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Content preview: since 1407utc I was playing around with the settings. that caused mni "glitches". so I switch the PA off now at 1500utc to make some "dry practices". until later Uwe Von: rsgb_lf_group@blacksheep.org Gesendet: 23.01.2014 13:57 An: rsgb_lf_group@blacksheep.org Betreff: Re: VLF: Transmit phase correction [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [194.25.41.13 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 2e1e3024a99876fb99374c85fed501dc Subject: Re: Re: VLF: Transmit phase correction Content-Type: multipart/alternative; boundary="----EC663CC79EB04514B562DC33CD9973EF" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, NO_REAL_NAME,PRIORITY_NO_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false ------EC663CC79EB04514B562DC33CD9973EF Content-type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable since 1407utc I was playing around with the settings=2E that caused mni= "glitches"=2E so I switch the PA off now at 1500utc to make some "dry practices"=2E until later Uwe Von: rsgb_lf_group@blacksheep=2Eorg Gesendet: 23=2E01=2E2014 13:57 An: rsgb_lf_group@blacksheep=2Eorg Betreff: Re: VLF: Transmit phase correction Hi Markus, now since 1238utc ZOA in 1pps_PLL=2Eusr mode on 8270=2E004Hz we will see GL Uwe Von: rsgb_lf_group@blacksheep=2Eorg Gesendet: 23=2E01=2E2014 00:24 An: rsgb_lf_group@blacksheep=2Eorg Kopie: Paul@abelian=2Enetcom=2Eco=2Euk Betreff: VLF: Transmit phase correction Hi Wolf, Uwe, Peter,=20 after a little experimentation, I think I have found a way to set up Sp= ecLab to=A0eliminate transmit phase=A0jumps caused by dropouts in the s= oundcard=A0output=2E=A0As a proof of concept,=A0I=A0generated an=A08269= =2E998 Hz audio=A0carrier=A0last night=2E This happened to=A0leak=A0fro= m the audio wires=A0to my VLF antenna, and produced a weak but well def= ined dash in the 42 uHz grabber window=2E=20 We can use SpecLabs GPS=A0tracking to take care of any irregularities i= n the sound input path to the ADC=2E When using the 1-pps reference wit= h=A0phaselock it can identify and correct short dropouts=2E Augmented b= y the built-in NMEA-based timestamping scheme, SpecLab can=A0in princip= le=A0even=A0provide a defined=A0absolute phase, referenced to the begin= ning of the UT day=2E =20 But the timing is always relative to the reference seen by the ADC inpu= t, and there is no way to directly sense latency variations in the buff= ering between the software=A0and the DAC output=2E Unfortunately on man= y machines,=A0buffer underflows or dropouts on the playback side seem t= o happen fairly often, especially when the PC is not left alone but is = used for other jobs on the side=2E=20 The idea is to feed back a sample of the analog output to the input, us= ing either an analog loopback (eg the audio mixer, but not a digital lo= op like VAC)=2E Or set up a pickup probe to sense antenna current or vo= ltage, which would also take care of=A0phase shifts from variable anten= na tuning=2E Then SpecLab can do a phase comparison to a=A0GPS-referenc= ed=A0internal generator, and steer the=A0frequency of an independent ou= tput oscillator to=A0bring the radiated signal=A0back to the correct ph= ase=2E=20 If you want to experiment with this method, you can download=A0the conf= iguration file =20 http://dl=2Edropboxusercontent=2Ecom/u/26404526/VLF_TX_1pps_PLL=2EUSR=A0= =20 which generates a 8270 Hz stabilised signal=2E To see how it works, tak= e a look at the circuit diagram in:=20 http://dl=2Edropboxusercontent=2Ecom/u/26404526/screenshot_VLF_TX_1pps_= PLL=2Ejpg=20 The output signal is generated by the digimode terminal block, which ca= n be set up either for a continuous carrier, or for QRSS or Opera modul= ation if you want=2E It feeds the DAC and the power