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Author Topic: Should I get the CW filter?  (Read 20806 times)
KK4CPH
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Posts: 154




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« on: September 04, 2011, 07:25:16 PM »

I have a Kenwood TS-440 and while it has a selectivity switch, the filter is optional.  There's a YK-88C 500Hz CW filter but they're not cheap. (IMHO) Anywhere from $90-$125.  There seems to be a lot of activity on 40m and I'm hoping that, with the filter, I can switch to "narrow" and get a good lock on a station.  Will the filter make a difference or should I just save my money?

Eric
KK4CPH
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N3PDT
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Posts: 75




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« Reply #1 on: September 04, 2011, 07:49:33 PM »

The filter is worth it. Can make life much easier.
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N2EY
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Posts: 3879




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« Reply #2 on: September 04, 2011, 07:50:27 PM »

You want the filter. 400-500 Hz is the optimum choice for CW.

Inrad makes drop-in filters for many rigs; you can often find them used for less than new. The "narrow" switch on your '440 will do nothing unless an optional filter is installed. (Are you sure one isn't?)

You *can* do CW without a narrow filter, but it's not easy. Why not use the available tools?

btw, I have found that, in most situations, CW reception is better if the AGC is turned off, the audio (AF) gain turned way up and the RF gain turned down. The RF gain is used for volume control.

Of course when you do this the S-meter won't work and you have to adjust the RF gain manually, but that's just part of the game.

73 de Jim, N2EY
 

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KK4CPH
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Posts: 154




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« Reply #3 on: September 04, 2011, 08:19:46 PM »

You want the filter. 400-500 Hz is the optimum choice for CW.

Inrad makes drop-in filters for many rigs; you can often find them used for less than new. The "narrow" switch on your '440 will do nothing unless an optional filter is installed. (Are you sure one isn't?)

You *can* do CW without a narrow filter, but it's not easy. Why not use the available tools?

btw, I have found that, in most situations, CW reception is better if the AGC is turned off, the audio (AF) gain turned way up and the RF gain turned down. The RF gain is used for volume control.

Of course when you do this the S-meter won't work and you have to adjust the RF gain manually, but that's just part of the game.

73 de Jim, N2EY
 



Thanks for the info.  I checked Inrad and they have a 250Hz and a 400Hz filter.  So the 400Hz would be the best one? Any issues with using the narrow filter? The owners manual shows how to install the optional filters. (CW and SSB)  Doesn't look to complicated.
I'm sure there's no filter installed.  Owners manual says that "N" and "M1" positions won't work without the filter and when I switch to either one, the radio goes silent.  I tried tuning around and nothing.  I don't know why they put a "Wide" selection on there... what a mess!   Smiley

Eric
KK4CPH
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W5CPT
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Posts: 557




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« Reply #4 on: September 04, 2011, 09:22:01 PM »

You will NEVER be unhappy you went with INRAD.  The 250 Hz might be a bit narrow for you - the 400 Hz would be my choice and can be used for RTTY also.

Clint - W5CPT -
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AB2T
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Posts: 246




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« Reply #5 on: September 05, 2011, 01:08:18 AM »

A 400 or 500 Hz filter makes zero-beating much easier and quicker.  This is a godsend for people like me who never could zero-beat by ear (I still rely on sidetone). 

73, Jordan
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K8AXW
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Posts: 3828




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« Reply #6 on: September 05, 2011, 09:22:09 AM »

I use the 500Hz filter in my old Kenwood TS-830s and it do make a difference.

I don't wish to throw crap into the game but let me suggest you Google SCAF1.  Read their information and listen to the .wave files they provide.

I haven't been able to scarf up the money for one but hope to one day.  If anyone reading this thread cares to comment on it, please do.

Get the filter OM.  Tune the band in the WIDE mode...3KHz filter....find the signal you want to copy and the switch to the 500Hz filter.  The signal will "pop" out and will seem to be by itself.
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KL7CW
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Posts: 71




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« Reply #7 on: September 06, 2011, 12:06:59 PM »

Any serious CW operator "needs" approximately a 400 to 700 Hz filter for normal crowded band conditions.  Either 400 or 500 HZ would be a good choice. OCCASIONALLY when the QRM is very heavy I switch to my 250 Hz filter which sometimes helps, however this is too narrow if it is your only CW filter. If you have a good 400 or 500 HZ IF filter, and want more selectivity you could always add an audio filter to narrow the passband a bit more.  Some audio filters also let you set it up as a LO PASS filter, so when you have your 3 KHZ IF filter selected you could set your audio filter for LO PASS operation at something like 1000HZ or 1200 HZ. This is great for tuneing around and general operating without so much hiss and very high pitch QRM, and when you are in a QSO you can easily select the 400HZ IF filter if QRM enters the picture.  Only if you are a hard core contest or DX operator operating in severe QRM conditions would a second CW IF filter at 200 or 250 HZ be occasionally worthwhile. I would get a QUALITY 400 or 500 HZ filter...not all filters are created equally.  If everything else is equal, I would choose the 500 HZ over the 400 HZ option, however I suspect most folks would now opt for the 400 HZ option....probably few (myself included) could tell the difference. !  A filter with more poles may be better.  Compare the bandwidth at something like the -20db and -40 db points.  A good filter will still be relatively narrow at these points.  There is much more to involved, such as the shape of the passband, etc. so if you have choices do some more research.     Rick    KL7CW   Palmer Alaska       99% CW for 57 years
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KK4CPH
Member

