|
Don't blame the little RasPi, it's not its fault
either. Stefan's signal actually looks quite pure from here (180
km). Though there exist -38 dB AM sidebands at +- 100 Hz caused
by the rectified mains ripple, these shouldn't cause a
significant problem except for an occasional extra decode.
However note that a strong and clean signal can be widened
up by the receiver if noiseblanking is enabled.
73, Markus
Sent: Sunday, March 27, 2016 7:14 PM
Subject: Re: LF: DK7FC WSPR bad quality problem
Andy,
This time its not really Stefan's fault :-,)
This is a problem , using the raspberry PI , the Pi
processor uses interrupts, which, cause the execution
time of the timing loops to vary slightly ,
the 'small' time variations , produce side bands .
This was evident during the development of a
R-PI routine for sending Opera , as the R-Pi
support documentation is not particularly comprehensive, its
'not' possible to fully address the i/o functions and as such
there exists a conflict with higher order irq requests
. Producing seemingly random widening of the
spectrum, depending on the irq deployments.
Ie the pulse train suffers from timing jitter
The alterative of the U3 beacon key'er , driving
the DDS 'oscillator' is a more elegant
solution, but as noted by Andy [rad-com] some time back,
the later U3 with the PPL suffers from
settling time issues , when commanded with , step
frequency changes. these sever to produce sidebands , at the step
changes.
73-G,
Sent: Saturday, March 26, 2016 8:36 PM
Subject: LF: DK7FC WSPR bad quality problem
Hello Stefan.
I am sorry, but this evening you have a very poor quality
WSPR signal on MF with many splatters, I think it is perhaps due to an overload
TX AF level.
That is not in phase with the normal ham spirit. So,
please be kind to stop now your transmission and correct this
problem.
On the way, can you say honnestly if your power is not
over the legal limit ?
Sincerly yours and my best 73 de Andy.
P.S.
Have a look below at some reports last hour showing the
problem :
|
2016-03-26 19:00
|
DK7FC |
0.475683
|
+12 |
0 |
JN49ik |
1 |
PI4THT |
JO32kf |
336 |
338
|
|
2016-03-26 19:00
|
DK7FC |
0.475783
|
-25 |
0 |
JN49ik |
1 |
PI4THT |
JO32kf |
336 |
338 |
|
2016-03-26 18:50
|
DK7FC |
0.475783
|
-23 |
0 |
JN49ik |
1 |
PE1RKT |
JO22fb |
418 |
316
|
|
2016-03-26 18:50
|
DK7FC |
0.475683
|
+14 |
1 |
JN49ik |
1 |
PE1RKT |
JO22fb |
418 |
316 |
|
2016-03-26 18:40
|
DK7FC |
0.475683
|
+12 |
0 |
JN49ik |
1 |
LA8AV |
JO59cs |
1153 |
4 |
|
2016-03-26 18:40
|
DK7FC |
0.475783
|
-24 |
0 |
JN49ik |
1 |
LA8AV |
JO59cs |
1153 |
4 |
|
2016-03-26 18:50
|
DK7FC |
0.475783
|
-28 |
0 |
JN49ik |
1 |
LA3JJ |
JO59bh |
1102 |
4 |
|
2016-03-26 18:50
|
DK7FC |
0.475683
|
+10 |
0 |
JN49ik |
1 |
LA3JJ |
JO59bh |
1102 |
4 |
|
2016-03-26 18:40
|
DK7FC |
0.475780
|
-28 |
1 |
JN49ik |
1 |
G3KEV |
IO94sh |
829 |
314
|
|
2016-03-26 18:40
|
DK7FC |
0.475679
|
+10 |
0 |
JN49ik |
1 |
G3KEV |
IO94sh |
829 |
314
|
|
2016-03-26 19:10
|
DK7FC |
0.475682
|
+13 |
0 |
JN49ik |
1 |
F6CNI |
JN19qb |
389 |
266
|
|
2016-03-26 19:10
|
DK7FC |
0.475782
|
-27 |
1 |
JN49ik |
1 |
F6CNI |
JN19qb |
389 |
266
|
|
2016-03-26 18:30
|
DK7FC |
0.475682
|
+15 |
0 |
JN49ik |
1 |
F5WK |
JN18hp |
452 |
261
|
|
2016-03-26 18:30
|
DK7FC |
0.475782
|
-22 |
0 |
JN49ik |
1 |
F5WK |
JN18hp |
452 |
261
|
|
2016-03-26 18:00
|
DK7FC |
0.475680
|
+19 |
0 |
JN49ik |
1 |
DL6II |
JO30nx |
205 |
327
|
|
2016-03-26 18:00
|
DK7FC |
0.475780
|
-18 |
0 |
JN49ik |
1 |
DL6II |
JO30nx |
205 |
327
|
|
2016-03-26 18:50
|
DK7FC |
0.475682
|
+17 |
0 |
JN49ik |
1 |
DL4RAJ/2 |
JN68kj |
326 |
109
|
|
2016-03-26 18:50
|
DK7FC |
0.475782
|
-22 |
0 |
JN49ik |
1 |
DL4RAJ/2 |
JN68kj |
326 |
109 |
|
