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Date: Tue, 23 Dec 2008 22:19:08 +0000
From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: Re: WSPR
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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 <g3kevmal@talktalk.net>:
> 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"
> <james.moritz@btopenworld.com>
> To: <rsgb_lf_group@blacksheep.org>
> 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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