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The one meter per hertz club |
Fred Beihold, NK1LAfter building a transceiver designed by Gary Breed and using it to work the Ukraine from Massachusetts with 5 watts and a whip antenna on a motorcycle, it seemed there was a need for rating QSO’s according to how spectacular they were. In Germany, I am told, Hams like to use simple antennas with simple stations, a wire in the backyard for a QRP station, for example. Here in the United States it is more common to use the largest possible antenna at all times. There could be plenty of good reasons for using one antenna or another, but wouldn’t it be great to be able to compare apples to apples? This leads to the system described here, a way to systematically divide Amateur Radio stations into thirty or forty classes. The smallest classes could be considered QRerP – low effective radiated power. Consider the Friis Formula1
Setting the range to 1 [m/Hz] takes frequency out of the equation.
For example at 1, 50 and 300 [MHz] a 100 [Watt r.m.s.] station inside
(10 [meters])3 would yield a received power at a similar antenna
of 1.1111(10-11) [Watts r.m.s.] at a range of 1 [m/Hz]. By containing
each station within a cube where each side in meters equals the
square root of the r.m.s. power in watts, over 30 classes of stations
are generated starting with the smallest: 1 [Watt r.m.s.] inside
1 [meter]3 . In this fashion, a change in station-class receives
equal contributions from transmitter power and antenna aperture.
By using the diagonal one may obtain a largest dimension within
the cube equal to
What is the limit to how many meters per Hertz a person can communicate? From previous calculations2, it seems that at around 5 [m/Hz] between two 1 [Watt r.m.s.] stations inside 1 [m]3 received power equals the noise power in a 50 [Ohm] system. So, in outer space distances somewhat beyond 5 [m/Hz] could well be likely, while terrestrially speaking, achieving 1 [m/Hz] during any particular hour of the day seems plenty challenge enough, the smaller the station-class, the better. My best 1 [m/Hz] contact to date is southern Chile from Massachusetts on 30 Meters from the truck, 100 [watts]. I’ve heard of one PSK31 contact that came within 14 dB of 1 [m/Hz] with 1 [W] inside 1 [m3] at each end! In the evening, with 1,000 watts from New England, it’s fairly easy to hit eastern Europe on 40 Meters during the Winter, so it’s been done, as they say. One could set a goal starting with the flip of the Sun’s heliomagnetic field and ending some 11 years later with the next flip — trying to work 1 [m/Hz] around the clock by operating a little here and a little there as time permitted, eventually collecting 24 different QSL cards from each of the 24 hours in a day. Here’s a suggested sample QSL-card for such endeavors: Figure 1: The front of a sample QSL-card designed to feature 1 [m/Hz] achievement while still serving general use. Figure 2: The back of a sample QSL-card showing how station classification can be recorded simply by entering the station power in each box (see text), along with an “unclassified” option. A simple explanation of the station-bounding imaginary cube is included. I’ve heard of two separate flips of the heliomagnetic field these past few years. In any case such double-flips would keep things interesting, the basic idea is to give Hams one 11-year cycle to achieve their goal, no matter how long that 11-year cycle actually turns out to be!
(0.16 at 300 [MHz] inside a sphere of 1 [meter] radius) not to mention various DSP modulation modes, applying the above discussion to future technologies could get very interesting. Sometimes the Earth becomes so quiet in the radio spectrum, that the noise energy approaches just the thermal noise. Sometimes the ionosphere seems to be like glass, skipping HF waves around the earth multiple times. With super low-noise receiver front-ends, small futuristic antennas, low-power and an eye to the solar-terrestrial physics it would seem interesting to begin a record of such events. Does the earth ever act as an amplifier? Now, how far could a fellow talk using 1 [Watt r.m.s.] CW with a spherical coil inside 1[m]3? 1). Kraus, John D. Antennas, second edition. (Boston, Massachusetts:
McGraw-Hill), 1988, page 49. |
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[Watts r.m.s.]
I
am avoiding three questions here: What about stations smaller than
1 [Watt r.m.s.], how does one relate peak-envelope-power to root-mean-square
power, and what is the legal upper limit to the classes? Let’s
deal with one issue at a time, and the focus here is on laying the
groundwork for station classification.
Some
practical considerations are that somewhere below 50 [KHz] the Friis
Formula won’t apply, since it assumes far-field. But, with
the clamor for lower frequencies, it would seem prudent to set a
lower frequency limit. Also, links should be limited to passive
reflections only, no repeaters. By 50 [MHz] this leaves moonbounce
as just about the only propagation mechanism that could yield a
50,000,000 [meter] link. The 10, 12 and 15-meter bands are in big
trouble since there is no terrestrial short-path long enough. For
starters, I would limit frequencies to 50 kHz through 18,168 kHz.
Later, maybe other frequencies, passive propagation mechanisms,
could be considered. What about a station that is class-10 in power
but class-11 in antenna aperture? The greater of the two class-numbers
wins out, this would be a class-11 station. The idea is to contain
the actual antenna’s aperture within the specified cube, and
not couple externally to a larger aperture that “happened”
to be there. An example of this mistake would be to consider the
feed of a parabolic dish as the station’s antenna. With the
current interest in small antennas (i.e. Fractals, wireless) and
the Chu-Harrington radiation Q limit3 for linear polarized small
antennas:
