[TenTec] cw creation

[Steve N4LQ]

The DSP stage in many modern rigs actully contains the entire radio. The 
rest of the rig converts the DSP's output to the right frequency. SSB, FSK, 
CW, AGC, Detection is all done inside the DSP stage. The input and output 
frequency of this DSP stage varies. The Jupiter/Pegasus DSP uses 11 khz for 
I/O. This means that the other conversion stages in the rig must convert the 
ham bands down to 11 khz for reception and back up for transmission. When 
you tap the cw key, you are actually causing the DSP to run a process that 
results in the DSP stage outputing an 11 khz carrier. This carrier is then 
converted to the ham bands and amplified. This is a far cry from "feeding 
audio into a mic. jack"! It is a computer process. The DSP could be 
programmed to quack like a duck when you hit the key. It's all in the 
software.
Contrast that process with what Collins was doing. They simply used the 
sidetone to generate a sine wave and fed that into the modulation chain. Any 
hum or distortion that developed in the chain got transmitted. I remember 
hearing a 32s1 back in the mid 60's and it sounded like someone slapping a 
wet fish on the sidewalk.
Am I making sense?
Steve Ellington
N4LQ at iglou.com
----- Original Message ----- 
From: "Bob Stephens" <bstephens1 at mindspring.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, April 24, 2005 7:31 PM
Subject: Re: [TenTec] cw creation


> 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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