Tim,
The filters were not thrown into the Orion...they are in there for a
specific and important purpose. Most all ham radios, to be competitive, must
have the ability to operate the FM mode. FM requires a 'wide' bandwidth of
about 20kc. So the receivers front end is always open to at least 20kc of
bandwidth (the IF is a different story). Ten Tec used the 9 MHz for the
first IF because they knew most Ten Tec owners already have those filters
available (and wouldn't normally have to buy more filters). They also
changed the receiver design such that the USER can select the roofing filter
(which is the 9MHz filters). If your NOT using the FM mode, you can drop the
front end bandwidth from 20kc down to 2.4kc, 1.8kc, or 500Hz...the USERS
choice. That really does make a big difference, especially if your into
chasing DX or contesting. THIS IS ONE OF THE MAIN REASONS I'M GOING TO BUY
AN ORION!
I, personally, am not convinced yet that DSP is the filter savior of
the world...have you ever heard of marketing?! I think if your mainly going
to work SSB, then DSP will help you. BUT if your going to mainly work CW
(me), your really going to have to have DAMN good DSP filtering to beat
crystal lattice filtering. (Keep in mind: my opinion)
It is true that the Pro II is a VERY competitive radio for SSB
operation. Only actual on the air test by USERS is going to determine how
the Orion stacks up against the Pro II. Naturally Pro II owners are going to
claim it's the best; and Orion owners are going to claim it's the best. But
of course the reality is that it is the individual user who decides what
suit's them best.
Tom/W4BQF
-----Original Message-----
From: tlogan7@cox.net [mailto:tlogan7@cox.net]
Sent: Tuesday, January 28, 2003 9:51 AM
To: tentec@contesting.com
Subject: [TenTec] Orion, NRD-545, DSP, filters etc
Hi all -
I love buying and playing with radios, but I must admit the Icom 756 Pro II
has stopped me in my tracks. My Omni's, Elecrafts, etc have all been sold
becuase the Pro II just does everything better - at least for me at my
operating station. So this leaves me wondering what new rig I could look
into. Only two really come to mind: The Orion and the 516. The Orion is way
out of my price range so I guess that answers that. And the 516.....well
it's really hard to sort through the various reactions on the 516
reflector...so I just don't know. But while I'm exploring, two questions
come to mind:
1)I've paisted below a description of the DSP in the Japan Radio NRD-545
receiver. It mentions 40 bit floating point processor with 18 bit over
sampling. The Pro II and the Orion are newer yet use 32-bit. In my simple
brain I have to ask why is that? How much of a difference does this make? I
don't pretend to understand DSP - so SIMPLE explanations would really
help:-)
2) My Pro II can hear anything my K2/100 and my Omni V did and has better
ability to narrow filters/notch/noise reduction etc. The Pro II does not
require me to buy additional filters (of a design that have been around for
years). That makes the Orion even further out of my reach. Why does the
Orion need those filters? I cannot imagine that 5 years down the road all
DSP radios will still have filters in them. After all, most companies are
trying to get away from such filters because the are getting more costly. So
why is Ten Tec throwing them into the Orion? How much better could it make
it than the Pro II? Can someone shed some light?
3) - I cannot figure out if the 516 is a flash in the pan, or here to stay,
and what the majority of users feel about it at this point? Anybody have a
clear impression there yet?
OK - here's the clip from Universal Radio about the NRD-545 receiver:
73/Tim NZ7C
"The NRD-545 uses a 40-bit extended floating point Digital Signal
Processor with an 18-bit over-sampling system A/D converter and a 16-bit D/A
converter. The DSP functions on 13 types of circuits after the IF,
previously configured using analog circuits. DSP is used for all-mode
detection including AM synchronous detection (ECSS). Incredible selectivity
characteristics are achieved by the use of an Infinite Impulse, structure
concurrent Chebyshev-type digital filter. In English this means, the NRD-545
gives you a continuously variable bandwidth from 10 Hz to 10 kHz in 10 Hz
steps. You virtually have 990 different bandwidths, each with excellent
adjacent channel rejection. DSP is also used to control Pass Band Shift,
another tool to reduce QRM. A 256 step DSP Noise reduction circuit and 256
step DSP Beat Canceller and DSP Auto-Track Notch are other new tools in your
arsenal to dig out difficult DX signals. The DSP AGC works in all modes and
is continuously variable from .0!
4 to 5 seconds in SSB/CW/RTTY"
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|