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Topic: Tropo duct

	TV-FM DX - Wikipedia, the free encyclopedia
		Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather.
		Tropospheric ducting of UHF television signals is relatively common during the summer and autumn months, and is the result of change in the refractive index of the atmosphere at the boundary between air masses of different temperatures and humidities.
		William Hepburn's VHF / UHF Tropospheric Ducting Forecast.
	en.wikipedia.org /wiki/Tropo_duct (5344 words)

	Propagation: Tropo (tropospheric bending) (Site not responding. Last check: 2007-10-30)
		Tropo is the other major form of DX propagation; as the name implies, it's dependent on conditions in the troposphere where weather takes place.
		Tropo ducting is a condition which seems to behave rather like "skip", in that a nearer station in the same direction, on the same channel, may not necessarily block out a more distant one.
		Ducting may appear at any time of the day or night, and is the cause of most tropo over 400 miles.
	www.ham.dmz.ro /radioamateur/propagation/tropospheric-bending.php (716 words)

	TROPOSPHERIC DX MODES
		Also..weaker tropo scatter stations that are normally not heard (because their signal strengths never cross the background noise threshold signal level) also begin to appear.
		Ducts located behind cold fronts ("post-frontal ducts") are notoriously unstable as paths can even be interrupted by things such as heavy rain showers associated with the cold front itself.
		Frequencies affected by ducting are determined by the vertical thickness of an inversion.
	www.oscarkilodxgroup.com /tropo.htm (1449 words)

	Inversion (meteorology) - Wikipedia, the free encyclopedia
		The signal, still more than powerful enough to receive even at hundreds or thousands of miles or kilometres, would normally be refracted up and away from the ground-based antenna, but is now refracted back down instead.
		This phenomenon is called tropospheric ducting, or a tropo duct.
		Much of the sound is thus trapped under the layer and the sound can travel much greater distances than normal.
	en.wikipedia.org /wiki/Temperature_inversion (959 words)

	[No title] (Site not responding. Last check: 2007-10-30)
		Durring a duct it is possible to hear stations on your scanner in the VHF and UHF band from about 50 to 900 mhz that includes picking up stations hundreds of miles away from your local police to fm radio to tv.
		The key word hear is "ducting" in your house you use ducts to shuffle warm and cool air around the house.
		Tropospheric ducting occurs mostly in the warm weather months of the summer and sometimes in the presence of large storm systems.
	www.angelfire.com /sc/scannerpost/tropo.html (388 words)

	Very Long Distance Propagation - Discussion of Results
		The tropo duct between EA8 and CT/EA7 ends at the coast line (or perhaps a little over the coast line), as during day time the warm convecting air will destroy the low altitude sea duct.
		The idea of a tropo duct enabling scatter up is an attractive one, but I doubt if the difference in loss is more than say 10 dB between ground and the "top duct" scattering.
		It could also be easy to confuse E's with Ducts, as from my experience here, I could make a contact via a duct to a station 900 km away and stations at say the 300 to 500 km mark can be totally missed as the duct rises and falls along its path.
	www.df5ai.net /ArticlesDL/VLDP_Discussion_EA8/VLDP_Discussion_EA8.html (3033 words)

	Tropospheric DX Modes
		A Tropo DX mode is any condition that scatters, reflects or refracts signals in the Troposphere allowing long distance reception (and hence interference) to occur in the VHF, UHF and/or microwave radio bands.
		Distances are no different than with tropo scatter..it's just that the signals are stronger and interference is more intense.
		Ducting may or may not occur simultaneously with enhancement (caused by nighttime cooling).
	www.dxinfocentre.com /propagation/tr-modes.htm (1424 words)

	Howard Oakley: Non-Ducting Tropo
		As with most matters of propagation, it is impossible to be certain whether tropo is ducting or non-ducting.
		Although you can get ducts and ducting conditions which allow paths connecting quite widely separated stations, normally stations working a duct are quite close together in space, at both ends of the duct.
		Ducts are commonest below 1 km, and very rarely accessible above 2 km.
	www.quercus.demon.co.uk /ducts.html (550 words)

