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Yes I remember those tests with Albert
, the results where totally different to the local
25 mile tests with the same set up early in
the same day . but that's live path testing
...
fsk , of course , but simplicity is the
object , switching the (led) light off and on
could reduce the duty by 50% where
heat is a problem , but that is for those who are
experimenting in that area , adding
a 17 KHz band to the modem simply
allows any one to try , with the minimal of
effort , at the moment the only path is
via conventional translation at 100% carrier ,
30 second burst should work on
satellite scatter , works fine at 50MHz with
aircraft ... I assume the optical link will not
have a dopper shift ?
And so into the night
73 -G.,
Sent: Wednesday, October 24, 2012 11:53 PM
Subject: Re: LF: OPERA OPTICAL BEACON (way off topic) but is based
on 17 KHz :)
Hi Graham,
similar...? WSPR decodes reliably at -29 dB,
Op-2 requires -23 dB. Both SNR figures are referenced
to carrier power vs noise in 2.5 kHz. Op-8 would be equivalent in
sensitivity but takes four times as long, and also conveys less
data.
In an optical subcarrier
system, FSK will be no more difficult to implement than ASK. And no average
power is being saved by using 50% duty cycle.
Regarding the over the air
comparison, please review the comment from PA0A, pasted
beneath.
Sorry, but some
statements just don't become more true by repeating them again and
again...
Best 73,
Markus (DF6NM)
Sent: Saturday, July 14, 2012 2:25 PM
Subject: Re: LF: DUAL BEACON WSPR + OPERA 500Khz
Graham,
Regarding your dual mode 500 kHz
tests yesterday. For me the absolute winner is WSPR, when Opera stopped to
decode, due to QSB, WSPR continued with decodes at least 3 to 4 dB deeper into
the noise.
73, Albert PA0A
Sent: Thursday, October 25, 2012 12:24 AM
Subject: Re: LF: OPERA OPTICAL BEACON (way off topic) but is based
on 17 KHz :)
What's you measured error ? ..taking
one is peak and one is average and
the beach mark is different as well, direct
read-out testing is not satisfactory.
Over a live radio path the statement is
reasonably correct , op2 may on the + side
and op4 on the - side
I think the statement is technically correct, however ,
the differences in the calibration and method
do present a technical quandary .
Similar = having a
resemblance in appearance, character, or quantity, without being
identical:
In parallel transmission test over
25 miles on 500 k , the two modes
randomly decoded at and around the same level
However system implementation is the key
, simplicity of use , with minimal hardware
requirements. as can be seen on the 136 band ,
many stations are using the system with
some very good results , hopefully for
field work with optical systems it
will give a reliable lap-top based SDR
measuring system .
73 -G..
Sent: Wednesday, October 24, 2012 10:48 PM
Subject: Re: LF: OPERA OPTICAL BEACON (way off topic) but is based
on 17 KHz :)
Sent: Wednesday, October 24, 2012 11:18 PM
Subject: LF: OPERA OPTICAL BEACON (way off topic) but is based on 17
KHz :)
...
> and OP2
has similar sensitivity as the wspr system.
...
this is definitely not true.
73, Markus
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