[Milsurplus] [ARC5] 1625 and Key Clicks.

Bob kb8tq kb8tq at n1k.org
Tue Jul 11 19:51:38 EDT 2017


Hi


> On Jul 11, 2017, at 7:42 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
> 
> On 11 Jul 2017 at 16:21, Bob kb8tq wrote:
> 
>> Hi
>> 
>> Time constant - how fast do you normally send? 
> 
> Around 30 WPM, most of the time. Sometimes a bit slower. There are a group of guys
> centered around 30 kHz up from the bottom of 40 and 20 who bang along at speeds up to
> 100 wpm. Some of their signals have very noticable clicks.
> 
>> 10 WPM is 50 characters per minute or about one a second. With normal 
>> spacing, you are at a character in a second. 
>> 
>> If you send a series of numbers, you have about 20 elements per second. Normal
>> letters will be a bit less. 
>> 
>> For reasonable "fidelity" you want a time constant / filter that will pass the 5th harmonic
>> of your keying "square wave". That gets you to about 100 Hz or so. 
>> 
>> This all scales with keying speed. If you normally send at 100 WPM, 100Hz becomes 1KHz. 
>> None of it is exact. You could go to "3rd harmonic" and cut them 2:1. ...You could go to the 
>> 9th harmonic and double the targets. It still works either way.
>> 
>> Bob
> 
> Thank you for that above, Bob. I'll file it in my file on keying methods.

No problem. I happen to be a fan of grid keying rather than cathode keying. It *does* take a separate bias
supply but it makes click filters much easier …

Have fun !!

Bob
KB8TQ

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