Posts: 154




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« Reply #8 on: September 06, 2011, 04:27:22 PM »

Any serious CW operator "needs" approximately a 400 to 700 Hz filter for normal crowded band conditions.  Either 400 or 500 HZ would be a good choice. OCCASIONALLY when the QRM is very heavy I switch to my 250 Hz filter which sometimes helps, however this is too narrow if it is your only CW filter. If you have a good 400 or 500 HZ IF filter, and want more selectivity you could always add an audio filter to narrow the passband a bit more.  Some audio filters also let you set it up as a LO PASS filter, so when you have your 3 KHZ IF filter selected you could set your audio filter for LO PASS operation at something like 1000HZ or 1200 HZ. This is great for tuneing around and general operating without so much hiss and very high pitch QRM, and when you are in a QSO you can easily select the 400HZ IF filter if QRM enters the picture.  Only if you are a hard core contest or DX operator operating in severe QRM conditions would a second CW IF filter at 200 or 250 HZ be occasionally worthwhile. I would get a QUALITY 400 or 500 HZ filter...not all filters are created equally.  If everything else is equal, I would choose the 500 HZ over the 400 HZ option, however I suspect most folks would now opt for the 400 HZ option....probably few (myself included) could tell the difference. !  A filter with more poles may be better.  Compare the bandwidth at something like the -20db and -40 db points.  A good filter will still be relatively narrow at these points.  There is much more to involved, such as the shape of the passband, etc. so if you have choices do some more research.     Rick    KL7CW   Palmer Alaska       99% CW for 57 years

The Inrad has 8 poles, the Kenwood has 4 poles.  Haven't found anything negative about Inrad except the price is higher.  I'm sure I'll get what I pay for.  Thanks all for the input.
73
Eric
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W8JX
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Posts: 5761




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« Reply #9 on: September 07, 2011, 05:47:25 AM »

The Inrad has 8 poles, the Kenwood has 4 poles.  Haven't found anything negative about Inrad except the price is higher.  I'm sure I'll get what I pay for.  Thanks all for the input.
73

Kenwood made a 8 pole 455 kc 500 CW filter that I used in a TS-140 I had many years ago. It was very tight and much tighter than 4 pole one and much bigger too.  Not sure if 440 uses same CW filters as a 140. I would look for used ones on line rather than new. There is nothing to wear out in them. They either work or not.
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VK2FAK
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Posts: 87




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« Reply #10 on: September 07, 2011, 08:32:43 PM »

Hi All....

So what effect does a 500 hz  CW filter have on the Pitch of the CW signal your listening to.

John
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PA3DEB
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Posts: 6




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« Reply #11 on: September 08, 2011, 02:42:54 AM »

Hi All....

So what effect does a 500 hz  CW filter have on the Pitch of the CW signal your listening to.

John
None whatsoever! The pitch is controlled either by the main vfo dial or the rit-control, not by the filter. A filter is meant to increase the audio-quality of the desired signal.

73
Kees, PA3DEB
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PA0BLAH
Member

Posts: 0




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« Reply #12 on: September 08, 2011, 05:31:41 AM »

The Inrad has 8 poles, the Kenwood has 4 poles.  Haven't found anything negative about Inrad except the price is higher.  I'm sure I'll get what I pay for.  Thanks all for the input.
73

What bothering about poles. Planet Earth has only two, and Poland 38 million. Eight of them bought snowtires in winter and complained in spring because they were melted. Guarantee was expired.

When you want to compare CW filters:
1. Look not only for shape factor (bandwith -60 dB divided by bandwidth - 6dB) but also for undesired decreased damping areas in the attenuation band.

2. Furthermore the phase characteristic is very important.

Test it the way it bothers you, that means use a signal generator or a colleagues ham that provides you with an on off carrier, that is a 100% AM modulated carrier with a block wave, with a frequency of 20 Hz, (put a bug on 48 wpm and push the dot paddle)

Look with a scope to the audio coming out of your receiver, when the audio signal envelope shows what is called severe ringing, you better don't buy it.

Look with google for the call PA0LQ. You will find a world know very simple active filter designed by that genius, very well suited for CW
and you can easily construct it yourself due to the schematic and adjustment instructions; be a real ham (that is a slaughtered pig) and do something yourself instead of buying, buying buying Japanese intellectual property.
« Last Edit: September 08, 2011, 05:37:54 AM by PA0BLAH » Logged
KC9TNH
Member

Posts: 304




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« Reply #13 on: September 08, 2011, 10:16:30 AM »

None whatsoever! The pitch is controlled either by the main vfo dial or the rit-control, not by the filter. A filter is meant to increase the audio-quality of the desired signal.

73
Kees, PA3DEB
Yup, kinda like trying to carry on a conversation in a very noisy & obnoxious office. Put up a couple of acoustic partitions and, voila', you & your colleague can understand each other better WITHOUT HAVING TO USE YOUR PLAYGROUND voice or missing the point altogether....

I initially did QRP CW w/o a filter - for about 30 days, and that was 29 days, 23 hours and 59 minutes too long.
 Grin
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73
Wes -KC9TNH
"Don't get treed by a chihuahua." - Pete
AE4RV
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Posts: 952


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« Reply #14 on: September 08, 2011, 10:46:28 AM »

Playground voice. Nice. I'm stealing that.
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