[DisasterRadio] Fwd: [sudo-discuss] diaster.radio modulation scheme tests

Jenny Ryan tunabananas at gmail.com
Mon Apr 30 18:41:07 PDT 2018

hey adam, this is rad!
fyi there's also a disaster.radio mailing list (fwd'ing)

---------- Forwarded message ---------
From: Adam <me at adammunich.com>
Date: Wed, Apr 25, 2018, 21:39
Subject: [sudo-discuss] diaster.radio modulation scheme tests
To: Sudo room <sudo-discuss at lists.sudoroom.org>

Hi all,

I ran some tests on LORA modulation schemes to get the best results I could
on a 100mW TX power budget.

I nearly ran out of gas during this latest test, and unfortunately I
managed to screw up my data logging, so I don't have RSSI or SNR data, but
this map contains all the places I stopped and got a two way signal on my
jet ski.

The transmitter was in my hand, the receiver was at pier 50, SF.

DIY half wave dipoles were used, with a center freq of 900MHz with a +/-
100MHz 3db roll off.


I found that quarter wave antennas are no good (see the red markers). The
blue markers are today's test, using RFM95's from HopeRF.

To get the very long range, I used the following modulation scheme using
the RadioHead library.

RH_RF95::ModemConfig modem_config =
/*Reg 0x1D: BW=125kHz, Coding=4/8, Header=explicit*/
(7 << 4) | (4 << 1) | (0),
/*Reg 0x1E: Spread=4096chips/symbol, CRC=enable*/
(12 << 4) | (1 << 2),
/*Reg 0x26: LowDataRate=On, Agc=On*/
(1 << 3) | (1 << 2)


In other news, you can still jet ski if your core body temp is 88F. Little
unpleasant though.

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I seek to understand, and aim to create.
Weblog: http://adammunich.com

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