After some tests I found the same problem as JOLOS-qth: QRN from external usb-hard disk LaCie Porsche 250 G. The power supply seems to be the source of bad noise on many frequencies. I am going to fix a new hd inside of the computer later on. Also an UPS-system is needed as there are often small power-out situations at my Village. When using SDR14 doing the recordings you can always (and must often do so!) turn off the LCD-screen - also uplug the power - to avoid noise from the LCD. What is more you have to use good calibration stations. I have found one of the best on upper MW to be the British syncro stations like 1215 kHz, probably also 1449. FR1557 seems to be pretty accurate as well. These can be used to check calibration when you do RF-recordings on upper band. Usually as a general station Pori 963 is widely used, however, it seems it can be 1-2 Hz down from the nominal as far as calibrating with other signals like 1215 & 1557. Of course you can hear TA stations during good conditions when the noise occurs, however you need at least 10 dB better signals. But there is a risk to loose the weakest stations ! Although you can use another RX (like I do usually using my ICOM9000) the noise can come via the splitter system!More results later on. Next thing I hope to put up my KAZ 10x40m (NW-SE) with fiber mast ("DX-wire") and soon a NE BOG will be put on the ground.
TK
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