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» Futaba -868/915mhz equipment
Frsky - 868/915Mhz equipment EmptySun Jun 09, 2024 10:47 pm by tsenecal

» Darnell type 21 submarine, need some help
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    Frsky - 868/915Mhz equipment

    david f
    david f
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    Frsky - 868/915Mhz equipment Empty Frsky - 868/915Mhz equipment

    Post  david f Mon Mar 20, 2023 1:40 pm

    Hi Tim,

    New topic, as requested.

    Hope the title is OK.


    Last edited by david f on Mon Jul 10, 2023 8:10 am; edited 1 time in total

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    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  tsenecal Sun Jul 09, 2023 7:07 pm

    Okay, now that i have had Geofrancis help me sort out my pile of FrSky r9 equipment, its time to start posting pictures and details in these three "vendor" 915mhz areas.

    FrSky is actaully on its third version of 915mhz equipment at this time.

    2 versions of hardware, and 2 versions of firmware.

    Frsky started out long ago as a clone maker of futuba receivers, then started making its own transmitter modules and receivers, then started making its own transmitters. they had T series receives (futaba fasst clones) then their own V and D series. then they came out with a newer version of the D series, "accst" or D16... at about the same time that they came out with their own transmitters.

    when 915mhz became big enough in the Drone world, FrSky decided it was a big enough market to get into. that created the first D series 915mhz equipment, basically the original black jr style transmitter module labeled "r9m" and a full size 8 channel pwm receiver with sport and sbus labeled "r9". they also created two smaller "drone" size receivers that supported primarily s-bus to a flight controller. both of them however did have pins for pwm output. the r9-mini has/had 4 pwm output, and the r9-slim has/had 6 pwm output... but those two just had individual pins, it was left up to the user to build an actual harness that could actually connect real servos to the receivers.

    these r9 915mhz devices also used the "accst" protocol.

    the problem is that this first version of FrSky's 915mhz equipment had both hardware and software problems. people did not like it. it was so bad that some people figured out that the first batch of r9m modules actually shipped with 2.4ghz antennas. FrSky probably sent out 6 different firmware updates for both the transmitter modules and the receivers in a one year period. people got tired of trying to figure out what version of firmware they needed to make everything work. FrSky was kind enough to change the color of the newer transmitter modules to the orange color, so you could avoid the original black modules that actually had a hardware issue. for a reason that i am not familiar with, they came out with a third version of the transmitter module specifically known as r9m 2019.

    some people abandoned FrSky for TBS Crossfire, another 915mhz system, that provided better support, and better performance, but it came at a price. the original TBS hardware was 4 to 6 times the price of the FrSky equipment.

    other people took their existing r9 equipment, and wrote new firmware for it. That firmware was/is called ExpressLRS. ExpressLRS is open source, and is now available on hardware made by at least a half dozen different brands.

    Then FrSky, for many reasons, most political, and not discussed here, decided to create a new protocol called "access" which did several things. it fixed a bunch of bugs in the original accst protocol, it improved latency in some scenarios, and it extended the capacity, from 16 channels to 24.

    you can still get accst hardware from r9m, but all the new radios are made to use access.

    FrSky has also decided it wants to go up market. you can still buy a $200 FrSky radio, but they have expanded their line.

    they have three basic radio families:

    entry/mid level:

    mid level:

    high level:

    The fundamental difference between the entry level and mid level is that the mid and high level radios now come with FrSky's own firmware, labeled "Ethos", while the entry level radios come with OpenTX.

    I bring this up, because the biggest difference between the Tandem upper level and Horus mid level is that true to its name, the Tandem series radios actually have both a 2.4ghz rf deck, and a 900mhz rf deck built into the radio.

    I currently own an original Taranis x9d (accst protocol), a QX7 (access protocol), and just recently picked up a Tandem XE (dual access protocol).

    In addition to that, i have 3 r9 receivers, an r9 slim, a r9 mini, a single r9-mm (all accst) as well as two r9-mm-ota, which are access. I also have two Jumper r900 receivers, which are basically a clone r9 (accst).

    My Posts for R9 hardware will be based on those devices, and any new access receivers i may pick up to use with the Tandem XE

    geofrancis likes this post


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    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  geofrancis Sun Jul 09, 2023 7:40 pm

    david f wrote:Hi Tim,

    New topic, as requested.

