Portable Magic Morse Decoder

This is my take on a Morse decoder based on a 08M2.

It uses a NE567 to detect the Morse tones from the audio input of a radio receiver and converts it into ASCII characters and displays them on a AXE133Y OLED or serial terminal. It will operate from a 5v supply or 3 x AA battery pack.

This is the first part of a portable unit I am building to detect and display Morse audio and data telemetry from a Lost Model Locator based on a Hope RFM42 RF Module.

The document uploaded here contains the description, pretty pictures, circuit diagrams and the code for the 08M2 decoder and AXE133Y OLED.

Thanks go to to M Burnette who authored the magic morse code.

And the two PICAXE programs are seperatly available here.

srnet said:

This is my take on a Morse decoder based on a 08M2.
<...>
Thanks go to to M Burnette who authored the magic morse code.

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A very special Thank-You to srnet for posting his code; it is by evolving concepts and existing code bases that code evolution occurs... posting the new, evolved code is the most sincere method to 'give back' to the community. Great job, srnet.

- Ray

No problem.

The PCB for the decoder, which has the options for a regulator so it can be powered from a 12V wallwart or batteries, does work. Although I did make 2 mistakes.

One was to use the wrong pin on the programming socket, easy to solve with a wire bridge.

The other was a crossed track on the multiturn pot, I wanted to allow for an inline pin pot or an offset pin one and the autorouter did not pick it up the linking track. Neither did I when I checked the Gerbers. That problem was solved with a scalpel and a link.

The PCBs cost me £15 delivered which was well worth it if it was ever to be a working portable device, but that price was for 10 PCBs, which I am unlikley ever to use.

If anyone wants one there are a few to give away.

I had a chance to do some range testing with the Morse decoder today, I was comparing the reception of data packets using a Hope RFM42 transmitter and RFM31 receiver versus a RFM42 transmitting Morse audio at 60WPM (sends a 5 digit number in 2 seconds) and picked up the Morse with a cheap eBay UHF tranciever and the Magic morse decoder. All transmissions 1mW at 434Mhz.

Range Limit for data telemetry 25M
Range Limit for Morse audio 305M plus, I ran out of space over the park.

srnet said:

Range Limit for Morse audio 305M plus, I ran out of space over the park.

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Brilliant!



- Ray

Here is picture of the portable field unit, self contained, runs off 6 AA NiMh.

Its powered by a 28X2 running at 64Mhz, with the same code as the 08M2 version.

I am working on a much smaller version of the decoder, which will use a version of the lost model locator (28X2 based also) as the processing engine.

Whilst I ran out of space at 305M, I fell it would have carried on working a fair distance after that. If the weather stays nice, there is a nice long straight bit of road a few miles away which I should be better able to measure the limits of the Morse decode.

I think there is scope to increase the decode speed also, maybe up to 120WPM. I also intend to compare against the PC soundcard based decoders such as FLDigi.

just out of interest, where do you get 10 boards fabbed and delivered for £15? I would certainly have a use for that service.
Great project too. I have a couple of model rockets that I keep meaning to add some form of telemetry to. Anyway thanks for sharing the project

http://iteadstudio.com/store/index.php?main_page=index&cPath=19_20

You will find some pictures of the PCBs from ITeadstudio in the documents in this thread below, they are OK.

http://www.picaxeforum.co.uk/showthread.php?19549-RFM42-Lost-Model-Locator

@Srnet, super project. I guess that the quest for speed could well be slowed down to 16 - 20wpm for us mere mortals on the receive side and a allow a limited number of unequipped others to assist you in your search, but that is not to slight your project in any way. it is indeed hot to trot.

I too am interested in the iteadstudio.com boards, but have yet to get to grips with DesignSpark. Other than being on another computer that isn't on 24/7, appropriate libraries are a bit of a mystery to say the least. I perceive that a fairly minimalistic set would meet my needs and perhaps save me from my current wooded situation where there are so many options that my grey cell is totally swamped. Other than that, I did watch a good tutorial on how to get started.

