maniattico
Posts: 24
Joined: Thu Jan 25, 2018 12:40 pm

RF 433 Mhz receiver only works at 3 cm.

Fri Feb 02, 2018 11:09 am

Hello.

I've this RF RX: https://www.amazon.es/gp/product/B073ZW ... UTF8&psc=1
And those remotes: https://www.amazon.es/gp/product/B0768F ... UTF8&psc=1

The receiver is plugged at 3,3v (in 5v PIN it isn't works)

When I run rpi-rf script, It only detects the signal when I push the button with the remote control closer than 3 cm. I've soldered the antenna provided, whit same result.

This is not normal, isn't it?

Regards

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joan
Posts: 14691
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: RF 433 Mhz receiver only works at 3 cm.

Fri Feb 02, 2018 11:24 am

No, it is not normal. My cheap units easily manage 20 feet.

btidey
Posts: 1634
Joined: Sun Feb 17, 2013 6:51 pm

Re: RF 433 Mhz receiver only works at 3 cm.

Fri Feb 02, 2018 11:30 am

Yes these cheap (regenerative) units should be giving at least 5 metres with an antenna.

Superhet based rx units tend to give even more range and are not that much more expensive.

I'd start checking the key fob battery in case it wasn't fresh as supplied.

Then maybe use the TX module attached to Pi (with antenna) and a test program instead of the key fob to see what range you get with that.
Last edited by btidey on Fri Feb 02, 2018 11:31 am, edited 1 time in total.

maniattico
Posts: 24
Joined: Thu Jan 25, 2018 12:40 pm

Re: RF 433 Mhz receiver only works at 3 cm.

Fri Feb 02, 2018 11:31 am

joan wrote:
Fri Feb 02, 2018 11:24 am
No, it is not normal. My cheap units easily manage 20 feet.
Thanks. Any recomendation?

I've 2 RX and 2 TX whit same result. Now I've soldered a 20cm. wire as antenna, and doesn't works.

I think that that RX unit works at 5v, and I plug it at 3,3v (however, at 5V nothing is detected)

Alex Konshin
Posts: 44
Joined: Sun Jan 29, 2017 10:02 pm
Location: Boston MA, USA

Re: RF 433 Mhz receiver only works at 3 cm.

Mon Feb 05, 2018 3:06 am

From my experience this module is bad. I had 2 of them. One did not work at all. Another one works but has bad reception.
I would recommend RXB6 or RF-R-ASK modules. Both of them work fine with 3V and you can connect them directly to RPi.
RXB6 module (I got the link from the list of recommendations from your links): https://www.amazon.es/WINGONEER-recepto ... GNNPASNQ6C
RF-R-ASK module (just to provide you a picture of the module): https://www.seeedstudio.com/433MHz-ASK% ... -2205.html
I made my antenna using this instruction: http://www.instructables.com/id/433-MHz ... d-antenna/

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mahjongg
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Re: RF 433 Mhz receiver only works at 3 cm.

Mon Feb 05, 2018 3:08 pm

Its possible the receiver is de-tuned, perhaps you can tune it back to 433 MHz by turning the core bit in the green coil in the middle.
There is a signal output (hole or pin) you can connect an oscilloscope to to assist in that, when you are transmitting nearby with the keyfob, the output should be a clear binary pattern, not random noise, or permanent high or low.

The receiver should also not be close to the PI (or any other switching digital device), as noise from the PI will disturb reception.

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