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'RF modules and antenna problems'
1998\12\04@050753 by Seyler, Jean-Yves

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 Hello Jochen,

You 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.

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 hope this helps clear some problems...

Greetings
Jochen DH6FAZ
---
I have currently such a problem since I have to "design" an antenna (433 MHz)
that fits into my tiny remote control TX box (# 4 x 3 cm). Have you any
experience with that ?
I have made several trials with single wire but it failed to send any power
when this wire is to close to the Hybrid TX !

Thanks for any comment

1998\12\04@052658 by Jochen Feldhaar

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Hello Jean-Yves,

a small patch of PCB, about 2*2 cm will be sufficient if the antenna is
designed on the PCB as part of the layout. The centre of the spiral can be
connected on the otherb conductor side of the PCB, but only a small line,
NOT a groundplane (This would help your problem all right, because ALL
transmitting would be next to Zero...).

Alternately, you can try a small cylindrical coil of standard enameled
copper wire. This coil can bhe so placed that the magnetic field will cause
less interference in one preferred direction... you have to experiment with
the size, about 3mm diameter and 10 loops will do the trick if range is not
paramount.

Feel free to comment...

Jochen DH6FAZ
spam_OUTjfTakeThisOuTspamdetektor.de


'RF modules and antenna problems'
1999\01\11@130038 by John Payson
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|a small patch of PCB, about 2*2 cm will be sufficient if the antenna is
|designed on the PCB as part of the layout. The centre of the spiral can be
|connected on the otherb conductor side of the PCB, but only a small line,
|NOT a groundplane (This would help your problem all right, because ALL
|transmitting would be next to Zero...).

What about having two spirals on opposite sides of the board,
connected in the middle (being sure to run the spirals in
opposite directions (so that if, e.g., current starting at the
top outside goes clockwise into the center, and then on the
bottom goes clockwise as well from the center out).  Hard to
describe, but one way would work (I think) and the other would
not work well at all.

Is that a good approach?


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