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RE: [wsjtgroup] Question about JT6M

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  • Barry Garratt
    Bill, as usual, has done a superb job explaining various propagation modes Mark. And, you will experience most of them at one time or another on 6 meters. I
    Message 1 of 6 , May 10, 2009
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      Bill, as usual, has done a superb job explaining various propagation modes Mark. And, you will experience most of them at one time or another on 6 meters. I say most because unless you are using a ground mounted vertical you will not experience ground wave propagation. And if you do then chances are pretty good the other station will also be using a ground mounted vertical or else you are very close to each other. A few miles at most. Ground wave propagation is vertically polarized and is a very low to medium wavelength mode. Typically you will find it from 30 kHz to roughly 30 MHz although at the high end it isn't very efficient because of the higher inherent loss in the earths surface.
      The Navy uses it for example to communicate with submarines in the 100 kHz range and your local AM broadcaster uses it as well. Of course there is a sky wave component from a vertical that comes into play but that relies on reflection from the various different layers. That's a whole different topic.
      Like Bill I live too far south to get any Au but knowing what that does to a SSB signal I have to agree that any of the WSJT modes will probably not work.
      Barry VE3CDX/W7 

      From: wsjtgroup@yahoogroups.com [mailto:wsjtgroup@yahoogroups.com] On Behalf Of Bill W5WVO
      Sent: Sunday, May 10, 2009 7:44 PM
      To: Jonathan L. Rosner; Jerry Siegmund
      Cc: Mark Lunday, WD4ELG; wsjtgroup@yahoogroups.com
      Subject: Re: [wsjtgroup] Question about JT6M

      Just to add a little to what Barry wrote earlier --
      Trying to figure out what combination of propagation modes you're seeing is, to me, one of the more fascinating things about doing WSJT on 6 meters. Since the Magic Band supports, at one time or another, almost every propagation mode known, it provides us with a real guessing game! One of the cool thing about WSJT, of course, is that you get a visual rendition of the signal, and this can really help figure out what is happening.
      Because of the prevalence of sporadic-E propagation on 6 meters during the summer and winter seasons, it is pretty common for any kind of propagation that doesn't look like a meteor ping to get labeled as sporadic-E. Sometimes it undoubtedly is, but often it's something else. If it's not sporadic-E season (roughly early May to late August) and there have been no reports of unseasonal sporadic-E in your area of the country, then what you're seeing is probably not sporadic-E. Some of the other things it could be:
      Ground wave signals, out to maybe two or three times the line-of-sight distance, are generally pretty stable, and get weak quickly as the distance increases. No QSB, no flutter, because the atmosphere isn't playing with the signal, just attenuating it.
      When ground wave is enhanced by tropospheric propagation, distances can be worked out to several hundred miles. Tropo usually is characterized by a very slow up-and-down QSB, with as much as a minute or two between peaks. On top of the slow QSB you will often see a fast QSB, where the signal appears to pulsate from about 1 to 5 times per second. The pulsation period also can vary slowly. The strength of tropo-enhanced signals can be anywhere from a mere whisper to quite strong, but the QSB characteristics described usually hold.
      D-Layer Ionoscatter is a mode that many folks may be unfamiliar with. This is a weak-signal mode that can best be exploited either with JT6M or with one of the EME modes; JT65B (normally used for EME on 2 meters) has proven to be especially effective on 6-meter ionoscatter. When you see a somewhat steady but very weak "floor" to a signal punctuated by meteor pings, the "floor" signal is usually either tropo or ionoscatter, depending on distance. Since the D-Layer is much higher than the troposphere, propagation distances up to 1,000 miles can be obtained using this mode. A more typical distance range is 300 to 600 miles.
      Meteor pings... There are many, many different kinds! Some of the things that affect what a meteor ping "looks" like probably include the meteor's mass, its composition (metallic or rocky), its degree of solidity or structural integrity, its entry speed, its entry angle with respect to the atmosphere, its entry angle with respect to your location, and so on. The ion (plasma) field generated by a meteor can disappear within milliseconds, or it can persist for many seconds, occasionally even for minutes. So don't assume that propagation persisting for 20 or 30 seconds is "sporadic-E" ; more than likely, it's just a really good rock! Meteors exhibit a variety of different waterfall traces, and I'm starting to work on creating a library of different trace classes -- but that work is just getting underway.
      During sporadic-E season (which is just getting started as I write this), contacts can be made using JT6M. When sporadic-E is strong, it is indistinguishable from a nearby ground-wave signal. Even a weak sporadic-E signal will look and feel much stronger on JT6M than it would on SSB! JT6M is an ideal transmission mode for weak-signal multi-hop sporadic-E.
      What about aurora? Since I live in New Mexico, I've never had the opportunity to visualize an auroral signal on the WSJT waterfall. I'd love to know what it looks like. The phase distortion inherent in auroral propagation, though, probably makes any WSJT mode effectively useless for actual communication. (If I'm wrong, tell us of your experiences! )
      Bill W5WVO
      PS -- Yeah, I know, I neglected to mention F2. Well, since F2 is probably at least four years out on 6 meters, I figure we have some time on that one!
      ----- Original Message -----
      Sent: Sunday, May 10, 2009 4:25 PM
      Subject: Re: [wsjtgroup] Question about JT6M

      Hi Mark... I find it a bit difficult at times myself to tell the difference. I notice an occasional Ping that I would guess to be MS.. However at times.. the signal is Loud for a few seconds, then fades, comes back for a second, fades again, and so on.. Now that could have also been MS and Echo's... but at times I can see the JT6M signal thru out the entire seq.. which I guess is either E Skip.. or perhaps, if the station is only 500 to 700mi away.. may be some sort of Ground Path.. some other type of Prop..or again, E Skip.. ?  I usually just 'Take them in Stride'..! Heck.. a contact is a contact in my books.. No matter which way it found my Antenna I guess! But if you see the entire JT6M signal thru out the seq.. I would bet on E Skip over MS.. If you only see a signal for a few seconds at the start.. then again for a few near the end of the seq.. could be either or I guess !  The more experience you get.. the quicker you can detect Prop Paths I guess.. but I found WSJT to be an 'On Going Learning Experience' here.. Still look at it that way.. main thing.. Have Fun.. and Make Lots of Contacts..! 73
      Jerry VE6CPP

      Jonathan L. Rosner wrote:

      On Sun, 10 May 2009, Mark Lunday, WD4ELG wrote:
      > I worked John W9SE, in Illinois about 1630 UTC, JT6M, 50,260. Now we are
      > in Es season (beginning), but I thought JT6M was HSMS prop mode for weak
      > signals? How to tell the diff? 
      > Mark Lunday
      > WD4ELG
      > wd4elg@arrl. net
      > http://wd4elg. net

      Hi Mark - I had a QSO this morning with N3TH which seemed to be a little
      of both. Very short pings at the beginning (almost certainly HSMS) but
      weak signals through almost the whole sequence at the end (likely the
      start of Es).

      Jon WO9S
      Jonathan L. Rosner Phone: 773-702-7694
      Enrico Fermi Inst., U. Chicago Fax: 773-702-8038
      5640 S. Ellis Avenue rosner@bquark. uchicago. edu
      Chicago, IL 60637 USA or rosner@... .edu

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