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Ham Operator Sets New Miles-Per-Watt World Record
Posted by
timothy
on Wed Jan 05, 2005 06:00 PM
from the bend-it-like-an-ionospheric-layer dept.
from the bend-it-like-an-ionospheric-layer dept.
DoctorPepper writes "A ham radio operator in New London, North Carolina correctly copied an 80 meter CW beacon in Wappingers Falls, New York, a distance of 546.8 miles. The kicker is, the beacon station, an Elecraft K1, was putting out 40.6 uW (40.6 millionths of a Watt) -- which works out to 13,467,980 miles per watt!"
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Even when it's horribly outmoded... (Score:5, Interesting)
Re:Even when it's horribly outmoded... (Score:2, Interesting)
Re:Even when it's horribly outmoded... (Score:5, Informative)
Parent
Re:Even when it's horribly outmoded... (Score:3, Funny)
KG4UYY - James L. "Lance" Bass
'N SYNC pop singer and cosmonaut wannabe.
Re:Even when it's horribly outmoded... (Score:4, Funny)
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Re:Even when it's horribly outmoded... (Score:5, Funny)
- Lawrence Olivier
- Calculon
- Miss Piggy
- Peter O'Toole
continue until bored...Parent
Re:Even when it's horribly outmoded... (Score:5, Interesting)
In addition to this, the VLBA will be used in interferometer mode (VLBI) in order to pinpoint the landing site of the probe on Titan to within 1Km!! This is equal to an angular resolution of approximately 170 microarcseconds. Thousands of times better than Hubble.
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Re:Even when it's horribly outmoded... (Score:5, Funny)
Yeah, but this is a World Record - anything to do with an interplanetary space probe is an Out-Of-This-World Record...
Parent
Re:Even when it's horribly outmoded... (Score:3)
Here's why:
Huygens is about 750 million miles away right now. With 10W at that range, we're talking about 75 million miles/watt. Only about 8dB more than the ham record. And while a 1000' Beverage is a big antenna, it's no VLBA.
On the other hand, the Huygens link has to work the first time.
Now, the interferometer measurement *is* impressive. I didn't know about that.
Ham Radio Not Outmoded (Score:5, Insightful)
My guess is that you think it has been made obsolete by the Internet. That strikes me as being palpably untrue, as well as a bit like saying the fact that so many people eat pizza means good restaurants are outmoded.
Two different technologies, two different sets of purposes and abilities.
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Re:Ham Radio Not Outmoded (Score:5, Interesting)
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Re:Even when it's horribly outmoded... (Score:5, Funny)
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Re:Even when it's horribly outmoded... (Score:5, Informative)
http://www.voanews.com/english/2005-01-05-voa24.c
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Re:coils? (Score:4, Funny)
Fully attracted by Milli's characteristic-curves, he soon had his resistance at a minimum, and his magnetic field fully excited. He laid her on the ground potential, raised his frequency, lowered his capacitance, then pulled out his high voltage probe and hit resonance. He inserted it into her socket, connecting them in parallel, then began to short circuit her shunt. Finally, Milliamp cried MHO MHO MHO !
With his plate tube generator at maximum plate dissipation, and her coils vibrating from the excessive current flow, Microfarad soon reached his peak also. They fluxed all night, trying various circuits and combinations, until his bar magnet lost all of its strength. Milliamp tried self induction and self excitation, but it damaged her solenoids. With his battery fully discharged, they were unable to excite their generators any further, so they reversed polarity, blew each others fuses, and went Ohm.
Parent
Re:coils? (Score:3, Interesting)
the above story was taken from webskulker [webskulker.com] or rec.humor [google.ca] and possibly other places.
Yes be creative and pass the funnies along but please give credit where credit is due.
errrr... (Score:4, Funny)
Re:errrr... (Score:3, Informative)
What happens, though, is that the wavefront becomes larger , and you have to build antennas also larger to capture the same amount of energy.
But, for example, if you completely surround the transmitter with your antenna then you will reclaim all the transmitted energy. This is one of fundamental principles of the field theory. Mathworld [wolfram.com] has a very good explanation that leads into Maxwell equations.
Also
Ham Geeks (Score:5, Interesting)
Re:Ham Geeks (Score:3, Interesting)
Further applications? (Score:5, Funny)
Cheers,
IT
Previous record? (Score:4, Interesting)
Ummmmm (Score:5, Funny)
Man B: what?
