To: | [email protected], [email protected] |
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Subject: | Re: LF: Re: EbNaut test transmission |
From: | Markus Vester <[email protected]> |
Date: | Wed, 18 Nov 2015 08:55:10 -0500 |
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Sender: | [email protected] |
Hi Andy,
thanks for sharing the link to Basil's beautiful web page. Last night his radio ghost appeared here numerous times, even though not in every ten-minute slot - see attached spectrogram and Eb/N0 plot.
All the best,
Markus (DF6NM) Von: Andy Talbot <[email protected]> An: rsgb_lf_group <[email protected]>; rsgb_lf_group <[email protected]> Verschickt: Di, 17 Nov 2015 11:50 pm Betreff: Re: [rsgb_lf_group] Re: LF: Re: EbNaut test transmission Ok, I'll leave it running overnight. After the rain stopped, antenna resistance fell and power output rose closer to 300 Watts of RF into the lower Rant, so EIRP is about +20dBm now.
To reiterate for any new readers:
Frequency 137780.000 +/- 0.2mHz
Coding 8K19A
Symbol period 0.5s (2 symbols / sec) BPSK with 10ms Gaussian shaped phase transition
Message length is 9 characters consisting of a callsign and the abbreviated name of a well-known cockatiel
PC time is synchronised using rsNTP, set for periodic updates which it appears to do every 30 minutes. So far it hasn't made a correction of more than 20ms (ignoring the first one back at 1611z)
The DOCXO (almost a TrOCXO) appears to have stayed well within 1ppb of its correct frequency all afternoon / evening. I check by comparing a divided down 1PPS signal against GPS, looking to see how many microseconds the two respective edges drift apart over a few hours. If it moves by more than that corresponding to 2 PPB (7.2us per hour) a slight tweak to the frequency control pot gets it back again.
For really serious work, the Caesium tube could be turned on, but that requires about 60 to 90 minutes for warm up to reach stable operation. Something only worth doing for long duration tests at lower rates.
The last part of the message comes from this chap, who's ghost still haunts my shack ... http://www.g4jnt.com/basil.htm
Andy G4JNT
On 17 November 2015 at 22:09, Markus Vester [email protected] [rsgb_lf_group] <[email protected]> wrote:
EbNaut_spectrogram_151118_0744.png
G4JNT_EbN0_151117-18.png |
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