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Shortwave Data Decoding Discussions regarding decoding digital signals on the HF bands, including HFDL, ALE, RTTY, CW, and others.

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Old 07-30-2011, 3:53 PM
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Default "Grinding" sound mode

I listen to shortwave broadcasts now and then, and one signal that piqued my curiosity is this "mechanical grinding" noise I hear around 4 Mhz (i have an analog tuner so I can't tell which exactly it is)

It sounds exactly like this recording, although this is not my recording: What's that sound on Shortwave 4345Khz?

Can anyone tell me what this mode is?
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Old 07-30-2011, 5:10 PM
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It's WEFAX. 4346 MHZ

99% of all digital modes are in USB -- and for WEFAX, the real frequency is 1.9khz minus the center frequency. So, 4344.1 in this case. If you download free WEFAX software and plug it into your computer's sound card you can get weather charts and satellite pictures.

Note: this can be hard to do with a shortwave portable -- you need a desktop shortwave receiver with good frequency stability and resolution.

Last edited by nickcarr; 07-30-2011 at 5:13 PM..
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Old 07-31-2011, 3:37 PM
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That's certainly not WEFAX - which is two tones. I have a transmitter near me on 4.250MHz that is just a continual roar on AM and SSB. It gives me an S9 signal but is very well controlled, only 2.5kHz wide. It seems to have a sort of 'rotating' sound to it. I notice similar sounding signals in the database (http://www.hfskeds.com/skeds/A11_Com...730b_2200G.zip) that say that they are CODAR radar transmissions but nothing mentioned in NZ on this frequency.

See this post in the "Shortwave Broadcast" forum - "On SW it sounds like an aircraft engine?"
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Last edited by majoco; 07-31-2011 at 3:42 PM..
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Old 07-31-2011, 3:40 PM
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CODAR tends to show up wherever it seems to please. I've heard it frequently around 4800 khz, but then I've also seen it lower and much higher (once around 9 mhz or so) - it's the bane of DXers all over. The equivalent of the Soviet Woodpecker of the 80s (anyone around that remembers that - AEA even came up with an outboard blanker for it that was supposedly pretty effective).

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Old 07-31-2011, 8:34 PM
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Quote:
Originally Posted by majoco View Post
That's certainly not WEFAX
It *IS* 100% absolutely WEFAX. I use to monitor/decode this frequency all the time many years ago.

First off all, the video shows in AM mode and then he switches to SSB. On a portable, the speakers audio fidelty isn't very good. Secondly, there are start/stop tones as well as others sounds. It's not a consistent signal.

This is a WEFAX station from Pt Reyes, CA.

Here is their schedule:

http://www.nws.noaa.gov/om/marine/hfreyes_links.htm

Last edited by nickcarr; 07-31-2011 at 8:36 PM..
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Old 07-31-2011, 8:39 PM
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Quote:
Originally Posted by ka3jjz View Post
CODAR tends to show up wherever it seems to please. I've heard it frequently around 4800 khz, but then I've also seen it lower and much higher (once around 9 mhz or so) - it's the bane of DXers all over. The equivalent of the Soviet Woodpecker of the 80s (anyone around that remembers that - AEA even came up with an outboard blanker for it that was supposedly pretty effective).

best regards..Mike
CODAR shows up from roughly 4500-4700 here on the west coast. There are some other minor areas as well but this is the stongest area for me.

The video link the OP provided was WEFAX however.
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Old 07-31-2011, 9:31 PM
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i thought it sounded like Stanag 4285.
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Old 08-01-2011, 3:53 PM
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The OP said:

Quote:
It sounds exactly like this recording, although this is not my recording: What's that sound on Shortwave 4345Khz?
..so how can you say that is what he heard? It wasn't his recording. I'm sure you can't make the two-tone Wefax signal sound like a grinding/roaring sound whatever mode of reception you use.
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Old 08-02-2011, 4:20 PM
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Brandon - have you had any success decoding Stanag 4285? Using Sigmira I can decode most everything else and I can decode the test file - but decode an off-air signal? Nah! No sign of the "Sync" light turning green apart from the occasional flash and FEC indicator doesn't move. Iv'e tried LSB and USB, offtuned the signal, narrow and wide filters, nuttin'! Any clues?
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Old 08-02-2011, 6:56 PM
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I can guarenty that it's not Fax. I've heard enough Fax to know that something that repeats like 5 to 10 ten times a second is not Fax. That is definitely data mode even if it is on a Fax frequency. Most likely it's broadcasting textual weather data using some unusual digital mode, during a time that the Fax transmitter isn't designated to operate. Usually there's Morse code station identifier beacons that operate during times the Fax isn't transmitting (4 warble tones, 3 letter station ID in Morse code, then the cycle repeats). However I've heard other strange sounds coming from stations like this some times during times of no fax transmission. This could easily be one such uncommon digital mode.
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Old 08-03-2011, 12:15 AM
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Most of the Stanag 4285 is encrypted. But some clear test broadcast can be monitored.
For example French Navy station "FUM" from Tahiti can be monitored in clear text.

Here is the output. It just repeats itself over and over.



I have also logged New Caledonia and Martinique in the past.

Unfortunately I have not had any luck with Sigmira either. It didn't run very well on my system.
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Old 08-03-2011, 12:40 AM
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Its hard to tell but it kinda sounds like DRM which does plague 4MHz at night.
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Old 08-03-2011, 2:30 AM
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Got any frequencies for those stations, Brandon?

Tahiti and Noumea shouldn't be too hard from here, but Martinique is a bit upper class, may need to upgrade my T-shirt....



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Old 08-03-2011, 8:25 PM
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From the sample above I parked my radio on 16959.3. It might take a few adjustments until it comes in. Another one I'm receiving at this moment is 13031.3 kHz (Fort-de-France Martinique)

FAAA


DE FUF


ZNR UUUUU


ZUI TESTING


RYRYRYRYRYRYRYRY


SGSGSGSGSGSGSGSG





NNNN
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