> Tony, Is there a case where THOR4 has better copy than Olivia 8/250?
> Warren - K5WGM
Warren,
That's another good question, they both handle mild selective fading about the
same, but there are vast differences in performance between the two when
testing under more severe HF path conditions.
THOR and Olivia, are both MFSK modes that have nearly identical minimum
signal-to-noise ratios so they should work line-of-sight down to their minimum
decode threshold.
But once HF path distortion is introduced, things change quickly. The mode that
passes the highest percentage of error-free throughput is the better mode for
that path. In the case of Olivia / Thor, the score was 100% Olivia vs.. zero
for THOR.
The THOR mode, like many others, tend to fall apart under severe path
distortion found on signals passing through the polar ionosphere and near the
equator where Spread-F conditions cause similar diffuse conditions.
In the case of THORN / Olivia 8/250 the simulator says Olivia is the better
mode for the most sever conditions.
With that said, there are so many variables involved with the real ionosphere
that their could be a set of circumstances where one mode wins out over the
other unexpectedly.
This is where experimentation comes in so please pass along your findings
Warren.
Tony -K2MO
From: "Warren Moxley" <k5...@yahoo.com>
To: <digitalradio@yahoogroups.com>
Sent: Sunday, October 04, 2009 6:59 PM
Subject: Re: [digitalradio] Re: Warren - How does THOR compare with DominoEX
and Olivia?
Tony,
Thanks !
Is there a case where THOR4 has better copy than Olivia 8/250?
Warren - K5WGM
--- On Sun, 10/4/09, Tony <d...@optonline.net> wrote:
From: Tony <d...@optonline.net>
Subject: [digitalradio] Re: Warren - How does THOR compare with DominoEX and
Olivia?
To: digitalradio@yahoogroups.com
Date: Sunday, October 4, 2009, 4:30 AM
Warren,
>I had my 1st THOR4 contact the
other day on 30meters. It is very good at very weak
>signals and a lot of noise. How do you
compare it with DominoEX and Olivia? >Warren - K5WGM
That's a good question and I took some time to
run each mode through the HF path simulator. I tried to get the bandwidth
/ word-per-minute rates as close as possible for an apples-to-apples
comparison. The wpm rates are approximate.
Test #1
In this test, we determined the lowest
signal-to-noise ratio possible for each mode (no HF path distortion) SNR @
3KHz BW.
THOR4
14 wpm 173Hz BW -14db SNR
OLIVIA 2/125
12wpm 125Hz BW -15db SNR
OLIVIA 8/250 17wpm
250Hz BW -15db SNR
DominoEX-4
27wpm* 173Hz BW -15db SIR
*Slowest DominoEx mode 27wpm.
In this test, all modes were tested with a
moderate high-latitude (polar ionosphere) disturbance. The SNR was
increased to -8bd; 7db above the minimum SNR.
THOR4 NO
COPY
OLIVIA 1/125 100%
COPY
OLIVIA 8/250 100%
COPY
DominoEX-4 NO
COPY
Selective fade test - the type of slow and deep
selective fading found on many paths. Same -8db SNR.
THOR4 100%
COPY
OLIVIA 2/125 100%
COPY
OLIVIA 8/250 100%
COPY
DominoEX-4 75%
COPY
Conclusion:
The high-latitude simulation was too much
for both THOR and Dominio-EX4 which is an indication that they would most
likely have difficulty with moderately disturbed polar ionosphere. Both
show an intolerance to frequency spreading fouund on these paths.
In the selective fade test which emulates
notch attenuation sweeping across the spectrum, THOR and OLIVIA
did well while DominioEX-4 showed signs of failure indicating this might
not be the best mode when selective fading is present.
It seems to me that since all 4 modes have nearly
the same sensitivity, it would be difficult to tell the difference between them
on a stable HF channel.
The DominoEX4 mode that did poorly on
disturbed paths would be the better choice during quite conditions since it
moves along at a much faster 27 wpm.
It all depends on conditions at hand.
Tony -K2MO
