Re: How do I limit my RF reception range?


Brad Kartchner wrote:
Hello, everyone!

I'm working on a project that requires wireless communication between
two devices but only within a small distance (2-3 feet at most). I
have settled on an using RF (2.4 GHz) to communicate between them, but
need to be able to limit my range.

Would tuning my antenna to a harmonic of 2.4 GHz work? Or would this
result in an unreliable communication link? I know antennas are VERY
complicated, but could I just play with reducing the length of the
antenna?

Any help would be appreciated.

reducing the length of the antenna causes power to reflect back into
the amplifier, causing problems. The creature you probably want is
called a PAD, its a small network of resistors that attenuates the
signal while maintaining correct impedances at the antenna, and output
amplifier. If yours is a single antenna system this may knock down
your receiver sensitivity as a side effect, and thats VERY BAD in non
spread spectrum systems and just plain BAD in spread spectrum. many 2.4
ghz devices use a switch between the transmitter and receiver to select
which are connected to the antenna.

I'm sure there are websites about SWR nowdays, so you should google
"standing wave ratio" which is kinda misnamed, it is the relation
between power leaving the antenna (good) and power reflected back from
the antenna (bad)

It depends on your device, if this is bluetooth and short ranged to
begin with , or something a lot more professional.

for two to ten devices, get a pad from say Minicircuits, for more,
have the device redesigned by a pro. 2.4 ghz is well past the point
where things get difficult for a non rf person.

Steve Roberts

.

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