Loads of discussion recently so I thought Id share the
final location of my PA0RDT probe - this photo taken at sunset today. http://kl1x.com/by3akl1x.jpg
The braid of the coax from the probe is bonded to the balcony which is
bonded to the building rebar.
At 137Khz this bonding knocks off some 30dB of noise -
power supply for the probe is lead acid battery, some 14V. Common mode choke of
some 30T of RG174 before the power injector and Im using just a 4T primary and
secondary type 77 material as the isolating transformer before the 50ohm feed to
the R75. This is pretty good and flat from 100Khz up to 15Mhz using the AIM,
even heard JA's on 6m!
The power injector has 3mH lossy dark Green toriod
material if I do use an external supply and decoupled using 0.1
polyprops ( as KL 1 X is wired) -
Unwanted Noise injection is still there and comes from
a) the Dell AC PSU - though I have a box of them and choose one that doesn?t put
a spoggy on my LF/MF freq - this DC supply again in choked and decoupled which
helps a bit
b) serial cable from PC to R75 - tried multiple turns on
lossy toroid which improves things but not perfect. c) slight coupling from the
unused wire input terminal on the R75 if your radio room is located in a very
noisy environment.
Picture of present "array" the total length of the
copper clad and flimsy 16 guage wire is 25cms. I employ a 7 element 500Khz
LPF between power injector and the receiver.
The key is the coax bonding here - In Alaska the
house is wooden frame and I don?t have much to bond too, though I do bond to
anything I can rebar wise. A few 8ft rods and in line chokes help a bit but
theres' nothing like a full Faraday cage which this place has.
73
Laurence, bags packed.
BY3A KL1X Tanggu China OM89UA
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