Since the early days of 144 MHz "Weak Signal" VHF DXing, Meteor Scatter (MS) has been the most consistent method
of making long haul contacts between 500 to 1400 Miles. The odds of completing a contact via Random Meteors (Rocks)
are relatively good any early morning and increase dramatically during one of the many Meteor "Showers" that occur each year.
How do I make use of this medium to work more grids on Two Meters (2M)? What are the mechanics involved? How do I know
where & when to beam my signals? How do I make contacts using MS? These questions and more will be answered within this
document.
What is MS?
MS is the term for sending your signals beyond the horizon via refractions off of the Ionized Gas trail that streams
out of a Meteor as it burns up while entering Earths orbit. As a "Weak Signal" VHF radio amateur, we are only concerned with
ones large enough to support brief contacts on 50 MHz and higher.
How does MS works?
The correct answer is "Very Carefully" all kidding aside, There are many factors that go into successfully completing
a MS contact. For simplicity sake I will only deal with 2M for now. Later on I will compare the bands, their effectiveness
and drawbacks. As a Meteor enters our atmosphere the friction of striking air molecules at very high speed causes them to
heat up and break down, leaving an ionized trail of hot gasses behind. It is this trail that refracts radio signals, sometimes
usable to as high as 450 MHz. Think of it as a long cylinder of hot gasses that once it forms begins to twist and turn until
it finally dissipates. Meteors that meet the Earth head on in the morning have a higher apparent velocity then those that
overtake the Earth behind in the evening, which is why Random Rocks work best in the hours just before Sunrise.
The larger the rock, the faster its apparent speed relative to the earth, the higher up it starts to burn, the longer
the burn, the denser the Ionized trail, the stronger the refraction (Over-dense Burn), the longer in distance and higher in
frequency it will support radio communications.
Consequently, The smaller rock, the shorter the burn, and the slower the rock the shorter the burn, The less dense
the Ionization, the weaker the refraction (Under-dense burn), the shorter the distance and lower in frequency it will work.
Due to the physics involved, the minimum MS distance you can work is around 500 miles with 1400 miles about the maximum.
This is all based on the curvature of the earth, thickness of the atmosphere, height at which the average meteor starts to
burn, etc. This distance can be lengthened by stations on one end or another operating from a tall mountaintop, use of high
power, CW (30 to 50 WPM), Linking into Sporadic E layer propagation on one end or another, a large/fast rock, etc. In 1994,
I worked 1433 miles from atop 8000 Pond Peak NV in DM09 to the very NW corner of LA in EM26. He was at the kilowatt (KW) power
level with a large array and heard me many times. I ran 150 watts into a 2.2 wavelength yagi up 15 at a very quiet mountaintop
receiving location. In the 1 hour & 4 minutes it took us to complete, I heard a total of 5 seconds from him, but it was
the right info to complete the contact.
How Do Meteor Showers Work?
Occurring roughly the same time each year, Meteor Showers are named for the constellation from which they seem to appear.
They can last from only a few hours to several days or more. The more popular showers range from 10 to 20 per hour to over
100 per hour, with the occasional meteor storm that measures activity from tens of hundreds to over a thousand meteors per
hour.
Using a pencil to aid in our understanding the mechanics of MS, Imagine a long cylinder of hot gasses formed as the
meteor travels to earth. It falls at roughly a 45 degrees angle, so hold the pencil the same way. Looking at it head-on, it
has a very small cross section. Looking at its side, the entire length of the burn adds to the cross section, providing much
more refracting surface and much louder signals. This is why it is important to know the mechanics of a meteor shower, where
the rocks predominantly fall from and what direction they fall towards. For example: If they traverse from NE to SW, the best
radio path would be from the SE to the NW and vice versa. The weakest returns would be from head on (NE to SW).
Also, as time passes from late evening to morning, the earth is still spinning and the apparent direction of the meteor
streams change in relation to your location. Moving the "sweet spot" roughly 90 degrees, or in this case from SE / NW to NE
/ SW, as the rocks now appear to fall from NW to SE. The earth can also get in the way causing the shower to "set" below your
horizon.
How Do I Know When a Shower Will Occur?
How long the shower is visible, where it will rise and set, Number per hour, avg. speed, etc, all its typical characteristics
are widely known and published many places from books and magazines to various Web sites. One of the best sources of information
is to use one of the many MS prediction software packages that are available for download. A complete list of showers and
software can be found at the end of this article.
