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Author Topic: Which CW Filters Do I Really Need?  (Read 709 times)
KI4EKN
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« on: April 11, 2004, 09:51:43 PM »

I have 2 TS-930S' and want to set one up for CW use.  There are a wide range of CW filters available.  Which one(s) would you suggest?  I don't want to spend the money to collect the entire set, so if you had to limit your choice to just one or two, which one(s) would it be?
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AC5E
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« Reply #1 on: April 11, 2004, 10:04:27 PM »

That's another of those "I do it this way, and if you do it any other way you are wrong" deals. So whatever you are told will absolutely be wrong according to someone else.

It's really a combination of personal taste and band conditions. When the bands are lightly occupied and I am looking for a QSO I generally go with or a relatively wide filter setting. In fact, a 2400 Hz SSB filter works just fine. But when the bands are busy or I'm trying to dig a DX station from under a pileup even 100 Hz is sometimes "too wide."

For general use - probably a 500 Hz filter would be the most used. So that should be your starting place. After you determine what you want need you will have a better basis to add filters as needed.

73  Pete Allen  AC5E

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N7DM
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« Reply #2 on: April 11, 2004, 11:01:06 PM »

Once again Pete has it right...   I have a 250 cycle that I use on contests, but it is SO bloody narrow that tuning around with it is hard.   "Wide"... and 500  will do virtually everything.
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N8UZE
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« Reply #3 on: April 12, 2004, 12:39:35 AM »

I start with about a 500Hz setting and then after finding a signal switch to a narrower setting, typically 200Hz or 300Hz.
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K0ZN
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« Reply #4 on: April 12, 2004, 01:14:01 AM »

Hi,
I agree with the comments above. It really kind of depends on what kind of operating you do and what times you get on the air (i.e how busy the bands are)
My experiences with several receivers has been that for "most" CW operations anything narrower than 500 cycles often causes some audio distortion, or ringing, etc....even with "good" radios. So about the only time I ever used anything narrower than 500 cycles is when QRM is really bad and I "desperately" want to hear the guy. For just rag chewing on CW, I find filters as wide as 1.2Khz just fine and more pleasant to listen to. SSB is the same situation... if you just enjoy chatting with people, the wider filters give better fidelity. 1.8 Khz starts distorting, but in a contest situation it can help. The differences in filters is a little more "blurred" on SSB due to the wider nature of the signals, than on CW. "That's my 2 cents..."

73,  K0ZN
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KB9CRY
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« Reply #5 on: April 12, 2004, 07:38:04 AM »

I use a 930S which has both International Radio cw filters in it, the 500 & 250.  I rarely use the 250 since it is very narrow; only during crowded contest cdx.  My suggestion is get a 500 filter and along with the VBT, notch, and IF shift, you'll have all the capabilities you'll need.  Phil  KB9CRY
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K8AC
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« Reply #6 on: April 12, 2004, 08:36:30 AM »

500 Hz is a good place to start.  I don't know if the 930 supports filters in two IFs, but if so, cascaded 500 Hz filters would be noticeably better than one.  You can supplement the filter with any of a number of tunable audio filters - doesn't have to be a DSP type filter.  For example, the old Autek QF-1A or one of the MFJs are available for less than $50.  My favorite CW filter when the rig has room for only one is a 400 Hz bandwidth.  International Radio makes those for some rigs.  Narrower filters are sometimes useful in contests, and theoretically should reduce the overall noise level, making it easier to copy very weak signals. Distortions introduced by those filters sometimes negates that benefit and you can actually copy better through the wider CW filters.  Does the 930 have passband tuning or IF shift?  You can often use that to narrow the effective bandwidth of 500 Hz filters for selectivity almost as good as having a narrower filter.
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NA9Q
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« Reply #7 on: April 12, 2004, 10:53:47 AM »

I run the TS940SAT and I had the YG455CN1 270 HZ filter in it for several years.  Although great for separating stations in a crowded contest situation, it was just too narrow for everyday CW ragchewing.  I replace it with the Kenwood matched YK88C1 and YG455C1 500 Hz filters.  Much more suitable for everyday operation and much easier to tune.  I would suggest this approach to your situation.  73, Mike
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W3JJH
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« Reply #8 on: April 12, 2004, 12:09:50 PM »

Here's another vote for cascaded 500-Hz filters--one at each IF frequency.  I doubt that the improvement in AGC action from using narrower filters would offset the increased difficulty in tuning.  Adding an external audio filter (analog or DSP) with tunable bandwidth and center frequency will allow you to zero-in on a particular signal when the band is crowded.
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N7DM
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« Reply #9 on: April 12, 2004, 12:33:09 PM »

I am a Ten-Tec guy, so I'm not sure how much of this 'air polution' is truly useful to the  Kenwood(?) user, but here goes.