I suspect that you had either prior experience or stripped away a lot of the noise to get a working set of libraries?

This is all tied up with a Lost Model Locator I built that puts out GPS information. The primary intention was always to transmit the GPS info as Morse numbers at about 15WPM, as this did not require any additional equipment to receive apart from an ear and a cheap UHF tranciever. I believed that Morse would by far offer the greatest search range, useful if your looking for someting lost, and this appears to be the case, data telemetry is very poor in comparison.

However not everyone can read Morse, and I thought it would also be handy to get a running display of how high and how far away my planes were in flight, hence the portable decoder. You can decode Morse through souncard software on a Netbook, but who want to carry a netbook around all the time ?

The transmitter now uses continuous PWM to output the Morse 'audio' tones, so a single delay parameter (the dit length) controls the Morse rate and already slows down to 15WPM for humans, and leaves 60WPM for psuedo telemetry decoded by a PICAXE.

I use Eagle PCB and get on with it OK. I was an Electronic Design Enginner is the days of Z80s and 6502s etc, but way back then PCB design was 2 sheets of polyester film, transfers and black crepe tape for tracks. Most of the devices in Eagle I have made myself, its just easier than finding the exact part matches in the Libraries.

I have shrunk the morse decoder quite a bit, but allowed for PIH components throughout. Just about to send the PCB off to ITeadstudio. The bits fit on a PCB 50mmx35mm, the charge for 10 of these boards delivered is just under £10.

How much of that distance increase do you reckon is down to the receiver being potentially more sensitive in the transceiver against the use or morse over serial? I'm interested in doing something similar for tracking lost hiking teams.

I have thought about that quite a bit, and the real answer is I dont know.

However I suspect a great deal of it is down to the extra sensitivity ot the UHF trancievers, they obviously use far more complex receiver circuitry. If you have ever taken a modern comms receiver to bits, you will note that the differerance in circuitry compared to a typical wireless module such as the Hope RFM31 is significant, as is the cost.

For long range location the lost model locator I did would be a better choice. It was designed to find a lost RC model using just a UHF tranciever as the location aid. You can get a direction using your body as a shield. The beacon tones change as you get nearer to the locator. As the frequency chosen was 434Mhz, there are plenty of readily available direction finding aerials, both ready made and DIY plans. From a suitable hilltop I was getting a direction reading from about 10KM away line of sight.

Not sure the Morse could be decoded automatically for a large enough distance for your application although at 15WPM you could read it by ear from a lot further away than the electronic decoding. The GPS capable Lost Model Locator PCB is about to be sent off, that uses a 28X2, and is about 25mm x 40mm. That is intended to strip out the GPS lat and long and transmit as Morse.

Lost hiking teams ? Teach them to navigate properly !!!!

(I am a Hillwalking trainer\assessor for Scoutleaders)

The non GPS lost model locator is here;

http://www.picaxeforum.co.uk/showthread.php?19549-RFM42-Lost-Model-Locator

Its similar to those fancy wildlife tracking systems, but at a fraction of the cost.

This is version 2 of the PCB for the Morse decoder.

After spending quite a while trying the Morse decoder for real, seeing how many errors the PICAXE produced during on air decoding, I came to the conclusion that the various options and enhancements suggested by the NE567 datasheet made little or no differance to the quality of the decoding. The 4069N filter line I had tried also mad little actual differance, particularly at 60WPM.

Hence a much simplified and smaller PCB, see attached.

The PCB is 50x50mm and uncludes a regulated supply. The odd looking bit at the top is a 18F26K22 based serial driver for an LCD, the whole unit (inc Morse decoder) can be mounted piggy back style to the rear of a LCD\OLED display. Or cut the unwanted bit off and use a standard OLED.

PCBs expected in about 10 daYS.

Ha ha small world, I'm a scout leader.

