This modem is able to receive and transmit HF-Fax images, traditionally used for weather reports. More technical information is available on the wikipedia article Radiofax. The focus is made on black-and-white images, color mode is still experimental. When entering any Wefax mode, the reception window opens, and optionally the transmit window.
This option, allows to closed by default, the transmission window, when entering Wefax mode. In embedded mode, this means that the entire window is used for reception Most common mode.
In floating mode, this implies that the transmission window is not opened by default. However, it is always possible to manually open or close the transmission window at any time. Each time an image is saved, it is possible to log this event, with the frequency and reception time, to the Adif file. This option is disabled by default. The default frequency is Hz.
However, it is possible to adjust for example to Hz for Deutsche Wetter Dienst. It non-continuous Non non-stop reception mode, an image is automatically saved when it has more than this number of lines Default lines. Once this number of rows is reached, the image is saved and a new image is read with the same parameters. This feature has two applications:. Additionally, they can be saved manually, at any time, using the button 'Save'.
Fax images are monochromes and are saved as such by default. However, it is possible to bypass this parameter and save them as color RGB images. To open the transmit window, you must of course select one of the two Wefax modems, and then right-click on the transmit blue window:. Then, you must open an image file using the button "Load".
The image is then displayed, for example like that:. During transmission, image reception is paused. The window will display each image line as it is sent. Please be patient, this may take a while. You might note that FlDigi status line displays the estimation transmit time, and the current stage Start, phasing etc To enter reception mode, one can click the "View" menu tab, and select "Weather Fax Image".
At this time, the reception window opens. A big blank picture is visible, this is where the received image will be displayed. Several controls are available:.Follow our tweets! This short tutorial shows you how to do this using your Macintosh computer. Five USGC stations transmit weather fax at various times throughout the day. Take a look at the HF Weather Fax Schedules further down in this document for time and frequency information.
Weather satellite image re-transmitted over HF This is a weather satellite image that was re-transmitted over shortwave radio. It's much easier to receive these re-transmissions than it is to directly receive the image from the satellite. How Weather Fax is transmitted over HF radio A fax is transmitted line by line, typically at a rate of lines per minute, or half a second per line.
For example, to send a weather chart, you would start in the upper left corner. You would send the value of that pixel dotblack, white, or perhaps a shade of gray. Then you would move over one pixel to the right, and send that pixel, and so on, until you reach the edge of the chart.
Then you'd move all the way back to the left edge, and move down slightly, one line, and repeat the process. Each pixel is converted into a certain audio frequency or tone. By convention, a tone of Hz represents black, Hz represents white, and frequencies in-between represent shades of gray. So if you listen to a fax transmission, you'll hear the different tones as each pixel is present. For example, listen to a chart with mostly white background being sent.
You'll hear mostl the high pitch Hz, and some lower Hz blips as each black pixel is sent. When a horizontal line is sent, you'll hear a long half second burst of Hz, since the line is all black.
A note for the purists: OK, The above was a simplification. In reality, the transmitting station frequency modulates the carrier.
That is, when a black pixel is transmitted, the carrier shifts down Hz. When a white pixel is transmitted, the carrier shifts up Hz. For a medium gray pixel, it stays on the assigned frequency. This is how most fax transmissions are actually made.
But, since we're tuning it in with a SSB receiver, it sounds to us as if the station is transmitting a variable frequency audio tone. Actually, the two processes are identical. But, this accounts for the confusion regarding what frequency to tune the radio to in order to properly decode the fax transmission.
Different stations list their frequency in different ways. It is important to remember that what's really important is tuning the radio so that a black pixel produces a Hz tone, and a white pixel produces a Hz tone. How to receive weather fax images In order to receive and decode fax images, you'll need an appropriate radio and antenna, and a cable to connect the audio output of the radio into your Macintosh computer's microphone jack.
You'll also need appropriate software to display the images - such as MultiMode. MultiMode decodes weather fax and satellite images on your Macintosh, without the need for extra hardware.
The only requirements of the radio are that it tunes the frequency ranges of interest. A general purpose communications receiver tuning MHz is ideal, SSB marine radios may also be used, if they can receive the frequency bands of interest. The radio must be able to tune in USB upper sideband mode. Inexpensive portable radios are not as satisfactory, although higher-end units can work well. The radio must be able to tune in small steps 10 Hzor have some sort of a fine tune adjustment.
A good antenna is a must. It should be located away from the computer, to minimize any pickup of radio interference.While I suppose it could be a case of weak Google-fu, my searches for info on how to decode weather facsimiles off of the shortwave turns up a whole bunch of not much.
With that in mind, here is my effort to make this seemingly daunting process a little easier to wrap your head around. In reality, this is a nearly 90 year old technology. People were doing this back in the early days of radio with tube powered equipment and lord only knows what for a printer. A radio. Yes its an obvious requirement, but you will need a radio capable of receiving upper sideband USB.
Since these signals are transmitted on frequencies not allocated to international broadcasting, it would be best if the receiver is capable of listening in on the entire HF band, and not just shortwave broadcasters.
A software defined radio will be a BIG help, but its not necessary. A computer.
Using HRD/DM780 for receiving weatherfax (HF-FAX)?
Decoding software. Just to keep things simple though, this tutorial will only focus on fldigi. Audio cable. Configuration of VAC is a little beyond the scope of this tutorial, but there are a lot of other VAC resources out there if you have problems. Guide to Weather Fax Frequencies. This is a comprehensive guide to all known weather fax transmitters around the world, and is very helpful when it comes to finding weather fax frequencies.
