I see. Was thinking along terms if change was slow it would make it easier for an AGC with bad dynamic range, i e a slow AGC loop would create less IMD so to speak, well slow at least not fast enough.
Interesting but I´m not expert enough, have to think about it more. / Jim SM2EKM -------------- On 2010-12-03 20:31, Joe Subich, W4TV wrote: > > > However by increasing the envelope fall time we will > > "help" a bad ALC system if you understand what I mean. > > Changing (increasing) the envelope fall time will not > eliminate AGC generated clicks on break ... it will only > delay their timing be a small fraction of a millisecond. > ALC will continue to hold the steady state "on" level > until it runs out of gain and then the sudden change > from a constant level to a N dB/ms slope will still be > a discontinuity in the envelope with the resulting click. > > The change in ALC generated clicks with changing envelope > decay is minimal. > > 73, > > ... Joe, W4TV > > On 12/3/2010 2:06 PM, Jan Erik Holm wrote: >> Yes 99% of all CW stations clicks at the "break" side. >> >> I didn´t think about the ALC but that is right, thanks. >> >> However by increasing the envelope fall time we will >> "help" a bad ALC system if you understand what I mean. >> >> Anyway I better can this before HHQ puts the lid on. >> >> /SM2EKM QRT >> ------------------ >> On 2010-12-03 19:18, Joe Subich, W4TV wrote: >>> >>> > 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
