Dockhead,
Don't have the time to go into details at the moment, but have enough time to definitively answer your questions about WeFax chart broadcasts and ways to receive them...and I addressed the various ways to receive wefax (and other offshore/hi-seas weather) in a thread here last summer (see below for link)....
Quote:
Originally Posted by Dockhead
The fourth approach might be to use a black box weatherfax receiver -- Furuno make one, for example. This would keep the radio free for other things. How long does it take to receive a weatherfax broadcast?
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1) A typical weather chart broadcast takes about 8 minutes...depending on the size of the chart, it varies a bit, from 6 minutes to as much as 10 minutes...
But, figure about 8 minutes....
{BTW, just a fun fact....facsimile is the oldest form of "image" communication....the patents date back to 1843...yes that's the 19th Century!!! And, first
commercial "telefax"
service started in 1865!!!
And, radiofax dates back to the 1920's/30's.....
Modern radiofax/wefax is a robust form of one-way
communications...and with modern receivers, it still works great!!!
Oh, and further according to the 2012
survey by the
WMO/jcomm Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology, HF WeFax is used my a majority of
commercial ocean-going vessels daily and will continue to be used by them daily, for at least the next decade....
So, HF wefax isn't going anywhere, any time soon!!!}
If you look at the broadcast schedules you'll see about 10 - 13 minutes between chart transmissions, the two that I use regularly, are USCG wefax broadcasts from Boston and
New Orleans...
Boston Radiofax Schedule with Links
New Orleans Radiofax Schedule with Links
2) As for a stand-alone wefax receiver, this is the approach that I used starting in the 1970's and still use today....
And, is still the preferred way for many professional commercial mariners...
Although nowadays, some like the idea of a standalone "black box" connected to a laptop, etc....but this adds the issue of a "laptop" now being a necessity in order to "get weather", and if you're going to do that, why not simply use your HF transceiver(s) for the receiver, or another HF receiver, and save the $$$???
It is a pricey way to go....but VERY effective and reliable...
A new Furuno FAX-408 will set you back about $2000....(I know, I bought one a few years ago, when my Alden MarineFaxIV's automatic timer would no longer function...it's nice to program it to turn-on and receive just the charts that you want, whether you're on-board or not, or on-watch, or asleep, etc...and I REALLY like my Furuno FAX-408...)
My FAX-408, as well as my old Alden can be seen in these photos of my Nav Station...
Nav Station
3) As for the "advantage" of receiving wefax charts (synoptic weather charts and forecasts prepared by seasoned maritime meteorologists) via an e-mail (saildocs) thru a PACTOR-modem radio link, rather than received directly from the USCG, UK Met/GYA, etc. etc..
If using Sailmail, the saildocs e-mail wouldn't take nearly as long as the open WeFax
transmission takes....about a minute or so, per chart ....
But, this DOES use up some of your daily 14 minutes (90 minutes/week) of Sailmail access....
(I've not heard of many that choose to use up their precious Sailmail minutes by getting wefax charts this way....unless they're having reception problems from the broadcasts and/or missed the chart they wanted!!)
The only advantage to using the PACTOR-connection (thru Sailmail, etc.) is that the chart is clean / clear of any "static"...as the PACTOR error correction makes sure that there are no errors received....so noise / static is removed...
BUT...
But, this does NOT mean that the PACTOR connection is better....just that it can produce a clean/clear chart...
Since the Sailmail stations are typically 150 watts PEP (50-100 watts average in PACTOR-II and PACTOR-III), vs. the USCG wefax transmitters being 4000 watts average, and UK, etc. stations as much as 10,000 watts average....
http://www.nws.noaa.gov/om/marine/rfax.pdf
And, further since the USCG, Aus, UK, SA,
Japan, etc. etc. wefax
transmission antennas are designed to provide gain on their freqs, and point their signals to the areas they're sending weather forecasts for, vs. the unknown antennas of Sailmail stations......and even worse the totally unpredictable antennas of WINLINK stations (possibly wide-band, zero-gain)....
In these cases, the real S/N "advantage" of PACTOR (theoretically as much as 15 -16db, typically 8-10db) is easily compensated for by the more powerful transmitters and better antennas of these HF WeFax transmission facilities...
4) Now last summer I spent some time writing a rather detailed
posting on the SSCA Disc boards about "how to get weather" when
offshore.....this was prompted by a specific question from an SSCA poster....
And then when I decided to re-post this information here I was rightly taken to task for using the word "accurate" in my
posting.....but since I included some very brief opinion, I found myself flamed for voicing such heresy as stating that if still works well for many/most commercial ocean vessels (and I've been successfully using it for decades), then this is what I primarily recommend.....
In any case, that is all water-under-the-bridge....
But, you can read what I wrote there about WeFax, etc. here....
http://www.cruisersforum.com/forums/...ea-103555.html
I hope this helps clarify things a bit....
Fair winds.
John
s/v Annie Laurie