[TenTec] Pegasus vs. Flex Radio

[Mark Erbaugh]

> Can anyone comment on how these radios are different,
> having had them both? What about the Kachina? Curious
> how they are similar or different in operation.

I have a Pegasus and had a FlexRadio for a while. I sold the FlexRadio
before they came out with the linear amp, so it was basically a receiver.

The Pegasus is really a complete radio that just uses the computer for
control, basically using the computer to set virtual front panel settings
(frequency, RF Gain, filter, etc). All the DSP is done with inside the
Pegasus by the firmware supplied by TenTec. The FlexRadio is basically a
mixer that mixes the incoming signal down to baseband (low kHz range) which
can be is digitized by the computer soundcard and DSP is done in the
computer.  Thus, the FlexRadio needs much more computer processing power.

The DSP filtering in the Pegasus is pretty poor by today's standards. The
narrowest filter is labelled 300 Hz, but it has a shape factor of around 2:1
and shows up on a waterfall display as about 500 Hz wide, which means you
can't really separate two closely spaced signals. In contrast, the FlexRadio
filter is determined by software running on the PC. With the software I used
(a year and a half ago), you could have nearly brick wall filters only 25 Hz
wide and they worked!

To date, TenTec has never released the source code to the firmware inside
the Pegasus so there's no (easy) way to modify that, though that was one
thing that TenTec originally implied would be available.  They did release
the source code to the control program, but there are limits on what can be
done at the control end. For example, you can't change the DSP processing
beyond what is in the firmware, such as adding a narrower filter. (but see
below).

The software for the FlexRadio is open source and the hardware is well
documented so you (or a third party) can easily write software for it. I
think that there is a PIC chip on the FlexRadio that handles some internal
control, but it probably won't need to be reprogrammed in the majority of
cases (unless you add new hardware), but basically there's no 'firmware,'
all the processing is done on the PC.

One problem I've heard of with the FlexRadio is that the delays (latency)
with most soundcards make it hard (or impossible) to do QSK at any
reasonable speed. That's not a problem with the Pegasus.  I don't know if
the FlexRadio could be used in the TOR modes as they require a pretty quick
T/R turnaround also.

I never had a Kachina, but I understand that it is more like the Pegasus
than the FlexRadio in that the computer is just doing control, not DSP.

* While you can't modify the firmware in the Pegasus, it's pretty simple
(just run a cable from a connection inside the Pegasus to the SPARE jack) to
bring the 12 kHz analog IF signal out of the radio. You can then feed this
directly to a soundcard input and do your own DSP processing. I've done this
to receive DRM signals and have been meaning to mess around with  some home
brew software. I suspect it would also be possible to modify the FlexRadio
core to work with this as it does with the SoftRock40 (or maybe it has
already been done!).

> I built that little $25 kit that allows me to use the
> Flex radio software on my computer (40 meters).
> Cheapest and best working receiver I can ever
> remember. ;-)

Unfortunately, I dragged my feet on ordering. and they sold out.

73,
Mark, N8ME