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Author Topic: CW filter on PC  (Read 3231 times)
KK4VAU
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Posts: 10




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« on: April 29, 2014, 01:59:06 PM »

I have an older rig with no filters.  I'd like to run the audio out to my computer and through a narrow filter.  What is the simplest software setup for getting a realtime narrow filter on Linux?  I used to run JACK for music processing, and I think there are probably plugins what would work with JACK.  But, it seems like overkill.  Is there anything simpler?  Anything CW-specific?
Any advise is appreciated.
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KQ6Q
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Posts: 965




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« Reply #1 on: April 29, 2014, 02:09:01 PM »

You'll be a lot happier with something like this : http://www.eham.net/reviews/detail/3075
use your PC for logging in contests...
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KK4VAU
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« Reply #2 on: April 29, 2014, 03:32:46 PM »

I probably would be happier with something like that, but I'm terribly cheap. :-)  I must give this a try.
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VA7CPC
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« Reply #3 on: April 29, 2014, 04:30:55 PM »

Three possibilities:

1.  "CW Get" (and maybe other CW decoders) will let you listen to the signal _after_ it's been passed through their narrow (50 Hz to 300 Hz) decoding filters.  There's  a "trial version" of "CW Get" that's free, and fully functional. 

2.  VoiceShaper is designed for mic-input audio processing.  But I bet you could set up a narrow CW filter with it.  Also free.

3.  If you're willing to spend some money, there's a Romac 10-band EQ that runs on a PC.  There's a trial version -- free -- available, but it's time-limited.

.      CHarles
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KB2HSH
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« Reply #4 on: May 05, 2014, 06:24:57 AM »

I found an ORIGINAL MFJ CWF-2 at the Keuka Lake hamfest last year for $10.  This is a 40+ year old filter that MFJ used to get started waaaaay back when.  It has settings for 180/110/80 Hz...and after 40 years it STILL performs like a champ.  180 is about right for the rigs I've used it on.

KB2HSH
Springbrook, NY
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AA4PB
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« Reply #5 on: May 05, 2014, 08:07:13 AM »

The issue with a PC filter, or any audio filter, is that the QRM signals have already impacted the receiver AGC. Only an IF filter built into the receiver can prevent that.
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K0OD
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Posts: 2521




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« Reply #6 on: May 05, 2014, 08:52:53 AM »

Exactly which "older rig" do you have?

The $19 HiPerMite is well regarded.
http://www.eham.net/reviews/detail/10681


I use a 20 year old Timewave DSP audio filter with my simple QRP radio for CW contesting. But I can tell you that going strictly with an audio filter, even a very good one, leaves a lot to be desired. Depends on your goal... occasional CW ragchewing, chasing DX in pileups, or in my case, a full weekend of contesting.

Yes, MFJ sold a bazillion audio filters over the years. Doubt they ever wear out and must go for just a few bucks these days.  
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KK4VAU
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« Reply #7 on: May 06, 2014, 04:23:44 AM »

Thanks for the advise. The rig is a Yaesu FT-101EE. I now know that the VFO is unstable. The transmit wanders around about 500Hz. I may need more than a filter (or in addition to an audio filter), maybe an external VFO.
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KB2HSH
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« Reply #8 on: May 06, 2014, 05:48:33 AM »

Thanks for the advise. The rig is a Yaesu FT-101EE. I now know that the VFO is unstable. The transmit wanders around about 500Hz. I may need more than a filter (or in addition to an audio filter), maybe an external VFO.

http://www.pongrance.com/

I had a Kenwood TS-120 that was DRIFTY as well.  This is the solution that was sent to me by my friend WB2VUO.

73 de KB2HSH
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K0OD
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« Reply #9 on: May 06, 2014, 06:45:11 AM »

Quote
The rig is a Yaesu FT-101EE. I now know that the VFO is unstable.

I have a 1977 Kenwood TS-820, a similar hybrid. It's pretty stable if allowed to warm up for 30 minutes.  GL
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K3TN
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« Reply #10 on: May 07, 2014, 03:42:05 AM »

You can buy used graphic equalizers on eBay, often for $10 or so. I've moved away from audio filtering, since I now use a K3, but I had an old Radio Shack one that was decent.

If you really want Linux software, PulseAudio is a good equalizer -  see http://www.webupd8.org/2013/03/install-pulseaudio-with-built-in-system.html

There are some inexpensive CW audio filter board kits - the QRP guys have one at http://www.4sqrp.com/HiPerMite.php but might not be shipping right now.

Another good source is the QRQ guys here: http://qrqcwnet.ning.com/forum/topics/cw-audio-filter-showcase

73, John K3TN
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John K3TN
ZENKI
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Posts: 906




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« Reply #11 on: May 07, 2014, 03:42:16 AM »

Datong FL2 with peak filter, its a very good tool to have as an accessory to be used with any radio. The analog APF filters seem to work much better than DSP implementations
of APF filters.
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KD7RDZI2
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Posts: 61




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« Reply #12 on: May 15, 2014, 02:08:16 PM »

The HiPerMite is cheap and works beyond expectations. CWget with WINE also works under Ubuntu just like on Windows and allows you to have a filtered output. However the HiPerMite simply sounds better.
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