When I say lost its more like misplaced by less than a km, these aren't in the middle of nowhere style hikes. We run a couple of district competition hikes a year and despite requesting to the troops that they only enter competent walkers (we offer a training team with adult option) we without fail always get 1 team going off at a tangent. Although we have several manned bases and a roving vehicle all connected with CB's its sometimes a bit hard to track the team(s) down, meaning the checkpoint staff are left waiting as we don't close them until everyone is accounted for.

We've noticed that it always seems to be the same few troop(s) that get lost and so I was thinking that it might be feasible to slip a small magic black box into their emergency folder in a hope that either a base or the vehicle at one point would be close enough. I was thinking that a GPS module sending in morse would be ideal, but your simple tone idea seems like it could work as well and potentially quite a bit cheaper too.

obroni said:

Ha ha small world, I'm a scout leader.

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Indeed, very small .

I recall that some years back we used to run a County trophy, a sort of navigation, incident, expedition activity in the Beacons.

There was one team that we relegated to a low level walk, all they had to do was follow a path along a river and turn left when they reached a canal.

You know what they actually did.

obroni said:

We've noticed that it always seems to be the same few troop(s) that get lost and so I was thinking that it might be feasible to slip a small magic black box into their emergency folder in a hope that either a base or the vehicle at one point would be close enough. I was thinking that a GPS module sending in morse would be ideal

Click to expand...

Well, there is no harm in having fun trying.

Its not something I would rely on, but you could build a transmitter and just try the locator mode.

The Lost Model Locator can transmit on any frequency from about 240Mhz to 930Mhz, all it needs is a PICAXE symbol change. So you could set the transmitter to run on the frequency used by the very cheap 'walkie talkie' type radios you can buy in Lidl etc.

So at least, and for not a lot of money, you would have a treasure hunting night game.

Thats actally a pretty good idea for an evening.....thanks

obroni said:

Thats actally a pretty good idea for an evening.....thanks

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I do have trouble persuading people that the locator beacon works with just a single (and cheap) receiver. The beacon tones are sent out as a sequence of tones, they fall in power as they rise in frequency. Thus as you get closer to the hidden beacon you hear more of the higher frequency tones. So by walking in one direction you can tell if you are getting closer or further away. All you then need is a logical plan. If the receiver has a removeable aerial (most UHF tranceivers do) then if you remove it it desensitises the receiver considerably, and you can use the tones to locate the hidden beacon to within 5M or so.

I must admit I have tried "fox hunting" with 2 PMR radios and it was a complete failure. I think the two radios must have been about 300M apart and I tried both body shielding and a piece of laminated tinfoil. I couldn't get the signal strength to drop no matter, maybe the radios were two powerful for the range I was trying.

I might get hold of a transmitter and give it a test. Just out of interest, where did you source the RFM42 in the uk?

QuasarUK have them, Farnell have them.

The RFM22, the combined receiver and transmitter can be found on eBay.

Body fade does work, but you really need a adjustable squelch, you adjust it such that as you turn around the signal just breaks through, you can get down to about a 45degree arc that way. Do it from two locations a few hundread metres apart.

It will be difficult with a contant power output transmitter to use body fade (without squelch) although with the decending power tones put out by the lost model locator, you can hear them come in and out as you turn around.

I did build and try the well known 'Handi Finder' and it does work, especially if you leave the transmitter carrier on (which wastes a lot of power of course) but its another bit of kit to be lugging about.

I have a 432Mhz/70cm 5 element ZL special antenna, which gives a good direction find from a long distance, but again bulky to be carrying around.

One thing I will try in future is some sort of collapsible 432Mhz beam antenna, the elements are only 35cm long so it ought to be possible to fit an compact packing high gain antenna in a bit of 2" plastic plumming pipe or similar.

Any inspiration here perhaps?

http://www.sotabeams.co.uk/SB270.htm

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Looks worthwhile, thanks.

The boom would have to be cut down of course, a 1M tube is way to big.

I have one of the poles for the mast already and keep it in the car, its part of my 'rescue plane from tree' kit.

I have a Carbon take a part pole too, which is stronger and does not rely on friction between the sections to stay up.