[sudo-discuss] diaster.radio modulation scheme tests

[Adam]

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 at 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 at 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
>>
>> _______________________________________________
>> sudo-discuss mailing list
>> sudo-discuss at lists.sudoroom.org
>> https://sudoroom.org/lists/listinfo/sudo-discuss
>>
>>
>
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