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Confused about a component

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I'm trying to make this Walkie Talkie circuit but I don't know about a component in the schematics that I have.

Schematics: http://www.talkingelectronics.com/projects/200TrCcts/images/WalkieTalkieWithLM386.gif

Can anybody tell me what that 'variable transformer type thingy' is on the top-left, with text 1t,2t,3t around it?

Thank you

That looks like a Variac (variable transformer) and I imagine the 1/2/3t are "turns" of the wire in the transformer.
I could be wrong, though. Seems like a esoteric component...
Also, when dealing with radio transmission, make sure you're operating within a band and power level where unregulated traffic is allowed in your country!

Well, on internet, I see very big components when I search for variac.

Is there any equivalent replacement for this part?

I think you have to make it yourself. My guess is that you need to get a ferrite core and some transformer wire. The "variable" part means sliding the secondary winding more or less onto/off-of the ferrite rod, IIRC.

In general, is there a particular reason you need this particular circuit to work? If all you need is wireless walkie-talkie, there are probably easier ways to do that these days, including crystal-based tuners, or microcontrollers with something like nRF24L01+ based transmitter, etc. A microcontroller can do class D microphone input, or simply use the A/D converter, and PWM analog output for phone level quality very easily. Put 32 bytes from that circuit into a nRF24L01+ packet network, and you have a much more robust solution than the analog circuit you're linking to.

It is an RF transformer. 2 turn primary, 4 turn secondary tapped 1 turn up and wound on bobbin with an adjustable (the arrow) core of powered iron (the two vertical lines).
This couples the antenna to the circuit while providing the correct impedance match.
It also is part of the Local Oscillator tank circuit.
What frequency does this transceiver operate at?

That circuit will not be easy to get working without a lot of experience with RF circuit and fiddling.
If you're good at fiddling and have some test equipment, O'scope, then go for it.


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