Hello all,
I've been watching the 100Hz sideband WSPR multi-decodes also from the other
two strong stations on MW,
DH5RAE and DB0ABR.They are located about 65km from me and generate S9++dB
signals here.
The deoded sidebands are also about 40dB down.
DB0ABR has tried a different power supply to no avail and both believe that the
DDS synthesizer is the culprit.
It is a AD9859,see
http://www.dj0abr.de/index_english.html
I have added a perseus screenshot with a bin width of 0.24Hz showing strange
lines in their signal.
I'm not sure if this is the DDS spectrum what we see here.
73
Clemens
DL4RAJ
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Andy Talbot
>Sent: Sunday, March 27, 2016 8:06 PM
>To: [email protected]; [email protected]
>Subject: Cheap and nasty sources - was LF: DK7FC WSPR bad
>quality problem
>
>It is unfortunate these cheap and simple low power solutions
>have come-about at all. The originators who worked out how
>to generate a few milliwatts of Rf from very non-purpose
>designed hardware presumably never anticipated that eh great
>masses would end up connecting this unsuitable kit to high
>power amplifiers. I hope they only ever anticipated their
>being used for very low power uses.
>
>As for the R-PI, that really does look like a bad way of
>generating narrow band RF. I don't know the details of its
>internal hardare, but strongly suspect that it uses a
>jittering Fract-N route to generating arbitrary frequencies.
> Again, fine for a few milliwats of test signal, but
>certainly not for amplification to hundreds of milliwatts.
>
>If you want a decent high power source, use a DDS chip or a
>modern Fract-N synthesizer like the LMX2541. That device has
>an internal VCO and an output divider that allows it to
>generate as low as 35MHz - and then any external CMSO divider
>will allow you to go lower. And they are CLEAN - especially
>so when divided down to LF / HF
>
>
>Andy G4JNT
>
>
>
>
>On 27 March 2016 at 18:14, Graham <[email protected]> wrote:
>
>
>
> 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,
>
>
> From: F6CNI - Andy - JN19QB <mailto:[email protected]>
> Sent: Saturday, March 26, 2016 8:36 PM
> To: RSGB LF Group <mailto:[email protected]>
> 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
>
>
>
>
>
DH5RAE+DB0ABR.png
Description: PNG image
|
