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Author Topic: What effect does changing the cw rise time on an IC7600 have?  (Read 1729 times)
W3HKK
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Posts: 593




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« on: January 19, 2014, 05:50:59 PM »

I see in the menu,  I can change the cw rise time,  from  a default 4 ms up to  at least 15 ms.

What effect does changing the cw rise time have?  Does it in any way prevent hot switching of an amplifier? Or does it just change the softness/sharpness of the cw  character to the human ear?

Tnx.
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KB4QAA
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Posts: 2264




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« Reply #1 on: January 19, 2014, 05:59:52 PM »

The faster the rise, the greater the chance for RF clicks and harmonics. 

Adjusting it would also change the tone.  First radio I've heard that had an adjustable function (I'm behind the times). 

The Feb issue of QST has a Oscope figure showing the keying  envelope of the TS-990 which should be an excellent example.  There are discussions about ideal keying envelope in the ARRL Handbook, and numerous QST articles over the years.

Hook up a dummy load and listen to your signal as you adjust it!
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WD8KNI
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Posts: 137




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« Reply #2 on: January 19, 2014, 07:03:10 PM »

The rise time of a CW signal is what controls the band width of the signal.  A good time is around 7ms.  IthHas nothing to do with keying the amplifier..  Some modern rigs are so bad you can't run them next to other rigs during field day or a contest because of clicks, and garbage they generate.  Just tune off frequency with a wide filter on some stations and you can hear how bad some 5,000 dollar radio's are.. my old DX60B sounds better...   

Mark Amos W8XR has about the best description I have ever read..  it is posted on Tom's website (W8JI)

  http://www.w8ji.com/cw_bandwidth_described.htm

Just curious what rig allows you to change it (good for them).  About the only manufacturer that really cares about CW quality is TenTec... my rig of choice..

Regards... Fred
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ZL1BBW
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Posts: 346




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« Reply #3 on: January 19, 2014, 09:30:50 PM »

Used to have little LC circuit at the key on one rig in the early days to "soften" the keying a bit always gave it a nice easy sound, not a chirp, but softer on the ears.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
WB6RXG
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Posts: 73




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« Reply #4 on: January 20, 2014, 04:30:36 PM »

Besides the IC7600 mentioned in the subject line the Kenwood TS-2000 allows you to adjust rise time.  I'm sure many other modern rigs do it too.

73,
Stuart
WB6RXG
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W3HKK
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Posts: 593




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« Reply #5 on: January 20, 2014, 05:41:37 PM »

Tnx Fred.  That helped a lot.

Next step is to drop my  rise time from 10-12 ms down to  8 ms.  The menus gives 4, 8, 12 ms as some of the options.

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