Dear LF,
the "big buzzer" is on again today... it's most certainly the EFR
transmitter at Budapest-Lakihegy, 135.6 kHz:
http://maps.google.com/maps?f=q&hl=de&q=47+22+17+N,+19+00+22+E&ie=UTF8&z=18&ll=47.373866,19.004492&spn=0.003426,0.005488&t=k&om=1
Several times I could hear relatively weak sweep signals, probably
generated by a network analyzer used for antenna testing. Most of the
high power tests were apparently applying a continuous 010101
sequence at 202.55 baud FSK, causing the hum-like sidebands. Reducing
the receiver gain by 7 dB cleared up the severe overloading effects
on the LF grabber. This left a set of thin red lines spaced at 101
Hz, reaching up to about 136.7 kHz. However with real data, the
sidebands will smear out and clutter the lower half of the band
during the telegrams.
Spectrum taken 06-09-11 6:41, 135.600 kHz at 1100 Hz.
Assuming that we will have to live with this beast, I wonder if there
is a way to extract its teeth. A signal processing software could
decode the data, model the filter transfer function and estimate the
FSK transition times. Then one could generate a local replica of the
signal, and use that to cancel it. Seems related to a key-click
filter algorithm ( http://www.dxatlas.com/Rocky/ ) - has anyone in
the group tried to implement something similar?
Kind regards
Markus, DF6NM
-----Ursprüngliche Mitteilung-----
Von: [email protected]
An: [email protected]
Verschickt: Sa., 9.Sept.2006, 11:47
Thema: Re: LF: Big signal with hum...
Dave G3WCB wrote:
Anybody else notice the ghastly big signal with 50Hz hum bars on around
135,500 kHz? It's been on and off all evening, and is on at the moment
(2250z)
> I thought it was local to me, but it also appears on Marcus's grabber :-(
> 73, Dave G3WCB IO91RM
Dave and all
The signal here was S9 + 50dB, "blackening" the whole band
See images ... if they make it here
Full band image still is on the grabber [time is in utc]
http://www.xs4all.nl/~nl9222/136grab.htm
Hopefully this device has been selfdestructed ;-)
73 de Ko, NL9222
