2017-05-22, 23:21
(2017-05-22, 21:28)hp3ak2 Wrote: Slowly rotating my 1m crossed loops will null the signal in one channel, while maximizing it in the other channel. I can make either channel very strong while making the other quite weak, or I can make both about equal, but very strong. It does not appear that moving the antennas, within this neighborhood, will do any good at all.
The loops don't *have* to be at 90 degrees. 90 degrees just produces a nice omni directional polar pattern. I have two VLF transimitters within 30 miles one at 285 degrees the other at 260 degrees, these produce huge signals. I have one loop orientated to pickup as little as possible of both transmitters, they aren't equal strength so the null of that loop is not on bearing 272.5 degrees but more towards the stronger. This channel has the LPF set to 54.7 khz (did I say there is also a 60 kHz time signal transmitter co-located with one of the VLF transmitters?)
The other loop has its LPF set to 17.3 kHz (the Tx's are on 19.6 and 22.1 kHz) and rotated away from the first loop such that the levels of the interfering carriers are the same for both channels. This means the angle between the two loops is only about 30 degrees. Yes the polar pattern is severly compromised but if I had the loops at 90 degrees the one "looking" at the transmitters wouldn't see anything other than those transmitters.
Perhaps you could do something similar? How well do you get on with the farmer with fencer? Would they llet you try supressing it? How well maintained is the actual fence? Are all the energised wires well insulated from ground and vegetation kept clear?
As for a guide for gains, thresholds etc, every stations enviroment is different so what works for one probably won't be particulary applicable to another. My station is in "automatic". There is a recomendation to have the first gain figure higher than the second on the settings page, ie use 10 x 8 rather than 8 x 10.