amplifier through L= 5=2E The output is brought back to the left input=A0(L1) and fed to the= "E" channel of=A0a colour-DF spectrogram=2E The right channel (R1) get= s the 1pps signal from the GPS=A0which is used=A0for=A0samplerate lock=2E= Lacking an appropriate GPS unit, I'm not using NMEA timestamps here, b= ut you could chose so if your unit provides serial data=A0with proper t= iming=2E=20 The=A0steady reference frequency is provided by the test signal generat= or -=A0this is where you enter your desired output frequency=2E It is f= ed to the second "H" channel of the spectrogram through R5=2E The colou= r (azimuth) of the trace=A0gives an indication of the phase difference = between L1 and R5=2E=20 The phase lock is implemented as a=A0macro in conditional actions: Ever= y 200 ms, it checks whether there is a valid probe signal at L1, and is= so, it=A0shifts=A0the digimode frequency within +-0=2E18 Hz according = to the phase difference=2E Check this by turmning the DAC=A0off and on:= =A0The trace comes back on with an arbitrary colour, but =A0it will alw= ays revert to green (180=B0) within about three seconds=2E=A0=20 So to get started,=20 -=A0set up the analog loop path and the 1-pps,=A0=20 - load VLF_TX_1pps_PLL=2Eusr,=20 - change the=A0test signal generator=A0frequency from Uwe's 8270=2E004 = to yours, =20 -=A0set the digimode teminal to send unmodulated test tone at TX freque= ncy=2E=20 - enjoy!=20 Hope this may be useful=2E=20 Best 73,=20 Markus (DF6NM)=20 From: wolf_dl4yhf =20 Sent: Sunday, January 19, 2014 7:01 PM=20 To: Markus Vester =20 Cc: Paul ; Uwe Jannsen =20 Subject: Re: DJ8WX 8270=2E004 Hz - transmit phase correction? =20 Hello Markus and all, Am 19=2E01=2E2014 18:43, schrieb Markus Vester: 30 dB =2E=2E=2Enot too bad, is it?=20 Still wondering about the nature of those transmit glitches=2E Assuming= perfect GPS sync,=A0all=A0possible interruptions in the input data str= eam could be detected by the timestamp identification=2E But=A0there=A0= is still a chance for undetected=A0buffer underruns in the sound output= =2E=A0Would that affect the phase permanently?=A0Or would the average f= ill state of the FIFO buffering=A0eventually=A0be pulled back to the or= iginal lag (probably not)?=2E=20 I have been pondering a scheme where one audio channel is getting 1pps = while the other is used to=A0sample=A0the transmitter output, eg with a= small pickup loop=2E That way all phase variations in the transmit cha= in would be caught, and the=A0software oscillator could be steered to r= evert to the original phase within a few seconds=2E With timestamping,=A0= we could even prescribe=A0absolute phase, allowing comparative measurem= ents=A0across different sessions=A0many days apart=2E=20 Wolf what do you think? If it makes sense, I might try to implement=A0s= omething=A0based on the Sndinput / Sndoutpt=A0combo=2E=A0 Yes, certainl= y=2E If there was a drop-out of the audio output, we cannot be sure if = the latency between 'application' and the arrival of the sample at the = D/A-converter remains exactly the same=2E Observing the phase of the *r= adiated signal* and steering the signal generated by software to get th= e phase 'back where it belongs' would be better because it would also c= ompensate phase deviations caused by the antenna itself=2E Have a nice evening, =A0 Wolf =2E Best 73,=20 Markus ------EC663CC79EB04514B562DC33CD9973EF Content-type: text/html; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable
since 1407utc I was playing around with the settings=2E that caused = mni "glitches"=2E
so I switch the PA off now at 1500utc to make some "dry practices"=2E until later
Uwe
Von: rsgb_lf_group@blacksheep=2Eorg
Gesendet: 23=2E01=2E2014 13:57
An: rsgb_lf_group@blacksheep=2Eorg
Betreff: Re: VLF: Transmit phase correction

