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  #1  
Old 12-03-2008
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Help with WeatherFax and SeaTTY

Hi,

There isn't a specific forum for electronic gear and/or geek stuff so I am posting here...


I started trying to get Weatherfaxes through my SSB receiver last week. The receiver is a portable Eton E5. It doesn't have a USB/LSB switch. I am able to hear the time signals and the Chubasco Cruising Net on it (I am in San Diego, California).
I think I am actually getting the fax signals into my computer but the image is messed up.
From looking at the resulting image (please see my attachment) it looks like there is some lack of synchronisation somewhere.
Also, the two frequency peaks of the signal seem to be slightly over 800 Hz appart, so I can never overlay both peaks with the vertical red lines...
I have set up (I think) the sampling frequency of my sound card at 11025 Hz (see my second screen print)
I am trying to receive from NOAA in Point Reyes at 8682 KHz, setting 120LPM, 576 IOC just like the NOAA website says.

Any ideas anybody? Please help!!
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Old 12-03-2008
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I think you need a USB switch and a fine tuning knob on the radio the get the fax in properly. As I recall...the fax signals are actually offset a bit from the listed frequency.
EDIT...I was right...it is offset and you need fine tuning...here's a bit about it:

Before making the connection from the receiver to the computer, spend some time listening to the signal. Listening will get you in the ballpark of the correct frequency. Use headphones or you’ll cause a mutiny in short time onboard – it’s just a series of high-pitched tones and beeps. At first, you’ll wonder if you’re even listening to the right frequency. But with practice, you’ll learn to use the fine tuning to get the pitch just right and to get the RPMs ticking along as they should (120 RPMs per line). It gets easier once you know what to listen for.
One gotcha you’ll need to be aware of is that when you’re grabbing a weather fax you need to set your radio to 1.9 KHz below the frequency stated by the schedule. For example, if the schedule says to tune to 17150.9 KHz, look for a good signal with your radio set to 17149 KHz. Use the fine tuning dial on the radio to make adjustments.
When you think you’re close to the right signal, try to see what you’re getting. Plug the receiver into the computer (headphone jack of the receiver attached to the microphone jack of the computer). In theory, a PCMCIA card could reduce some of the noise in the system, but at the price of added complexity. If you have a PCMCIA card, bypass the microphone jack.
Turn the receiver on and launch your weather fax decoding software. The charts begin when the station broadcasts a “start” signal. If the receiver is tuned correctly, the download to your computer should kickoff automatically. If it’s not tuned correctly, you may have to manually start the download. A weather chart will slowly start to draw itself on the screen, line by line, from the top down. At the end of the chart broadcast a similar “stop” signal is sent. This lets the software create individual files for all the charts you’ve received. As with the start signal, if your radio isn’t tuned perfectly, you’ll need to manually stop the download.
At times, you’ll need to use manual mode for critical maps and to baby sit the download to be sure you’re getting what you need. There is probably a learning curve for every software system out there. I found that if I jump in after a fax chart broadcast has started, I need to make adjustments to the image. Those adjustments are called the skew of the image. Once I mastered the skew feature, I was able to line up everything and see the image well.
After you start receiving a fax it’s very useful to enlarge the image being downloaded to 100% so you can continue to fine tune reception to get the best image possible. If you’re seeing all black try moving the dial up to a slightly higher frequency with the fine tuning. Once dialed in you should be getting mostly white, except for satellite photos.
*************
If you need a great portable radio with fine tuning I suggest:
Super Sangean 909

this is a modified version of the 909 which is an excellent radio even before the mods here:
Amazon.com: Sangean ATS-909 All Band Digital Shortwave World Band Receiver: Electronics

if you just want the cheapest one that will perform adequately...try the Kaito Kaito AM/FM Shortwave Receiver

...or ask Santa!!


I used SeaTTY some years back with a Grundig YB400 and it work fine but took plenty to play with before I got the hang of it with the skewing and stiching. . Keep trying ...once you get the routine down it works just fine but you do need an adequate radio.
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Old 12-04-2008
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Screenshots

Thanks,
I am already doing all that, I am going 1 or 2 KHz below, hearing the signals, fine tuning, getting them to the PC (I can see the frequency spectrum of the signal on SeaTTY with the two peaks), and it is getting auto-start signals sometimes but the fax image just looks like crap.
I meant to add a screenshot but maybe I forgot. I'll try that again to see if the image triggers some idea of what can be wrong.
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Help with WeatherFax and SeaTTY-seatty_screenshot.jpg  
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Old 12-05-2008
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Desierto...that doesn't look like a wefax signal to me. I don't think you have it tuned right. It's been too long since I used mine to give you much help I'm afraid. Sorry!
The best thing I can tell you is to listen to the sound samples here:
-+- www.JVComm32.de Homepage -+- System Anforderungen Deutsch

If what you are trying to decode sounds like that...then you just have to play around with the menu items or contact tech support over at SeaTTY
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Last edited by camaraderie; 12-05-2008 at 01:33 AM.
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Old 12-05-2008
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Past that roadblock!

Thanks a lot, for your moral support if nothing else...
I finally received some meaningful images and then discovered the next set of problems but I am making headway.
Sometimes the image turns into what you saw in my previous screenshot. There is some source of electrical noise that I can't control. Everything is turned off in my boat but I am in a Marina and next to a Navy base so who knows...
It just had happend that on previous trials the noise had been there the whole time.
In the attached image (besides a loss of synchronicity) you can see the noise hitting in the middle of a reception.
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Help with WeatherFax and SeaTTY-081205-074405.jpg  
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