One-Way Propagation?
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Kevin, KD5ONS, wrote:
"One way propagation is not unheard of..." Is there really such a thing as one-way ionospheric propagation? My intuition says no, but I don't have the physics knowledge to back it up. On the other hand, sometimes it sure seems that stations who ought to be able to hear my QRP signal cannot. 73 & 72, Jeff WB5GWB Long Island, NY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Howdy Jeff,
If you get on 20 meters in the morning, while you are in the early morning hours and the operator with whom you are working is in an area later in the day, you will find some odd occurrences. Some days you hear better than the other op and some days it is the reverse. The ionosphere is not a perfectly spherical reflector. From empirical evidence I have found it to be quite oddly shaped indeed. Think of the layer you're bouncing your signals off as a boiling layer where the surface changes direction rapidly. This describes rapid QSB. Other times you'll hear very slow, but deep, QSB. At that point the reflecting layer is starting to calm down a bit but there are still bumps in it. Under perfect conditions the received and transmitted signal meet a perfectly smooth reflective sheet which allows the two of you to communicate quite equally. As far as being truly one way? Occasionally I hear ops extremely well but they cannot hear me. I hope it is not that they are ignoring me but simply cannot hear me. This is what I call one-way propagation. Please accept this as a non-scientific, entirely empirical experiment of my own accord on propagation characteristics. Kevin. KD5ONS On Thu, 30 Nov 2006 17:05:12 -0800, Jeff <[hidden email]> wrote: > Kevin, KD5ONS, wrote: > "One way propagation is not unheard of..." > > Is there really such a thing as one-way ionospheric propagation? My > intuition says no, but I don't have the physics knowledge to back it > up. On the other hand, sometimes it sure seems that stations who ought > to be able to hear my QRP signal cannot. > > 73 & 72, > Jeff > WB5GWB > Long Island, NY Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Consistantly over the past 40 years I reaffirm on a daily basis that, at
least on 40M, as the sun lowers in the west I can hear European stations about 45 minutes to an hour before they can hear me. I have no explanation for it but suspect that the signal level is the same on both ends but the background noise from the daylight side masks the signal as it appears in Europe. Tom K2TA ----- Original Message ----- From: "Kevin Rock" <[hidden email]> To: <[hidden email]> Sent: Thursday, November 30, 2006 10:17 PM Subject: Re: [Elecraft] One-Way Propagation? > Howdy Jeff, > If you get on 20 meters in the morning, while you are in the early > morning hours and the operator with whom you are working is in an area > later in the day, you will find some odd occurrences. Some days you hear > better than the other op and some days it is the reverse. The ionosphere > is not a perfectly spherical reflector. From empirical evidence I have > found it to be quite oddly shaped indeed. Think of the layer you're > bouncing your signals off as a boiling layer where the surface changes > direction rapidly. This describes rapid QSB. Other times you'll hear > very slow, but deep, QSB. At that point the reflecting layer is starting > to calm down a bit but there are still bumps in it. Under perfect > conditions the received and transmitted signal meet a perfectly smooth > reflective sheet which allows the two of you to communicate quite equally. > As far as being truly one way? Occasionally I hear ops extremely well > but they cannot hear me. I hope it is not that they are ignoring me but > simply cannot hear me. This is what I call one-way propagation. > > Please accept this as a non-scientific, entirely empirical experiment of > my own accord on propagation characteristics. > Kevin. KD5ONS > > > > On Thu, 30 Nov 2006 17:05:12 -0800, Jeff <[hidden email]> wrote: > >> Kevin, KD5ONS, wrote: >> "One way propagation is not unheard of..." >> >> Is there really such a thing as one-way ionospheric propagation? My >> intuition says no, but I don't have the physics knowledge to back it up. >> On the other hand, sometimes it sure seems that stations who ought to be >> able to hear my QRP signal cannot. >> >> 73 & 72, >> Jeff >> WB5GWB >> Long Island, NY > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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At 10:39 01/12/2006, Tom Althoff wrote:
>Consistantly over the past 40 years I reaffirm on a daily basis >that, at least on 40M, as the sun lowers in the west I can hear >European stations about 45 minutes to an hour before they can hear me. > >I have no explanation for it but suspect that the signal level is >the same on both ends but the background noise from the daylight >side masks the signal as it appears in Europe. I think that Tom has made an important point here. Our ability to copy is based on the signal to noise ratio. I think that the path loss will be the same in both directions. However, if the transmitting station uses more power or the receiving station has a lower noise level, then the ability to copy will be markedly different in each direction. Local band noise, QRN, QRM and so on can make a big difference. Using a directional antenna for receive can greatly improve S/N. One thing that I regularly notice as 20m starts to close to North America from the UK is that while overall signal strength can fade over half an hour by 2 or 3 S units, the band noise also drops, so sometimes readability is hardly impaired. Eventually, of course, the signal level drops to the point where S/N is degraded and then you have to wrap the QSO up fairly quickly because it disappear within fairly quickly after that. Seasons greetings, David, M0DHO. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: One-Way Propagation?
