UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )

david, it is a problem associated with 433.... and telemetry... the problem is 3 things:

1) when you turn on telemetry, the receiver is now transmitting 50% of the time, so it is now the largest rf emitter inside the submarine. forget about capacitors on a brushless motor, this makes that look like the radar outline of a duck vs a b52

2) the "antenna" wire lengths needed to carry that signal out to the servos (as interference) is only 6".... about the same length as a servo wire.... in the 75mhz and 40mhz world, that length needs to be over a meter.

3) the antennas that all the systems ship with are monopole. they aren't grounded in any way (dipole), so they are less efficient and generate more noise.


it seems to vary from submarine to submarine. my skipjack and delta are completely un-affected, while my blueback suffers so badly that the servos actually twitch about an 1/8th of an inch.

in order to even make my blueback work, i had to wrap the servo wires around ferrite rings to kill the interference. something like this: http://www.ebay.com/itm/301198587261?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

i put one of those on every servo wire (including esc)

those are the exact ones i bought, and they dropped the interference to a point where the sub can now work. I assume that if you have room to install a proper dipole antenna, that would reduce the interference as well.

Many thanks for the information. I find it amusing that I have just been cheerfully removing all those ferrite rings only to have to put them all back!

(I used to use them a lot on 40Mhz gear in the "belief" that they cut down on servo glitches.)

Certainly one of the very nice things about this openLRS UHF equipment is the smooth response without glitches. So it is a shame that the telemetry introduces interference.

I wonder if a way out of this issue couldn't be done with a
modification to the openLRS software itself?

Would it be acceptable to have telemetry data less frequently? Perhaps only on demand?

If so a signal from the transmitter could be used to turn telemetry on briefly.

(There is already a similar feature in the lost model beacon part of the software. Pressing the walkie talkie transmit turns the beacon on. This works well.)

Some shots of  Dave J's excellent Type 9 operating on openLRS.


https://www.theassociationofmodelsubmariners.com/t1555-furness-mbc-regatta-barrow-june-2015#9567

Another pegboard heads for the skip! (Although my range problems with the Turkish Nordenfelt indicate that there are still some wrinkles which need to be ironed out.)

David

John Wrennall wrote:Query?

3v3 seems to be used a lot with these 433/458 modules. Is this just a programming "enable" voltage or the main supply voltage?

Anyone got a link to the data sheets?

John

It appears that today is not a day where my focus is at its best.... lets just say, i have answered the 3.3v question, as well as others.... but, for completeness, here are links to the data sheets.

the systems use the HopeRF rfm22b rf module for the 100mw setup, and the rfm23bp for the 1 watt setup, here are hopeRF's spec sheets:

http://www.hoperf.com/upload/rf/RFM22B.pdf
http://www.hoperf.com/upload/rf/RFM23BP.pdf

I just noticed that the OrangeRX 100mw futaba transmitter module on hobbyking.com is selling for $9.99

Good news about the reduced price for Orange modules.

It is rather important to us that they carry on selling and making them. We wouldn't want the market to dry up for us as it has with lower frequencies.

I have been doing some more antenna trials, mostly to solve the short range problem I've been having with just one model. (The Turkish Nordenfelt)

I re-configured the telemetry option to help with this displaying on the LCD screen.(Tim's suggestion to include some ferrite rings does reduce the servo tremor.)

I put in  a home made aerial (175mm) which was in water (insulated but sticking through a bulkhead into the free flooding area.

It worked as well as the previous aerial inside the WTC - but still gave about half "normal" range!

It is puzzling because I use the same WTC  with the Turkish Nordenfelt and get good range. The range seems to be specific to this one hull.

At the same time, I re-commissioned my Holland 1 with open LRS. This has a great big aluminium sealing ring, great big aluminium piston tank  and a brushless motor. You would probably expect range problems with such  a packed small model  but it worked fine over 100's of feet - until you couldn't see it to control it!

So all together rather puzzling but I will carry on the experiments with the Turkish Nordenfelt.

Hello David,
                   I have been following this thread with some interest because although I have several Futaba M6 Tx and Rx outfits on 27meg which should last my sub modelling time, progress is slow, I always feel it's a good idea to have a plan B handy, government being as it is. With regard to your problem with just one particular model led me to wonder have you used any carbon  fibre or aluminium filler powder in the construction which presumably is grp? Or even metalised finish or primer?

               Trevor

I have a friend who built a sub with carbon fiber, guess what does not go through it? Yes, radio signal.

Thanks all!

No, the hull is fairly standard grp using polyester resin. Halfords plastic spray primer and satin black topcoat.