Man A: 13,467,980 miles per watt
Man B: What?
Man A: Watt?
Man B: What!?!?!?
Man A: Watt!!!!
Man B: Forget it, I'm not playing this stupid thing, go be an A$$.
HAM Geeks (Score:5, Funny)
"I'm thrilled the record was set by an all-American team using all-American equipment." The Ten Tec receiver is manufactured in Severville, TN and the Elecraft transmitter is produced in California and offered as a kit.
yes, so relevant...
Re:HAM Geeks (Score:3, Informative)
Plus, the Elecraft K1 is a kit. If you want one, you get a board, a metal box, and a bag full of parts. Some assembly required. For some people (like me), this is a feature, not a bug.
Re:HAM Geeks (Score:3, Interesting)
Now, who's for embargos on goods produced by underpaid workers? Let's bring the minimum wage to the developing world!
Hmm.. check your math (Score:5, Insightful)
So increasing the power wouldn't give you a linear increase in distance like the OP seems to believe it would.
Simon.
Re:Hmm.. check your math (Score:3, Insightful)
Re:Hmm.. check your math (Score:5, Informative)
The far field of an antenna starts at a point where the radiated wavefront is practically flat. One such measure of this distance is
2* D^2
R = ----------
wavelength
where D is the largest dimension of the antenna. With a satellite dish, this is the reflector diameter typically; with a monopole ("stick") antenna it is the antenna length. There are other measures that are also used to calculate the start of the far field, but I can't recall them now; I will say that whichever one yields the furthest distance is the thumbrule used.
Your orientation to the radiating antenna also plays a role. A "stick" antenna (dipole or monopole) has more energy radiated perpendicular to the mast than along the mast axis. In free space with no reflections, you can stand at either end of a stick antenna and not receive squat, as long as you are in the far field. Thus, you must also consider the gain of your antenna in the direction of interest. A stick antenna has about 3dB gain perpendicular to it, and negative infinity gain along the antenna axis.
The actual equation to get the power density Pr when distance r from the source is:
Pt * Gt
Pr = ----------
4pi*r^2
Pt = Power radiated
Gt = Gain of your antenna
That's why the change in power to distance isn't linear. May have been long-winded but I spent most of the afternoon doing power density calculations so it was fresh in my head.
Parent
Obligatory... (Score:3, Funny)
Ohm my! That Hertz!
It is non-linear (Score:5, Informative)
In worst case it is a power^1/3. So for 40 milliwatts to 1 watt amplification you'll get some 30x distance (at worst), but never 2500x, unless some wicked atmospheric conditions happen.
Whiners. (Score:5, Insightful)
While the ability to receive a very weak signal is always interesting (and exciting for QRPP operators), converting results into "miles per watt" is an absolutely useless way to express results!!
The whiner goes on to say:
At 1.5 MHz data in CCIR Thirteenth Plenary Assembly (vol VI report 264-3 p 108) shows attenuation increases ~10 dB when path length goes from 500 km to 1000 km. Doubling skywave path length at 500 km when at 1.5 MHz increases loss 10dB, NOT 3 dB. Doubling distance again (same frequency) from 1000 km to 2000 km results in an additional ~15 db loss! 2000 km to 4000 km is about 22 dB more loss. This is based on measured data.
While most of the numbers leave me with a blank look, one thing is clear: the poster missed the point. The accomplishment is cool because of the geek factor, not because it's going to lead to a new radio in your car. Therefore, the measurement of the achievement doesn't *have* to be "useful".
Miles per Watt? (Score:5, Informative)
Example using round numbers. Philip transmits 10 miles using a 10W transmitter. Sally transmits 19 miles using a 20W transmitter. If you use miles per Watt to compare, it looks like Philip achieved better results, when in fact Sally did.
Yawn (Score:4, Funny)
bitty power output.
Re:Yawn (Score:5, Informative)
No, it can't. That is why there are those little bars showing signal strength. You're lucky the newer digital units can get two miles to a tower (where it is then pumped thru an ATM link over a T-1 to the landline network).
Funny, fine. But to whomever modded that post "Informative" needs to go back to school.
