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Title: RFM69 lowest possible range
Post by: markus1234 on April 22, 2017, 01:41:35 AM

Hi,
to recieve a secure number, I want to limit the range of a RFM69 to its lowest possible minimum (ideal would be only a few centimeters).
A simple 433mhz antenna wire is attached (and non removable).

Is there any other way beside setting the tx power to near 0? (This will give me at least 4 -6 m of range, which is too much)

thanks in advance

Title: Re: RFM69 lowest possible range
Post by: captcha on April 22, 2017, 07:52:57 AM

Replace the antenna with a 50ohm SMD resistor and you'll have a range of around 5m.

Title: Re: RFM69 lowest possible range
Post by: markus1234 on April 24, 2017, 02:31:15 AM

thanks for your answer but I'm looking for an software solution to switch from high range to "nearly no" range :)

Title: Re: RFM69 lowest possible range
Post by: ChemE on April 24, 2017, 07:53:03 AM

Quote from: markus1234 on April 24, 2017, 02:31:15 AM
thanks for your answer but I'm looking for an software solution to switch from high range to "nearly no" range :)

I think then that you need to experiment with detuning your broadcast antenna so that there is a significant mismatch between Tx and Rx frequency. That is software and should be able to cripple range pretty effectively.

Title: Re: RFM69 lowest possible range
Post by: joelucid on April 26, 2017, 12:23:44 AM

Quotethanks for your answer but I'm looking for an software solution to switch from high range to "nearly no" range

In my experience if you use an HW as W or the other way around on the TX side you get very minimal range.

Joe

Title: Re: RFM69 lowest possible range
Post by: perky on April 28, 2017, 03:55:29 PM

Turn off all the PA amps. You'll get a tiny signal coming out, only a few 10s of cm. This was one of my very first debugs ;)

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Hardware support => RF - Range - Antennas - RFM69 library => Topic started by: markus1234 on April 22, 2017, 01:41:35 AM