very cheapest remote controlled toys. Crystal controlled with carrier detect (and a motor driver hung off the detector, to boot!)

Typically these receivers have at least a resonant LC at their input. But who knows, maybe they leave it out in the very cheapest ones? And what's wrong with inductors?

Tim.

or

That's a tall order! You can build a transmitter with 2 transistors, but it's not so easy to build a receiver: receivers require a lot of gain - which takes several stages of amplification; also, if you want crystal control, you'll need a transistor for the local oscillator.

You could make a high-gain, super-regenerative detector with a single transistor, but that usually involves inductors. I've never seen a regen. circuit using a crystal resonator insteads of an LC tank. That would be novel.

Would you consider integrated circuits? Realistically, I think this is the only way to do it without inductors. How about an NE602 / SA602 front-end (rf amp, crystal controlled LO, mixer) ?

What's your objection to using inductors anyway? You won't get far without them.

Do you mean a receiver with a crystal oscillator? There are lots of those around, they are popular with radio amateurs. They are usually tunable over a small range by 'pulling' the crystal with a variable capcitor.

Leon

Actually I have nothing against inductors. Its just that its difficult to buy inductors with what ever reading we want (like buying caps or resisotrs). So I'll have to always make my own inductors.

Andrew Holme wrote:

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SA602

Do you have an LC meter and/or a grid dip oscillator?

They remove the stress and guess work. You can check your inductors, and the resonant frequencies of your tanks before powering-up the circuit.

The selection certainly isn't as broad as with capacitor, but I've found that you're much more likely to end up winding your own inductors for switching power supply designs than for RF designs (where you can get adjustable inductors or just squish/pull apart air cores). And with switchers for cheap and sleazy prototyping you can wind them quickly solenoidal style and spray a little flux around the room before you finalize component values and wind a nice toroid or pot core or whatever...