Gilbert Park devises a low-cost solution to receive weatherfax information using a portable radio, an aerial and a tablet device…
When offshore, the ability to receive weather forecasts when there is no phone or VHF reception is crucial as it gives you the time to avoid or prepare for a storm. There are many ways of doing this. Satellite internet access is becoming increasingly common, but the equipment and running costs remain high.
Shortwave radio is another possibility, but again the equipment costs are high, there are a limited number of sets available and a license is needed to use one. On the positive side, though, sending and receiving information is free.
I am planning a trip that will take me offshore for four days when I do the practical for my RYA Ocean Yachtmaster. Hiring a satellite phone was one option but to hire one with a charger, receive it and pay for the data then send it back would cost at least £100-200.
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I already have a satellite tracker (SPOT X) that will let me stay in touch with my shore contacts as it can send and receive SMS messages inexpensively. I started looking at other alternatives.
It took me almost a year (it was a great lockdown project) to develop a system that I feel is reliable enough to use safely for this trip. It uses freely available data from Navtex (Navigational Text Messages), synoptic weather charts from Fleet Weather in Northwood and Deutscher Wetterdienst (DWD, the German Weather Service) as well as Radioteletype (RTTY) Weather forecasts also from DWD (in English and German).
There are three parts to the system: the receiver, the aerial and the software transcription of the information received.
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Satellite tracker/messengers are popular in many forms of watersports
1. The receiver
The receiver is a portable radio that has short wave bands along with the ability to receive upper side band (USB). There is usually a button labelled SSB (single side band) to select this. Some shortwave (SW) radios do not allow USB reception and will not work well, if at all.
A SW radio wave has a carrier frequency and also a band of frequencies higher or lower than the carrier frequency. The frequencies above and below the carrier wave are generated by the voice or data transmitted and their height is the signal (amplitude modulation – AM).
As the upper and lower frequencies (band) are mirror images of each other, only one is needed. Similarly, the carrier frequency is unnecessary. When the SSB mode is used the radio will add back in the carrier wave. Losing these frequencies reduces the amount of power needed to transmit messages and reduces overcrowding in the bandwidth.
I bought a Tecsun PL880 that was reduced to £180. Among other features it has a USB and LSB as well as a huge number of memory slots, a fixed level audio output and an aerial socket – and it works well.
The Lowe HF150 reciever isn’t in production any more but can still be found second-hand on various websites
Having read some reviews I also bought a Lowe HF150 battery operated receiver for £90 and it works brilliantly. It lacks the value after the decimal point when tuning, but this is not a great loss as you can fine tune by ear or using the app (see later).
I have also tried a NASA Target HF3, but didn’t find it as sensitive as the Tecsun, but still very usable. Neither the Lowe nor the NASA receiver are still in production, but can be sourced from various internet sites selling used equipment.
If you just want to receive RTTY information then NASA used to make an inexpensive receiver. This has now been discontinued, but still appears on various websites. You only need one or other of the Tecsun, Lowe or NASA receivers.
The SPOT Gen4 GPS messenger
Satellite tracking
SPOT uses the commercial SPOT satellite network to transmit your location and status. Among the current tracking/messenger devices to use it is the Globalstar SPOT Gen4, which costs around £115.
Popular with outdoor enthusiasts – kayakers, paddleboarders and climbers – it has four functions:
- It can send messages to family and friends in the event of a non-life threatening emergency.
- SPOTcastingSM allows others to follow your progress in real time, sending a position every 10 minutes for 24 hours or until SPOT is powered off.
- The check in function allows you to tell others you’re well and let them know your location
- It can alert the GEOS Emergency Centre in a life threatening emergency. The Centre can then alert the local Emergency services wherever you are. You will be kept informed of developments by text message. Importantly, it is not part of the Global Maritime Distress and Safety System (GMDSS) so an emergency position-indicating radio beacon (EPIRB) or other device should be on board.
2. The aerial
The next part is the aerial. The Tecsun comes with a built-in telescopic aerial. This works surprisingly well and enables nearly all of the weather stations to be received on one frequency or another. I did find the problem with this was interference that meant poor quality images and data was received.
My next ploy was to buy an ‘active’ aerial that amplifies the signal. This was an Improvement, but not a great one.
After that I went for the simple solution – a 20m length of insulated wire strung outside initially along guttering and later up the mast. This was connected into a socket on the side of the Tecsun with a 2-pin 3.5mm jack plug, connecting the aerial to the centre and another wire to the earthing connection of the plug. The earth connection made a vast improvement.
At home it was a crocodile clip onto a radiator (so long as you have copper, not plastic, piping) – in the boat just a wire over the side works.
To try and reduce interference at home I used a coaxial cable from the receiver to the aerial outside. I sought advice about this from various experts and they suggested I also added a 9:1 Balun. The theory about this device is complex and I found it made little or no difference compared to earthing the receiver.