My budget didn't stretch to carbon fibre, Tom! I don't think any of those paints contain metal and we did a range test in air which was fine (screening would have affected this, I think.) The problems seem to start when the model is in water.

The model has long brass control rods and a brass prop shaft (all about 500mm long)

I initially thought that the problem was the extensive metal superstructure but I have replaced it all with ABS (Plasticard)

Next thing to try is swapping receivers (I'm told that Hobbyking stuff can have variable quality control.) or could it be some diffraction phenomenon (the shape of the water over the WTC??)

Overall it doesn't mean a problem for openLRS, plenty of subs with no problems. It just makes its use more interesting!

(This sub will be going to Norwich "as-is" in any case.)

David

is there any chance the water is getting to the antenna wire core? If you swap thar RX to another boat that has the antenna in the wet does it work. I guess I am saying does it follow the antenna, RX, or boat.

The antenna wire is inside a 4mm nylon tube which goes through a gland in the WTC bulkhead. The end of the nylon tube is sealed with a silicon rubber cap. No water coming in there.

Yes, you're right it does now come down to the antenna, RX or boat. So the next step is to try swapping the RX with stock antenna which worked well in the Holland. If there is no range improvement, then put the same antenna and RX in the same WTC back in the Turkish Nordenfelt (which worked well at Bournville).

If that continues to work well then it just has to be something about the Russian Nordenfelt hull as it sits in the water.

Subs are always interesting!

David

Well I have carried out a significant experiment this week out on the pond to investigate the low range with the Nordenfelt. (about half the "typical" range.)

3 models all using openLRS (Holland, Turkish and Russian Nordenfelts.) Telemetry on and monitoring RSSI with the LCD. Stock antenna used throughout.

The Nordenfelts share the same WTC.

The first thing was to test if a sub-standard RX was the cause. So I swapped the RX's over between the Holland and the Nordenfelt WTC. Result - no change.  The Nordenfelt was still poor and the Holland was very good. So RXs are not the problem.

I then swapped the WTC back to the Turkish Nordenfelt. A rather shock result - the range was also poor.

This was a surprise because I have used this Turkish Nordenfelt several times in the past with good range  (not least at the Bournville event.)

So the conclusion is that it is some detail about the configuration of the internals of the WTC. It is densely packed and had I changed this detail since Bournville?

I tried moving the RX and antenna up to the top of the WTC (it had been at the bottom so deeper underwater?) No improvement in range.

That is where things stand to date. I will take the Russian Nordenfelt to Norwich as it is.

It hasn't turned me off openLRS. It has very significant benefits and I don't expect to be using 40Mhz again. (I have just ordered and received another 2 Hobbyking Orange openLRS receivers.) It does however still have some development aspects to sort out.

Over to you out there to have a go and report back.

David

A piece I wrote for the Barrow in Furness MBC magazine. It is a summary of where we are. (Included with permission.)

GOING ORANGE - trials of open source Long Range System(openLRS) on 458Mhz.

You may have recently noticed Dave Jacques and me at the pond with
strange stubby aerials and small orange boxes plugged into our
transmitters.

Well we have been doing the first trials of this technology for
model submarines in the UK.

You may be aware that in recent years model submariners have been faced
with a dilemma created by the widespread adoption of 2.4Ghz equipment.
This technology is a significant advance with big benefits for the
modeller - mainly  being able to drop the dreaded pegboard.(The radio
"frequency hops.") The only problem for the sub modeller is that 2.4Ghz
is hopeless since it penetrates less than an inch of water!

So sub modellers have been faced with the slow death of their hobby by
having to rely on a small and diminishing stock of second hand 40Mhz
equipment.

But then along came First Person View (FPV) flyers. They needed longer
ranges than were possible with 2.4Ghz. Open source software (openLRS)
was developed by their community. This incorporated a lot of technical
advances, frequency hopping, use of data packets and error checking,
telemetry and even a useful "lost model beacon" transmitted by the
receiver. (Transmitters and receivers both transmit and receive.)

A model submariner in the US (Tim Senecal) noted that this technology
worked well for subs at 433Mhz.

We saw that the 458/459 MHz band was available for air and surface
modellers in the UK. The openLRS software could be set to this
frequency. We checked with the BMFA that this was legal. OpenLRS
equipment is easily and cheaply available from a number of suppliers
(including Hobbyking)

And so that is where we stand at the moment. The equipment seems to work
reliably and well. So far we have only tested it with 2 people using it
simultaneously. So maybe model subs have a future in the UK!