    Hope the title is OK.


    it works on 868mhz and 915mhz.

    tsenecal likes this post


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    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  tsenecal Mon Jul 10, 2023 3:54 am

    Yep, Geofrancis is correct.

    ALL of the "915mhz" equipment is only 915mhz where it is legal to be 915mhz.  (USA)
    in other parts of the world, it is 868mhz...   being from america, i am only concerned about what is legal in america.

    i am not 100% certain where all the 915mhz countries are, or where all the 868mhz countries are...

    PLEASE verify which frequency your country uses, and use that.

    Posts : 314
    Join date : 2015-04-01

    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  tsenecal Mon Jul 10, 2023 4:28 am

    One more thing to add:

    FrSky r9 equipment will work with both OpenTX/EdgeTX/Ethos based radios that can communicate via the serial based XJT protocol to the module, or with less "intelligent" transmitters that can output PPM.

    The minimum and maximum power output that you can select for the r9m and r9m lite are 10mw minimum and 1w max for r9m, and 250mw for r9m lite. There is now an r9m lite pro, which is has a max output of 1w.

    In all my testing i have not found any significant advantage to transmitting at a power level higher than 250mw

    geofrancis likes this post


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    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  tsenecal Tue Jul 11, 2023 4:04 am

    The short list of manufacturers of r9 hardware:

    r9m 2019
    r9m 2019 access
    r9m lite access

    All tandem transmitters have a r9m 2019 access rf deck built into the radio

    r9 stab
    r9 mini
    r9 mm
    r9 mx
    r9 slim
    r9 slim+
    and many others i simply don't know about.

    Jumper (receiver only)

    where you can find them

    worldwide distributor:

    US distributor:

    UK distributor:

    you can also find the jumper r900 and all the other FrSky brand items on pretty much any online site known to man, amazon, aliexpress, banggood, etc.

    Last edited by tsenecal on Tue Aug 29, 2023 8:27 pm; edited 1 time in total

    Posts : 314
    Join date : 2015-04-01

    Frsky - 868/915Mhz equipment Empty Re: Frsky - 868/915Mhz equipment

    Post  tsenecal Tue Jul 18, 2023 10:23 pm

    Moving into another topic that many might find interesting, and some might find useful.


    FrSky now lives in two worlds as far as telemetry is concerned. they have their traditional s.port based sensors, that originated in their 2.4ghz world, and were moved enmasse into their R9 world without alteration. this includes sensors for signal strength and quality, voltage, current, temperature, air pressure, compass heading, and GPS coordinates.

    for the vast majority of these, they are usable by submarines, the only telemetry that cannot be received while a submarine is underwater is GPS/Glonass. this is because they are a receiver themselves using the 1200-1500 mhz frequency ranges for GPS, and 1600+ for glonass. GPS and Glonass are basically the same, GPS being the US standard, and Glonass being the European standard. both basically use satellites to triangulate your location. since they both use frequencies higher than 900mhz, they do not interfere, but they also basically penetrate water only slightly better than 2.4ghz does.

    Like everything else FrSky does, they have a second way of connecting to sensors, designed for use with Flight Controllers, called fbus. it is basically sbus, but not inverted, so it is easier for inexpensive flight controllers that lack built in inverters to use.

    FrSky also lives in two worlds with their voltage sensors. for more traditional batteries like SLA and Nimh, they offer one or two analog 3.3v max inputs on most of their receivers, basically connect a wire from the positive side of your battery through a voltage divider to drop its total voltage to less than 3.3v, and you get total battery voltage. They also offer a series of sensors labeled "FLVS" which are more complex, and basically connnect between s.port and the lipo battery's balance socket. this sensor will return the voltage of each individual cell in a lipo battery.

    the s.port system has been around long enough that many different groups have reverse engineered it and there are free opensource libraries for products like arduino, allowing DIY builders to create their own sensors relatively easily.

    the entirety of the FrSky telemetry environment has been implemented in OpenTX, EdgeTX, and now Ethos. anything you can connect to an r9 receiver can be viewed on a transmitter.

    the s.port system is actually FrSky's second pass at telemetry, their original D8 series used an entirely different hub based system that was adopted by OpenLRS, and David F and I have both built sensors that worked for the OpenLRS systems.

    david f, SimonH and geofrancis like this post

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