The other thing that made a big difference was switching off various electrical items, such as the fridge on the boat and a phone charger that caused significant interference. I haven’t tried it underway yet, only at anchor, at various sites in the UK, but alternators and the like can also cause interference.
3. Data display
Once you have the signal the next part is to get the data to display, in my case on an Android tablet. You don’t actually need to physically connect the receiver to the tablet – the audio signal from the receiver can be picked up by the microphone in the tablet.
There are clear disadvantages to this, such as interference and having to listen to the noise. It’s better to connect using a cable. The output from the radio is usually a two or three pole jack plug while the input to a tablet is a four pole jack plug.
Plugging a double ended three pole connecting lead into the tablet doesn’t work (I tried it) you have to use a four pole jack splitter lead that has separate sockets for a microphone and headset.
NAVTEX will work from 200-400 miles offshore and besides weather information gives a lot of other information such as navigational hazards, subfacts and gunfacts. Even cruising inshore it provides a whole host of information that is very useful and supplements the Maritime Safety Information broadcasts. Notice the waterfall for tuning.
Software
Once into the tablet the data has to be translated. For this I used three software packages from Wolphi Solutions on Google Play Store:
Droid Navtex (£8.99) enables you to receive both International and national Navtex broadcasts and stores them in a searchable database. It’s very easy to use and the only problem I’ve found with it is that the auto-rotate feature on my tablet doesn’t work. It has an alarm clock function which, when paired with that feature on my Tecsun, lets me receive broadcasts when I am asleep without leaving the equipment fully on flattening the batteries. There is no print function with the app, but there is a search function available for all the data (by station or type). If you do want to print it out then a screen shot would solve the problem. When I make my trip I will be able (I hope) to receive the French, Spanish, Italian and Maltese stations all broadcasting in English at various times during my voyage.
HF Weather Fax (£8.99) allows me to receive weather faxes as synoptic charts from Northwood and DWD. These include the Mediterranean, North Atlantic and give forecast charts for up to 48hr. Using this piece of software does involve a learning curve. The software can be configured to synchronise with a start signal and save the chart in the pictures file, from where it can be printed. There are also adjusters for slant correction and if the start column is in the wrong place. Finally, there is the black and white slider that lets you have white on black or vice versa as well as adjusting the contrast. There is no switching on or off facility. The fax is saved as a picture so can be viewed or printed easily.
DroidRTTY (£4.99) allows a text weather forecast to be received from DWD for up to five days in advance. As well as the Mediterranean it gives forecasts for many other areas. As with DroidNavtex there is no print function, but a screenshot solves this problem.
his is an example of the type of weather forecast from DWD sent using Radioteletext (RTTY). Notice at the bottom there is a waterfall display of the tuning – it makes fine tuning into the signal straightforward
A synoptic chart from Northwood. Note the line (sometimes slanting) a little way in from the left. This can be adjusted easily in the Weather Fax software so the whole chart is shown properly
Northwood and DWD show many different types of forecast at different times of the day. This schedule from DWD – received on Weather Fax – shows both the type and time of forecast and frequencies in use
Tuning in to offshore weather forecasts
Tuning in the radio for the transmission needs a bit of care. Firstly, the best reception is usually found 1-1.5kHz below the stated frequency. You can tune using sound or, better still, all of the apps have a display of the signal strength as a waterfall or analogue display.
Once you have found the best frequency you should save it to the memory of the receiver and make a note of it. In the table (left) I have listed the frequencies that are published and work for my ‘rig’. They may be different for your set up. Those frequencies that don’t have a working frequency I haven’t been able to receive.
A two day weather forecast received on Weather Fax from DWD
What are the alternatives for receiving offshore weather forecasts?
There are alternatives to my simple, inexpensive solution. You could buy a Navtex receiver and aerial. Simple to install, you can even get a Bluetooth version (that works well) for about £130 so you don’t need to fit another instrument at the helm. If you are not going far offshore this may be all you need (the range is about 250-400 miles).
A further alternative is to buy a shortwave receiver (available for £25-30 from eBay) and link it up to your laptop. I did buy one of these but haven’t used it as I decided that a tablet (that I would have out anyway) and radio was my preferred way of going, rather than a receiver and a laptop, which I would find cumbersome on a small boat.
There are also other apps for tablets but the Wolphi ones have the highest ratings and I know from personal experience the developer is only too happy to help with any problems.
I see there has been enthusiasm for learning new and honing old skills during the Covid Pandemic. For me, aside from celestial navigation (see PBO June 2021), it’s deciphering synoptic charts in the areas I am interested in on a daily basis.
Dreaming of sunny days in my boat, secure in the knowledge that gales are not expected, gives me something to smile about.
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This feature appeared in the April 2022 edition of Practical Boat Owner. For more articles like this, including DIY, money-saving advice, great boat projects, expert tips and ways to improve your boat’s performance, take out a magazine subscription to Britain’s best-selling boating magazine.
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