mikie333
Member
So i'm new to all of this...and i've been on the forum for a few months and either never noticed this or its new...but what is "Skip/Tropospheric Ducting"
???
thanks!
???
thanks!
What...?
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JoeyC
Senior Member
mikie333
Member
tom_guess said:
thanks! and how is this done? (i don't need a huge technical explination, plain and simple willl do)
thanks again!
scanjunkie
Member
Basically it is what Tom said and it is usually due to atmospheric conditions that provide a "duct" so to speak for the signal to travel in. I live in PA and have heard transmissions from CA...
eorange
♦RF Enabled Member♦
Certain radio signals, like HF (0 - 30 MHz) can travel far - 1000's of miles - by bouncing their way through the atmosphere. This is typical. It's also classic "ham radio" where you can talk to people all over the world, and classic "shortwave radio" where you can hear radio stations from other countries.
Other signals, like VHF (~116MHz to ~160 MHz) and UHF (~225 MHz to ~470 MHz) used by public safety just don't go that far. It's just the nature of those signals to travel "tens" of miles and that's it. This is also typical.
Sometimes, though, the atmosphere does funny things, and suddenly the UHF and VHF signals start propagating 100's of miles across the U.S. This is exciting because you can now hear police and fire transmissions from many many states away. This is "skip".
Tropospheric ducting involves an atmospheric depression over a large body of water (think ocean, great lake), thus forming a "duct" where VHF and UHF signals propagate by bouncing along the duct.
Hope this helps!
P.S. - Go to http://en.wikipedia.org/wiki/TV-FM_DX for a great intro.
Other signals, like VHF (~116MHz to ~160 MHz) and UHF (~225 MHz to ~470 MHz) used by public safety just don't go that far. It's just the nature of those signals to travel "tens" of miles and that's it. This is also typical.
Sometimes, though, the atmosphere does funny things, and suddenly the UHF and VHF signals start propagating 100's of miles across the U.S. This is exciting because you can now hear police and fire transmissions from many many states away. This is "skip".
Tropospheric ducting involves an atmospheric depression over a large body of water (think ocean, great lake), thus forming a "duct" where VHF and UHF signals propagate by bouncing along the duct.
Hope this helps!
P.S. - Go to http://en.wikipedia.org/wiki/TV-FM_DX for a great intro.
Last edited:
gcgrotz
Member
Sporadic E
That what is most likely what you're hearing. Probably double hop. Rarely, during peak sunspot times, low VHF can propagate via F layer. Sporadic E happens a lot this time of year.
Ducting forms at a boundary layer between 2 air masses, usually a few thousand feet up. This mostly occurs along the coast. I know on the east coast it is often a result of "thermal inversion" which is the same thing that traps smog and pollution. Certain alignments of Low pressure systems can cause it too. Trans-Gulf of Mexico ducting is common, as is the CA to HI pacific ducting. Ham experiments on the west coast have shown from the mountains that small differences in elevation can make or break a path.
You could probably find a lot of articles on www.arrl.org or try the monitoring times web site or ac6v.com or Google tropospheric ducting.
scanjunkie said:
That what is most likely what you're hearing. Probably double hop. Rarely, during peak sunspot times, low VHF can propagate via F layer. Sporadic E happens a lot this time of year.
Ducting forms at a boundary layer between 2 air masses, usually a few thousand feet up. This mostly occurs along the coast. I know on the east coast it is often a result of "thermal inversion" which is the same thing that traps smog and pollution. Certain alignments of Low pressure systems can cause it too. Trans-Gulf of Mexico ducting is common, as is the CA to HI pacific ducting. Ham experiments on the west coast have shown from the mountains that small differences in elevation can make or break a path.
You could probably find a lot of articles on www.arrl.org or try the monitoring times web site or ac6v.com or Google tropospheric ducting.
Hi Grotz, Mikey and all,
When it comes to the ARRL for the real skinny he'll have to buy the books.
Mikey, your best bet IS to buy the books, not only can you order them from the League but they're also sold by local ham stores. If you don't have one in your area again you can order on line, Ham Radio Outlet is one place. The reason is simple, a picture is worth a thousand words. Far more informative text with graphics will teach you much better than we and our keyboards possibly can, they're professional tech writers, we're not.
Not to put you down guys but he's a beginner who needs to learn from the ground up so he's better off with a Dick and Jane coloring book than with us talking over his head and some aren't so good with words.
When it comes to the ARRL for the real skinny he'll have to buy the books.
Mikey, your best bet IS to buy the books, not only can you order them from the League but they're also sold by local ham stores. If you don't have one in your area again you can order on line, Ham Radio Outlet is one place. The reason is simple, a picture is worth a thousand words. Far more informative text with graphics will teach you much better than we and our keyboards possibly can, they're professional tech writers, we're not.
Not to put you down guys but he's a beginner who needs to learn from the ground up so he's better off with a Dick and Jane coloring book than with us talking over his head and some aren't so good with words.
nd5y
Member
If you don't want to buy books then read some of the web pages listed here
http://www.ac6v.com/propagation.htm
I would start off with this one http://www.anarc.org/wtfda/propagation.htm
http://www.ac6v.com/propagation.htm
I would start off with this one http://www.anarc.org/wtfda/propagation.htm
gcgrotz
Member
kb2vxa said:
But that's the fun of it, learning new stuff, right Warren?
I say Welcome! The more the merrier. And don't be afraid to ask. I've made a fool out of myself a few times already since I joined RR, and I'm an old geezer (well almost).
And Warren - I love your sig line. Many years ago I worked for a bank vault/safe company. We loved to tease the customer with that line when their safe locked up and had to be drilled open. The looks on their faces were priceless!
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