	Amateur Radio propagation modes for radio communications
		Tropo generally is weather induced when inversion layers are formed.
		You must be in the duct to be able to hear the signal.
		In some parts of the country ducts are known to form on a somewhat regular basis.
	www.nr6ca.org /propagation.html (2019 words)

	Tropo (Site not responding. Last check: 2007-10-30)
		Duct 9A - SM Ducts in JN86 are rare enough to be one of the most interesting propagation phenomena in JN86.
		We had only 3 strong and long-duration duct openings here in the period of 10 years, and most beautiful one was opening to SM 18th and 19th of October 2001.
		Good duct conditions were over wide spread over north DL and SP Baltic Area, OZ and SM, ending in SM4 at north.
	www.qsl.net /9a1cal/tropo/smduct.htm (444 words)

	VHF Signal Propagation
		Tropo scattered signals are characteristically weak, "fluttery" signals that often suffer from random fading.
		Ducted signals are typically quite strong, sometimes so strong that they can cause interference to local signals on the same frequency.
		Subsidence ducting is often intensified during the evening and early morning hours when the effects of radiation inversions are added to the mix.
	dxfm.com /Content/propagation.htm (5763 words)

	Hepburn Tropo Index (Site not responding. Last check: 2007-10-30)
		Tropo Index of 1.4 = Seems to be the average threshold of discernible tropo.
		Later I developed the Hepburn Tropo Index to attempt to quantify the strength of Tropo Ducting Areas.
		Often, if you are within line-of-sight or within tropo scatter range of a duct located nearby, you may get in on that duct.
	duxpond.com /weather/hti.html (810 words)

	The radio propagation (Site not responding. Last check: 2007-10-30)
		Extended "tropo ducting" represents a super refraction in which the height and dielectric characteristics of the layer are so important at large scale that it offers true airways to VHF waves.
		Like in Aurora traffic, to work with tropo it is preferable to use stacked directive antennas and to point a predetermined area in the sky with the hope that VHF waves can reflect and reach a remote station.
		We define this "TS" traffic the same way as the Tropo with this difference that here signals are scattered in a tropospheric area shared by two amateurss by the effects of temperature inversions and irregularities in the level of moisture, pressure, and maybe dusts of the atmosphere.
	www.astrosurf.com /lombry/qsl-propa6.htm (2912 words)

	DX Radio - Extreme radio and television reception (Site not responding. Last check: 2007-10-30)
		Tropo occurs quite frequent, with a good antenna and receiver you'll be able to notice it almost every day, but weaker equipment will hear far staions very rare times.
		We divide tropo propagation in few particular modes: First, most common is so-called "tropospheric enhancement", when radiowaves reflect from the layers of humidity and go everywhere around in not precised directions.
		Second tropo mode is Tropospheric Ducting, occuring very rare times, but very exciting experience to each FM DXer.
	radyoslaw.w.interia.pl /index_english.htm (1189 words)

	VHF tropo condx on Cyprus
		With support of sea tropo condx, some time, I am quite sure, would be highlighted future first VHF QSO between Africa and America, which would be possible make between D44 and Caribic relatively soon, when on both sides will be VHF stations with appropriate TX power, antenna and experience.
		Much less known are extraordinary tropo condx in East Mediteranean, to that we already referred within last weeks.
		If that "crazy" kind of tropo condx monitoring is not conclusive for you, let's notify, that it similar to situation, where in Middle Bohemia you would be able indicated GSM networks from Germany, Austria, Slovakia and from Poland...
	www.home.karneval.cz /00000104/kypr/cyprus_condx_en.htm (727 words)

	Introduction to Propagation
		Dxing MS is a great way to fill in the gaps left by Es and tropo Dxing --- often in the 400-800 mile range --- and to hear/see new states at any distance up to 1400 miles.
		Semi-local and tropo stations are anathema to MS DX'ers.
		DX'ers in the southern tier of states from Texas to Florida should be on the lookout for TE in the spring and fall; September 1 is the traditional start of the fall TE season.
	www.anarc.org /wtfda/propagation.htm (3400 words)

