DISCLAIMER

DISCLAIMER: I have no association with UVB-76 station, neither do I have any clue what is the content I am relaying. I can only assure, that the signal is received on 4.625MHz AM-modulated 900km NW from supposed origin and retransmitted unaltered. In no way can I guarantee this service, nor be considered responsible of any content re-transmitted. The only purpose for this relay to exist is because lot of people who do not have equipment or are located too far from station seem to be interested about listening to it. Should the UVB-76 station- or transmission content owners feel violated in any way, please contact me at uvb76.repeater@gmail.com and we will work it out.

Note, that because of shortwave radio signal propagation specifics the station can be more or less reliably received from around 4pm to 6am GMT on summertime. It is almost 24h audible during the winter, with short "skip-zone" blank-out around 6pm GMT.

The USB feed is considered as main source of audio today, as the voice messages are much better audible there than on the AM stream. However, the buzzer sound from the AM stream is somewhat more pleasant to listen at, so both feeds are kept simultaneously.

Monday, November 8, 2010

Why had the buzzer go to maintenance .. ?

As some of you may have already noticed, there are some archives published at the page what you get when pressing the 'test' tab on top of this page.
The reason I havent announced it yet is, that having just 200Mb audio files downloadable is sort of semi-useful solution, so I have been wrestling around to get them visualized somehow and link that to online player of a sort.
If one thinks the utilities for performing FFT (fast fourier transformation) analysis on 1Gb+ audio files (as some of the UVB-76 Repeater archives are) are readily available from the internet, one has to reconsider .. and write such utilities from scratch! :)

And so I did. Only to realize, 10 minutes ago, that I should have had done something like that already ages ago!
The first decent output generated by my new tool (call it a MP3toJPG or whatever :)) was so revealing, that I thought I will share it!

The picture below is a spectral analysis of the archive from August 28, 2010 and displays about 80 hours worth of audio (MP3 file size was 850Mb):

(Click on image to view/download)

The timeline goes from left to right and the frequency goes from bottom to top, i.e. lower frequency is at the bottom of the image and higher frequency (4000Hz) is at the top. The file is over 7000 pixels wide, so beware! :)

The bright markers are where the UVB-76 buzzer is transmitting, although you will se about every 10'th or so buzz there (the total "length" of this picture is 80 hours, remember).

However, what you clearly see is that the buzzer what is supposed to be transmitting more or less consistent signal, is drifting up and down in frequency as it pleases!
Its not the analysis software, as you can see sometimes a morse signal kicking in and having no deviation whatsoever.

Two possibilities - either the buzzer was meant to move around like that because of the desired functionality of the signal, or the equipment neded some serious maintenance. Considering that the signal disappeared shortly after for several weeks, I would assume the latter ...

3 comments:

  1. Have you analyzed the "new" Buzzer with your tool
    and is it still drifting ?

    My feeling is that have made several changes including changes to the transmitter and also a
    new buzzer device.
    I have played with a software called Spectrum Lab
    http://www.qsl.net/dl4yhf/spectra1.html which is very good and I found out that a sawtooth on around 181 Hz fits the same overtone spectrum as the buzzer. I used the builtin test tone generator and by using AM mod with squarewave on about 3 sec I'm getting the on/off.

    But I have no SSB transmitter so I can test how it's looks/sounds in real.

    /Lars

    ReplyDelete
  2. 14:34 11/11/10
    Voice and something like a cell phone heard.

    ReplyDelete
  3. found this on youtube
    consists of over 11 minutes of clear voice transmissions thats did not consist of numbers and names but of a conversation that talked about the buzzer itself (quoted from a rough translation)
    http://www.youtube.com/watch?v=VpQ_AGshkUY

    ReplyDelete