Hi Markus,
now since 1238utc ZOA in 1pps_PLL=2Eusr mode on 8270=2E004Hz
we will see
GL
Uwe
Von: rsgb_lf_group@blacksheep=2Eorg
Gesendet: 23=2E01=2E2014 00:24
An: rsgb_lf_group@blacksheep=2Eorg
Kopie: Paul@abelian=2Enetcom=2Eco=2Euk
Betreff: VLF: Transmit phase correction

Hi Wolf, Uwe,= Peter,
 =
after a littl= e experimentation, I think I have found a way to set up SpecLab to eliminate transmit phase jum= ps caused by dropouts in the soundcard output=2E As a proof of concept, I generated an 8269=2E998 Hz audio carrier last night=2E This happen= ed to leak from the audio wires to my VLF antenna, and prod= uced a weak but well defined dash in the 42 uHz grabber window=2E
 =
We can use Sp= ecLabs GPS tracking to take care of any irregularities in the sound input path to the ADC=2E When using = the 1-pps reference with phaselock it can identify and correct short dropout= s=2E Augmented by the built-in NMEA-based timestamping scheme, SpecLab can&n= bsp;in principle even provide a defined absolute phase, referen= ced to the beginning of the UT day=2E
 =
But the timin= g is always relative to the reference seen by the ADC input, and there is no way to directly sense latency va= riations in the buffering between the software and the DAC output=2E Unfort= unately on many machines, buffer underflows or dropouts on the playback side = seem to happen fairly often, especially when the PC is not left alone but is us= ed for other jobs on the side=2E
 =
The idea is t= o feed back a sample of the analog output to the input, using either an analog loopback (eg the audio mixe= r, but not a digital loop like VAC)=2E Or set up a pickup probe to sense anten= na current or voltage, which would also take care of phase shifts from variab= le antenna tuning=2E Then SpecLab can do a phase comparison to a GPS-referenced internal generator, and steer the frequ= ency of an independent output oscillator to bring the radiated signal = ;back to the correct phase=2E
 =
If you want t= o experiment with this method, you can download the configuration file
http://dl=2Edrop= boxusercontent=2Ecom/u/26404526/VLF_TX_1pps_PLL=2EUSR <= /div>
which generat= es a 8270 Hz stabilised signal=2E To see how it works, take a look at the circuit diagram in:
 =
The output si= gnal is generated by the digimode terminal block, which can be set up either for a continuous carrier, or= for QRSS or Opera modulation if you want=2E It feeds the DAC and the power ampli= fier through L5=2E The output is brought back to the left input (L1) an= d fed to the "E" channel of a colour-DF spectrogram=2E The right channel (R= 1) gets the 1pps signal from the GPS which is used for samplerate lo= ck=2E Lacking an appropriate GPS unit, I'm not using NMEA timestamps here, bu= t you could chose so if your unit provides serial data with proper timing=2E
 =
The stea= dy reference frequency is provided by the test signal generator - this is where you enter your desired o= utput frequency=2E It is fed to the second "H" channel of the spectrogram thr= ough R5=2E The colour (azimuth) of the trace gives an indication of the phase difference between L1 and R5=2E
 =
The phase loc= k is implemented as a macro in conditional actions: Every 200 ms, it checks whether there is a valid p= robe signal at L1, and is so, it shifts the digimode frequency wit= hin +-0=2E18 Hz according to the phase difference=2E Check this by turmning= the DAC off and on: The trace comes back on with an arbitrary col= our, but  it will always revert to green (180°) within about three seconds=2E 
 =
So to get sta= rted,
- set up= the analog loop path and the 1-pps, 
- load VLF_TX= _1pps_PLL=2Eusr,
- change the&= nbsp;test signal generator frequency from Uwe's 8270=2E004 to yours,
- set th= e digimode teminal to send unmodulated test tone at TX frequency=2E
- enjoy!
 =
Hope this may= be useful=2E
 =
Best 73,
Markus (DF6NM= )
 =
=
Sent: Sunday, January 19, 2014 7:01 PM
Subject: Re: DJ8WX 8270=2E004 Hz - transmit phase correction?
<= span style=3D"font-family: arial; font-size: 13px;">
Hello Markus and all,

Am 19=2E01=2E2014 18:43, schrieb Markus Vester:
30 dB =2E=2E=2E= not too bad, is it?
 
S= till wondering about the nature of those transmit glitches=2E Assuming perfect GPS sync, all possible interruptions in the input data stream cou= ld be detected by the timestamp identification=2E But there is stil= l a chance for undetected buffer underruns in the sound output=2E = ;Would that affect the phase permanently? Or would the average fill state= of the FIFO buffering eventually be pulled back to the original lag (probably not)?=2E
 
I= have been pondering a scheme where one audio channel is getting 1pps while the other is used to sample the transmitter output, eg with a small pickup loop= =2E That way all phase variations in the transmit chain would be caught, and the software oscillator could be steered to revert to the original= phase within a few seconds=2E With timestamping, we could even prescribe absolute phase, allowing comparative measurements a= cross different sessions many days apart=2E
 
W= olf what do you think? If it makes sense, I might try to implement something based on the Sndinput / Sndoutpt combo=2E 
Yes, certainly=2E If there was a drop-out of the audio output, we cannot be sure if the l= atency between 'application' and the arrival of the sample at the D/A-converte= r remains exactly the same=2E Observing the phase of the *radiated signal* and st= eering the signal generated by software to get the phase 'back where it belongs' w= ould be better because it would also compensate phase deviations caused by the = antenna itself=2E

Have a nice evening,
  Wolf =2E

B= est 73,
M= arkus
 
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