Hi, this will be a little long-winded, but I'll keep it as brief as possible:-

I'm making a small Arduino-controlled robot car, and want to be able to make it home in on it's charger from a distance. Once close, I can use an ultrasonic sensor, then IR LED / sensor pair to get the car onto the charger 'ramp', but want to try to use the RSSI output from a 433MHz RF receiver to get into the general vicinity of the charger from further away, out of line-of-sight.

I'll use a 2kHz square-wave to modulate the transmitter carrier, so that it will be relatively easy to get a constant RSSI value at the receiver, independant of the actual data.

My plan, (so far), is to use a small DF loop attached to the receiver, but as I understand DF loops the car won't know if it's pointing directly towards or directly away from the transmitter.

My thought was to shield one side of the loop with a grounded tin shield, to provide a null area in that direction, so that the antenna is truly mono-directional.
I don't know a lot about RF, so don't even know if this is a feasible idea.

Can anyone provide advice on this? It would be very much appreciated.

Edit: And if there's a better way to go about this, I'm all ears....

... Old Steve.

Thank you for the reply, loose-electron. I'll check out arrl.org. I've checked out a couple of hobbyist robotics sites, but couldn't find anything suitable.
(I noticed that my question was comparatively low-tech when I looked at some of the other posts, but thought I'd try anyway.  :) )

... Steve

loose-electron wrote on Oct 14^th, 2015, 10:00am:

I've done a fair bit of research and some testing since posting here. RF 'fox-hunting' provided some good leads, but I came up against a basic problem that I'd overlooked - noise. There's so much noise in the 433MHz band that the RSSI signal is always very strong whether or not I'm transmitting. Maybe someone more knowledgable in RF could get around this, but I couldn't.
In desperation, I dropped the RF idea in favour of 25kHz ultrasound. (I'm already using 40kHz for ranging, so had to go to 25kHz for homing.) A lot trickier for echoes, but far less background noise than the 433MHz RF that I was using. I even tried putting the whole receiver in a large, earthed biscuit tin and still got heaps of noise.
Thanks for your help anyway. I appreciate the fact that you went to the trouble to post again.