RE: LF: Opds-2H hints

[Laurence KL7 L <hellozerohellozero@hotmail.com>]

thanks Markus
 
WH5XBA loocator is BP51IP
 
 
Laurence KL7 L
 
WH2XBA/5
 

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From: markusvester@aol.com
To: rsgb_lf_group@blacksheep.org
Date: Thu, 6 Mar 2014 23:44:16 +0100
Subject: Re: LF: Opds-2H hints

Opds-2H monitoring on the bottom window of the opds page: http://dl.dropboxusercontent.com/u/26404526/opds.htm

424 µHz Spectrogram on the bottom of the VLF grabber: http://www.df6nm.de/vlf/vlfgrabber.htm

NAA and 29.5 kHz plot: http://dl.dropboxusercontent.com/u/26404526/plot.jpg

 

Here are my SpecLab settings for 96 kHz samplerate:

 http://dl.dropboxusercontent.com/u/26404526/opds2H_29k5.USR 

Using these will probably require a few edits:

- define data folder for SpecLab FFT export and opds.ini (mine is c:\spectrum\data2H\)

- change the source for the samplerate detector to your favourite MSK transmitter (I'm using a locally generated tone) 

- enter your calibrated samplerate in the audio settings and in opds.ini

- edit screenshot settings in periodic and sceduled actions.

 

Good luck all,

Markus (DF6NM)

From: Markus Vester

Sent: Wednesday, March 05, 2014 11:22 PM

To: rsgb_lf_group@blacksheep.org

Subject: LF: Opds-2H hints

Opera deep search users,

 

here are some details on how to adapt opds to the new Op-2H mode for 29.5 kHz.

 

If you are using an USB receiver, you could tune to 27.98 kHz *** dial and process the audio band around 1.52 *** kHz. This will put Bob's QRG near the middle of  the passband of standard Opera software, so if you want you can run both side by side. The following settings will then let opds analyze a 3.9 Hz wide passband centered on 29.500 kHz:

 

Audio samplerate: 12000 Hz

FFT decimate (divisor): 1536

FFT length: 65536  (119.2 µHz bin width).

FFT center frequency: 1520 Hz  ***

Number of exported FFT bins: 32768

Waterfall scroll interval: 30 minutes

L2 bandpass filter before noise blanker: center 1520 Hz ****

 

**** Note: According to later info, Opera -2H actually wants 1550 ... 1600 Hz audio. So if you like to run Opera and opds on the same receiver, you should select 1575 Hz for SpecLab's center frequency and filter, and tune to 27.925 Hz USB "dial".

 

In opds.ini, the following lines need to be edited:

 

opspeed=128     'Op-2H speed (approx. minutes)
spotdelay=116   'delay spot timestamp the same way as Opera (seconds)
fc=29500           'FFT center frequency (Hz)
sr=12000           'your calibrated samplerate (Hz)
dec=100663296  '1536*64K decimation * FFT length

 

Many built-in soundcards are now supporting 96 kHz ADC samplerate. If you own one of these, the much prefered option would be to connect the antenna directly to the soundcard, doing away with the receiver and it's possible drift. In SpecLab, you would then directly enter 29500 Hz center frequency for the bandpass and the FFT, select an approximately 8x higher FFT decimator from the dropdown list (13824 instead of 1536), and modify the dec factor in opds.ini accordingly (dec=905969664). You can then use samplerate correction with one of the military MSK stations to remove any remaining drift.

 

Finally you will have to enter potential transmitting stations to the search list callsloc.txt:

 

WH1XBA fn12lq
WH2XBA fn42hi
WH3XBA fn31ls
WH4XBA em95tg
WH5XBA bp51gn
WH6XBA em47em

 

Disclaimer: These are untested "theoretical" settings, please post if you find errors or corrections.

 

Good luck!

 

73, Markus (DF6NM)