David and i have a few threads here now on using OpenLRS systems instead of the traditional PPM base frequencies, in an attempt to move submarines into the 21st century.
Both David and i have found great success in 433mhz in the USA, and 458mhz in the UK.
There is one small problem with 433mhz in the USA... it requires that you have a HAM radio license to be even close to "legal"...
There is, however, a different frequency that some OpenLRS makers/sellers have used in the past. 915mhz. It does not require any additional licensing, and because of that I own a few receivers and one transmitter module that operate using the OpenLRS protocol in 915mhz, and they seem to work okay, as best as can be expected, giving me up to 3 feet of depth in the right circumstances...
The issue is that no-one now seems to be making these... my last ebay source has told me that he has moved on to other items for sale, and he will require minimum quantities before he will make more...
I have started looking around for other 915mhz equipment.
By shear luck, a very large Chinese radio manufacturer, FrSky, has started producing a range of products using 915mhz. they sell it as a long range option for drone flyers... with quoted distances of up to 20km by some reviewers (air usage). again, what i have discovered is that i can get anywhere from 18" to 36" below the surface and still have excellent control of the submarine using 915mhz.
I have spent the last 3 months testing both the 7 channel receivers that use OpenLRS on 915mhz, and two of the FrSky recievers that use the 915mhz frequency.
The modules i have tested are the OpenLRS TX module and a separate 7 channel RX that was sold by a russian ebay seller,
I have also been testing the FrSky R9M module, and both their R9 receiver, a full size 8 channel receiver, and their R9 Slim, a small 6 channel receiver designed for drones. I also just recently picked up a brand new receiver they sell, the R9 mm/mini. an ultra micro 4 channel receiver designed for tiny racing drones.
I have tested both the R9 and R9 slim in my Norbert Brüggen Delta submarine, and the R9 slim in my SWM blueback. i have just recently put the R9 mm in to the blueback, and will be testing it as soon as possible.
to give you an idea of how big the R9 mm is, i have attached a photo.
the R9 slim and R9 mm are not designed to attach directly to servos without a little extra work, they are primarily designed to connect to flight controllers for drones with only 3 wires (positive, negative, signal) and they can operate on a single lipo cell (3.7v), but with a little work (soldering up connectors or a harness) they can be made to work with standard size or miniature servos.
more to come.