> Waveform? When you have a 1 ms raise/fall time no way you
> can shape the waveform so it doesnt click.
That's not the case. If the first and second derivatives of
the power output are minimized, the waveform does not click.
There are many studies about bandwidth vs. rate of change in
digital modulation that will provide the information to show
that principle.
In the specific case of CW as long as the transitions from
the "rise" to the steady "on" state and from the steady "on"
state to the fall are properly shaped (first/second derivative
minimized) the apparent clicks will be minimized.
The traditional "feedback" ALC system almost guarantees clicks
on the *trailing edge* of the CW element. Traditional ALC
attempts to maintain the output as the key is opened and will
increase system gain as the driving waveform starts to decay.
The output level will only begin to fall when the ALC gain
has reached maximum - at which point there will be a major discontinuity
in the waveform. A properly designed feedback
ALC system would be incorporate sample and hold to maintain
steady system gain during the "ramp up" and "ramp down" parts
of the CW waveform to prevent the "corner sharpening."
Again, rise time controls the basic CW bandwidth but "clicks"
are a feature of discontinuities in the CW envelope. Please
do not confuse the two.
73,
... Joe, W4TV
On 12/3/2010 9:46 AM, Jan Erik Holm wrote:
> Waveform? When you have a 1 ms raise/fall time no way you
> can shape the waveform so it doesnt click.
>
> /Jim SM2EKM
> ---------------
> On 2010-12-03 15:29, Guy Olinger K2AV wrote:
>> All the click complaints for years and still Yaesu doesn't take care
>> of the waveform. It's not like there aren't tons of reads on the
>> subject, no excuse at all since Google. It's more like they just
>> don't care, or are simply convinced it doesn't matter. After all,
>> isn't CW obsolete, and nobody uses it anymore, right?
>>
>> 73, Guy.
>>
>> On Fri, Dec 3, 2010 at 9:08 AM, Paul Christensen<w...@arrl.net> wrote:
>>> 4 ms. Given that the FTdx5K rise/fall is roughly double the time of the
>>> K3 -- and that the K3 at 2 ms consumes significantly less bandwidth than the
>>> FTdx5K at 4 ms, the CW transmit quality of the K3 is far superior. I would
>>> like to hear QSK on the Yaesu, compare it with the K3's QRQ mode, and note
>>> any audible artifacts in the headphones -- especially for signs of clicks
>>> and DC thumps.
>>>
>>> Referring to the December, 2010 QST Product Review on p.45, take a look at
>>> the leading edge of the second pulse (lower trace) in Figure 1. The sharp
>>> rise and sharp edge at the top of the waveform is what is consuming the
>>> bandwidth. Based on that waveform, it was absolutely generating clicks at
>>> some distance from the Fc. That pattern is characteristic of a deficient
>>> ALC system.
>>>
>>> A deficiency in the ALC system then takes us into SSB Tx IMD. The published
>>> FTdx5K Tx IMD numbers look great with the ARRL's steady tone method but
>>> arguably, that's probably more relevant to data modes. The question is
>>> "what is the FTdx5K's ALC doing to undermine the rig's otherwise excellent
>>> SSB Tx IMD numbers, especially in Class A?" Really, the published Tx IMD
>>> figures are meaningless unless dynamic testing is conducted to simulate
>>> rapid changes in power associated with voice modes.
>>>
>>> Paul, W9AC
>>>
>>> ----- Original Message -----
>>> From: "Jan Erik Holm"<sm2...@telia.com>
>>> To:<elecraft@mailman.qth.net>
>>> Sent: Friday, December 03, 2010 8:27 AM
>>> Subject: Re: [Elecraft] Fwd: New Sherwood report
>>>
>>>
>>>> Yes but to what rise/fall time was the radio set? AFAIK in
>>>> the FT5000 it can be changed.
>>>>
>>>> /Jim SM2EKM
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
