The Shipyard ( Dry Dock ): Builds & Questions > Submarines
Anyone used the FrSky R9M 900MHz Long Range System for model submarines?
Davy1:
Does anyone have experience of the FrSky R9M 900MHz Long Range System for model submarines?
It is normally used for drones but it is reported that you can achieve control at depths down to about 2 feet.
Model submariners have the twin problems of a growing shortage of r/c control equipment for model submarines and the use of higher and higher frequencies so that the signal is absorbed by water. The FrSky system is easily available and can be used "out of the box" by relative newcomers to the hobby,
More background information here:
https://www.theassociationofmodelsubmariners.com/t83p150-openlrs-and-2-4-ghz-and-submarines#11450
JimG:
One problem with it's use in the UL for submarines is that this is not a recognised frequency for radio control. Use is therefore illegal, if drones are using it then they are breaking the law. Of course if they are flying long range out of site then they are illegal anyway and don't bother about the laws. The 900MHz band is used for other legitimate purposes.
Jim
Davy1:
Thanks Jim. I should perhaps have phrased the question as "approximately" 900MHz.
868/915MHz has been talked about as UK legal but I am not sure. I'm just hoping to find someone who has used this gear at these kind of frequencies and can comment on its use underwater. (Model submarine users are slowly being painted into a corner with respect to higher and higher frequencies by "air" users.)
David
tsenecal:
I am using the following setup with limited success:
FrSky Taranis x9d
FrSky R9M module (2)
FrSky R9 receiver (1)
FrSky R9mm receiver (3)
FrSky R9 slim+ receiver (2)
they all work reasonably well, i use the word "limited", because the depth afforded by the system is less than two feet. the "less" is dependent upon particulates in the water, like chlorine or minerals. In all other respects it is just like using their 2.4ghz system, you get as many as 16 channels using s-bus based servos (or servo adapters) you get FrSky's x series telemetry, and of course you get all the "joys" of OpenTX.
there is one considerably large negative to the current system:
there have been about 7 updates to the firmware for these devices over the last year or so, and i myself basically am forced to run through all the devices every time i buy a new module or receiver. updating firmware for the traditional "accst" based systems is not simple. there is a three pin cable, unlike a standard servo cable, that you must use to connect the receiver to the back of the transmitter, so that the transmitter can send the firmware file to the receiver. each receiver make requires a different cable. there is no way of knowing what version of firmware a device has until you own it.
FrSky is in the midst of updating their protocol (new protocol is labelled "access") and the new protocol allows for updating receivers via "over the air" methods, meaning the firmware is transmitted to it as a giant data packet, so unlike what i am doing now, i would not have to figure out a way to attach a cable from the receiver to the transmitter to update each receiver.
all of the receivers but the original R9 are meant to be used with "drones" and their associate flight controllers, so they need to have a wiring harness made for them that will allow them to be used with traditional servos. most of the receivers that require this will come with a short pigtail that can be used to build half of the harness, but the other half of the parts for the harness need to be bought, and the harness needs to be soldered together.
i will post pictures of my setup if you think they would be of help.
even with all these issues using the system, i find it more agreeable than using 2.4ghz with its necessity of rewiring the antenna so that it is protruding from some location high above the water. several of the submarines i have built are "research subs", and they don't have a readily excusable periscope in which i could place the antenna, and i simply don't like the idea of having a 2 foot long antenna sticking out the top of my sub.
i have tried one other 915mhz system base on the OpenLRSng protocol, called ChipLRS, but they are no longer in production, as well as the 433mhz OpenLRSng setups from both hobbyking and others including DTF-UHF. I abandoned 433mhz when all the major players left the market. Hobbyking is the only remaining player making 433mhz equipment, and i consider their equipment one step above junk.
Subculture:
Bob tried it and didn't seem too impressed.
https://www.youtube.com/watch?v=hGDxRDqIfdk
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