> There is no turn on/turn off. That's what I'm trying to tell you. The
> smooth phase transition that occurs as the tones change from one to
> the other is exactly the same as slowly turning the knob on a linear
> (as opposed to a PLL digital) VFO. NO CLIX!!!
No, I've watched WSJT and the output does not sweep from tone to tone.
There is a shape to each tone. That shape will be destroyed by a
class C amplifier.
> Strong RTTY does indeed generate clix in some receivers, at least
> they do in my "economy" DSP if filterd radios. NB makes it worse
> in those radios.
Then you need a better receiver.
> Any time you turn on and off a "signal" you generate sidbands
> (sinX/X). You can modify the wave shape and reduce the sidebands
> (also known as clix) but you cannot eliminate them entirely.
A carrier that is keyed (modulated) properly will not have hard
(or wide) sidebands and the sidebands will not be made harder
(wider) by a linear amplifier. However, a class C amplifier
will change the modulating waveform by turning on abruptly and
by saturating (compressing/clipping).
73,
... Joe, W4TV
On 5/23/2010 7:55 PM, Larry wrote:
>
> On 23-May-10 3:49 PM, Joe Subich, W4TV wrote:
>>
>> I don't care what kind of transition Joe has programmed into the
>> DSP. The rise time/wave shaping makes little difference with a
>> class C amplifier because the sharp turn on/turn off characteristic
>> and saturated operation will always square up the pulses.
>
> There is no turn on/turn off. That's what I'm trying to tell you. The
> smooth phase transition that occurs as the tones change from one to the
> other is exactly the same as slowly turning the knob on a linear (as
> opposed to a PLL digital) VFO. NO CLIX!!!
>
>
>
>
>>
>> A Class C amplifier requires a certain level of drive to "turn on"
>> and operates in saturation ... the turn on threshold will remove
>> much of the low level ramp up and the saturation will create sharp
>> "corners" at the top of each pulse. Even the most basic measurement
>> with a dual trace oscilloscope will show the difference between a
>> linear amplifier and one run in class C. Run a string of dits
>> through a class C amplifier and compare the difference between
>> the drive signal and the output.
>
> Any time you turn on and off a "signal" you generate sidbands (sinX/X).
> You can modify the wave shape and reduce the sidebands (also known as
> clix) but you cannot eliminate them entirely. At least not until the
> signal is either on all the time or off all the time or looks like a
> sine wave. If the keyed wave form looks like a sine wave there will be
> no sidebands generated.
>>
>> The clicks are not receiver generated ... they are generated in
>> the transmitter/amplifier by pulse squaring and eliminating the
>> wave shaping created in the exciter. W7AY has done extensive
>> work with wave shaping and can show the "damage" caused by non-
>> linear amplifiers in FSK and AFSK systems.
>
>
> Strong RTTY does indeed generate clix in some receivers, at least they
> do in my "economy" DSP if filterd radios. NB makes it worse in those
> radios.
>
> If the RTTY tones are "keyed" as you imply above, then yes I agree they
> can and will make clix. However if the tones phase is seamlessly
> transitioned at the zero crossing, there will be no clix. It all depends
> on who did the DSP programming on a SSB type setup or who designed the
> radio internals on a direct keyed setup.
>
> An amplifier that is only conditionally stable "in band" will also
> generate clix as it tries to self oscillate over a small portion of the
> RF cycle during phase transitions. Not common, but I've seen it happen.
>
>
>>
>> > Last I looked Duty Cycle was defined by the ratio between ON time and
>> > OFF time. No time limit specified.
>>
>> Any calculation of "duty cycle" must include a time limit ...
>
> Why "must" it? Duty cycle specified on transformers, motors, is not time
> limited. Duty Cycle implies unlimited time operating normally. Normal
> operation of a ham amplifier includes RX periods as well as TX periods.
> By your definition, CW has a 100% duty cycle since you only want to
> count the time when it's actually transmitting. I think we are confusing
> duty cycle of the modulation envelope verses duty cycle of the SYSTEM.
>
>>
>> Simply put, when one limits the calculation to transmission
>> periods, AM, FSK/AFSK, WSJT, etc. are 100% duty cycle modes.
>> CW is a 50% - 60% duty cycle mode (depending on message
>> content) and SSB is up to 60% (depending on compression or
>> clipping levels). If you start adding "receive time" all
>> of those numbers will decrease but it still does not eliminate
>> the fact that AM/RTTY/WSJT/etc. are as much as four times as
>> taxing on an amplifier than CW at a similar peak power level.
>
> By the above numbers, FM/RTTY/WSJT is still only 2x taxing. 50% CW vs.x
> 100% WSJT/FM/RTTY. AM is not even close. 100 watt carrier is 25% of the
> 400 watt PEP of an AM signal. With modulation at full PEP assuming tones
> not voice the average is still only about 50%, so same same as CW.
>>
>> Good for you ... however, the Eimac data sheets clearly show 400 mA
>> single tone (CW) plate current in AB2 service at all plate voltages
>> from 1500 - 3500 (http://www.g8wrb.org/data/Eimac/3-500Z.pdf).
>
> I stand corrected, that spec sheet does indeed show 400 ma. As much as
> those things cost these days even 350 makes me nervous!
>
> 73, Larry
>
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