The Shipyard ( Dry Dock ): Builds & Questions > Submarines R&D:

Modifying an old TX for openLRS at 458MHz

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If you are having problems finding 40Mhz gear for subs or time is hanging heavy in these "lockdown days" it may be a good time to have a go at converting an old TX to openLRS.

All you need is an old TX you can gut. An Arduino Nano and a Hobbyking TX module and receiver. (Both still available at Hobbyking for about 25 and 11 respectively. Not sure about delivery times at the moment though?)

The instructions and software are all available (My thanks to John Wrennall for finding this and Phil Green for doing all the hard work) at:

(Go to the archive page and and find " P17]  Sketch for 7 channel proportional encoder using the Arduino, with Single-Channel mix [Superseded - see below]" for the Arduino sketch I think I used.)
More information at:
A good way to spend ones "Covid 19 isolation days?!

Keep well!


Fred Ellis:
Nice one ☝David

Thank you!

I should have clarified that you don't necessarily need to gut ALL the transmitter electronics. If you disable the existing RF section (remove the crystal and aerial) you can  feed the Hobbyking module from the existing TX electronics via the trainer socket.

I did this initially but then ended up doing a "full-gutting" and I then used Phil Green's excellent Arduino software to replace the TX electronics completely.

It could make a very good introduction to Arduino use and it will not break the bank!


coch y bonddu:
ok now we all know that any transmitter by law has to have a max transmitting power how does this conversion compare is it more or less than the the permitted power under UK Law...not trying to be a party pooper here not by a log way and also if two of you are stood next to ea other does it bleed over the other as the OP states it is an open Lrs system and are they open to being over powered by anything else being curious thats all


Thanks for the question. I understand from Ofcom that the 100mW modules are legal in the UK.

In theory the system uses frequency- hopping (like 2.4 Ghz) so there shouldn't be a problem. In practice we have never had more than 2 users in one place, with no problem.

The system was developed by drone users but it offers a bit of a life line to model submariners who are unable to use 2.4 Ghz and are therefore excluded from mainstream commercial r/c equipment.

Keep well!



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