-Charles
Parent
Why would you measure miles/watt? (Score:4, Informative)
power is 1 over r _squared_ (Score:5, Informative)
The units here are watts per square mile. Your typical FM radio station has a range of maybe 50 miles and is running maybe 10 kwatts, so they're doing 4 watts per square mile. This guy is doing much better. My own power/distance record, back when I was active in ham radio, was 7000 miles on about 25 watts, or 5.10204082 × 10**-7 watts per square mile.
You might wonder how it's remotely possible for there to be a gap of seven to ten orders of magnitude. Why aren't we bothered by FM radio stations on the other side of the world? There is a qualitative difference between the behavior of radio waves above and below about 30-50 MHz (the FM band starts at 88 MHz). Conditions permitting, the lower frequencies can refract in the ionosphere and come back down to earth along non-straight-line paths. That's why shortwave radio stations on other continents can be heard.
Spread spectrum (Score:5, Interesting)
Below noise signals sounds paradoxical, but people do it all the time. If you're in a noisy restaurant, you can pick out individual noises even though they are much quieter than everyone else. The key is that you have an idea of what you expect to hear - you generally know the tone of their voice, know what sounds make words, know what words make understandable sentences.
Imagine if the signal had been spread-spectrum. Spread-spectrum signals are stealthy because, they to, can be recovered from below the noise floor. Basically, with an idea of what to expect, the receiver's processing can effectively raise the signal above the noise floor [maxim-ic.com]. Instead of sending short tones for each bit, a series of tones are sent for each bit (a chip) - one chip for zero, and a different chip for one. It's a lot easier process a sound and see which chip it sounds closer to than it is to see if one particular tone is there or not.
So, in summary, this guy's brain played a lot in the reception to pick out a signal from the noise. I wonder if the next record will be set with a spread spectrum transmitted signal and a digital processing receiver.
Just to be a nitpicker... (Score:3, Informative)
For maximum pessimism, say that it's currently putting its maximum 315 watts into "phoning home" -- I work this out to 26.1 million miles per watt. (My guess is that realistically it's more like 1e3 times that.)
Sorry HAM-guy, but Voyager still kicks yer butt.
Cheers,
Richard
Re:Just to be a nitpicker... (Score:4, Informative)
Now imagine how hard that is to see from 7 billion miles away.
Parent
1000 Miles per watt award (Score:3, Interesting)
Shannon limit? (Score:3, Interesting)
Ham Radio (Score:3, Interesting)
Obviously never heard of the inverse square law... (Score:3, Informative)
This is stupid (Score:4, Insightful)
If I wanted to break this 'record' I would simply replicate the experiemnt from a distance of 273 miles (half the distance) where I could pick up the signal with 1/4th the required signal strength (inverse square law) and suddenly I have a 'record' of 26,935,960 miles per watt! Heck, if we put the transmitter on the same circuit board as the receiver I could create an 'efficiency' that would let me contact quasars with a hamster wheel.
Bah.
Miles per watt? Get a unit. (Score:3, Interesting)
What kind of unit is miles per watt? I could see watt per square mile, or preferably watt per square meter.
If 80 meter radiation penetrated the ionosphere, the detection at a range of 880 km would be about 5*10^-17 W/m^2. I'm fairly sure 80 meter bounces both from the ionosphere and the earth itself, which results in some amplification over the inverse square law value.
In contrast the detection threshold for SETI@home is about 5*10^-25 W/m^2, or a factor of 100 million smaller.
In my amateur radio days (Score:4, Interesting)
They were all VERY happy to receive my QSL-card
Oh, if anyone remember me, I was 45SR101
Re:Sounds impressive (Score:5, Funny)
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Re:Sounds impressive (Score:5, Informative)
The listener had really good ears and was able to pick out the code from a lot of background noise, with a really good antenna setup.
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Re:record (Score:3, Informative)
The record is quite impressive given that there is more land and civilization between the new points of the new record. Still probably used ionsphere to bounce it forward, but there would be less ground effect in the new record than in the old.
These guys have advanced antennas but its still way cool that with a QRP rig and even a simple wire antenna, you can communicate over great distances with the
Tell that to Port Blair residents (Score:5, Insightful)
And you say this 2 days after the Slashdot article entitled
Ham Radio Served as Main Link to Disaster Area
http://slashdot.org/article.pl?sid=05/01/02/23432
That's a quick death it died after having proved that it's still worth having as an alternative.
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