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In reply to this post by Kevin Rock
Jeff, as Kevin says 'you will find odd occurrences', and so called 'One Way
skip' does occur probably more often than people used to believe. There are several explanations as to how this could take place which are too lengthy to discuss on the Reflector, but one thing is for certain which is that the more people find out about "Propagation", the less we really know! As Kevin says the ionospheric layers are usually oddly shaped and constantly in a state of flux and do not resemble those squeaky clean things seen in many text books. To add to the mix layers within a layer will quite often appear at some time of the day centred over one or more places on the planet. Out of this confusion it is possible to find the path that a signal might follow from A to B, and why a signal from B to A might start off using the same path back to A but is refelected to another path back to earth and is not heard at A, but might be heard somewhere near A. This is part of the story! 73, Geoff GM4ESD On Friday, December 01, 2006 3:17 AM, Kevin KD5ONS wrote: > Howdy Jeff, > If you get on 20 meters in the morning, while you are in the early > morning hours and the operator with whom you are working is in an area > later in the day, you will find some odd occurrences. Some days you hear > better than the other op and some days it is the reverse. The ionosphere > is not a perfectly spherical reflector. From empirical evidence I have > found it to be quite oddly shaped indeed. Think of the layer you're > bouncing your signals off as a boiling layer where the surface changes > direction rapidly. <snip> > As far as being truly one way? Occasionally I hear ops extremely well > but they cannot hear me. I hope it is not that they are ignoring me but > simply cannot hear me. This is what I call one-way propagation. > > On Thu, 30 Nov 2006 17:05:12 -0800, Jeff <[hidden email]> wrote: >> Is there really such a thing as one-way ionospheric propagation? My >> intuition says no, but I don't have the physics knowledge to back it up. >> On the other hand, sometimes it sure seems that stations who ought to be >> able to hear my QRP signal cannot. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: One-Way Propagation?
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In reply to this post by Tom Althoff
Tom,
Have you noticed any change in the direction of path skew during the 45 minutes around your sunset, or is it always a 'Great Circle path'? 73, Geoff GM4ESD ----- Original Message ----- From: "Tom Althoff" <[hidden email]> To: <[hidden email]> Sent: Friday, December 01, 2006 10:39 AM Subject: Re: [Elecraft] One-Way Propagation? > Consistantly over the past 40 years I reaffirm on a daily basis that, at > least on 40M, as the sun lowers in the west I can hear European stations > about 45 minutes to an hour before they can hear me. > > I have no explanation for it but suspect that the signal level is the same > on both ends but the background noise from the daylight side masks the > signal as it appears in Europe. > > Tom K2TA _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In addition to the other issues mentioned on this subject, the Earth's magnetic
field causes bending, twisting, and rotation that may not necessarily obey the law of reciprocity in the reverse direction. 73, de John, KD2BD Visit John on the Web at: http://kd2bd.ham.org/ . . . . ____________________________________________________________________________________ Yahoo! Music Unlimited Access over 1 million songs. http://music.yahoo.com/unlimited _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Jeff-229
In a message dated 12/1/06 7:23:14 AM Eastern Standard Time,
[hidden email] writes: > Consistantly over the past 40 years I reaffirm on a daily basis that, at > least on 40M, as the sun lowers in the west I can hear European stations > about 45 minutes to an hour before they can hear me. > > I have no explanation for it but suspect that the signal level is the same > on both ends but the background noise from the daylight side masks the > signal as it appears in Europe. > Well, the *theory* makes sense, but not this particular *application*. If you're in NY, and they're in EU, when it's late afternoon/early evening at your QTH, it's already late at night where they are. They've been in full darkness for hours when you see the sun going down in the west. If daylight noise is a factor, shouldn't you be having more of it than hams in EU at that time? -- Of course "noise" takes all forms. Perhaps the noise is manmade electrical noise that disappears/decreases late at night in Europe. Or maybe it's QRM from highpowered SWBC stations there, who QSY or change antenna patterns after a certain hour. 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: One-Way Propagation?
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On Saturday, December 02, 2006 2:02 PM, [hidden email] wrote: > If daylight noise is a factor, shouldn't you be having more of it than > hams > in EU at that time? > > -- > > Of course "noise" takes all forms. Perhaps the noise is manmade electrical > noise that disappears/decreases late at night in Europe. Or maybe it's QRM > from > highpowered SWBC stations there, who QSY or change antenna patterns after > a > certain hour. ----------------------------------------------------------------- Ham QRM could be a factor when using CW on 40m as the European 'locals' are still very loud around sunset NY time. During a contest the East Coast usually starts to come through well before their sunset. 73, Geoff GM4ESD _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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