Re: H-field receiver at Todmorden
- Hi Paul,
Happy New Year!
> > Direction?Ah, that explains the absence of "Nulls".
> Varies. It's a 2-channel rx, there are two loops at right
> Or maybe there's a way to synchronise theAccording to 4Front:
> pair of M-Audio 192 cards that I'm using. Any suggestions?
It's possible to lock the sampling rate to the S/PDIF or world clock inputs by setting the envy24.sync setting in ossmix to SPDIF.
sid@sid-fh: > ossmix
Selected mixer 0/M-Audio Audiophile 192
Known controls are:
envy24.sync <INTERNAL|SPDIF> (currently INTERNAL)
Other M-Audio cards (1010?) have a "World Clock Mode" input which can be used by OSS.
The Kiel Longwave Monitor has moved to a new location, ~30km NW.
The HBG-receiver works fine there. The broadband receiver still suffers from local interference sources and I'm trying to find a sufficient place for the antenna. Data uplink to the server is performed by UMTS now.
Peter, 54N 10E (still)
- That reminds me of an unplanned experiment I did a few years ago. I was
sitting in an open area in the forest listening to an E-field receiver
and I found the hum level surprisingly strong as this location was about
a kilometer from powerlines and houses. With the RX still grounded with
a large screwdriver pushed into the soil, I rotated the RX and let the
tip of the 1.5m whip antenna touch the wet ground in various directions.
There was well defined "hum gradient" in the surface, two maxima ~180
degrees apart and two minima at ~90 degrees to the maxima. The
hum/sferics ratio also changed with this angle. I am quite sure that the
signals I heard was indeed caused by "earth currents". When I tried this
in some other locations, there was no distinct minimum to be found.
Perhaps different current phase angle in different directions.
BTW, this inspired me to try a stereo version with three ground stakes,
one central stake for "common" and two "signal stakes" for left+right at
90 degrees to each other (wrt the gnd stake). The signal stakes were
about 10..20m from the gnd stake iirc. The sound did have some spatial
effect. My first plan was to build a diff' amp' and use four stakes but
I changed my mind when I couldn't foresee any common mode trouble that
far from civilization.
> Made some tests today at a new antenna site which is three times
> further away from the nearest mains. Used a 1 metre square
> loop, about 100 turns straight into the mic input of the N140.
> Was hoping for a significant reduction of mains hum but the
> levels are not that much different at the new site. Not what
> I expected and quite disappointing.
> I wonder if, at the existing site, I am already far enough
> away from the neighbourhood power lines and what I'm picking
> up is actually the hum field from more distant sources.
> I tested two sites, one a fair way up the hillside, and another
> lower down where the ground is more horizontal. The hum
> there was lower. I wonder if the distant hum H vector is
> oriented vertically and the hillside is distorting that to
> give a horizontal component. The hum is much stronger in the
> loop oriented across the hillside.
> Will try to make another test to see what angle H is to the
> vertical. Perhaps I will have to tilt the loop away from the
> hillside to null the hum.
> Paul Nicholson