[TenTec] Hello Orion Users

[Adam Farson]

Bill,

Carl is correct.

The 14 kHz analogue IF signal enters the ADC, which converts it into a
digital bitstream. The DSP processes this bitstream according to algorithms
stored in firmware; one of these algorithms is IF filtering (bandwidth
determination), and another is demodulation (conversion of IF to baseband).
Demodulation may or may not be the final operation which the DSP performs on
the bitstream, depending on the task allocation in the DSP design. The
baseband, still in the digital domain, now enters the DAC, which converts it
to an analogue signal (audio).

The 14 kHz IF is not audio. If you pass the 14 kHz bitstream into the DAC,
and attempt to listen to the DAC output, you will not hear the recovered
audio from the received signal.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: tentec-bounces at contesting.com
[mailto:tentec-bounces at contesting.com]On Behalf Of John L Merrill
Sent: Monday, May 05, 2003 16:06
To: tentec at contesting.com
Subject: RE: [TenTec] Hello Orion Users


I would think it depends how you define audio. In my thinking audio is what
comes out of the speaker. Anything before that is IF/RF.

John N1JM

-----Original Message-----
From: tentec-bounces at contesting.com
[mailto:tentec-bounces at contesting.com]On Behalf Of Bill Tippett
Sent: Monday, May 05, 2003 7:00 PM
To: tentec at contesting.com
Subject: [TenTec] Hello Orion Users


N4PY wrote:
 >The Orion DSP filters are NOT audio DSP filters.

I beg to differ Carl...from page 52 of the Orion manual:

 From A3, cable 11 brings the IF signal to
the 9-MHz IF (A4), where the hardware
noise blanker operates in a wideband
environment. Cables 14A and 14B route
the wideband IF signal through the
Sweep Amplifier (A13) to A7 for use in
ORION's band scope feature. Three
standard and three optional crystal filters
(normally selected by the BW control)
define the tuned signal bandwidth ahead
of DSP filtering. This stage provides
enough amplification to maintain the
receiver sensitivity despite unavoidable
filter losses. The amplified and bandlimited
signal feeds the IF Converter
(A5) via cable 16.

A5 provides conversion to the 2nd IF,
amplification, filtering, and conversion to
the 3rd IF for processing in the A7 Logic
board. Cable 18 carries the 14 kHz third
IF to the DSP in A7.
After digital signal processing in A7, the
recovered audio travels through the
Motherboard to the headphone jack on
A8 and to the EXT SPKR and AUX I/O
jacks on A12. From A12 wire cable 36
runs to the internal speaker.

DSP is done at the 14 kHz 3rd IF which is clearly audio.
Believe me, you could not afford DSP done at RF frequencies.

                         73,  Bill  W4ZV

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