Thanks Andy and all interested in the
group for the information.
Surely there is nothing like a practical
experiment for proof of WSPR effectiveness against QRSS3 on 500KHz. I have been
running that experiment since the 17th of November 2009.
Results so far have been, hundreds of WSPR
reports from 7different stations and not one mention of the QRSS3 content.
My MEPT runs a 100% Transmit cycle, hence once
I got a reliably detectable signal out I posted this to the UK500KHz Group on the 28th of November 2009. :-
“Between the WSPR is QRSS Morse and some small font Hell which
looks best
on Spectran QRSS3 Mode. This means it's a continuous TX sequence. I
think at the bottom of the WSPR Window and with such low power it should
not cause any problems to any other stations. Please let me know if
there are any concerns.”
I have run MEPT’s on continuous
transmit tests at the bottom the WSPR slot on other low occupancy bands without
any problems too. I always use QRPp. After all who is going to complain about the
QRSS3 etc. content of the signal that has never been seen?
As I have mentioned before, there has to be
a challenge in there somewhere for the guys with big antennas. There is a
simple 2 letter ident in there in 2 QRSS3 modes as well as more complex stuff
and full Call Sign..
-----Original
Message-----
From:
[email protected] [mailto:[email protected]] On Behalf Of Andy Talbot
Sent: 10 January 2010 21:20
To: [email protected]
Subject: Re: LF: Link budget
calculation or estimation of dist for given power on WSPR
Making comparisons
between WSPR and QRSS should take into account the signalling rate, and it is
only fair to compare like with like.
A WSPR transmission
carries a callsign, a locator and a power level. Approximately 12
characters worth of data, or in Morse code terms around 2.4
words which it sends in 2 minutes - hence about 1.2 WPM. If 12WPM
beans 100ms dots, then this rate corresponds to a dot interval of 1
second. So for a fair comparison, you must compare WSPR with 1s
QRS - which I believe is faster than most ops actually use. The
version of Argo I have only goes down to 3s dots which infers 5dB bandwidth
improvement immediately.
So if, as I recall
someone saying here, WSPR and 3s QRSS give similar decoding capability, then
that immediately suggests WSPR is 5dB 'up' on QRSS, or QRSS takes three
times longer for the same message.
Its rather more
complicated in reality, as this simple ccomparison assumes the QRS signal
is copied with zero errors. As it involves fuzzy logic and human
interpretation, we can probably say it contributes the error correction
To compare data modes in
noise, its best to use a normalised data rate expressed in
Bits/second/Hz
See http://www.g4jnt.com/MartleSham.htm where
I come up with an empirically determined estimate that the WSJT modes, WSPR,
JT4, etc give about 6dB enhancement in S/N vs. decoding than CW - when
normalised for an equivalent signalling rate.
Andy
www.g4jnt.com
This email has been scanned for damaging side-effects by the health and safety
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contribute to dissolving the nether and polar regions
2010/1/10 Roger Lapthorn
<[email protected]>
Fair
comment Mal, and one of these days I'll try QRS and see how it performs.
It should be possible to get a pretty good idea of the theoretical range limit
for WSPR on 500kHz based on required S/N (which can be as low as -30dB for
WSPR), path loss calculations, ERP etc.. I shall be interested to see what
"the experts" say.
73s
Roger G3XBM
2010/1/10 mal hamilton
<[email protected]>
Had u been on QRS CW he probably
would have copied u since he saw ur trace. I often see traces that do not
decode for some time but had the trace been keyed it could have been
identified.
I have been making this point for
some time, avoid guesswork and speculation and use normal CW or QRS CW
Regardless of erp transmitted the
weakness is often at the RX end Little antenna Little signal Big antenna Big
signal and environment regarding noise.
RX loop antennas not optimised
towards ur stn, these situations cannot be calculated just guessed and
meaningless.
Get into QSO mode and see how far u
can get in real time.
----- Original Message -----
Sent: Sunday,
January 10, 2010 7:02 PM
Subject: Re: LF:
Link budget calculation or estimation of dist for given power on WSPR
Certainly
GM4SLV has a much lower noise floor than most stations on 500kHz Jim. I think
he estimated about 10dB lower, so it may be easier for him to hear very weak
signals than many others.
For what it's worth, my 1mW ERP has been received at -18dB S/N at 990kms range
in S.Germany (and at around -23dB a few times), so assuming another 10-12dB in
hand, that must be good for another skywave "hop" under favourable
conditions. I am still hopeful that TF3HZ might just spot me on a good night.
The magic 1000kms barrier is tantalisingly close. RN3AGC says he might just
have seen a "whisper" of a trace from me the other night and he is
2400kms away, but if it was me it was far too weak to decode.
It will be interesting to see what people say is possible based on the
propagation theory etc.
73s
Roger G3XBM
2010/1/10 James Cowburn
<[email protected]>
Dear LF,
Has anyone any
ideas or suggestions on a resource for calculation of a link budget for WSPR
over a set distance?
As it seems I
can get up to GM4SLV reasonably consistently on my current antenna/power
setting with a SNR of around -22dB and the limit for WSPR is around -30dB then
is there a means for roughly estimating or indeed accurately calculating the
Expected Max Range (EMR) at that power setting and antenna configuration?
Clearly, there
are differences between separate Rx stations but if one knows the ratio between
two or more Rx stations then it should be possible to pro-rate or estimate at
least the signal strength at a given Rx based on its performance with other
known signals.
If I can do
916km with an SNR of say -22dB then how much further would the remaining
8dB or so of WSPR detection get me, assuming the other Rx has the same
capability as GM4SLV and if their capability is different, then is it fine to
factor for the dB difference over known paths/signals?
Thanks in
advance for any answers or pointers and best wishes to all for a great 2010
With best regards
Jim
Dr. James Cowburn G7NKS
E
[email protected]
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