Nigel Goodwin

You still haven't told us what you are attempting to do?, nor have you asked about the coupling winding you will need to use a ferrite rod (unless you are building a high impedance front end?). Connecting it to a normal low impedance transitor front end will seriously dampen the tuned circuit, resulting in poor sensitivity and poor selectivity.

Assuming this is for a standard medium wave radio?, I would suggest looking at existing circuits for suitable circuits.

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JimB

Good point Nigel, the problems of impedance matching had occured to me, but lets get the number of turns calculated first, as that was the original question.

A parallel tuned circuit will have a high impedance and will match nicely into the gate circuit of an FET (or the grid circuit of a valve).

If you want to feed into a low impedance circuit such as the base of a bipolar transistor, a link winding with about 10% of the turns of the main winding would be a good starting point.

If you wish to build a ferrite rod antenna of your own, have a look at a comercially built radio, it has been done many times before!

JimB

Zener_Diode

I am not going to do something. just I heard about that, and wanted to know more detailes. thats all.

In the futer I wanna do a robot that will have a wireless comunication.

Nigel Goodwin

In which case you're talking about the wrong range of frequencies - you certainly don't want to be using medium wave - also you couldn't get a licence to do so!.

There are various licence free UHF radio modules available in most countries, theses are legal, easy to use, and cheap - there's really no reason to try and build something diferent - particularly with the legal aspects!.

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Zener_Diode

yea, but if it be in 0.5W - 1W. I don't think that anyone will feel it.

Nigel Goodwin

It's still highly illegal, and could wipe out vital communication links or disrupt hospital systems? - if you're caught I presume penalties are fairly severe in Israel?.

Don't forget, 1W on medium wave could easily travel 50-60 miles!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk