Re: Mains powered very low power transmitter - need help please


"nina.p20" <nina.p20@xxxxxxxxx> wrote in message
news:1124173827.485384.84010@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> I need to build a mains powered FM transmitter, for relative short
> distances, about 100 - 200 meter. Going to use them in a kindergarten
> and they have to be very audio sensible, and at the same time to work
> 7/24... Frequency - about 100MHz..
> I'm aware of the safetly rules, they will be placed near the ceiling;
> I've seen several devices as "surveillance or spy devices", and I mean
> exactly the same devices, but for other purposes. The devices - as I've
> understood are powered by a capacitor (250V), a diode bridge, a
> regulator and an electr. cap. for filtering.
> One of the most important things - they use no ANTENA, but how this can
> be made is "misterious" for me. They claim they use the MAINS wires as
> antena....
> I'll be very thankful for any help, idea or circuit :)
> TIA,
> Regards, Nina


Why dont you just get a baby monitor or walkie talkie and hack/midify it to
suit your needs? They tend to have channel select switches so you can
select the best one to suit your needs and you dont need a license for it.

Naveed


.

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