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Re: LF: EbNaut

from [Alex R7NT] [Permanent Link][Original]
To: [email protected], [email protected]
Subject: Re: LF: EbNaut
From: Alex R7NT <[email protected]>
Date: Sat, 19 Jan 2019 22:55:52 +0300
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Jay,
This is a good question.
As well as "Is WSPR2 or WSPR15 better?" or "Is DFCW3 or DFCW30 better?" DFCW10 or DFCW120, "Is OP8 or OP32 better?" etc :))
Successful far reception on 136 for short modes (DFCW3, WSPR2, JT9-1, short simbols in sec EbNaut etc) is possible with excellent propagation and big ERP power.
But the fundamental principle remains under all modes:
"Theoretically, how many times the duration of the parcels is longer, exactly as many times can be less power. It is necessary that the energy E of one premise be greater than the average thermal energy (if the noise is not thermal, then naturally the effective temperature is implied) i.e. greater than kT, where k is the Boltzmann constant, and T is the temperature.
Energy E can be “gained” either by power or by duration. E = Pt " RA9MB
Not sure of the accuracy of the translation into English - SRI
I believe this is also true for the all-digital mode. 
Visual mode (QRSS, DFCW) we are in their heads restore complete information on the fragments received.
See my best QRB reception (7h long time period) and best QRB transmission (3h) 
How abt QRSS3 or DFCW3 mode in this case?
Transmit longer, but less...
73! Alex R7NT  136.73.ru    AWLF 136.73.ru/h_aw/


сб, 19 янв. 2019 г. в 14:36, [email protected] <[email protected]>:
Alex, Riccardo & EbNaut-eers
 
Unfortunately no copy of either station last night. Alex ... understand your TX frequency may have been moving around.
 
I wonder if a 1 hour transmission is too long for 137 kHz? Recalling spectrograms of QRSS going back many years seems to indicate a QSB pattern of approximately 15 - 30 minutes. Both receptions of IZ7SLZ and IW4DXW (a while back) were 'one and done' with no hint of the signal in adjacent time slots ... using 30 minute transmission times. Even DK7FC's normally big signal shows big QSB swings from one half hour period to the next. Can't help but wonder if 20 or 30 minute transmission periods make better use of the QSB characteristics on 136 kHz.
 
Comments?
 
Jay W1VD      
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