On 18 Apr 2014 at 7:45, Tom Thompson wrote:
> Hi Ken,
>
> I modified a Sony radio by connecting to the AGC. I did not have a
> schematic but was able to poke around and find the AGC line. Most
> radios of this sort use a single chip so I just took a DVM and poked
> around until I found the right pin. I offset the voltage with an op amp
> and used a Radio Shack meter. I also put a 60-dB attenuator between the
> antenna and the radio.
Yes. I read what you posted to some site somewhere about that. I had
already thought to do much the same thing. I have plans for the attenuator,
and I had planned to use one of the very large external meters that are an
accessory for the Stoddart "meters". At least I can read that one with pretty
fair accuracy despite my old eyesight.
However, I sat last night until well after 11:00 PM staring at the map my son
and I had made a week or more ago and came to some conclusions.
First of all, I have 4 very clear bearings all pointing to one place about 1/2
mile from here.
Looking carefully at the bearings my son wrote down, I find that an error of
only one or two degrees in reading the bearings would significantly "move"
the resultants to make them not exactly coincide at the far point. Even 1/2
degree error at the distances we took the bearings would be significant.
Therefore, I am going to mount a "sight" on the loop support rod that would
allow more accurate bearings, then will revisit those sites from which we took
the previous bearings in order to attempt to "accurize" them. This device will
be another piece of wood, about 12" long,which will be fastened very
securely to the side of the main rod and as perfectly in line with the normal
to
the loop as I can possibly make it.
I also bought a Brunton compass, which, I hope will make it easier to make
our bearings more accurate.
Secondly, it is VERY clear that at least two of the bearings we took were
effected by something in the near vicinity which threw them way off. One in
particular, specifically, the one we took in our driveway, pointed almost 90
degrees from where we expected it to, but when I moved the receiver only
about 12 feet further to the west, that same bearing swung around to be
more in line with the others, including the one we took in the back yard near
my antenna. There is a connection from the power pole to our home directly
overhead, which possibly is the cause.
Thirdly, I was able to take another bearing a day or so ago from a parking lot
on the local highschool's property which pointed almost exactly to the same
spot which the previous 4 bearings had shown. That makes 5.
Lastly, while examining the map, I determined that IF my source is where the
previous bearings suggest it might be, I can take two more bearings that will
pretty much confirm it.
Then, I have to go to that area and try to find the exact source.
One trouble is, in the vicinity of where my bearings cross, there appears to
be a very bad power line problem which is either interfering with my
determining the source of "my" noise, or else that power line leak is itself
somehow manifesting itself at MY location AS "my" noise.
As I mentioned yesterday, I have also, in the process, determined two other
sources of noise which I am going to have to eventually find and deal with,
one of which is particularly annoying when it occurs: this is that "very
unstable wobbly carrier-like" noise, which appears to be located at the local
highschool.
Although I seem to be making progress, I am also concerned that I may be
misreading or misinterpreting something important. After all, I've never done
this before now.
I sure wish I still had the old military DAG-1 portable RDF I had when I was
much younger... :-(
Anyway, more work to do.
Ken W7EKB
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