# Antennas?

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I was wondering if anyone knows how to go about making a very short-range transmitter/receiver for electronic signals, particularly music. The size of the transmitter wouldn't have to be that big, but the receiver would be preferably small enough to hook to a ear bud.

I was thinking of cutting a headphone cable, and attaching an antenna to the jack, with a pair of receivers on each bud. Would this work, and if it is possible, how?

-Anjruu

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For protection against noise I would suggest putting A to D and D to A converters at transmitter and receiver (think of the difference between old analog wireless phones and the now-common digital wireless phones). You should be able to use the following block diagram:

Analog Signal input -> AD Converter -> TX Circuit -> TXAntenna ~~~~~~~>

RXAntenna -> RX Circuit -> DA Converter -> Analog Signal output

I built something similar to this in an engineering course (though not with sound) and it worked pretty well (though our system was to cause two wireless "units" have corresponding lights turn on and off at the same time, the idea should be basically the same).

Just as a note, your receiver may be quite a bit larger than you'd like if you're going to use commercially available AD Converters and RX Circuits... You're also going to need something to power both systems.

The use of bluetooth is also an option, but I don't know anything about making bluetooth-enabled systems, but if you look at the bluetooth cellphone earbuds that are on the market, one would think it would be pretty easy to sync those up to your music system

A quick google on the topic yielded:

http://www.amazon.com/exec/obidos/tg/detail/-/B000BK1QSE/ref=pd_sim_wl_2/002-7584979-1141606?v=glance&s=wireless

http://www.geeks.com/details.asp?invtid=980397-0403-DT&cat=MP3

Buy that, rip it open and mod as you like.

Or, if you'd like to wait a little bit, wait until the "Plantronics Versa" comes out:

http://www.oneandco.com/casestudy_12.html

(NOTE: I'll have you know you got me wasting a lot of time surfing around looking at this topic

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I used to build "Bugs" FM 250mw that had a working distance of About 2 kms, and would fit on an old 5p piece (just smaller than the current 2p).

Ive sucessufully sent data over these in the past too (9600 baud).

since the bandwidth is quite large and will send at freqs past 200mhz (with a 2n2222 output trans) 9600 need not be the limit at all! (thats all I could send at in 1987 with my current modem).

the reciever was a normal FM radio tuned a little above "Normal" freqs (above 108 mhz) but now you CAN buy mini auto-scan FM radios not much bigger than a pound coin.

it might be worth looking into also

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