Radio Communications

Most cruising boats are equipped with a Pactor Modem. This is a device that interfaces between a PC and a single sideband radio (SSB) to facilitate email, downloads of weather data, etc.

Britannia is not equipped with a Pactor. Rather, I've been using a program called RMS Express that skips the Pactor hardware and just uses a PC soundcard device to interface with the SSB. I have been curious to see how and if this was going to work as we get farther and farther away from North America (where most of the recieving stations are located). As we're now about three days away from making landfall in the Marquesas, I feel like I can comment with some authority on the efficacy of RMS Express and Winmor:

When we were on the North American coast, we could connect 24/7 almost without exception. Connection speeds ranged from between 250 bytes/min to about 5K bpm, but averaged around 1K. Boats we've talked to using Pactors report connection speeds of 3K bpm as a more typical average. An email such as this one will average maybe 1500 bytes, so connection speeds aren't a big issue for us (what do we have to do that we can't wait a minute and a half for an email?).

I have been afraid that as we've gotten away from the US, we'd lose connectivity, and in fact we have to a degree. The first 1000 miles offshore, I noticed almost no difference in our ability to connect. In fact, some stations were coming in stronger since we didn't have a land barrier. Between 1500 and 2000 miles offshore, things have gotten a bit more sporatic. I can no longer connect at will, and connection speeds have dropped to an average of closer to 500 bpm.

However, I've discovered that if I pay attention to propogation (rather than just logging on whenever I want) I can still connect fairly reliably. I've been booting up at sunset, and the night before last had a blazing connection at 3K bpm. Unusual, but fun to see.

There are two weather downloads that we get (or would like to get). One is GRIB files, and the other is weather faxes. GRIB files vary in size, but to get an accurate picture of where we are, I usually request a file that's about 3.5K. That's still a reasonable download, but I'm starting to be unwilling to download GRIBs with abandon. Weather faxes can be up to 30K and are out of the question (plus, they can be downloaded without email straight through the soundcard on the PC).

Boats next to us with Pactors are still getting connection speeds of better than 1K bpm, however they're reporting that they have to start paying attention to propogation times as well.

We'll see how things pan out as we get farther west and farther south. We're close to the end of our big passage, but still have many thousands of miles to go before the stations in Austrailia or New Zealand start to become closer than North America.

Bottom line:

If I could afford a Pactor, I'd have gotten one - it'd be nice. But, so far RMS Express remains functional, and not having the Pactor hasn't hurt too badly. Stay tuned.