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Author Topic: Should I get the CW filter?  (Read 22032 times)
N3PDT
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Posts: 76




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« Reply #45 on: September 19, 2011, 09:21:31 PM »

 Smiley That's great Eric! Hope to hear you on the bands.
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K3STX
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Posts: 1050




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« Reply #46 on: September 19, 2011, 09:22:19 PM »

i second that emotion. After listening to 450 Hz sidetone for years, 800 Hz seems pretty shrill. And it is amazing what you can dig out with the low sidetone.

Congrats on the filter, anything to help out!!

paul
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KK4CPH
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Posts: 154




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« Reply #47 on: September 20, 2011, 09:45:21 AM »

Eric,

Congratulations on the installation (when I purchased my TS-440S, I had AES install the filter for me).  One other modification you may consider is choosing the pitch frequency.  As I recall, the 440S offered the choice between 400 Hz and 800 Hz, selected by a diode.  Some people (including me) prefer a low pitch frequency to help the internal "filter between the ears" to discriminate among closely spaced CW tones.

73,
Chuck  NI0C

Not familiar with the diode.  Is it one you swap out or is it an open spot on the board?  There was plenty of room for the CW filter (And there's also a spot for an SSB filter though personally, I don't see a need for one) but everything else is packed in there.  Would hate to burn the unit up with my rookie soldering skills!   Shocked

73
Eric
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NI0C
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Posts: 2418




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« Reply #48 on: September 20, 2011, 10:17:44 AM »

Eric,

As I recall, the CW pitch selection is described in the TS440S owner's manual, and it involved snipping one lead from a diode to go from a high pitch (800 Hz, I think) to a low pitch (400 Hz, I think).  If you don't have a manual, you can probably locate (or even download one) online. 

I'd suggest snipping the lead in a manner such that you could easily restore the connection with a solder bridge in case it ever needs to be changed back.

73,
Chuck  NI0C
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NI0C
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Posts: 2418




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« Reply #49 on: September 20, 2011, 10:27:53 AM »

Eric,

I just downloaded a manual from: http://www.oz1bxm.dk/manuals/TS-440/TS-440S-Instruction-Manual.pdf 

Look at section 5-8-5 on page 26: "CW Zero Beat Selection."  (It's D73).  While you're at it, you may wish to cut D66 to get 10 Hz display resolution (instead of the default 100 Hz resolution). See section 5-8-4. That came in handy when I operated RTTY with my 440 (and Commodore 64 computer). 

73,
Chuck  NI0C

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N3OX
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Posts: 8847


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« Reply #50 on: September 20, 2011, 08:29:09 PM »

Be aware that if you snip the diode to lower the pitch to 400Hz on a TS-440, the sidetone will remain at 800Hz.  The sidetone oscillator is an analog circuit (a RC phase shift oscillator) with its frequency set by fixed components.

If you use the sidetone to help you zero-beat the station you're working this can be a problem.. and it just bothered me... it was just weird.  I wanted my transmitted pitch to match my received pitch.  I had a keyer with an adjustable frequency sidetone but then the sidetone wasn't in my headphones.

I figured out a mod, but it requires adding stuff to a surface mount board.  This is deeply annoying given that there are almost no surface mount parts in a TS-440S but there are a couple little surface mount daughterboards and one of them is the sidetone oscillator Grin

http://n3ox.net/files/N3OX_400Hz_sidetone_mod.pdf

Took me a minute to figure out that the little blue guys were just jumpers Undecided
« Last Edit: September 20, 2011, 08:32:50 PM by N3OX » Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KB2FCV
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« Reply #51 on: September 21, 2011, 07:32:22 AM »

If you plan on using CW alot, I'd reccomend a filter. I find it nice when trying to operate a weaker station but there is a much stronger station nearby making it difficult to copy. Also, it's nice during contests when the band is packed full of signals. Most of the time a 400-500hz filter will do the trick.
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K3RAP
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« Reply #52 on: September 21, 2011, 08:25:14 PM »

