LF,
I have been receiving a peculiar broadband noise over the past week or so and
would appreciate comments. Please see attachment. Note that times are local
(UTC + 1 hr) and the frequency scale is an offset from 136.7 kHz approximately
(I have problems with the RS 232 interface to the receiver and can not set the
frequency except with the tuning knob, which limits me to a precision of about
100 Hz). On the loudspeaker, the signal sounds like a mix of television time
base and LORAN A. It is sufficiently strong that it effectively wipes out F5WK
and F4DTL, both of whom are normally very good signals.
The signal was first noticed on Monday of last week and on most days from
about 9 AM local time to the end of the afternoon. Last Friday it disappeared
at about 3 PM and was not received here at all on Saturday and Sunday, nor on
Monday (which was a public holiday in France).
The sudden jump in frequency, which occurred on a number of occasions, did not
seem to coincide with the start or finish of the cheap rate electricity periods
here.
We have not introduced any new electronic equipment here in the past week, nor
as far as I'm aware have we changed the way we use what is already installed.
The antenna here is a 2 m square eight turn loop whose plane is approximately
north-south (it is adjusted so that a null points at France Inter - a high
power longwave broadcast station on 162 kHz).
The receiver is a Lowe HF250 in CW (USB) mode set to a nominal 136.7 kHz. Note
that the vertical line at 600 Hz on the display results from a receiver defect.
The BFO is a little too far into the pass band and consequently the LSB
rejection is not as good as one would wish. The receiver therefore responds
somewhat to (I think) the Hungarian data station.
1820 loal time: the noise is still there.
John F5VLF
JN17vg
>
|