The actual connection can be as simple as running a cable from the headphone jack of the radio to the microphone input of the computer, but keep in mind you might need a stereo to mono adapter to make it all work. Your mileage may vary. The only difference between the two that I know of is that the other standard gives you smaller maps, so stick with IOC for now. The bottom one is a view of the signal as it arrives, and is where you can make fine adjustments to the tuning.
Now, take a look at the guide to wefax frequencies and find a station relatively close to you. All should work though, just choose your frequency based upon the time of day. Without getting into the nitty gritty details of radio waves and sidebands work although that might make a good future blog entryjust remember to aim low.
For example, if we are trying to tune into a fax station onyou will want to enter in something like into your radio and start tuning around.HF Fax uses the same principle, but instead of squirting the tones down a phone line we modulate them onto an HF carrier.
The charts are still transmitted from a number of locations around the world, using very high power 5 to 20 KW HF stations, so reception is easy even with a modest antenna. You can use one of the online KiwiSDR to display the maps, this allows you to select the FAX overlay option in the top right-hand box, then region and download the image. FLdigi can also be used to display the images on your screen. Using the schedule of transmissions tune your HF radio to The transmission schedule is quite extensive, so you never have to wait long to resolve an image.
I am getting a series of weather maps as. I have decoded in the Kiwi, but its work in progress for the decoder. Thanks, I suspected as much. Your email address will not be published. To prove you are a human, please solve the following This site uses Akismet to reduce spam. Learn how your comment data is processed. Dave M0TAZ.
Weather Fax (HF-Fax)
John G8DZH. Gary M0NIF. Dave, did you get that screen grab using KiwiSDR? Leave a Reply Cancel reply Your email address will not be published.QRZ Forums. FlDigi Weather Fax receiving After abt 2cm drawed picture - fldigi breaks and saves them as file I have set now lines bus still same 2. The addes picture shows 1. I now also assume, the signal is marginal.
Additional, I am too closed in the black part, maybe. Now slowly get success From picture I only made a negative with IrfanView. Yes the signal is weak - just signal was partiell away on In the bottom right-hand corner, try unclicking your squelch button.
If the signal is low enough to cause the squelch to activate, the program will think that the transmission has ended, and will save the image. That could be the problem. NQ7CSep 26, TNX I found it. But I could read them. This post is old now but I'll carry on!!!
I think the program is highly noise-sensitive and when I changed antennas to one which had a low SWR on KHz KHz and less noise, the picture improved a lot. Having said that, when QRM rises locally, the picture again deteriorates!
TNX its ok. I recognized that the bandwith is too narrow. Also no success with the FTA also too narrow. I'll try another receiver. With the HAM receivers I could only guess a picture You must log in or sign up to reply here. Show Ignored Content. Share This Page. Your name or email address: Password: Forgot your password? Register for a free QRZ account.This grabbed my attention because I like maps and I like to see things to do with the weather.
After very little searching, I discovered that fldigi can receive fax pictures. I soon had it configured correctly and so the next stage was to find what frequency the WEFAX pictures are transmitted on.
A quick search around and an ask via Twitter pointed me towards this document which lists various transmitting stations around the world. I first started listening on the UK frequencies but heard nothing so I switched over to Germany and over the course of the week, I received a lot of pictures.
The 3, This morning I switched to the Northwood frequency of 4, For Germany, put in the Frequency shift box or leave it at for UK reception. If you switch between the two transmitters, remember to change this figure. Make sure you hit the Save box at the bottom. Set LPM lines per minute to in the box below the receive window.
Tune your wireless in to one of the frequencies in the list I posted above and wait. You can click on any of the images above for a higher quality version. This site uses Akismet to reduce spam. Learn how your comment data is processed. Enter your email address to subscribe to this blog and receive notifications of new posts by email. Email Address. Search for:. Skip to content. Receiving weather fax pictures on HF using fldigi Posted on January 26, by g6nhu.
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All rights reserved. Web design by paomedia. Sorry, your blog cannot share posts by email.Without a doubt, decoding digital signals at the software level has grown in recent years, easily supplanting the hardware decoders, since software packages can be updated and are generally free of hardware constraints there are a few that need a dongle, though.
These packages run the gamut from free to the ultra-expensive - and often with the jump in price, you get more complete analysis tools, which may not necessarily be useful for someone starting out.
Note that anything in green can interface with some Software Defined Radios. There are a few programs that combine radio control and digital decoding.
This is a category that isn't well explored by most manufacturers, but is unique for its all in one approach. Without a doubt, most of the active development has been in the area of decoding using a simple connection to a sound card in a computer.FLDIGI Tutorial How to decode amateur radio RTTY signals
Many such packages now exist, with more gradually making their way onto the market. Even here, some have extensive aids, waterfall displays and other devices to help decode and sometimes analyze an unknown signal.
See the Testing Your New Setup article in this document for a listing of these broadcasts. These applications are for use on Android driven devices. Please see the software's page for more detailed requirements.
While radio amateurs - including the astronauts onboard the International Space Station - are the primary users of this mode, HF Pirates have been known to use this as well. You can either use the built in speaker, or better, a connection between your receiver and unit. These links come from the Black Cat Systems website. What if you're using a less expensive program, or perhaps using a PK and would like a better tuning aid, or would like to do some NAT viewing with an analyzer?
Software By W1HKJ & Associates
Well, up to a few years ago, you were out of luck. With the development of DSP processing, and the popularity of soundcard programs, such programs are now readily available. Some allow you to create your own filters, view a signal with an audio spectrum analyzer, and more.
The RadioReference Wiki.