[TenTec] Ten-Tec Rig Comparisons

[Dr. Gerald N. Johnson]

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