Eric, I agree with Jim - N2EY. The best post came from VK3GDM "buy one and try it". Opinions are like butt holes, everyone has one. See for yourself. It's your opinion that counts since it's your money. Buy the 400HZ Inrad filter. Inrad is a great company. They will take it back if you don't want it. I would bet it's a keeper. I have a TS-570DG. It only has one mechanical filter slot. I called Inrad and asked for advice since I work SSB and CW. They sent me a 2100, 1800 and 400HZ and told me to pay for the ones I liked and send the others back. WOW! I love my 400HZ Inrad filter. For me, because I love CW, it was a great value. But that's my opinion, discover yours. You have nothing to lose.
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N2EY
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Posts: 3911




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« Reply #53 on: September 22, 2011, 04:23:17 AM »

There's two more issues involving the filter: "Intentional" interference and band usage.

Imagine a situation where everyone is using 400-500 Hz wide filters, and is trying to be considerate. Those who intend to call CQ will naturally tune around looking for unoccupied pieces of band before doing so. With a good narrow CW filter, all they need is a couple of hundred Hz of bandspace for a "clear spot".

But with a wide filter, the "clear spot" has to be a lot wider too. This puts fewer people in a given bandspace.

And if you have a mix of folks using wide and narrow filters, the "wide" folks may think they are being intentionally QRM'd, when in fact the others can't even hear them.

IOW, if A has a narrow filter, and B comes on the air 1.5 kHz away, A may never know it if A's rig has decent dynamic range. But if A has a wide filter, B can come roaring in, causing QRM, because A's filter is so wide.

73 de Jim, N2EY

 
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AK7V
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Posts: 251




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« Reply #54 on: September 22, 2011, 07:57:28 AM »

There's two more issues involving the filter: "Intentional" interference and band usage.

Imagine a situation where everyone is using 400-500 Hz wide filters, and is trying to be considerate. Those who intend to call CQ will naturally tune around looking for unoccupied pieces of band before doing so. With a good narrow CW filter, all they need is a couple of hundred Hz of bandspace for a "clear spot".

But with a wide filter, the "clear spot" has to be a lot wider too. This puts fewer people in a given bandspace.

And if you have a mix of folks using wide and narrow filters, the "wide" folks may think they are being intentionally QRM'd, when in fact the others can't even hear them.

IOW, if A has a narrow filter, and B comes on the air 1.5 kHz away, A may never know it if A's rig has decent dynamic range. But if A has a wide filter, B can come roaring in, causing QRM, because A's filter is so wide.

73 de Jim, N2EY

 


This is why I suggest using a "wide" filter (1K or more) unless there's a need for narrow.  I always tune around with the wider filter.  When looking for a place to call CQ, I do it with the wide filter and keep it wide when listening for a response, especially since some people don't zero-beat and will answer outside of a narrow passband.  Once the QSO is going, I may switch to narrow for better SNR or especially if someone else starts transmitting near our frequency.
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KE7FD
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« Reply #55 on: September 23, 2011, 10:59:41 AM »

So let me throw this out as an inquiry with regards to narrow filtering for CW: What about add-on audio DSP filters?  Has anyone used them and are they effective enough (heavy on the enough) to take the place of a single purposed CW filter?  Reason I ask is there's bound to be newcomers to Ham radio who also like CW who want an affordable way to get good filtering for CW but might want to have some additional filtering for SSB.  Some general purpose DSP filters might fit the needs of this group (albeit narrow ).  But I admit, my experience with CW predates the invention of dirt so someone with more current use of CW filters and external [audio] DSP could shed some light.

Glen - KE7FD
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KK4CPH
Member

Posts: 154




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« Reply #56 on: September 23, 2011, 05:02:11 PM »

Eric,

I just downloaded a manual from: http://www.oz1bxm.dk/manuals/TS-440/TS-440S-Instruction-Manual.pdf 

Look at section 5-8-5 on page 26: "CW Zero Beat Selection."  (It's D73).  While you're at it, you may wish to cut D66 to get 10 Hz display resolution (instead of the default 100 Hz resolution). See section 5-8-4. That came in handy when I operated RTTY with my 440 (and Commodore 64 computer). 

