Re: [Paddlewise] HF Internet

On Fri, Mar 5, 2010 at 6:55 PM, PeterO <rebyl_kayak_at_energysustained.com>wrote:

>
> I've recently come across HF internet, that is using shortwave radio to
> access the internet. http://www.winlink.org/ Makes me wonder how practical
> it would be to download a synoptic chart onto a handheld computer linked to
> a portable SW receiver. I'm not sure yet how its done, whether one needs an
> HF transmitter or whether hooking up to a shortwave receiver is enough?
>
> Does anyone have any experience in this area?
>

The biggest drawback to using HF radio for internet connections is the lack
of bandwidth. To simplify, bandwidth requires... wide bandwidths.... and HF
radio is limited in its frequencies (essentially 2mhz to 30mhz) so much that
no more than about 9600bps(if that!) is possible. You can improve that
somewhat by using compaction algorythms but the bandwidth is still nowhere
near "fast".

Then there are the comlpications caused by multipath, distance, phase
differences, etc. which further reduce throughput.

Weatherfax is, however, entirely possible using HF frequencies and most
modern weather services and coast guards use it. It's not new but it's
effective most of the time. But this is by no means a new technology.
Winlink is normally used for email and is pretty satisfactory for that but
attachments are still problematic because of the bandwidth limitations.

I used to use an ancient Zenith Z-181 laptop for weatherfax and morse
broadcasts when I was working on ships. It was valuable because I didn't
need to use paper... we could just receive a fax, look at it, print it if it
was pertinent and if not just wait for the next one. The problem with a
handheld will be getting the audio into the computer but there is no reason
you couldn't use an Iphone (or similar) or any netbook computer to do the
same things.

I recommend fax for weather and winlink for email.

Craig Jungers
Moses Lake, WA
www.nwkayaking.net
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