	G4LOH 144MHz Blog: July 2005 Archives
		The tropo forecast looked good all this week but only on tuesday was anything heard with strong ducting to EA8 (probably beyond) again, several stations were 59 and at 15:44 I worked EA8/DL4DWA who had 25W and an HB9CV antenna.
		The tropo path to IM57nh from here is obscured by EA1 and all of CT but the duct to EA8 was so effective that I could hear the backscattered signal from Joe beaming South West, extraordinary.
		I initially thought that this path was caused by tropo backscatter within the duct but actually the signals were not distorted so I am now convinced that it was a reflection from the Tiede volcano or other reflectors of the Canary Islands.
	www.champagnebohemian.com /g4loh/archives/2005_07.html (661 words)

	(meteorobs) Reception (Site not responding. Last check: 2007-10-30)
		Your description is consistent with enhanced tropospheric scatter, or, more likely, tropo ducting.
		The signals can be very strong (or weak), are usually (not always) in one particular direction or quadrant, usually are good out to 200-400 km but can be good to well over 1000 km on rare occasions.
		If it's ducting, the signals can be caught in the "duct" and, if the duct is elevated above the surface of the earth at the midpoint, can even "skip over" stations in the middle.
	www.meteorobs.org /maillist/msg26245.html (287 words)

	Summer 2003
		The term tropospheric ducting refers to the stratification of the air within our weather atmosphere, abruptly changing the normal refractive index.
		He points out that a “sufficiently thick” super-refractive layer may minimize signal losses through the top area of the duct and be sufficiently elevated so as to minimize losses on the bottom side of the duct.
		“Under ideal ducting conditions, a signal from a transmitter 5000 miles away may have the same field strength as an identical transmitter only 70.7 miles away from common frontal layers and early morning radiational cooling of the lower layer of the atmosphere,” adds Eggers.
	www.cq-vhf.com /Watch%20the%20Weather%20for%20VHFUHF%20Summer%2003.html (640 words)

	NationMaster - Encyclopedia: Temperature inversion
		Sunlight filters through a thin layer of fog on a crisp winter morning in Albuquerque, New Mexico.
		The worlds largest antenna system designed for receiving distant 88â€“108 MHz broadcast FM signals is located in southern Sweden.
		Tropospheric ducting (also known as tropospheric refraction) is a type of radio propagation that tends to happen during periods of stable, anti-cyclonic weather.
	www.nationmaster.com /encyclopedia/Temperature-inversion (1815 words)

	Howard Oakley: QTH Details (Site not responding. Last check: 2007-10-30)
		Getting into a duct, for instance across the Channel, is very unlikely, as my radiation to the south will reach the Channel at fairly high elevation and heading rapidly upwards.
		It is thus unlikely to be able to enter such low-level ducts (below 1-2 km above sea level) at a low enough angle of incidence (less than 1-2 degrees), although refraction might sometimes help overcome this.
		Non-ducting tropo (NDT) really does require a low angle of takeoff to achieve good DX, or the radiation will quickly attain high altitudes and fail to achieve any significant common volume (these issues are discussed more on
	www.quercus.demon.co.uk /qth.html (490 words)

	Unidentified station - Contributions
		I would assume the duct is mearly a vehicle to carry the signal.
		My thought was the signals were ducted by the front to the mid Atlantic and then by scatter on to you.
		Coastal tropo on low VHF here is quite common, but not at this time of the year.
	www.dxradio.co.uk /contributions.html (13004 words)

	G4LOH 144MHz Blog: August 2005 Archives
		Alex RW1ZC/MM is still QRV from the coast of Mauritania and I was hoping to try some Meteor Scatter tests with him over a 3500km path, using his reliable tropo to CT to extend the normal 1500-2000km MS range.
		The tropo path was open to EA8 again and again signals peaked at around midday with EB8AYA over S9 again.
		Switched on about 0900 Z and heard Peter EA8AVI IL28fc calling CQ but the pa was off and he was gone by the time it warmed up, someone in chat mentioned that RW1ZC/MM was qrv somewhere off the African coast and had been spotted earlier, I hadn't seen the spot.
	www.champagnebohemian.com /g4loh/archives/2005_08.html (954 words)

