Re: LF: RE: WSPR Reports

["Clemens Paul" <cpaul@gmx.net>]

This phenomen,or rather bug,has been reported here by several list members.

I have made the same observations.

Reducing the RX BW from e.g. 250Hz to something below 100Hz results in

an increase of *reported* SNR of up to around 15dB!

I've done some tests with a friend 20km away on 10m and we've found out that the *real* SNR

is not improved a bit or in other words an extreme weak wspr signal which was just below

the decoding threshold in 250Hz BW coudn't be decoded with 20Hz BW either.

 

73
Clemens
DL4RAJ 

----- Original Message -----

From: Andy Talbot

To: rsgb_lf_group@blacksheep.org

Sent: Wednesday, January 27, 2010 9:44 PM

Subject: Re: LF: RE: WSPR Reports

All the critical filtering is done in the software, and results in a 1.46Hz noise bandwidth - which is what the software measures and reports upon.

 

Your observation that a narrower IF bandwidth is interesting.   Its most likely based on the fact that typical signals are corrupted by pulsed non-gaussian noise which upsets the frequency bin detection process, and upsets sync recovery.

 

Andy
www.g4jnt.com

This email has been scanned for damaging side-effects by the health and safety police, is guaranteed to contain no substances hazardous to health, but may contribute to dissolving the nether and polar regions

2010/1/27 Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>

Andy,

 

maybe the "magic" lies in a narrow filter (either IF or audio).

If I switch from a 2.5kHz (SSB) filter to a 270 Hz filter I also get a significant increase in SNR values reported by WSPR.

Unfortunaely it hardly affects the decoding level (minimal SNR needed to get a positive decode), that rises by almost the same amount.

 

73, Rik  ON7YD - OR7T

---

Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Andy Talbot [andy.g4jnt@googlemail.com]
Verzonden: woensdag 27 januari 2010 21:26
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: WSPR Reports

Has F6CNI managed some sort of magic noise reduction system, or is it a just a case of being in a very quiet location...

These are pretty impressive S/N values

 

 

2010-01-27 20:14	G4JNT	0.503875	+13	0	IO90iv	+23	0.200	F6CNI	JN19qb	391	243
2010-01-27 20:08	G4JNT	0.503875	+10	0	IO90iv	+23	0.200	F6CNI	JN19qb	391	243
2010-01-27 20:02	PA0A	0.503900	+15	0	JO33de	+37	5.012	F6CNI	JN19qb	502	312
2010-01-27 20:00	G4JNT	0.503875	+14	0	IO90iv	+23	0.200	F6CNI	JN19qb	391	243
2010-01-27 19:54	G7NKS	0.503920	-5	0	IO92ub	+20	0.100	F6CNI	JN19qb	422	262
2010-01-27 19:54	G4JNT	0.503875	+14	0	IO90iv	+23	0.200	F6CNI	JN19qb	391	243
2010-01-27 19:44	G4JNT	0.503875	+10	0	IO90iv	+23	0.200	F6CNI	JN19qb	391	243
2010-01-27 19:40	PA0A	0.503900	+15	0	JO33de	+37	5.012	F6CNI	JN19qb	502	312

 

Andy
www.g4jnt.com

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