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Author Topic: Copying in the mud  (Read 46781 times)
K4FTW
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« Reply #30 on: September 23, 2013, 08:12:58 AM »

One thing I haven't seen mentioned in the thread is to use a headset. Audio from a speaker is OK with a strong, clear signal, but a headset will go a long way towards helping copy those down in the mud.

Dick K4FTW
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KX8N
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Posts: 542




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« Reply #31 on: September 27, 2013, 04:12:09 PM »

This may not help any as I cannot remember the name of the program, but I swear that about 10 years ago I had a CW learning program that would let you insert white noise as you listened. I believe you could choose how much noise you heard, to simulate different conditions.  I'll look around and let you know if I figure out what it was.
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AG1LE
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« Reply #32 on: September 27, 2013, 05:17:36 PM »

This may not help any as I cannot remember the name of the program, but I swear that about 10 years ago I had a CW learning program that would let you insert white noise as you listened. I believe you could choose how much noise you heard, to simulate different conditions.  I'll look around and let you know if I figure out what it was.

Here is a set of audio files with -10 dB to +20 dB SNR @ 2kHz https://www.dropbox.com/sh/2j9chxsizxjeqgp/Gj97asYzpW that I just created for testing a new Bayesian Morse decoder.  The files contain 50 WPM random text  (see random.txt on the shared folder) - 200 words of 5 letter/number each.

Let me know if these are useful.

73
Mauri AG1LE
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WX2S
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« Reply #33 on: September 29, 2013, 10:06:27 AM »

For some of the really weak ones, I sometimes use an outboard active audio filter that "peaks" a specific narrow audio bandpass.  This acts much like the old-timers' Q-Multipliers in that it will bring one single tone up out of the mud.  If the bandwidth is too narrow, it can cause ringing, but when set just below that point it works to keep one signal front-and-center.  The filter I use most is an old MFJ unit (forgot the model number) but I also have an old homebrew filter as well.

I use one of those SCAF filters for that very same reason. It doesn't always work, but the incidents where it does, it makes a world of difference.
The APF (Audio Peak Filter) in the K3 works wonders sometimes, too.
73,
Chuck  NI0C

Chuck, I find the APF in my K3 to be pretty limited on weak signals.  I cant seem to get weaker signals to pop out of the mud.  If the signal is a little stronger then I can.  Perhaps you can expand on how you are using it.  Thanks -Joe
I tried the APF yesterday -- had never used it before. Seemed to help.

Wx2s.
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
N4DSP
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Posts: 148




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« Reply #34 on: October 02, 2013, 05:55:24 PM »

Hi, all,

Not sure where to post this, so I'll try here.

I'd like to improve my ability to copy CW signals that are close to the noise floor. This would be useful for QRP, DX, or just general hamming. Can some of the wise folks here give me any practical advice?

Thanks and 73, - Steve WX2S.


You have the correct answer already Steve. Copy signals at the QRP and SOTA frequencies. Once you find those unreadable signals then use those knobs on that receiver and try to peak that signal. Try turning off the AGC and turning your RF Gain fully counterclockwise and AF Gain fully clockwise and slowly turn the RF Gain up till you hear the signal. If you have passband tuning use that trying to 'peak' the signal. Spend time with that receiver learning what it can do till it's second nature. When not much is going on dx wise I find signals that are totally unreadable and have a go at it with my receiver's knobs bringing that signal up. Good Luck.

john/n4dsp
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VK3HJ
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Posts: 601




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« Reply #35 on: October 12, 2013, 09:15:23 AM »

I built an SDR rig about 3 years ago and find it fantastic for digging out the weak signals, and analysing the DX pileup. The spectrum display helps to find the active frequency quickly. I have the main Rx in both ears and the sub Rx in the right ear, for QSX up. For weak signals, or busy frequencies, I always use headphones. Phones help one focus on the signal.
Whilst I can adjust the DSP filter to any width, I tend to use 400 or 250 Hz.
As already mentioned, a receiving antenna for low bands is very helpful.
Another skill is riding the QSB. Make the most of the rising signal.
73,
Luke VK3HJ
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