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Author Topic: Copying in the mud  (Read 43348 times)
WX2S
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Posts: 657




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« on: September 13, 2013, 07:21:00 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.
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
KB4QAA
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Posts: 2239




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« Reply #1 on: September 13, 2013, 07:28:59 PM »

Experience, experience, experience.  Proper use of filters and radio settings.

I don't know what kind of radio you use, but the more modern it is the more gadgets there are that get between you and the signal, e.g. DSP, NR, NB, Passband/IF Shift, AGC (should be OFF or Fast), Notch Filter/ANF, AF/IF Filters, RF Gain

When copy gets tough, turn everything off and add the gadgets back in one at a time.

Sooo, Experience in code copy, and experience in gadget use are the keys.
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NI0C
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Posts: 2380




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« Reply #2 on: September 13, 2013, 07:35:42 PM »

Try the pileup simulation program, Pileup Runner, available free at: http://www.dxatlas.com/pileuprunner/

Of course, it emphasizes QRM, but you can look at the waterfall display to find weak signals.
73,
Chuck  NI0C
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WX7G
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Posts: 5908




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« Reply #3 on: September 13, 2013, 08:03:24 PM »

None of the CW simulator programs I know of simulate a signal at or below the noise floor. Some suggestions for obtaining such practice:

1. Tune around for suitable signals
2. Inject RF noise into the antenna (I can post the schematic of a wideband RF noise generator if someone can tell me how to post a pic here)
3. Play a recording of a noisy frequency with no signal into the headphones along with a simulated or off-the-air CW signal
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NI0C
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Posts: 2380




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« Reply #4 on: September 13, 2013, 08:25:02 PM »

None of the CW simulator programs I know of simulate a signal at or below the noise floor.
Pileup Runner does produce such signals.  Just to check this out, I just "worked" a station with a rated strength of 0 dB.  (After logging the "QSO," the program indicates the signal strength of the station).   
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WX7G
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Posts: 5908




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« Reply #5 on: September 14, 2013, 03:04:18 AM »

NI0C,

thanks for telling us about Pileup Runner. I tried it and it's pretty good but the version I downloaded would not allow the average S/N ratio to be set lower than 3 dB and it does only pileups. A useful modification of this program would be single station QSOs with S/N ratio settable to -10 dB.

I'll be practicing with Pile Runner this weekend.

« Last Edit: September 14, 2013, 03:08:35 AM by WX7G » Logged
M0LEP
Member

Posts: 199




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« Reply #6 on: September 14, 2013, 05:06:20 AM »

I think G4FON has some signal twiddling options which might simulate poor signals...
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W1JKA
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Posts: 1616




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« Reply #7 on: September 14, 2013, 05:42:42 AM »

  Playing in the QRP cw mud hole is my favorite part of the hobby since I'm into qrp/dx.Via three years of trial/error/experimenting I have ended up using my home based K-1 with a cheap Hi-Permite  outboard audio filter. With this combo I can seperate/pick out and work weak noise level qrp stations by simply using the narrow F3 K-1 filter to seperate and then fine tuning the cw pitch on the Hipermite to a level I can distinguish the note from other louder on freq. or close by stations. I also use these hipermites with my MFJ Cubs to accomplish the same.
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K8AXW
Member

Posts: 3599




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« Reply #8 on: September 14, 2013, 07:51:39 AM »

Steve, if ya wanna play in the mud, you're just gonna have ta get down in the mud with them!

Be prepared to get "dirty", get headaches, have losses and some discouragement.  But when you shut off the radio you'll look like the glassy-eyed, grinning little boy who has just had a wonderful session with a mud puddle!
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AD9DX
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Posts: 1464




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« Reply #9 on: September 14, 2013, 12:17:26 PM »

Steve check your facebook private message box, I know we have the same rig, so I sent you a few "tips" on ways to declutter the mud pit.  But as said above, your are not trying if you don't have a bottle of aspirin next to your headphones. 
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EX, KC9TRM, KB9IRZ
N3QE
Member

Posts: 2029




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« Reply #10 on: September 14, 2013, 12:38:08 PM »

With weak signals, I always make sure AGC is off.

If it's lightning crash type noise, having a lightning crash reduce the gain through AGC (until AGC time constant increases it again) is the worst.

Rarely will I turn the gain up so much that band noise is loud. That's just too much gain and counter-productive for picking out the signal.
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WX2S
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Posts: 657




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« Reply #11 on: September 15, 2013, 04:07:37 AM »

Thanks to everyone for their help. I've put AD9DX's settings suggestions into practice and they do seem to make a difference.

What are all of y'all's thoughts on using the sub in pileups? Is it more important to hear the pileup or to get the DX in both ears?

73, -WX2S.
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
AD9DX
Member

Posts: 1464




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« Reply #12 on: September 15, 2013, 05:59:37 AM »

I don't have one on my K3 yet. I typically just hit the REV button then use the main VFO knob to figure out where the other side of the QSO is, then spin just above that guy and wait my turn. There are a lot of different strategies figuring out the pattern of a DX station. For me, I would much rather have a Pan Adapter than a sub reciever although given enough time, I will have both  Cheesy
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EX, KC9TRM, KB9IRZ
AD9DX
Member

Posts: 1464




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« Reply #13 on: September 15, 2013, 06:01:18 AM »

Also, since the DSP, EQ and ACG settings I gave Steve are K3 specific, I did not publish them here. If anyone wants them I will gladly send them to you just email me bigbadjon (at) gmail . Com
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EX, KC9TRM, KB9IRZ
KH2BR
Member

Posts: 98




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« Reply #14 on: September 15, 2013, 08:10:01 AM »

I would like to work some of the weak ones also but they have to slow down. When the signal is weak and they are going blazing fast, you just cannot copy.
To make things worse, EU stations are copied on a polar path and there is a lot flutter on there signals at my qth in southern California.
I guess they are not interested in making weak signal contacts or they would slow down if they were.
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