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"whiskey-tango-foxtrot" moment while reading power point presentation on LORAN

unclejed613

Well-Known Member
Most Helpful Member
https://web.stanford.edu/group/scpnt/jse_website/documents/Enhanced_Loran_rv2-short.pdf on slide 35, they say the antenna top has 0 volts on it, but the feedpoint has high voltage. that's backwards, the open end of an antenna is a current zero, and a voltage maximum... when visualizing standing waves on an antenna, you begin at the open end assuming a voltage maximum and current zero. at resonance, an antenna behaves as a series resonant circuit, so the current is maximum at the feedpoint, and voltage is low, because, at the other end of a 1/4 wave piece of wire (or tower) the current is zero, and the voltage is maximum. it's the same with a 1/4 wave open feedline section (open 1/4 wave stub).
 

JimB

Super Moderator
Most Helpful Member
I think the guy has his voltages and currents mixed up.

One of those things that you write, but when you look back later you think "Did I really write that!"

JimB
 

unclejed613

Well-Known Member
Most Helpful Member
yeah, happens occasionally, thinking one thing but typing something completely different...
 

JMW

Member
If I'm not mistaken LORAN stations have been decommissioned. They may have some in foreign nations.
It was a great system. The Apollo moon shots used it. I once read the accuracy was equivalent to shooting a pea from NYC, to S.F. and hitting the saucer as opposed to the cup.
 

unclejed613

Well-Known Member
Most Helpful Member
actually, LORAN C is being recommissioned. several well known instances of GPS spoofing (which is very easy because of the very weak satellite signals can be easily overcome with a local transmitter with power levels of a few milliwatts) prompted the decision. LORAN C signals are difficult to spoof because of the large antenna structures and large amounts of transmitter power required to meacon a LORAN station (meaconing is a military term for spoofing a navigation beacon).
 

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