Category Archives: Electronics

Practical Range for HF Weatherfax Reception

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I spent a bit of time rigging a long-wire antenna at home today to see what sort of range is practical for HF Weatherfax reception:

  • The antenna is now about 20 metres long, made entirely from inexpensive hookup wire.
  • The antenna is L-shaped, with one leg oriented East-West and the other North-South.
  • I’ve also connected an earth wire to a copper stake just outside my window, significantly reducing background noise.

To my delight the little Degen DE-1103 receiver pulled in the Wellington MetService broadcast on two of the four frequencies! That’s 1,000 nautical miles! Local weatherfaxes from Charleville (WMC) are now clean and crisp.

HF Weatherfax received in Sydney from Wellington

HF Weather Fax Reception

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It hasn’t been really necessary on my last trip, being mostly within range of VHF weather forecasts, but getting offshore weather via HF WeatherFax has intrigued me.

If you’re carrying a notebook computer anyway, the only thing you need is an HF receiver with SSB (Single-Side Band) capability. Most people think megabucks when they hear “HF” and “SSB”, but a very inexpensive receiver will actually do the job. I bought a Degen DE1103 off E-Bay. You simply connect the output from the receiver to your notebook’s microphone input and then use one of the available software packages to decode the fax data received on the appropriate frequency at the given time! I use SEATTY from DXsoft, an amazing piece of software that literally does everything for you!

Receiving a fax using SEATTY

I was amazed at the ability of the little Degen DE1103 receiver (read some reviews here). Even at home, with the supplied 12 metre long wire antenna strung among trees, I can usually get quite clear fax reception. Out at Curlew Island one night, I strung the wire antenna from the forestay to the backstay, and found the receiver was overloaded with the sensitivity switched to “DX”. On “LO” I had perfect reception!

HF Weatherfax received with Degen DE1103 receiver and notebook running SeaTTY

VHF Interference from Autopilot

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I noticed in the web log stats that someone had searched for “VHF interference tiller pilot”. This reminded me that I had a problem which occurred soon after the new electrical panel was wired: whenever I turned on the autopilot, there was a constant buzzing interference audible on all VHF channels.

The source was as I had expected: an earthing problem. I used the Seatalk cable to connect to a NMEA multiplexer and the NMEA input to connect to my chartplotter, both of which were earthed, but the primary power input negative (earth) was not connected (d’oh!). The resulting high currents on the signal earths for Seatalk and NMEA caused RFI which was picked up by the VHF antenna.

Many years ago I built an audio (hi-fi) amplifier which had earth loops because of multiple return paths to earth – the AC mains hum was unbearable! Fortunately I remembered that lesson.

The best strategy is always to run all earths (and power supply grounds) to a single earthing point such as the main negative terminal on your electrical distribution panel.

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Freedom from the “Tyrrany of the Tiller”

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I have an ST4000+ wheelpilot on my 33ft Dick Carter sail boat. IMHO it is an essential piece of safety equipment when you are sailing shorthanded, or even just with a smaller crew (i.e. less than 4 people).

I recently had a challenging night offshore after splitting the mainsail in a squall (just after putting the 3rd reef in). Even though I had two crew, they were both too sea-sick to be of much use, and the autopilot steered perfectly under motor while I lashed the main to the boom and set the storm tri-sail.

The benefits in freeing you from the “Tyrrany of the Tiller” is obvious.

It is vitally important though that you:

  • fit a rudder angle sensor, otherwise the Autohelm performance will be mediocre at best, but probably next to useless;

  • select the location for the fluxgate compass very carefully to avoid magnetic and RF interference.

  • Getting it as close as posible to the keel will also minimise unecessary movement of the fluxgate, making the Autohelm more stable;

  • make sure all wiring is done professionally, cable joins are avoided as far as possible and cables are routed in dry areas (keep them out of the bilge if possible).

The Autohelm on Sunny Spells was pretty useless when I bought her, but after fixing the problems listed above, she now helms perfectly downwind for hours on end. I’ve had an 11 hour run downwind with poled out genoa and main by the lee without touching the autopilot controls (on wind-vane mode) other than accepting wind shift alarms.

The best $1000 you can spend!