I know when and where, Now What?
There are several ways to successfully complete a Analog (SSB) MS contact.
- R
andom or unscheduled contacts take place on or near the calling frequencies depending on level of meteor and
station activity. When there is lots of either you will find stations +/- 20 kHz or so, when there little of either, seldom
does anyone stray from them.
- S
cheduled contacts are picked up via Telephone, Snail Mail, 3.818 MHz, Email, or one of several web sites established
for the purpose of soliciting Skeds. A list of appropriate web site will follow this article as well.
- T
ailend someone. Youre tuning around and find someone running a sked with someone else. You hang around till they
finish and then start calling the station you want using the same time protocol of the station they were just working.
Whats a Time Protocol?
To minimize the chance of transmitting on top of one another (a collision) you take turns transmitting and receiving
based in quarter periods of a minute. The furthest west station would transmit on the 1st and 3rd quarter
minute and the eastern most would transmit on the 2nd and 4th. This reduces collisions and assures someone
is always listening for your transmission. When CQing on Random Rocks I try and transmit for 5 seconds and listen for 5 seconds,
starting at the top of the minute. When long burns or lots of rocks are falling, this process gets sped up considerably. Use
your best judgement.
OK, I now know when but WHAT do I send? And Why?
Simply put, what you send is based on what you have heard from the other station. It also prompts the other station
to end what you need to complete the contact (QSO or Q). To be considered a "Completed Contact" you must hear both calls,
exchange one piece of data, and confirm reception. Stations start out sending both callsigns over and over during your 15-second
period. You continue to send " Calls" until you have heard both yours and his, though they need not be in any order. Once
you have received "Calls" OK, you then send calls and a report during your 15-second period. (The typical report is "S2" what
dates from the beginnings of MS and stands for burns or "Pings" of 1 to 5 seconds in length. These days "S2" is the equivalent
of saying "59" on HF.) If its a random contact, the best thing to send is your grid square. That way the other station know
where you are and it helps others point the right way to try and work you as well. Once the other station hears calls he will
send calls and a report as well. Once you have both calls and report you switch to sending "Roger Report" for the full 15
second period (Whatever your report, S2, your Grid, Whatever, is what your sending him along with "rogering" that you copied
what he sent). This goes on till you hear him send "Roger". At that point it is a complete contact, but traditionally you
would confirm his Roger with a stream of "Roger 73". Hearing that, he would send a stream of "73" thus letting everyone know
its a done deal. In the beginning you may feel self conscious about screaming "Roger 73 Roger 73" over and over for 15 seconds
but fear not, you will loose that feeling once you start working new grids! You may, as I did, become a certified crazy known
affectionately as a "Ping Jockey". Youll joyfully howl strange things into your microphone into the wee hours of the morning,
fighting sleep deprivation, hunger, a sore throat, and loving it!
What is MS like on other bands?
MS can support brief communications from HF through 432 MHz. As you go higher in frequency, the usable burns fewer,
shorter in duration, and weaker in strength. For example, at 28 MHz a typical burn lasts a few minutes. That same burn at
50 MHz is 20 seconds long, at 144 MHz it lasts 2 seconds, less than half a second at 222 MHz and at 432 MHz yields a brief
"Ping". With persistence and determination it is possible earn VUCC through UHF without the use of Moonbouce or EME (Earth-Moon-Earth).
Places to find more information on Meteor Showers
Several fine publication now exist to help you understand MS and how it can help you work distant stations using "Weak
Signal" VHF / UHF techniques. Attached is a partial list of titles
VHF/UHF Handbook - Edited By G8DPS - 1997 RSGB
41st Annual West Coast VHF Conference Proceedings Edited By KK6CG 1996 - S CA 6M Club
The VHF/UHF DX Book - Edited by G3SEK - 1995 RSGB
The VHF "How To" Book By N6CL 1995 CQ
Beyond Line Of Sight Edited By W3EP 1992 ARRL
VHF Amateur Radio By W6SAI 1988 Radio Publications
VHF Handbook By W6SAI 1964 Radio Publications
VHF for the Radio Amateur - By W6AJF - 1961 CQ
Places to find More Meteor Shower Information
http://medicine.wustl.edu/~kronkg/meteor_shower.html
http://ns.ilk.de/sites/gap/ms.htm#by
http://www.panix.com/clay/ham/propagation.html
https://k7xc.tripod.com/K7XCweaksignal/
