FS1000A for short/medium range

Other Hardware General Electronics
1

Hi,

My apologises for my english,

I am using the FS1000A (emitter) and the RF-5V (receiver) for a 433MHz transmission.
My aim is to receive an information from the emitter at the maximum distance of 60-80cm, which means that if the receiver if within the range, it will receive the signal from the emitter, but will not receive anything out of this range.
Ideally I would like to have this type of directional pattern : http://www.labbookpages.co.uk/audio/beamforming/files/delaySum/polar.png and no signal received wanted behind.

I tried a few things:

  • No antenna on both modules: the receiver does not receive anything even from 5 centimeters.
  • I made an helicoidal antenna of -7 centimeters (random test), the receiver receives better from the sides than in the front, it is really weird. I don't need to mention that I can also receive behind the emitter.
    -I put an aluminium foil behind the emitter, it does not seem to reflect the radio waves.
    -I put the antenna of the emitter inside a glass cup, it does not seem to attenuate or reflect.

Both modules are supplied on 3.3V. I also put a 10Kohms resistor between the GND and DATA pin of the receiver.
I am planning to buy a proper spring antenna (helicoidal), I am hoping It will be a directional antenna.
I also would like to avoid an antenna on the receiver for limited space reason. The communication is intended to be used indoor.

Does anyone have any clue?

Thank you for your help in advance.

2

It is impossible to limit radio transmission range as precisely as you hope.

Radio waves are reflected and absorbed by everything in the vicinity, and add (form interference patterns) in ways that simply can't be predicted for a changing environment.

You can use a short bit of wire (a few cm) on both transmitter and receiver to limit the maximum range to a few meters, but you will find that distance to be quite unpredictable as you move the TX/RX pair around the room.

3

RF location like that requires much more advanced techniques. I haven't seen anything cheap for that ( I saw one for like 70 bucks per module recently)

4

Thank you for your replies.

I think I will combine this with RSSI data, I heard the module superheterodyne RXB6 can do that. The main problem will be human body proximity which will attenuate the results.

5

RSSI indications at short range are highly variable.

Small changes in the orientation of transmitter or receiver can have a very large effect.