Re: LF: G3XDV IO91VT M0DSZ IO82LS Novel s/n / time 136/op32

["F6CNI - Andy - JN19QB" <f6cni@orange.fr>]

Hi all.

 

I had this test reports with G3XIZ. 3 reports on day time around 1100 TU and others at evening from 1820 to 2004 TU. For this RX test, the antenna was a 9 m base loaded vertical tube without top hat, RX FT1000MP and no preamplifier.

 

As expected, the evening  G3XIZ S/N computed by the WSPR at 422 km distance shows a regular drop. You can see also that the reports around 1100 TU gave  10 to 15 dB better S/N.

 

 

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr	Reporter	RGrid	km	az
2016-07-16 20:04	G3XIZ	0.137445	-25	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:56	G3XIZ	0.137445	-25	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:48	G3XIZ	0.137445	-24	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:38	G3XIZ	0.137445	-22	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:32	G3XIZ	0.137445	-22	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:26	G3XIZ	0.137445	-21	-1	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:18	G3XIZ	0.137445	-21	-1	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:08	G3XIZ	0.137444	-20	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 19:02	G3XIZ	0.137444	-20	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 18:56	G3XIZ	0.137444	-20	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 18:50	G3XIZ	0.137444	-20	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 18:40	G3XIZ	0.137444	-19	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 18:30	G3XIZ	0.137444	-19	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 18:20	G3XIZ	0.137444	-19	0	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 11:00	G3XIZ	0.137444	-12	-1	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 10:50	G3XIZ	0.137444	-9	-1	IO92ub	0.05	F6CNI	JN19qb	422	141
2016-07-16 10:42	G3XIZ	0.137444	-10	0	IO92ub	0.05	F6CNI	JN19qb	422	141

 

I made 3 mesurement of the noise level using my Peggelmesser SPM3 :

 

• At 1050 TU : 40 µV   band noise, the sun site in my QTH was 59° ;
• At 1830 TU : 120 µV band noise, the sun site in my QTH was 10° ;
• At 1956 TU : 250 µV band noise, the sun site in my QTH was -3°.

 

Conclusions :

 

• The signal level stay the same, but the band noise increasing explain the drop in the S/N computed by WSPR ;
• At 422 km the site angle for a single hoop is about 45°. That is over the value of the pseudo Brewster angle on that frequency, and the back return efficiency is below 10 dB !
• The increasing in noise is due to the drop D layer absorption.

 

Well, that is not a scoop ! Have a look at the 30 / 40 years ago LowFERs States experimentations on the 1875 meters band and after on the 1750 meters band. Some very good informations about that was published in old issues of QST and more in CQ magazine.

 

73 de Andy.

 

 

From: F6CNI - Andy - JN19QB

Sent: Saturday, July 16, 2016 7:03 PM

To: RSGB LF Group

Subject: LF: G3XDV IO91VT M0DSZ IO82LS Novel s/n / time 136/op32

 

 

Yes I agree 100 % with you Mike.

 

Remember : in the years 1999 to 2003 there was a lot of CW activity on LF, and daytime was the best for QSO up to 800 / 1000 km. At night, only some more distant QSO can be acheived with the help of layer reflexion as OH1TN... Below about 500 km on LF the level signal stay about the same on day or night, but the noise level increase after evening, that is especially sensible on summer, so the S/N be not so good.

 

Of course, that is a bit different on the MF band even My friend F5WK at 90 km gives me about 6 to 8 db Better S/N on daytime than on night, when I am transmitting WSPR 2 on 630 m band.

 

73 de Andy.

 

 

-----Message d'origine-----

From: Mike Dennison

Sent: Saturday, July 16, 2016 6:11 PM

To: rsgb_lf_group@blacksheep.org

Subject: Re: LF: G3XDV IO91VT M0DSZ IO82LS Novel s/n / time 136/op32

 

Well, I think the clue is in the phrase "signal to noise". The noise

level is much greater after dark than in the daytime, especially at

this time of year, so for the same signal strength the S/N is poorer

at night.

 

Mike, G3XDV

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