That is what it looks like, although we might better say that the
smaller antennas needed or present at higher frequencies intercept less
energy due to their smaller size.
This affects path loss, because all antennas, even a perfect (and
imaginary) point source isotropic antenna, have a calculable effective
aperture; for the point isotropic it's, wavelength squared, divided by
4*pi. Check out the path length nomogram for a pair of these amazing
creatures at http://www.qsl.net/vk3jeg/pathloss.html
Also see
http://highered.mcgraw-hill.com/sites/dl/free/0072321032/62577/ch02_011_056.pdf
Start at a distance with HF (if necessary) and VHF, move higher towards
UHF and, near the culprit, a *higher gain. more directive* UHF or
microwave antenna if signals are weak and you need that much accuracy.
You might not.
I chased around Petaluma CA once to find 3.52 MHz cable-company-billing
power line modems. Had to use a mobile antenna to find the right block,
then house to house with a handheld receiver and homebrew untuned three
inch loop to find the building and room. Once I got what looked like a a
good fix from an advertizing sign pylon -- the source was really in a
development across the street. Happy days.
Near the end of that little project I noticed people running out their
front doors and into their back yards as I drove slowly down the street.
Later, I figured out why. It was the day of a big game, and they were
hiding illegal taps they'd connected to a neighbor's cable service. Heh!
Cortland
ka5s
On 6/23/2014 2:23 PM, k9muf@comcast.net wrote:
The RFI signal does not travel as far at UHF as it does in the VHF range.
The power lines here are at the back of property lots about 150 ft. from the streets. One time I was able to pick up an RFI noise from the street with my HB 3 element yagi and and an aircraft monitor receiver operating on about 135 Mhz. The power co. guy could not hear the noise with his multi element yagi and commercial equipment from the street operating in the UHF range of about 300 or 400 Mhz.
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