Hermann wrote:Hi David,
the 433MHz band is a band for so called ISM Equipment (Industrial, Scientific and Medical) and in this scope also radio control with so called low power devices with a maximum transmitting power of 10mW are still legal, so remote car key control may be used and other applications for closer distances. But in former days 500mW transmitting power was permitted for model Radio control and that was cancelled. I think 10mW would be too low in practice for submarine purpose.

Maybe you will find a little more 40MHz equipment on the German ebay platform but I am not so sure.

And as I know obviously most of the German model companies do not have 40MHz RC sets in their program any more.
Even worse - the two biggest companies, Graupner and Robbe, had got severe financial difficulties. Graupner went bankrupt about one or two years ago and was bought eventually by that Korean Company SC that made the RC sets for Graupner. Today Graupner is not the same as it was as the equipment for model production had to be sold. And actually Robbe has also difficulties. Perhaps the withdrawal of the model submarine kits by Robbe was a first indicator for upcoming financial problems. We must see how the story will go on.

The key problem in my opinion is the lack of young people following us "old men" in our Hobby - so one day   the market will become too small for several big model companies. In my youth that is more than 40 years ago modelling was of very great interest among my friends at School, our favorite literature in the breaks were the catalogues of Graupner, Robbe, Hegi, Engel, AeroNaut ..... And in every mid sized town you could find a model shop or at least a toy shop with a model department. And today?  

Kind regards
Klaus-Dieter

During my first look around I thought it was also prohibited in Belgium....so chapter closed. But this 433MHz stuff kept running in the background of my CPU. So I have made some inquiries concerning the Belgian allowable broadcasting frequencies. It's allowed to broadcast in the 433 MHz but with a max power of 10mW. Same as in GER.

So I asked Tim (tsenecal) if he was still running his 433MHz system with the power of the TX at 6mW output as in the beginning and if he had any problems with it.
If so this could open some opportunities for me.

He made some test and bought some equipment to give me a proper answer (And what an Answer I got).
You can find it here:

http://www.subpirates.com/showthread.php?5173-OpenLRS-433mhz-RX-and-TX-modules-what-it-is-where-to-get-it/page3
From post 29 onwards

So the system works properly below 10mW, so it can be used here too.

Thanks again Tim.


Grtz,
Bart

That's very good news!

Let us know how you get on.

David

david f wrote:That's very good news!

Let us know how you get on.

David

I will do David.
Grtz,
Bart

guys,

i have posted a couple replies over on subpirates on some new 433mhz stuff i have been playing with. nothing earth-shattering, and when i finally get a chance to really play with them (local boat club is having its annual regatta in a week) i will post "reviews" of the new hardware here, subpirates, and subcommittee.

starting with post #5 on this link:
http://www.subpirates.com/showthread.php?5255-Yet-another-Transmitter...&p=53176#post53176

and a new thread:
http://www.subpirates.com/showthread.php?5256-Yet-another-another-Transmitter....

I'm in the process of buying an secondhand Futaba T9CP TX with a 35Mhz and a 2.4Ghz module, nothing more, no RX.

The guy wants 90 GBP (140 USD) for it. Is this fair and square?

I have no idea I haven’t been into this for a very long time.

Thks
Grtz,
Bart

Bart, $140 us is more than fare for that TX with two modules.

I sold two for $200 each with 75mhz synthesized modules 5 months ago.

Ok thks for the feedback Tim.

Grtz,
Bart

First step made...picked up the TX Futaba T9CP today.
Next up is ordering the HK parts.

Grtz,
Bart

Hi All
May I ask for assistance with the 433 Tx module (below)



The socket (indicated) plugs into the back of the Transmitter but what signals are the five pins for?

I have a five pin header plug ready for wiring into my Home built TX but have only three leads to connect - positive,negative and PPM stream. Does an over-the-counter TX have only three pins or does it utilise all five pins?

As yet I have not opened the TX case for the programming lead cutout until I have it working on 433, it may be that the pins are marked on the PCB

Regards
John

Hi John,

I have just opened up the TX module I used, to have a look, and edited and added to this post which seems the most relevant for you:

https://www.theassociationofmodelsubmariners.com/t1553-using-an-old-tx-with-458mhz-openlrs#9563

All the Orange modules I've seen have helpful printing on the pcb.

David

Hi David

Cheers for the pin connection info, progress can now continue with the build.

Camera on charge for another interim shot....

John

guys, i have this image, from a long time ago, picked it up while building my own scratchbuilt transmitter...



please note, even though it says 9.6v, i have used as little as 7.4v, and as much as 12.4v