Tracking down some serious HF interference
- when we moved into our home years ago, the HF bands were quiet
and wonderful to listen to - this was before our era of DVB and
ADSL/LAN...
-
escpecially since over a year ago, the noise level on HF has
gone up (measured with an SDR-IQ) to almost intolerable levels, so
something needed to be done
-
in an attempt to get a rough idea of what the sources may be, I
turned off the mains supply, leaving only my UPS powered equipment
running
-
turned out that the TV/HiFi system was one serious source of
interference and more specifically the DVB-T set top box receiver
-
simply adding a home brew galvanic braid isolation modification
to the antenna cable (betwen the receiver and wall receptacle) cleared
things up quite a bit
-
next to find the interferer that is one of the devices
powered by the household UPS system (amazingly, none of the electronic
fluorescent lamps caused RFI)
-
the second severe interferer turned out to be the SAM
Magnetometer Aurora Detector
- disconnecting the sensor cable braid killed practically
all interference
-
pretty stupid of me at the time, but it all came back as a
flashback looking at my documentation (am I happy that I documented
this too)
-
our cable was a shielded underground 3 * paired wires affair that
ran short of contacts, so we decided to use the braid as DC and PWM
Data return - how daft
-
unfortunately this cable runs almost parallel to my 80 m current
balun fed, balanced dipole - hence the challenges
-
switching off the SAM processor unit resulted with the same
effect of course (disconnecting the braid effectively powers down
the sensors)
-
next part of the project: dig up the old grease cable and replace
it with a shielded/ruggedized multicore cable a.s.a.p. !
-
copy of a short e-mail I sent to our OH ham reflector regarding elimination of braid currents (in Finnish)
Updated 13.01.2019/OH2AUE
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