Weatherfax, ICOM-725, JVComm and a USB connector.

[whipper_snapper]

I agree he is apparently receiving and it is as you say out of synch but the sprocket holes are in fact the word 'demo' printed at intervals over the page because it is an unregistered trial version of JVComms. The help files should say how to get in synch and as you say it will take a few goes to get it right.

I hope I am wrong, but I am afraid that I see no evidence at all of a signal in the screen grab!


My suggestion is to turn off the computer for now. Until you are clearly hearing the fax, there is little point in asking the computer to decode it. You should be hearing a rhythmic series of fast beats, they will change in pitch as you tune up and down. If reception is poor it sounds 'mushy' but should still be readable. Until you are hearing something that is clealry not noise, you are wasting your time with the computer!

Once you have the signal, connect the computer. If you immediately loose the signal you have a problem with computer noise. Otherwise start your fax program and fiddle the tuning to get the peaks in the right place.


This is what it should sound like:
http://www.trifid-nebula.de/hffax/fax.ra


The initial clear tones are the synching signals, most of the time you hear that rhythmic crackling.

 

[whipper_snapper]

The NOAA Low Earth Orbit (LEO) satellites do polar orbits (south to north) about once every 93 minutes and rely on the rotation of the earth to make sure that on its next pass, the earth will have rotated and therefore a different area is being scanned. There is always an overhead pass at least once or more in any 24 hour period. I am not currently up to speed as to which NOAA LEO birds are flying and talking?

See here:

http://www.oso.noaa.gov/history/first-launched.htm

'Similar' 137MHz transceivers (not Icom as in the YouTube video) are for sale on e-Bay for about £86 from Hong Kong or other ham rado shops or you can purchase a dedicated 137MHz FM WeFax receiver which is what I would do personally. The 137MHz FM band is not subject to the same vagaries as is the HF SSB bands and far 'cleaner' and easier to work with in terms of signal reception.

I receive these every day, you can see them here http://azizi.ilri.cgiar.org/wx/

I see there are some dropouts, not sure why - I must investigate - I have left the system running without any human intervention for months.


BUT the information COMPLETELY different from the HF fax broadcasts. They are not forecasts, there is no pressure information. They are simply a view of the ground beneath the satellite. So possibly useful on a boat to see what is happening around you, but not at a weather forecast!

 

[Bilgediver]

This all sounds very reassuring - and thank you everyone, I am extremely grateul for all the help and support.

I think I can extend my cable to move my laptop away from the radio, Ill give this a go next chance I get.

Mark

It should make a big difference.... You may not get a clear picture initially due to sloping if the time bases are not matched. We can then help you correct your JV time base using the tools icon.

Basically you download a fax or part of a fax and then stop it and using tools trace a line over the fax image following the line of the fax. then a bit of clicking will generate a correction.

This may have to be done two or three times to get an absolute vertical image but once done should be final.

The other important thing is to get the signal image to the tallest thinnest tower you can with a minimal low skirt and lined with the right hand marker.
This will give clean clear faxes.

 

[smartcom]

Hi,
I'm a bit confused as to whether you are trying to receive weatherfax (i.e. weather maps giving a synopsis and forecast) or weather satellite images (i.e. photos from the satellite as it passes overhead). The 137MHz is for satellite images whereas a list of weatherfax frequencies from the UK and Germany is given here http://www.yachtcom.info/Weather.htm, for example.

When tuning in for weatherfax, don't forget to knock about 2kHz off the listed frequency - I'm sure the radio hams will explain why better than I can. I've only done weather satellite with a dedicated receiver, so don't know if you need to for this.

In either case, before playing with JVFax, just listen to the radio to familiarise yourself with the transmission sound, and adjust your tuning and other radio settings to get a good, crisp sound.

Yes, interference can be a problem, e.g. with flourescent lights, laptop power supplies or engine electrics, but don't worry about that until you are getting some sort of image in the first place.

I think you'll find Mike Harris has written a useful book on weatherfax.
Tim

 

[Obi]

Thanks, so there is plenty here for me to work with.

I cant help thinking that I might want to wait until Im out of Portsmouth Harbour though.

Note - Its weatherfax I want to get working.

Mark