Hi Tony,

OK so if your RX and PC time is stable, we can give it a try.
-You need a stereo input soundcard and feed the PPS signal to the right channel. Just run it at 48 kS/s. The PPS signal must be DC decoupled and the level must be limited to 80% of the ADC range, simply use 100nF and a resistive divider. The values will depend on your GPS module and its output level.
-Download the latest version of SpecLab and install it to the recommended folder.
-Turn the RX to 136.00000 kHz USB and use a 2.5 kHz wide SSB filter. Connect the RX to the left channel of the soundcard input.
-Download the usr file in this mail and open it into SpecLab (File -> Load settings from...)
-Click on Components -> Show Components. A box opens. In the top left corner, click on "SR cal". Another box opens. The Status must be green, showing pps peaks OK. If the level is to high, click on "scope" and see the peak form. Then you need to adjust the divider of your GPS module to reduce or increase the PPS level. The box must be green for most of the time in the end. Click to scope again, there is a pulse counter PC and an error counter EC. The error should be lower than 2 % or so, for example PC=1000 EC=16. Just let it run a few hours and see if the tracking is stable.
If you have problems in this step, tell us what the problem is.
-Wait a few hours and check if text files appear at C:\Spectrum\data After the first 40 minutes, a file should appear each 10 minutes.
-Ask someone to transmit a short EbNaut message at 1s symbols and make sure to record on this time.

So far. Then we can continue with part 3 :-)

73, Stefan


Am 23.10.2016 19:09, schrieb Tony Baldwin:

Hi Stefan
 
My receiver is an Elad FDM-DUO SDR with a 10 MHz GPS input.
Unfortunately SpecLab doesn't have that radio for an SDR input, so I have to use the sound input via USB.
I could send the 1 PPS to my computer via RS 232 as well if that helps.

73, Tony, EI8JK.

On 23/10/2016 17:51, DK7FC wrote:

Hi all,

I started to write the second part of this tutorial but when finished i was not happy with the result.

The first thing one can say is that you will need a very frequency stable receiver. There is no chance without an external reference signal. For generating wav files using SpecLab you will also have to use a ref signal to compensate the drift of your soundcard. Some people have already prepared things in the past. You can use a 1 PPS signal for soundcard drift compensation or a down divided 10 MHz GPS reference or a stereo soundcard receiving VLF MSK signals on the other channel to compensate the drift.
Also the SpecLab configuration depends on your receiver type.
Now i could simply make some assumptions what your equipment may be but this may be not a good way.
So now i think it's better that we start with one example, one (or more) of the stations who are interested in EbNaut decodes on LF should describe the available system components. Then we can work it out what must be done.
We will need to have a stable RX frequency and a drift compensated soundcard frequency in the end.

So who of those who are interested wants to start?

73, Stefan