On Thu, 12 Feb 2004 22:01:56 -0500, William Liporace - NA2NA wrote:
>At the tower (with in a foot)
>810 1 volt/meter
>980 1.3 volts/meter
>1540 10+volts/meter
Yes, these are some pretty high field strengths. Are you sure they are
correctly measured? I suspect they are not. Perhaps your antenna is
influencing the measurement. Exactly how far are you from the 1540 kHz
station's antenna? What power are they running? Is their antenna
directional or non-directional? You can easily find all of this
information on the FCC website.
http://www.fcc.gov/mb/audio/amq.html
I just looked there, and this is a 50 KW 3-tower directional, with the
same power and pattern day and night. The field strength in the main
lobes appears to be roughly 4.7 volts/meter at 1 km. If the coordinates
of your license are correct on qrz.com, he's 3.9 miles from you. At
this distance, the MOST field strength he could have at your location
(if you're centered in his main lobe) is on the order of 750 mV/m, with
NO ground losses. Ground losses will knock that down a dB or so.
That said, you do need to get serious with bandpass filtering if you
want to work 160. And you probably need to be using a receiver with
one of the better front ends. Elecraft and TenTec tend to have the
highest scores in this category, although I don't know how well they do
at rejecting the top of the AM broadcast band. I'm sure others here can
help with that, and also give you some guidance with other filter
options.
One solution is a receive-only filter. ICE makes one for 160 that
starts to have some rejection at the top of the AM broadcast band, but
1540 kHz pretty close to their cutoff frequency. They can probably
tweak it to give you some more rejection. I would look at the various
receive antenna options for 160 offered in the various ARRL antenna
publications.
Jim Brown K9YC
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