Andy,
I would say that's not quite the case .. I found on top band a while ago
that 'a lot' of cw inside the 200 hz search band would prevent decodes of a
relatively strong wspr signal , ie showing well on the display and on
speclab .. ok it was during a cw contest but all the same , the cw signals
did not cross the wspt trace.....
I had some odd decodes 4 mtrs 70.030 and after posting a note in a few
groups a lot of reply's spoke of false decodes which, till then I had not
associated with the wspr system.. I'm still not totally convinced, but
without knowing the full depth of the 'best fit' routines its not
immediately obvious.
I noted in the decodes from the usa , (BadMsg) appears , is this a tx
code or rx de code error message ?
G ..
--------------------------------------------------
From: "Andy Talbot" <[email protected]>
Sent: Tuesday, December 23, 2008 10:19 PM
To: <[email protected]>
Subject: Re: LF: Re: Re: WSPR
No,
the receiver can demodulate all the 6Hz-wide signals that may be
present within the 200Hz Rx search bandwidth.
The operational Rx bandwidth for receiving purposes is 6Hz, generated
by the DSP filtering, so interfering signals within the 200Hz
bandwidth will not corrupt the wanted signal unless it actually
overlaps it, and places enough jamming energy into the 6Hz passband.
Andy G4JNT
www.g4jnt.com
2008/12/23 mal hamilton <[email protected]>:
Tnx Jim for the info but in actual fact 200 hz is required and not only 6
hz
as some have specified, in other words if there was other acty within the
200 hz bandwidth it would corrupt the target signal.
mal/g3kev
----- Original Message ----- From: "James Moritz"
<[email protected]>
To: <[email protected]>
Sent: Tuesday, December 23, 2008 7:19 PM
Subject: LF: Re: WSPR
Dear Mal, LF Group,
The transmited WSPR signal has a bandwidth of about 6Hz.
SSB mode is used for transmission in order to translate the soundcard
audio
to the appropriate RF frequency. But the signal bandwidth remains 6Hz
At the receiver, a 200Hz bandwidth is extracted from the receive audio
by
the DSP routines in the PC. This allows the transceiver to switch from
TX
to
RX without changing modes. (In my case, I have configured the rig to
use
the 250Hz CW filter as the "narrow SSB" filter, so the RX bandwidth is
only
250Hz anyway).
This 200Hz of bandwidth is then sub-divided into numerous narrow 6Hz
sub-channels, that can be simultaneously processed to receive lots of
WSPR
beacons operating simultaneously on slightly offset frequencies within
the
overall 200Hz range. That's the beauty of DSP.
Overall, this means one transceiver can alternately transmit a WSPR
beacon
signal and then receive many different WSPR signals within a 200Hz
range,
during different 2 minute time slots.
Cheers, Jim Moritz
73 de M0BMU
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