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Author Topic: How do you copy cw through qrm,qrn and qsb  (Read 1908 times)
K2ACB
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Posts: 64




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« on: January 18, 2008, 05:15:30 PM »

I am a casual cw operator. I have an extra class license and took my test under the FCC when 20wpm was required. I can send a lot quicker than I can receive. I prefer to send and copy around 15wpm.Alas,I find very few cw operators in the extra class portions of the cw part of the hf bands  send under 20wpm.                                                                                                        My main problem is that I have a lot of difficulty receiving and understanding cw whenever I encounter a lot of qrm,qrn and qsb.I also have difficulty in cw pileups where there is a lot of qrm.                                                                                                          I presume that one, if they are on cw long enough,gets a knack for copying through qrm,qrn or qsb or just tries to guess as to what is being sent from the gist of the qso and the words and letters one can make out. This is what I try and do. Sometimes I am successful and other times I am not.                                                                                                          I just wonder how the experienced cw operator compensates for qrm,qrn and qsb or like me they do a lot of guess work and hope they are right.                                                73-Alan-K2ACB                                                                                                                                                                                                              
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KE3WD
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Posts: 5689




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« Reply #1 on: January 18, 2008, 07:31:09 PM »

CW FILTERS can help you out a lot here.  

Don't get too narrow of a bandwidth to start out, though.  500Hz is a good choice for CW.  

Also, DSP can help a lot, too.  Those who enjoy a rig that has IF level DSP may or may not need the additional physical filter install.  

AF DSP plus a filter can be a very good choice, too.

If wanting to know the order, I'd buy the CW filter for the radio first, then consider adding outrigger DSP later.  

The filter can cut way down on the QRM.

So can proper use of the RF gain control.  Once a station is heard, part of tuning it in is reducing the RF Gain until the signal to noise ratio is better, this can also cut down on adjacent channel interference a bit, too, depending on signal strength of the undesired signals, of course.  


KE3WD
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AD5X
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Posts: 1432




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« Reply #2 on: January 19, 2008, 05:25:15 AM »

As stated above, a good narrow CW filter will make a world of difference.  You should have at least a 500Hz CW filter.  I actually prefer a narrower 250Hz or 300Hz filter for CW.  I tune around with a wide SSB filter, and then punch in the narrow CW filter when I'm ready to operate.

Phil - AD5X
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K7UNZ
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Posts: 691




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« Reply #3 on: January 19, 2008, 07:03:16 AM »

Filters are a big help, for sure....but training yourself to listen to the tone of a single signal helps a lot more.  You would be amazed how well your brain can filter out the crud....

All my rigs are chock full of filters, but I do most of my operating with just the 2kHz filter punched in, and let my brain do the rest.  

Also helps to recognize the fist of the other operator compared to whatever else you may be hearing.

Jim/k7unz
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NU4B
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Posts: 2287




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« Reply #4 on: January 19, 2008, 11:56:17 AM »

I agree a CW filter would be a big help. I would go with a 250 HZ filter though. If your going to get one, and I assume you don't have one now, wht not get the full benefit. The cost for a 500HZ and 250HZ filter for your rig are probably the same or close to it.
In either case a filter sure makes it easier on the ears and most likely will make it much easier to copy.
If the QSB is bad - well it can be a struggle. A filter is not going to stop that. But it might help to copy more of the message by knocking out some of the surrounding QRM and QRN.
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K7PEH
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Posts: 1124




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« Reply #5 on: January 19, 2008, 01:10:44 PM »

Of the three: QSB, QRN, QRM, I find QSB the most frustrating at times but then at the same time that is indeed the fun and challenge of CW.  I have 500 Hz and 250 Hz filters on my rig and I mostly use the 500.  I only switch to the 250 if I need to and that is only if there is another station right on top of us.