	[No title]
		The duct dissipated the next day, but returned on June 20 to 23, bringing LA thru Tijuana again, of which San Clemente 107.9 was the only now logging.
		Conventional wisdom holds that the CA/HI duct is usable only from the 8000 foot level on Mauna Loa, and indeed there is undoubtedly more FM and TV DX up at that site, judging by reports of the hams who word 144 MHz and higher from there.
		And, one duct into another is not that rare and given the geography of Southern California, a duct that goes from Imperial westward to the coast at some elevation is in fact not unusual during August-September (a side effect of a weather condition called "Santa Ana Wind").
	www.worldofradio.com /dxld3094.txt (12366 words)

	Ham Radio Forum :: View topic - equipment performance (Site not responding. Last check: 2007-10-30)
		And with the help of good conditions "Tropo Duct", other states should not be a problem!
		You can have a high gain yagi mounted 75ft up on your end and recepiant has a small yagi mounted too low, reception distance will be shortened a great deal, especially when you dont have tropo ducting on your side (normal weather conditions)...
		With high gain antennas and help from good tropo duct people can WAS (work all states) using 2M ssb.
	www.hamforum.com /viewtopic.php?t=1744 (357 words)

	HowardForums: Your Mobile Phone Community & Resource - Wave skipping
		It definitely was not skip as ham radio operators and cb'ers refer to signals bouncing off the upper atmosphere.
		In the military we were always concerned about “skip” and “ducting” and such of our secure communications, but there is no way any low power UHF signal like cellular would carry 240 miles unless some repeaters were involved.
		It would take some serious ducting for the signal to travel that far something that an 800mhz signal isn't too prone to do.
	www.howardforums.com /printthread.php?t=75641 (813 words)

	Duct 20th to 22nd April 2005
		ASL, nothing is heard at Canberra as the duct is blocked by hills.
		the Canberra repeater end as its probably in are area of the duct.
		the duct height is usually between 1500 and 2600m ASL and gradually drops to
	www.users.bigpond.com /vk2krr/duct_20th_to_22nd_april_2005.htm (711 words)

	Contest uitslagen
		Dat de Tropo goed was bleek direct al aan het begin van de contest door de diverse SP's die ons aanriepen en de GM's die gewoon 59+, met de antennes richting oost, waren.
		Het tropo duct over de Noordzee leverde veel G, GW en GM op.
		Helaas zaten wij zaterdag EN zondag net buiten de duct naar Polen en Finland en het was voor ons dus een 'gewone' contest.
	www.xs4all.nl /~pa0nzh/uitslagen/sept05.html (6657 words)

	New Years Record setting Duct
		I was checking the 4 day weather map forecast and Hepburn Tropo Ducting forecasts.
		The morning was a little overcast still in the east, but I awoke to a nice signal from the Adelaide 144.450 beacon at 762 Km west.
		While Boddington is further south from Perth with only a very weak signal, probably as its closer to the main area of ducting, but still a bit far north.
	www.users.bigpond.com /vk2krr/new_years_record_setting_duct.htm (989 words)

	AMSAT
		That’s a fact: If you are going to squeak a long-range VHF or UHF signal to that station 1500 miles away through a tropospheric duct, the horizontal beam cannot be beat.
		If signals are coming in just above the noise floor from that distant tropo station, the beam will hear it, and even a stacked pair of loops won’t.
		The KH6HME beacon that comes through every July and August is usually strongest when I enter the duct at about 1500 feet,” adds Alber, explaining that he can literally see the inversion layer where signals from the Hawaii beacon 2500 miles away begin to swamp his receiver.
	www.cq-vhf.com /Spr04%20Loops%20for%20Omni%20Weak-Signal.html (517 words)

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