In the Corsairs, the crystalling provides a beatnote of 700 cycles ...when the carriers are zero beat. I really don't like that note, I prefer around 500.... aging hear-holes, etc.  I tune to a good strong signal, following Mr.T-T's choice. Then I use the BFO tuning to move to the note *I* like.  Of course, that moves it out of the center of the pass band, so THEN I use the pass-band tuning to re-center on the IF of *MY* choice. I leave it there. So much for DM's use of PBT.

Another thing that may effect the various effects of our filters.  T-T uses eight pole  filters. There are eight (Cool xtals on each filter board..you can see and count 'em. That effects the shape factor of the filters. AND, T-T uses an eight pole jobbee in the other IF as well.   I dont' have a CLUE of what is in the other brand filters. Except that I do own a ICOM R-70 that I use for monitoring, antenna bridge work, etc. I put a 250 in it.   *TINY* little thing. difficult to solder in. I wonder what is in it?
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NI0C
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« Reply #10 on: April 12, 2004, 05:22:25 PM »

My vote goes for as much selectivity as you can get.  My first encounter with a 270 Hz filter was during a Field Day contest about 15 years ago, and I didn't like it because I was used to tuning with a 500 Hz filter.  Since that time, though, I've progressed through cascaded 500's, 270/250, and am presently using INRAD 250/125 in my TS-850.  In each case, the tuning took about a week to get used to, but I like the better signal to noise ratio and QRM rejection.  My TS-850 also has a selectable fine tuning rate to help out in this regard.  As an experiment, recently I took out the 125 and tried the 250 in its place once again, for about a week.  The 125 went back in and it's going to stay there.  I realize mine is probably a minority view, so take it with a grain of salt.  I'm also a low band CW  DX'er working with weak signals most of the time.

73 de Chuck  NI0C
 
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N7DM
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« Reply #11 on: April 12, 2004, 06:43:30 PM »

YES!  Chuck brings up a point I had forgotten !  Signal to Noise Ratio.  When you run in the narrowest possible bandwidth you greatly reduce the amount of 'racket' that also comes thru the receiver.  Add to that the little used but excellent concept of MANUALLY adjusting your R.F. gain [not running AGC], and you are close to having 'squelch'...   You either hear the signal, or you hear nothing!

But it is still a pain to tune across a Non-Contest band...
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X-WB1AUW
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« Reply #12 on: April 13, 2004, 02:41:20 AM »

Many DX stations use 250 cycle filters.  As a result, if you want to try and "zero-beat" the station that the DX is working, you'll need a narrow filter.

Inexpensive external digital filters work great at taking the signal from 500 cycles to 250, and narrower.

Bob
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N7DM
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« Reply #13 on: April 13, 2004, 11:26:58 AM »

Well, Bob, while it is true when RAG-CHEWING with the Eu guys, we zero-beat....If you want to think the Devil just climbed all over you, call a DX station in a pile up ON HIS FREQUENCY!    "UP....."  is the Standard place to call him.  UP 5, 10..even 20 or 30 KC.....
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KT8K
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« Reply #14 on: April 14, 2004, 03:45:15 PM »

I like having a 250 hz filter, and think 500 Hz would be too wide, but I'm a pretty hard core CW op (90%).  The real ticket, in my book, is having good wide and narrow crystal filters AND a good audio filter.  The combination of the two is great.

For years I had only the RF gain and an outboard audio filter.  Now that I have a rig with a *real Crystal Filter* I am much happier.  There are night's on 40m when I can scan nicely with the tight filter on, but most times on 15m and above I can open the reciever all the way and still have no QRM.
Hope to catch you on the bands!
73 de kt8k - Tim
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