On Fri, 4 Dec 1998, Jochen Feldhaar wrote:

> Hi,
> I would like to comment on the antenna problem.
> At the moment I myself am designiing a somewhat similar system, and have
> learned that the manufacturer chooses the output impedance so that the
> transmitting power is maximized for the proposed operating voltage. This
> gives about 300 Ohms. Therefore, a matching network is advisable, also for
> filtering the output signal at the same time.

This is interesting. It should be 50 or 75 ohms, for an open quarter wave
dipole ?! How did you determine the output impedance ? Remote power meter
or microwatt transmatch ?

> As to the form of the antenna: It is best located in "free space". A ground
> plane next to the antenna is ABSOLUTELY not workable. The best design is to
> have a loop or several loops formed like a spiral, the best form is to test
> various sizes.

I was going to borrow a TV service wavestrength meter / receiver and set
it up for 'free space' metering with a rubber duck at 3 meters distance
or so to get the antennas right. Did you do something like this ? Do you
have a method that works better ?

> I hope this helps clear some problems...

Yes ! Thank you.

Peter