On 5/1/2010 7:31 AM, Hulett, Russell wrote:
> Jerry,
>
> Thanks for the summary, that is the sort have been looking for, and it
> prompts a few questions:
>
> Which of the Ten-Tec rigs marked the change from "conventional" radios to
> "computer with knobs"?
Having owned an Argonaut V and now an Omni VII, I know both of those
use "bootloaders, firmware,
and digital processing". Somehow I thought the Paragon was the first
where software and digital
processing played a major role, is that correct?
>
The Paragon used computer for control, I think. Its manual (paragon II)
says its as much computer as radio, but the functions available to the
user are all control, mostly frequency control. The Omni V used a micro
for control. The Omni VI+ and maybe the VI also applied a DSP to audio
filtering functions. The Corsair II used a microprocessor for frequency
counter and built in keyer but not for radio control logic or any signal
processing. When the processor in the Corsair II quits working the radio
continues to work, just without a frequency display.
The Jupiter, I think, began the radio plus computer with knobs era where
signals in and out were processed digitally. Unlike the Flex radio and
Soft Rocks, Ten Tec designs that are highly dependent on DSP processing
still have quite a large fraction of radio still using the same filters
as the old Omni and Omni D vintage radios. I wonder if their designs
might be simplified considerably and the performance enhanced if at the
location of the 9 MHz roofing filter that the rest of the radio was
removed and replaced by a SoftRock RxTx and a PC with open source code.
> Besides the Omni VII, I own a 505, 509, 540, 544, and 546. I enjoy all of
> them, though the
505 is in need of a PTO rebuild. How do the features of the 560 and
561 compare with the 546?
I don't know the 546, or keep them identified much by number. I do own a
Corsair II (561).
In their day, the Corsair and Corsair II were the top of the line
radios. The Corsair included a band output for automatcally switching a
linear or maybe an antenna tuner that never was made. They included band
pass tuning with the added 6.3 MHz IF that allows one to achieve a
narrow CW passband while using only the most simple pair of SSB filters.
I had my Corsair II the better part of a year before I got around to
putting in the 6.3 MHz 400 Hz filter because I was able to get narrower
pass bands by offsetting the SSB filters, though with more gently
sloping skirts, but good enough for my uses. These rigs include an audio
based CW filter and a notch filter at audio. AGC is derived at audio and
the relaxation oscillator for side tone has a raucous tone, but it
starts and stops as fast as one can send, even with a computer. They
have room for several filters at 9 and 6.3 Mhz. Audio derived AGC with
16 poles of filter delay can lead to thumps on strong signals when the
AGC controls stage gains before the filters so some strong signal gets
passed through the filters. That's made tougher by the relatively slow
rise time of the audio level detector. But in a radio with a single AGC,
deriving it at audio after the audio notch and passband filters make
sure than a rejected signal in the IF filter pass band isn't what
controls the audio out of the receiver chopping up the desired signal.
Today with the complex filtering and processing at IF and at audio, a
receiver needs at least two AGC loops. One to protect the detector or
A/D, and another to level the audio to the user after all the
processing. The it needs a computer to convert from those two gain
controls to the actual input signal level.
The classic S-meter as used in ham rigs since that display was invented
actually only displayed the AGC voltage as signal strength. Often the
meter was in the screen circuit of an AGC controlled IF stage, just to
multiplex that stage as both an IF gain stage and as a simple high
impedance DC voltmeter.
>
> 73, Curt KB5JO
>
>
I'm not that Tentec historian, I've not used most Tentecs, I might trade
off my Corsair II though I've not yet applied it as IF for VHF and up
transverters as was my original intention. And I have opinions of how
radios could be designed, whether using DSP or not. Some of those
opinions have leaked into this post.
73, Jerry, K0CQ
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