73,
Chuck  NI0C



I have the owners manual. (Previous owner kept everything) I looked that page over.  I can even calibrate the display.   Cool
Think I'll leave those mods alone for now.  I'll get on the air and see how I like it.  But thanks for finding this.  I wouldn't think that Kenwood would give tips for opening up their unit and doing modifications.

73
Eric

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GW0NSR
Member

Posts: 2




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« Reply #57 on: September 29, 2011, 07:46:08 AM »

Whatever rig you use for CW, you really should be using a narrower filter than the standard SSB device. I'm assuming that you are relatively new to the mode, (apologies if I am wrong) and as you progress through the various stages of CW operating, you will be trying to winkle out weaker signals from the qrm that abounds on some bands. This is where the 400hz filter will come into its own and repay every cent that you paid for it. Try to listen to cw on a friends rig that is so fitted. You will be truly surprised at the difference it makes. Ease of copy, elimination of hiss, little or no interference. A different world altogether!
73 de Tony, GW0NSR.
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VK3GDM
Member

Posts: 28




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« Reply #58 on: November 03, 2011, 05:02:19 PM »

AK7V's method works for me. Tune around with the wide filter, then switch to the narrow filter when in QSO.
If the band is quiet, I often don't switch in the narrow filter.

In response to KE7FD:
The add on DSP filters are good, but generally only process the base-band audio signal.

Unwanted signals that the audio DSP filter out can still come through your wide IF filter and affect the AGC.

So for example, you could be listing to a week signal with you audio DSP set to narrow and suddenly a strong signal appears just off frequency, but still inside your wide IF filter band pass.  The strong signal will cause the AGC to reduce the receiver gain, which will quieten the receiver and your wanted signal may completely disappear.  You can't hear the unwanted signal because the audio DSP is removing it.  The only indication you get is the quieting effect, sometimes referred to as 'AGC pumping'.  It is like your receiver is being muted.
You can attack this problem by using the pass band tuning control, adjusting AGC fast or off, adjusting the RF gain and switching to CW reverse.
Far better receiver performance in terms of selectivity and sensitivity will be achieved with narrow filters.  When the unwanted signal is outside the IF pass-band, the wanted signal receives the full benefit of the receiver sensitivity.

I experience these affects using my TS480SAT which has audio DSP built in.  I had no narrow IF filters installed for the first two years.  When I finally got around to installing them my operating pleasure was greatly increased.

Not sure if you can get after market DSP filters that insert into the IF?  That would be worth doing.

Experimenting with all these add on features (toys) is fun and often a good learning experience.

73
David, VK3GDM





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VE3XDB
Member

Posts: 139




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« Reply #59 on: November 07, 2011, 04:47:55 AM »

Hello,

With no optional filters installed, the 440 has 2 available filter slots.  I don't work SSB, so I purchased 2 cw filters, the YK88C (500 Hz) and the YK88CN (270 Hz).  Setup of this combination of filters is described in the TS440 instruction manual.  This setup worked very well for CW.  In my current rig (Kenwood TS-570D/G) I have an Inrad 400 Hz filter, and it does a good job. 

Someone previously mentioned the SCAF1 filter.  With another 440 (I have had 3-4 of them in my hamming career) I used the SCAF1.  If you learn to use it correctly, it is also a very good filter.  Takes all the noise, hash and adjacent qrm away.  But it is an AF filter, so all the crud comes through all stages of your radio.  The IF filters clean things up earlier in the chain, and it makes for a better result. 

My recommendation would be a 400 Hz Inrad filter to start, then see if you need the narrower filter as well.  The 400 should suit you just fine for casual operating, DX and even some contesting. 

Best regards,

Doug VE3XDB
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