UVB76 The Buzzer is DOWN !!

  

UVB76

'UVB76 The Buzzer is DOWN !!'

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The WebSDR at the University at Twente is often used for listening to the UVB76 signal , often called , The Buzzer on 4625kHz.
http://websdr.ewi.utwente.nl:8901/

At least 1 or 2 times each hour a visitor in the chat box will ask -  ''
uvb 76 - it's down ? ''

The answer is The BUZZER is NOT DOWN !

Due to the signal not being heardon the WebSDR some come to the conclusion that the Transmitter is not working.
Some have said it was turned off for maintenance.
Some claim that it only is turned on at night time.
Even some say that that it is now transmitting at lower power.

And on and on the stories go.

The facts is that the UVB76 Buzzer is turned on and is running 24 hours a day.



So why then can't it at times be heard ?

The reason is because of the low frequency of 4625kHz that it is on.
In the HF bands , low frequencies are more affected by atmospheric absorption than higher frequencies are.
The Buzzers low 4625kHz frequency is
In a part of the shortwave spectrum where transmitted signals suffers very greatly from atmospheric absorption during daylight hours.

During the day the signal will be able to be heard up to a few hundred or so kilometers away by Ground Wave propagation , but due to absorption of the ionospheres D layer at that time , not very long distances will be possible.

This diagram shows the transmitted signal arriving at the D layer , but there it gets effectively absorbed and its trip ends there.
D Layer absorption


At night time things change as the D layer dissipates.
The absorption effect reduces , and this allows the signal to reach the upper F layers of the ionosphere , and when this happens , the signal can be reflected / refracted down to to Earth at much further distances away via
Sky Wave propagation.
The WebSDR's location in the Netherlands is too far away for the Ground Wave to reach , so it relies on the signals arriving to it through Sky Wave propagation.

F Layer propagation

At nigh time the Buzzer signal from Russia arrives
through Sky Wave propagation and can then be heard on the WebSDR in the Netherlands.

So the Buzzer is NOT down , it is just that it cannot be heard in
the Netherlands during daylight hours in Europe.



Fortunately for Buzzer fans there is an alternative to the ineffective WebSDR in the Netherlands.
You can listen to a live stream of the Buzzer from a receiver located in Helsinki Finland.
This location can hear the Buzzer 99% of the time.