>
>Rich and others, collectively, wrote:
>
>>>>This is precisely whan happens. The first cycle out of the exciter can
>>>>be anything up to the limit of the Final Unit.
>>>
>>>
>>>Surely not in practice.
>
>>This is what my oscilloscope indicates.
>
>That is the mark of a very poorly adjusted exciter, Rich.
It is a misstatement. My exciter is adjusted to deliver 100w, which is
100v-pk.. When the VOX trips, the 100v level is reached in a bit under
2mS. This is not enough time to charge the screen bypass cap.
>Just as the 3/2
>power law is, in fact, a law that physics will enforce regardless of our
>desires, so, too is the relationship between the time domain and the
>frequency domain. That relationship has been variously set forth by the
>likes of Oliver Heaviside, Fourier, LaPlace, and many others who predate the
>3/2 power law by hundreds of years.
>
>If your exciter really does produce a signal whose amplitude is full power
>at the first RF cycle, you will be generating key clicks that are extremely
>wide.
True enough. .
> Far wider than the 100 or so kHz you are claiming was produced by a
>DAF amplifier.
>
Only one of the DAFers was capable of producing such a signal, Fred. The
bandwidth of the other two was on the order of roughly 30KHz. When CHR
was really crankin', it was close to 150KHz.
>A properly adjusted "cw" rig (I put "cw" in quotes because our on-off keying
>method is not scientifically cw, which would be a continuous carrier, or A0
>modulation), MUST shape the keying waveform to eliminate key clicks. As
>Steve alludes, the effective bandwidth of the signal is roughly equivalent
>to 1/3*(rise time of the signal). I emphasize the word "roughly", but it is
>within an order of magnitude. If properly shaped, a 'morse' code signal has
>a bandwidth of about 1/5 the speed in words per minute. If the rise time is
>too fast, key clicks will result - the cw equivalent of "rotten splatter".
indeed
>You can feed your oscilloscope's waveforms into any free version of SPICE,
>or, for that matter, any Excel-based FFT algorithm to see for yourself.
>
>Rise times on the order of 100 microseconds to 500 microseconds are what
>I've measured in the past.
>
Agreed. Do you feel that a typical screen bypass C can be fully charged
in 100uS in a DAF amp.? This is the real issue here. My guess is that
Mr. Thornley was not able - or was too lazy - to build a proper screen
supply and bias supply .
>I believe an RF source CAN produce a full power waveform in the first RF
>cycle.
This would require an antenna charging current of quite a few kA.
>I just hope to not be on the band when it happens.
W6CHR comes close.
>I remember when
>I first saw this in action. I was listening about on 40 metres one day and
>heard a lot of clatter. I was tuning about the high end of SSB, perhaps
>7.28 MHz, and wondered what the noise was. On the fast AGC setting of my RX
>switch, the peaks were about S9. I tuned lower to find the signal. It was
>a local ham on about 7.040 calling CQ. His main signal was only S9 + 15dB!
>I called him on the phone to see what he was using for a rig. He'd recently
>installed "relay QSK". He had a relay doing the TX/RX switching. The
>timing was such that the relay was making AND breaking with RF actuated. So
>it was a guarantee that his first RF cycle was full power and his waveform
>also was cut off with the same rapidness. Unfortunately, I could hope his
>relay would wear out, but as he was running a mere 10 watts, I had no such
>hope. I was a lad of only 20, and he an old timer of 60, so there was also
>no hope of convincing him otherwise.
>
Alas. There is no fix for jello-brain. If 17 year olds are too young to
vote, 67 year olds should be too old to vote. Older is definitely not
always better.
>Many of the reflectees have scopes. Next time you think of it, see if you
>can gather a sample of your cw waveform.
I have. Risetime is c. 2.5mS .
> Don't even try it with an
>oversampling digital scope. You'll have to use a single-shot digitizing
>scope or an analog scope to get the true picture.
>
>Cheerio,
>
thanks for straightening me out, Fred. Your turn. .
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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