AVR-Chat

Well, yes, but....

That "transmitter" would have been almost as "dirty" as the
old spark-gap guys in the early days. Harmonics would be
horrendous.

Now, you CAN do it at low frequencies using function
generator techniques to generate low distortion AM sine
waves (up to 5MHz, perhaps).

Receivers are more difficult because you need to
discriminate between the signal you want and the many,
many, signals you do not want. Think AM broadcast stations
as a simple but almost ubiquitous example.

However, if the original query is about VHF or UHF where
there are many fewer interfering signals (except for those
really strong TV and FM stations and cellphones and FMRS
radios and mobile 2-way radios and ....), its almost
interchanged.

You CAN use a very low sensitivity receiver so that you
only hear relatively strong signals (such as a low power
transmitter) that is relatively close. The transmitter can
rely, to some degree, on transmission-line resonators (and
thus not use coils in the strictest sense). 

So, what might be done depends on so many things. The
original poster needs to help us with more description
about the requirements (range, type of information,
information bandwidth, etc).

Jim Wagner
Another RF Engineer on the list

On Tue, 01 May 2007 20:04:30 -0000
 "kernels_nz" <kernels@slingshot.co.nz> wrote:
> Hi Zack,
> 
> Cant say I fully agree, I cant recall the exact detail,
> but I have
> built a voice-AM transmitter without any coils, I went
> something like:
> 
> Buy a 4-pin crystal oscillator outputting square waves at
> the
> frequency of carrier your looking for, I believe mine was
> 1MHz, then
> vary the supply voltage depending on the "voice" input
> voltage.
> 
> Cheers
> Hein B
> Auckland, NZ
> 
> --- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz@...>
> wrote:
> >
> > 
> > It can't be done. You will need a coil at least for
> your
> antenna/matching.
> > 
> > How much power are you talking about?  What range do
> you want to cover? 
> > For what purpose?  What frequency?  What are the laws
> in your country 
> > regarding license-free transmissions on that frequency?
> > 
> > Inquiring minds want to know, especially this RF
> engineer.
> > 
> > Zack
> > 
> > On Wed, 25 Apr 2007, azza eldessoky wrote:
> > 
> > > please friends,can any one  send me a circuit design
> for AM
> transmitter or receiver without  any coils .
> > >    thanks alot 
> > >        azza 
> > >
> >
> 
> 

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