First, I better admit that I'm a curious "appliance operator" who reads
more than he understands <g>. I'm trying to understand audio type keying
and how it relates to TT rigs.
Let's start with what Steve Ellington wrote:
"A lot of newer rigs develop their keying in the DSP stage. Even the
TS-950sdx did that and it's ancient history. If you think about it, shaping
the envelope just right should be much easier in dsp than trying to key or
shift the frequency of an RF oscillator.
The Collins 32S-1 transmitter keyed an audio oscillator and fed it into the
ssb modulator. Unfortunately it had terrible keying and Collins was forced
(by the FCC) to revert to grid block keying in later models. This gave a bad
name to audio type keying but now it appears that technology has improved.
[thanks Steve]
I also read an article about High Speed CW for Meteor scatter work called
"Utilizing the Constant Bombardment of Cosmic Debris for Routine
Communication" by Shelby Enis, W8WN He explains how "cw" is produced as
used in one type of meteor scatter work and he writes:
"Keying is done by an injected audio tone [using sound card technique] (as
is done with many of the digital modes), ...<snip>. The emission type is
designated J2A. This method produces keying that is indistinguishable from
on/off keying of the main carrier, and is the *same method* [my emphasis]
used by many rigs to produce CW."
So, let's see if I understand this correctly . In many modern rigs keying
is done by audio type keying that results in J2A rather than true A1A
emission. On the receiver end we can't tell the difference. This was first
done unsuccessfully in the Collins. In modern rigs today this is often
successfully done using DSP. Is this basically true?
Questions:
1.Can I assume that the Orion, Jup/Peg and perhaps the 756/746 are all
producing J2A?
2. Can non DSP rigs be used to transmit legal J2A if sound card technology
is used ?
3. Were there other rigs (besides Collins) that used audio type keying
without DSP? Is DSP the only way to produce clean legal J2A ?
4. Can I assume that the classic TT rigs produce A1A and not J2A?
5. I still don't really understand what J2A audio type keying is. What is
the difference between J2A and simply keying the rig in SSB mode while
holding the microphone to the output of a code practice oscillator?
It is possible that I'm totally clueless <grin> ... and so I ask questions ;-)
tnx & 73
Bob, KB1CIW
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