Hei Jukka!
At 03:29 PM 5/9/03 +0300, you wrote:
>Is Orion not using synthesizer?
It is...but with good phase noise. Many of the past synthesized
radios (Kenwood's TS-940S comes to mind...yuck!) were not careful about it.
"LO phase noise: -136 dBc/Hz typical from 0.5-20 kHz. (see Figure 2 below)"
http://www.tentec.com/TT565.htm
>Do they really have good (Yaesu FT1000 series performance) filters plus
>in-par-with-ICOM 756ProII DSP in the Orion?
9 MHz 1st IF roofing filters are 8-pole crystal filters. 15 kHz
(for FM),
6000, 2400 and 1000 are standard, 1800, 500 and 250 are optional (250 is
a 6-pole). But remember that this is compared to Yaesu MP's 1st IF roofing
filter
fixed at 12 kHz at 70 MHz. This is why Orion has much better strong-signal
characteristics. The other radios are trying to filter at later stages in the
IF chain, after the 1st IF has already passed distortion products that will
fall within subsequent IF passbands. I don't know that much about DSP in the
756PROII DSP, but imagine Orion is similar since they both use 24-bit
ADC/DAC's
(which determine the dynamic range) and 32-bit DSP processors. You can read
more below but here's a good summary by Doug Smith:
The winning combination therefore includes a synthesizer having exceptional
phase-noise characteristics, a strong analog signal path, an ADC with large
dynamic range and a DSP that preserves signal integrity. That is the
combination necessary to be able to ignore your 30-over-9, 1-kHz-away
neighbor. Heck, you might not even know hes on the air-- Doug Smith, KF6DX.
(Unfortunately this assumes your neighbor has a signal as clean as Orion's.)
http://www.doug-smith.net/dspdynamics.htm
>I think you say Orion has a synthesizer.
>And the DSP is not excactly as good plus the filters are not really as
>good as the benchmark.
The key is WHERE the filters are. Orion's 1 kHz (lowest of standard
filters) at 1st IF versus MP's 12 kHz fixed (which cannot be changed). DSP
is at the 3rd IF after strong interfering signals are removed at Orion's
1st IF.
>There is one good radio with your description: IC781.
>I have two Yaesu radios for my SO2R setup..
I don't know that much about the IC-781, but the ARRL Test Report
below says it uses a 46.5 MHz 1st IF, and that it receives FM. They don't
state exactly what the 1st IF BW is, but my guess is that it is the same
scheme as most current radios except Orion, i.e. a 12-15 kHz roofing
filter at a very high 1st IF. This means it will also have problems with
IMDDR3, BDR, IP3, etc for signals spaced closer than 15 kHz. They go
right through the filter! The quoted IMDDR3 of 102 dB and BDR of 134 dB
is indeed excellent...BUT they are done for signal spacings of 20 kHz! How
many 20 kHz holes do you find in the band during a contest? This is
exactly why ARRL went to 5 kHz spacings for IMDDR3 and BDR beginning
with Product Test Reports in July 2001. Even 5 kHz is wide IMHO, but
Orion's stock 1000 Hz roofing filter should still work well for spacings closer
than 5 kHz. I am going to add the Inrad 400 Hz optional filter so I can
hopefully
get excellent strong-signal performance with 500 Hz spaced interfering signals.
http://www2.arrl.org/members-only/prodrev/pdf/pr9001.pdf (IC-781 Test Report)
>And remember, also the Drake R4C had to modified before it was really the
>top class RX.
Simply adding the $135 Sherwood 600 Hz roofing filter puts it at
the top of this list instead of well down the list at 58 dB for 2 kHz spacing
("R4C Stock). BTW, note where the IC-781 falls...it degrades 21 dB at 2 kHz
spacing versus 20 kHz, and 11 dB below the modified R4C at 2 kHz spacings:
http://www.sherweng.com/table.html
Others mighty be interested in this so I'll copy the reflector. I
could certainly be proven wrong on all this since we haven't yet seen any
independent tests of Orion (ARRL has ordered one for their Product Test),
but what I see makes me feel Orion is a major advance in the kind of
performance I care about. Time will tell.
73, Bill W4ZV
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