A half wave wire will give better results. Don't try to hard wire it, just 
run the device up & down the length of the wire.  Horizontal  vs. vertical 
will make a difference. Insulation on the wire can make a big difference in 
the physical dimensions of the antenna. A fat wire (Al foil) will have a 
broader bandwidth.

Placing the unit a little less than a 1/4 wave in front of a reflecting unit 
(file cabinet?) may exhibit some gain as well.

John Ferrell
http://DixieNC.US

----- Original Message ----- 
From: "Mike Hord" <mike.hord@gmail.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Friday, January 28, 2005 3:11 PM
Subject: [EE] Small FM Transmitter Antenna


>I have a fancy new toy, a Neuros 2 audio player.  It has a built-in FM
> radio transmitter, and a jack on the package which is tied to the
> transmitter.
>
> If I observe the signal on that jack, I see ~ 20 mVp-p signal.  I'd
> like to find a fairly small design for an antenna that'll do a good
> job turning the now-pathetic range (<<3 meters, in most cases) to a
> bit better, perhaps as much as 5-10 meters in line-of-sight
> conditions.
>
> Any suggestions for this?  Most antenna designs I'm finding are NOT
> for this type of application; they are intended for hams or pirates
> and are usually quite bulky.  No one has as yet tackled this on the
> Neuros 2; the original Neuros has been hacked to do crazy things with
> RF, but it appears it has changed quite a bit internally.  My most
> recent attempt was a piece of coax with a 1/4 wavelength (@100 MHz)
> copper rod at the end.  Seems to do more than nothing, but still not a
> lot.
>
> BTW, anyone in the market for an audio player should check this
> product out.  While they seem to be having some quality issues, they
> are tops about replacing and repairing under warranty, and the other
> features generally outweigh the problems.  Built-in FM
> transmit/receive, USB 2.0, up to 80 GB of storage.  Best of all, the
> schematics, database format and client info are freely available on
> the web.  Firmware was, and probably will be yet again.  Lots of room
> for people like those on this list to play with!
>
> http://www.neurosaudio.com
>
> Mike H.
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