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Tom – : : personal interface : : http://tomas.jansta.eu Tom ad6xp Wed, 03 Jan 2018 12:31:38 +0000 en-US hourly 1 https://wordpress.org/?v=4.9.3 WebSDR servers online http://tomas.jansta.eu/websdr-servers/ Sun, 08 Jan 2012 15:30:18 +0000 http://tomas.jansta.eu/?p=1 A few months ago I found the WebSDR portal collecting a list of currently active WebSDR servers. Very nice job done by people at University of Twente in Netherlands, especially by PA3FWM. He is running his wideband [0.000 – 19.440 MHz] direct sampling receiver http://websdr.ewi.utwente.nl:8903 using fast ADC and FPGA connected to 2 x 10 meters dipole.

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Ionosphere conditions http://tomas.jansta.eu/ionosphere-conditions/ Tue, 22 Nov 2011 10:26:55 +0000 http://tom.interko.eu/?p=20  

Ionosphere conditions seem to follow a predicted tendency to reach a maximum in 2012/2013, so we may experience a long lasting DX openings and maybe blackouts :/ too.

This situation is obvious from the diagrams at NOAA Space center:

http://www.swpc.noaa.gov/SolarCycle/

http://www.swpc.noaa.gov/SWN/index.html

 

Signals often travel in mysterious ways, so we can reach Australia and Austria stations simultaneously from central Europe. It seems to be an effect of ionosphere reflections both low angle and Es and maybe some direction dependent reflections or scatterings as can be sometimes seen on ionograms, directograms and spectrograms.

Ionogram from station Pruhonice shows such a suspect reflections from E – NNE direction upto 9MHz f0F2 (light blue area).

 

Interesting effects can be seen on weak narrow bandwidth signals as WSPR are.

Below is the main window of WSPR codec in receive mode. Here you can see a repeating pattern of a fuzzy signal of unidentified transmitting wspr beacon because its frequency drifts too much. The cause of this drift is probably due to some ionospheric effect and Doppler shift [?]. Note the local time and the frequency!

 

 

 

Let’s see how beautiful show the mother nature is preparing for us in the next years.. 🙂

 

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Mysterious signals at 126 MHz http://tomas.jansta.eu/mysterious-signals/ Mon, 02 May 2011 22:23:23 +0000 http://tom.interko.eu/?p=41 While I was measuring a harmonic content of the signal from an oscillator in HF range, I tuned the great Kenwood TH-F7 TRX to VHF band. The receiver mode was set to USB and the frequency band to 108-138 MHz, where any jamming signal should not appear (air traffic control voice and data communications reside there).

At 126MHz appeared some strange sounding signals. I listened a while then connected the TRX to PC audio input. Spectral analysis revealed following spectrograms.

 

Fig. 1.  Spectrogram #1: Antenna 10meter horizontal dipole, RX tuned to 125.998MHz

Mystery signal 126MHz

Fig. 2.  Spectrogram #2: Antenna 2m vertical GP unipole, RX tuned to 125.998MHz

 

The signal record is here: 125998kHz-11m-ant01-3sig (mp3, 250kB).

There are many signals of this characteristic at the same base frequency and some of them are just active sweeping while others idle. The pattern of the frequency sweep is dynamic in time and every signal has different variable timing and frequency track. Also, the frequency change is not monotonous (steps look like a dotted curve on the spectrogram where the change is steep).

It should be noted that the signals exhibit no fading in amplitude, no doppler shift and signal strength is quite low (20dB S/N max. estimate) with any tested antenna. I could receive them almost everywhere (locator JN89) in the urban areas and outside as well. One of the possible sources are the BTS (GSM cell phone transceivers).

Sometimes in the free time I’ll take a directional antenna and try to locate the source.

Or is there anybody who knows the truth? Please drop me an email or comment.

 

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