I am amazed though at how much CW cuts through all of the problems of crowded airwaves and propagation.  The other day, I had a brief QSO with another station but QSB raised its ugly little head and ended things after a few exchanges.  I was operating 100 watts and the other station gave me a report of 599 (of course, :-) ) and then said "VERY LOUD SIGS".  The other guy though was not that strong but an easy 599 copy before the QSB.  But, the QSB came along and we lost it but not before I learned that this other station was operating 800 milliwatts QRP!  Not bad for a station in Long Beach, CA and I am up in the Seattle area.  This was on 20 meters in the middle of the day (last Tuesday).
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KC2MJT
Member

Posts: 59




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« Reply #6 on: January 19, 2008, 01:23:56 PM »

In addition to the sound advice above, turn off your preamp. When QRN and QRM are high the preamp will intensify everything you don't want to hear.  You'll find the weak signals easier to copy without it.
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W8ZNX
Member

Posts: 1




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« Reply #7 on: January 19, 2008, 02:13:09 PM »

it's something you learn

many of us old timers
that came up as 75 watt rock bound novice ops
using el cheap o receivers

learned to copy
through the crud

had to
40 meter novice band was kill or be killed
all us kids rock bound running split

you can also learn how to do it
open up your receiver
tune around till you hear two or three stations
that are not dead nuts on the same freq

focus on  copying one sig
don't worry about solid copy
or any kind of speed

at first its hard
you will only last a few min
before you head starts to hurt

more you do it the easier it gets
till you can copy with
two three or more signals in the band pass

its not too hard once you
learn how to do it

( if im tired or had a few beers all bets are off )

using your brain filter
helps modern filters
work even better

I seldom use narrow filter
unless to improve a weak sig
sig to noise ratio

most of the time use very wide
or no filters

nice to hear what is happening
think of it as a audio band scope

sometimes you catch something
you would otherwise not hear
using a 300 or 500 cycle filter

mac

read or die
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W8ZNX
Member

Posts: 1




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« Reply #8 on: January 19, 2008, 02:15:55 PM »

oh Alan

do you use cans/headphones
find i can copy thrugh the crud
much better when wearing
a set of cans

yours truly
Mac
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NI0C
Member

Posts: 2408




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« Reply #9 on: January 19, 2008, 03:27:25 PM »

Alan,

You've gotten some good advice so far.  I would just add the following:

If you miss a word or a character for any reason (QSB, static crash, QRM) don't fret for even a millisecond about it.  Just concentrate on what's coming up.  You might even be able to figure out what you missed from the context-- but just let it happen-- don't let it bother you.  

Also, as your receiving speed increases (and it will with the practice you are doing) you will find that having a margin between your receive speed and what is actually being sent will give you confidence.

Finally, some ops (and I include myself among them) copy weak signals through bad conditions better using very low pitch settings in your receiver (250 to 450 Hz is generally considered low pitch.  Experiment with pitch settings and see what your ears prefer.

73 de Chuck  NI0C
 
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N4KZ
Member

Posts: 599




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« Reply #10 on: January 19, 2008, 08:11:46 PM »

Practice, practice, practice and a good filter or two.

73, N4KZ
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N3EF
Member

Posts: 247




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« Reply #11 on: January 20, 2008, 06:37:17 AM »

  I would like to re-iterate what KE3WD said about turning down the gain. Iv'e seen so many ops running at full RF gain and never cutting back on it. You can really reduce the noise level and still hear the cw just fine.

Eric N3EF
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NG0K
Member

Posts: 334




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« Reply #12 on: January 20, 2008, 01:32:01 PM »

Even when the bands are quiet, reducing the RF-gain a little bit can reduce the internal receiver noise improve the quality of the CW.

73
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73, Doug - NG0K
K7NNG
Member

Posts: 42




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« Reply #13 on: January 21, 2008, 06:40:46 AM »

PRACTICE, PRACTICE PRACTICE, PRACTICE and, learn how to use the rig properly.
Sending faster than you can copy is a bad habit for CW OPS....Practice until you can comfortably copy what ever your goal is....Never send faster than you can copy.
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W5ESE
Member

Posts: 550


WWW

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« Reply #14 on: January 21, 2008, 07:11:19 AM »

I agree with the suggestions others have made.

On the lower bands especially, I enable the RF
attenuator on the front end, which can help reduce
the noise, and I turn down the RF gain to about
the mid-point.

It helps to have a rig with a narrow IF filter.
If your rig can only accomodate 1 filter in CW mode,
I would make it 400 or 500 Hz. In some rigs, you
can select from one of several IF filters, which
are available as options. My Ten-Tec Omni 6 can
hold 4 in the second IF, and 2 in the first.
That's one of the main reasons why I bought it.

Learn to use the IF shift or passband tuning
controls if your rig has this. It can make a
big difference in avoiding QRM.

And like Mac said, using headphones instead of the
speaker helps alot, too. I keep the volume quite
low, to protect my hearing and reduce distracting
noise.

73
Scott
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