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868/915 Mhz as a viable frequency for submarines. - Page 4 EmptyYesterday at 7:31 pm by Leogtleo*

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    868/915 Mhz as a viable frequency for submarines.

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    geofrancis


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    868/915 Mhz as a viable frequency for submarines. - Page 4 Empty Re: 868/915 Mhz as a viable frequency for submarines.

    Post  geofrancis Fri Jul 07, 2023 9:24 pm

    tsenecal wrote:Sadly,  the problems that you and i have had getting all these receivers to work has not helped my opinion of FrSky's work in the 900mhz area vs others like ExpressLRS (still my favorite) and TBS.


    But it is nice to know that I know have an entire suite of 4 different protocols in the 900mhz frequency range to test and post my results on.

    Because so many people have problems with frsky r9, I have been able to pick up modules for around £20 each because no one wants them.

    I looked at Crossfire but its far more expensive, The mavlink telemetry implementation has a lot of problems and there is no way to have a 1W bidirectional link. ExpressLRS is all about low latency, there is a version for mavlink but its experimental at the moment.  The only other options for that are dragonlink and the RFD900 but you are still looking at over £200 for a set compared to £40 for a pair of R9M modules.
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    tsenecal
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    Post  tsenecal Sat Jul 08, 2023 2:17 am

    yep,

    once i discovered the matek crsf pwm boards for the expresslrs receivers, i have basically standardized on expresslrs. the new v2 tbs crossfire stuff is considerably cheaper, but not as cheap as the expresslrs stuff.

    and the betafpv 915mhz nano transmitter module fits perfectly on the tandem XE, as well as the radiomaster zorro. I just picked up two of the betafpv superd diversity receiver. i want to test that against a standard receiver and see if properly orientated antennas help any.


    both tbs and elrs make r9 look like a much lesser 3rd place product. the only 900mhz product that is of less use to us is the jeti duplex stuff. that makes tbs v1 stuff look cheap, and 900mhz is only a secondary receiver. it can never be used as the primary receiver.
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    tsenecal
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    Post  tsenecal Sun Oct 01, 2023 2:22 am

    So...

    I spent the 23rd and 24th of September running 7 submarines with 7 different radios.

    The venue was the Fly Casting Ponds at the Golden Gate Park in San Francisco CA.

    868/915 Mhz as a viable frequency for submarines. - Page 4 20230910

    It is a cement "pond", with angled sides, 180' x 120', and about 4' deep.


    The radios tested were:

    Radiomaster Zorro
    Radiomaster TX12
    Radiomaster Pocket

    Jumper T-20

    TBS Tango 2

    Frsky QX7
    Frsky Tandem XE


    The Radiomaster radios were used with ExpressLRS trasmitter modules, either Nano or Micro size, running at 250mw, with dynamic power on, and with 100hz, std telemetry, and wide switch mode.  firmware version is 3.3.0.  all Radiomaster radios were running EdgeTX version 2.9.0.  I used both a Happymodel TX module, and two different BetaFPV (nano and micro) transmitter modules.

    The Jumper T-20 was also running the same version of EdgeTX, a branch of OpenTX, and the same version and configuration of ExpressLRS firmware on its internal RF deck.

    The TBS Tango 2 is using its own "FreedomTX", a branch of OpenTX, and has its own built-in TBS crossfire RF deck, running at 250mw dynamic on, max power.

    The QX7 is running OpenTX version 2.3.15, and was used with ExpressLRS micro tx module, TBS Crossfire micro tx module, and an FrSky access r9m module.

    The Tandem XE uses its own Etheos firmware, and has a built-in r9m access rf deck.


    The Submarines were as follows:

    a 1/8 scale Norbert Bruggen Delta research submersible
    a 1/96 scale Skipjack class USN nuclear fast attack submarine
    a 1/96 scale Blueback class USN diesel electric submarine
    a 1/35 bronco Type XXIII german ww2 u-boat, using an R&R model engineering wtc.
    a 1/32 scale "Proteus" 16" long submarine from the movie "Fantastic Voyage"
    a 1/32 scale "Nautilus" from the disney movie "20,000 Leagues under the Sea"
    a 1/32 scale "Flying Sub" from the movie "Voyage to the Bottom of the Sea"

    868/915 Mhz as a viable frequency for submarines. - Page 4 20230913
    868/915 Mhz as a viable frequency for submarines. - Page 4 20230911


    The receivers used were as follows:

    TBS Crossfire 6ch PWM Nano RX
    BetaFPV ExpressLRS Nano RX w/ Matek 6 channel PWM adapter
    BetaFPV ExpressLRS Nano RX w/ Matek 8 channel PWM adapter
    Happymodel ExpressLRS EPW6 PWM RX
    Frsky R9 sx six channel PWM RX


    There really is nothing odd to report here.  Of the 10 gentlemen and 29 submarines that were brought, myself and one other gentleman were using 915mhz.  The other 915mhz equipment was an FrSky horus x10s express, with an r9m module, and a r9 sx receiver (identical to what i used in the QX7).

    Neither of us had any issues.  I tested the ExpressLRS, TBS Crossfire, and R9 systems in the same submarine (The Proteus) because it was easily configurable/modifiable, and could be easily seen anywhere in the pond.

    The Testing consisted of running the submarine in a tight figure 8 circle about 20 feet from the northwest corner of the pond, at a depth of 2 feet, with me walking backwards away from the submarine, toward the south end of the pond, until the "Telemetry Lost" notification was emitted by the transmitter (the 180' length of the pond).  I had a spotter watching the submarine at the north end of the pond, verifying that it was still under control.

    IN ALL CASES,  I lost sight of the submarine before i heard any "Telemetry Lost" notifications.

    The only difference between configurations was that which differed between protocols.

    there is no way to set dynamic power on the FrSky system, so it was set to 250mw.
    there is no way to set telemetry packet ration in FrSky or TBS, but i did have telemetry turned on in all cases, and i also had "vbatt" telemetry, and "Cells" telemetry available on the ExperssLRS and R9 receivers.

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    tsenecal
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    Post  tsenecal Thu Feb 29, 2024 8:34 pm

    Not saying this is "New", but i just found out that Futaba supports "CRSF" protocol output on a few of its radios.

    a short list of known transmitters that allow you to connect either an expresslrs or tbs-crossfire module:

    Futaba 12K
    Futaba 16sz
    Futaba 16iz
    Futaba 18sz
    Futaba 32mz

    however, this has one or two caveats depending on which model transmitter you are using:

    none of the transmitters supports bidirectional (telementry) data transfer. the protocol is outbound only, it is basically changing what was the s.bus output, and allowing it to support both s.bus and crsf. there are only 3 wires on the connecter (gnd, vcc, tx) so the inbound (rx) pin does not exist.

    on the 12k, 16sz, and 16iz, the power line is not available, so a secondary power input needs to be used to provide power for the module.


    This was basically provided over 4 years ago as a firmware update for the radios that existed at that time, and all new radios out of the box since then.

    Given the cost of these radios ($450-$3000) i would only recommend this option for someone that already owns one of these radios,
    since any of the opentx/edgetx or ethos based radios fully support crsf/expresslrs (including telemetry) for considerably less money.

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