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Author Topic: SSB & CW Filter Question  (Read 414 times)
K5PEW
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Posts: 223




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« on: October 27, 2007, 08:30:29 PM »

Dear Elmer,

I understand what filters do, but I have little practical experience using them.

The Kenwood TS-440sat has two choices for SSB; 2.4 and 1.8Khz, and two for CW; 500 and 270Hz.

I'm wondering what the criteria should be for intelligently choosing which filters, if any, to install.

My typical activity is hunt and pounce DXing during contests, and general DXing, both on CW and SSB.

Is there a certain point called "Too narrow" for a certain use, and what negative effect does a too narrow filter produce on CW and Sideband?

Thanks for your time.

Graham Welch - K5PEW (In memory of Paisley Elizabeth Welch)
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K6RMR
Member

Posts: 58




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« Reply #1 on: October 27, 2007, 10:08:05 PM »

There is no since in installing a 2.4Khz filter
because there is one that came installed from the
factory. The 1.8Khz (YK88SN-1) filer does sharpen
the receiver up but it will also make the SSB sound
high pitched because it is so narrow. A normal
SSB signal is about 2.4Khz wide.The 1.8Khz filter is very usefull when you have a lot of noise or have signals
near your frequency or just splatering up and down the
band from someone pushing their ALC to hard near you.
The 270 Hrz filter is way to narrow for normal CW
but again is usefull for crowded band conditions.
for Narmal CW I would rather use the 500Htz filter.
Both filters will make the CW sound high pitched.
most people like me like to hear a crisp tone of
about 800 Hrtz.
You will lose that with most CW filters.
By the way if you work PSK 31 the 270Hrtz filter
would be great.
You can
use the 1.8Khz filter on CW as well.If I was only
going to buy 1 filter for that 20 year old radio
And I worked CW and SSB I would get the 1.8Khz filter.
By the way on that old radio you are going to have to
lift the upper PC board to solder in those filters.
In the newer radios they are mostly plug in.
         Stan
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KB9CRY
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Posts: 4283


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« Reply #2 on: October 28, 2007, 04:29:12 AM »

Go with the factory SSB filter and install a 500 CW filter, reasons as posted above.
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NI0C
Member

Posts: 2408




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« Reply #3 on: October 28, 2007, 05:58:50 AM »

Some of the advice offered thus far is just plain wrong.  For instance:
 
"The 1.8Khz (YK88SN-1) filer does sharpen
the receiver up but it will also make the SSB sound
high pitched because it is so narrow."

A 1.8 Khz SSB filter actually cuts out some of the higher frequencies in voice. It can improve copy under some conditions, though.  I used one in a TS-850S strictly for DX work.

Also:

"Both filters will make the CW sound high pitched.
most people like me like to hear a crisp tone of
about 800 Hrtz.
You will lose that with most CW filters"
 
Changing CW filter bandwidth does not change the pitch of the signal!  With your TS-440S, you have the choice of only two CW pitch frequencies: 800 Hz (factory default, but way too shrill for most experienced CW ops).  By clipping a diode in the rig, you can set the pitch to 400 Hz.  (I did this with a TS-440S that I owned).  

I wouldn't even think of using a 1.8 KHz filter for CW-- that's far too wide, even for the most casual CW operation.  I use 400 Hz CW filters in my TS-930S and 250 Hz filters in my Omni 6, supplemented by audio DSP filtering as needed.  When I owned the TS-850S, I used cascaded 250Hz and 125 Hz INRAD filters, which were great for DX work.

In addition to minimizing QRM, the narrow filters (for both SSB and CW) improve the signal-to-noise ratio.

73,
Chuck  NI0C
   

 
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AC5E
Member

Posts: 3585




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« Reply #4 on: October 28, 2007, 06:57:43 AM »

Hi Graham. That's a question that will elicit about as many varying answers as there are responders. From my perspective.....

Loss of higher audio frequencies can be corrected if desired with PBT (IF shift) and the narrower bandpass can be a sanity saver when the bands are crowded. As they usually are whenever there is propagation. I had rather have a choice of a narrow filter and no filter than a choice of wide filter and no filter.

Under noisy or crowded conditions I have never found any filter to be "too narrow." I have had to widen my filter settings when the calling stations RX is more than 100 Hz off his TX frequency, but narrow filters block much QRM and improve the signal to noise ratio. That is very desirable under many conditions.

Of course, if you have the option, I think both 500 and 250 have their place, and if I had only the one filter slot I would add an outboard DSP unit to narrow the audio bandwidth as much as possible.


73  Pete Allen  AC5E
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WA3SKN
Member

Posts: 5496




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« Reply #5 on: October 28, 2007, 07:43:31 AM »

Go to Inrad and check out their 2.1 khz filter for SSB.
For CW, most prefer the 500 hz, but 250 and 300 hz can be useful... very subjective, depends on your CW preferences.

-Mike.
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WA9SVD
Member

Posts: 2198




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« Reply #6 on: October 28, 2007, 04:22:20 PM »

If you're going to spend money on a filter, goiung from the default bandwidth of 2.4 kHz to 2.1 kHz probably won't yield that much improvement.  The 1.8 kHz will give you the "best bang for the buck," meaning the greatest improvement; but as already said, will sound "different " than the stock bandwidth.  Wit a lot of QRM, though, it can make a significant difference.

    BTW, Kenwood has discontinued that series of filters, so supply is limited to what's in the inventory.
    Inrad makes excellent filters, and make a 1.8 kHz filter, which sells for a bit less than the Kenwood unit.
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WA9SVD
Member

Posts: 2198




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« Reply #7 on: October 28, 2007, 04:59:35 PM »

One way to decide on whether a filter will benefit you (and it it's sound is something with which you can live) would be to find someone (a fellow Amateur, a store like AES or HRO) who can demonstrate the improvement provided.  It doesn't really have to be the same model or even a Kenwood; while all radios sound difference, the comparative difference between filters will still be applicable.  If the 1.8 kHz filter sounds too unnatural, it probably wouldn't sound all that good in your radio, either.  If you can, take a pair of your own headphones when you do a comparison, since speakers especially can "flavour" the sound of a radio.
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KT8K
Member

Posts: 1490




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« Reply #8 on: October 29, 2007, 11:57:02 AM »

For CW especially, crystal filters RULE!  In contests and crowded conditions, narrow filters are essential for phone or CW.  You'll see, though, in the rig reviews, that different rigs sound different with different filters.  The narrowest CW filters, on some rigs, can "ring", which is not very nice to have to listen to for any length of time.  And 1800 Hz is the bare minimum for SSB -- In contests I usually run my filter/DSP system around 2050 Hz and adjust it up and down depending on conditions.

DSP is a nice addition, but no substitute.  In fact, I'd say that in most applications DSP is feature-rich but performance-mediocre.  (I was going to say performance-poor, but it's probably not THAT bad -- I just wouldn't want to have only DSP.)  

I _often_ use my narrowest filter (250 Hz) on CW, and dial the DSP down to 100 Hz on top of that.  I'll be doing a lot of that in next weekend's contest (Sweepstakes CW).  C U then, hopefully!
Best rx & 73 de kt8k - Tim
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