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
Hi Joe, your carrier was well visible as a straight line on 137777.000 Hz. If the phase had alternated every 50 seconds it should have split up into two lines 20 mHz apart, accompanied by additional
Another approach: Make a LF loading coil with bifilar wire. For HF in differential mode the coil will just be a large common-mode choke. You can either connect relay at the bottom end where LF voltag
Hi Domenico, got your 15, 16 and 17 UT transmissions ok, with Eb/N0 3.1, 11.8 and 9.0 dB respectively. It looks like the symbol timing is a bit over one second late. Best 73, Markus (DF6NM) --Ursprün
As far as I can see the transmission is on the nominal frequency. I needed the offset because I had set my center frequency to 136171 Hz, minus 0.0175 Hz due to known RX DDS rounding. The sequences s
Paul, interesting spectrum... but before ripping the RX apart I would't rule out propagational Doppler. The main component is half a mHz low which seems reasonable after dusk. The companions are a co
Very nice, congratulations! Markus --Ursprüngliche Mitteilung-- Von: Andy Talbot <[email protected]> An: rsgb_lf_group <[email protected]> Verschickt: Do, 19 Nov 2015 8:55 pm Betreff: R
Yes, same here when using the show_rawsyms3a utility. The peak in the skyblue spectrum-of-squares will conveniently guide you to the correct frequency and time offset if Eb/N0 is above 4 dB or so. T
My former loading coil was made of RF litzwire, 243 x 0.05 mm strands. These strands are grouped in 3 bundles, which can easily be separated and soldered individually. I haven't measured characteris
John Lennon - at 5.5 dB Eb/N0 I can almost hear him ;-) Nice one! 73, Markus --Ursprüngliche Mitteilung-- Von: IZ7SLZ <[email protected]> An: rsgb_lf_group <[email protected]> Vers
... but you could additionally increase wire diameter by sqrt(2) for the same coil length. Assuming skin effect regime, this will decrease R by another factor of sqrt(2). In other words, same coil Q
Hi Paul, looking at your spectrograms three weeks ago, your direct-sampling LF receiver actually seemed to be doing rather well! It's surely sensitive enough, and apparently not limited by ADC noise
Hi Joe, phase shift is working - two peaks at +- 10 mHz, as expected. Updating spectrogram: https://dl.dropboxusercontent.com/u/26404526/EbNaut_spectrogram.png Yes the start of the message and the bi
Unfortunately someone has come up only 0.09 Hz above your QRG, apparently sending fast QRSS mode in the TA slot. Callsign is no readable here. The signal is blue on my DF, and relatively strong on th
Yes your signal is really good now! Not exactly "audible" here but easily visible in Stefan's QRSS-10 slot, and sometimes faintly discernible in my wideband colour-DF in 0.67 Hz FFT bins. The QRM has
Yes a 0.5 mHz (not Hz) hourly drift won't affect decoding much. I think the reason for chirp tolerance is simply that a quadratic phase associated with a linear frequency drift has smaller excursion
Great! What type of coding (8K19A ?) and how many characters will you send? 73, Markus From: [email protected] Sent: Sunday, November 22, 2015 11:04 PM To: [email protected] Subject: LF: EbNau
No worries Joe, no hurry. Weekend's over and we'll have to go to bed soon. But the receiver will be collecting data by itself, and I'll take a good look tomorrow morning. Good luck and 73, Markus --U
I found a way to seamlessly stitch together data chunks from a sequence of partially-overlapping exported FFT's, allowing me to analyze phase evolution over arbitrary periods of time. Attached plot i
The cat sat under the stars... Confirming Paul's observation. The strong unmodulated carrier was well visible in the grabber spectrograms. Got an error-free ** decode of the 0:00 transmission: found
