25 Apr
2018
25 Apr
'18
9:47 p.m.
Yes, the quarter wave ones really do not work well unless earth grounded.
Highly recommend that vertically mounted dipoles be used instead.
I made them using 82mm of wire per leg, soldered to RP-SMA connectors and
heat shrink-ed to BBQ skewers.
Modem frequency was 920MHz.
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I seek to understand, and aim to create.
Weblog: http://adammunich.com
PGP Public Key: https://pgp.mit.edu/pks/lookup?search=adam+munich
On Wed, Apr 25, 2018 at 9:44 PM, Marc Juul <marc(a)juul.io> wrote:
Wow very nice!
Were the quarter and half wave antennas both DIY?
On Wed, Apr 25, 2018 at 9:38 PM, Adam <me(a)adammunich.com> wrote:
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.
https://www.google.com/maps/d/u/0/edit?mid=1dE2QZS9cgX_oHLWy
zmUNAYrjlbX0wJpE&ll=37.75708554224248%2C-122.33675183183021&z=13
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)
};
RF95.setModemRegisters(&modem_config);
In other news, you can still jet ski if your core body temp is 88F.
Little unpleasant though.
- - - - Begin automatically generated footer - - - -
I seek to understand, and aim to create.
Weblog: http://adammunich.com
PGP Public Key: https://pgp.mit.edu/pks/lookup?search=adam+munich
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