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Author Topic: Of Rise Time and Key Clicks  (Read 405 times)
VE7ALQ
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Posts: 349




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« on: April 29, 2006, 07:00:18 PM »

I just bought an Icom IC-756ProIII expen$ive radio.  I am very pleased with it.  One thing (amongst many others) is an adjustable rise time.  I can select {2,4,6,8} milliseconds, with the Icom default being 4 milliseconds.  I have always preferred "firm" keying, verging on the border with "clix", as I have found that firm keying, like the Yaesu FT-101B gets through, whereas mushy keying like the HeathKit SB-101 doesn't  (I have had both rigs)  I wonder if the 2 millisecond rise time is too abupt and will make me enemies on the band?  The Icom IC-756ProIII defaults to 4 milliseconds rise time.  I have been told that there are no "clix" with this 4 millisecond setting, but have yet to try it at 2 milliseconds.  Comments?
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VA7CPC
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Posts: 2388




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« Reply #1 on: April 29, 2006, 11:23:37 PM »

Roughly speaking, the bandwidth of your signal is the inverse of your rise time.

So a 2 msec rise time will give you a 500 Hz bandwidth.

That's a lot of splatter !

You can check this by having someone monitor your signal using PSK31 "waterfall" software (e.g. Digipan).    Broad CW signals show up clearly.  

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NC0B
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Posts: 9




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« Reply #2 on: May 05, 2006, 07:09:29 PM »

The most recent rigs I have tested, that had adjustable rise times on CW, have measured faster than the menu suggested. Both the Orion II and the IC-7000, even if set to 8 msec, had a rise time faster than 3 msec.  I will test my Pro III on May 7th, and post the information.  I used a Tektronix digital storage scope to make the measurements.  So at this point, my recommendation is to set it to 8 msec, and keep the band as clean as possible.  
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NC0B
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« Reply #3 on: May 07, 2006, 11:37:46 AM »

The Pro III rise time is much faster than the menu reading, but the fall time is rather close to the options of 2, 4, 6 and 8 msec.  At 2 msec, there is a small spike on the leading edge, in addition to a very fast rise time. I don't hear a key click on the "break" at any settings, but the radio is much cleaner on "make" at 6 msec than at 4 msec, and even cleaner on 8 msec.  When set to 8 msec, the actual rise time, as defined in the Icom manual, is actually is a little over 2 msec, with a fall time of about 8 msec.  
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