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Author Topic: How do you copy cw through qrm,qrn and qsb  (Read 1778 times)
W5ESE
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« Reply #15 on: January 21, 2008, 08:21:34 AM »

One other thing I forgot to add; there is a good
article on using IF shift (also called passband
tuning) on the ARRL web site:

http://www2.arrl.org/qst/2005/04/passband.pdf

Most newer transceivers include this feature, but
I have the impression it is often not used. But
it can help alot, especially if a narrow IF filter
is installed.

73
Scott
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N5XM
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Posts: 242




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« Reply #16 on: January 22, 2008, 06:51:57 AM »

IMO, unless you have a truly gifted ear, learning to copy in these kinds of conditions only occurs over time.  The more you do it, the better you get.  I would say, listen to contests with headphones.  Even if you don't participate at first, by listening and practicing focusing on one signal, you train the brains' "adaptive filtering system".  You must be patient and persistent, but don't pressure yourself.  The key is learning to focus in an easy fashion, sort of like being in the "zone".  Certainly, a radio with passband tuning and adjustable DSP filtering would help, but it is really a matter of experience and time.  I don't know of any shortcuts.
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WR8D
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Posts: 165




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« Reply #17 on: January 28, 2008, 12:45:08 PM »

Cw filters help as some have said and just filling in the blanks sometimes is all one can do.

Put some headphones on and you'll be less distracted.

Good Luck
73
John WR8D
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KB2FCV
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« Reply #18 on: January 28, 2008, 01:44:55 PM »

I have a narrow filter in my rig (350 or 500 I think) but I don't use it as much. I use the ole' noggin as the main filter. I guess sometimes I like the sound of the wider filters in the rig and just filter out stuff in my mind what I don't want to hear. It takes a while to get good at it but years ago my novice rig gave me little choice.
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N3YZ
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« Reply #19 on: January 31, 2008, 03:00:19 PM »

Alan I'm like you... cw is certainly not a strength. But its fun. I have a Yaesu FT-857D. However, I also use an older Autek QF-1A audio filter. After a bit of a learning curve, I find that the variable peak filtering capability is a tremendous help in focusing on the received cw and in pulling it out of the qrm, qrn and qsb, as you indicate as the problem. These Autek QF-1As are superb, reasonably priced and fairly common. 73s! John
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K0DXC
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« Reply #20 on: January 31, 2008, 03:15:10 PM »

I personally like to shift the carrier, or simply use a good filter



73 de Calvin K0DXC 13 yrs
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5P1CC
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Posts: 15




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« Reply #21 on: February 01, 2008, 04:03:13 AM »

I think all the advice in this thread here are just right ..

I use a FT107 with 500hz cw filter, pass band tuning and variable audio filter. Or at least, thats what my rig is equipped with...

Once i start copying a signal i often forget to switch to any of those, because im focusing on copying, and not so much on how annoying the qrm are.

And you can learn to distinguise between 3 or more signals slipping trough the filter after some time.

My first rig had a 5khz filter and nothing else so i simply had to..:-)

And i used to have a resonant cw-loudspeaker that really made a difference too, but it vanished years ago when i sold most of my gear. It was homemade and very easy to replicate if it needs be.

73 de Claus
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WA4DOU
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« Reply #22 on: February 03, 2008, 11:33:55 AM »

Generally speaking, diligent use of cw leads to proficiency. Few, if any, ever become proficient without working at it and virtually no one is born with a gift for it. If you view it as "the only mode" you'll likely invest the effort. If you view it as "one of many modes" you may not. It's entirely up to you.
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VE3XDB
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Posts: 139




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« Reply #23 on: February 27, 2008, 07:11:44 AM »


I have been a cw operator for about 15 years.  In addition to a CW filter, and turning down the gain, here is another thought that has helped me quite a bit.  Build yourself a passive RC audio filter, with a cutoff frequency at about 1000 Hz.  Put the filter between your rig and external speaker or headphone.  It really takes away the high pitch noise, which causes fatigue, and makes CW copy much more pleasant.  

A passive low pass RC filter can be made with one capacitor and one resistor, although the one I built has two of each - the same circuit in series.  It's just a resistor in series on the input side, and a capacitor in parallel on the output side of the circuit.

That's it!  A simple junk box project.  To calculate the cutoff frequency, use:

f = 1/(2*pi*r*c)

Here are a couple of good links:
http://www.tonmeister.ca/main/textbook/node110.html
http://en.wikipedia.org/wiki/Low-pass_filter

Best regards,

Doug VE3XDB
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VE3XDB
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Posts: 139




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« Reply #24 on: February 27, 2008, 04:05:30 PM »

I forgot a couple of things.  You need to use a non-polarized electrolytic capacitor in the low pass filter, and you should match the resistor to the impedance of the speaker.

Here is the link I was looking for earlier:

http://www.ldblake.ca/radio/noisecancel.htm

Cheers,

Doug VE3XDB  
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