Andy: Congratulations on the 6 meter MS contacts. Since it is primarily a digital mode, I thought I'd arrange a few general theory notes and tips on meteor scatter to help those that may be new to the mode. Let me know what you think - it's unedited...
Tony KT2Q __________________________ Why Meteor Scatter? Meteor scatter can be used to make VHF contacts when there are no other propagation modes available. The earth's atmosphere is constantly being bombarded by a low-level meteor shower and some of these particles produce ionized trails that reflect radio waves out to 1300 miles. Time of Day: Hourly meteor rates vary with the time of day due to the earths rotation into and away from it's orbital direction around the sun. In the morning, the forward-facing earth runs a collision course with meteors increasing the number reaching the atmosphere and intensifying the ionized trails left behind due to the combined speed of the two bodies. In the evening, the meteors reaching earth are those with enough speed to overtake it; the maximum meteor rate occurs at 6am and the minimum at 6pm. Generally speaking, it's best to operate a few hours either side of the 6am peak; expect diminished conditions when operating near the 6pm lull. Seasonal Changes There is a noticible change in raido meteor activity during the year. Seasonal changes in meteor rates are said to be caused by the non-uniform density of space debris along the earth's orbit. Peak activity occurs in June and July; a lull occurs in February. Signal Characteristics: It's easy to distinquish the short bursts of underdense radio meteors from other types of propagation. Signals 'pop' out of the noise and usually last a second or less. Doppler shift can occur due to the motion of the meteor and the drifting motion of the inoized trail. Overdense meteor reflections (big rock) can sometimes last for a minute or more and mimic a sudden Es opening. These are far and few between though and are more common during major showers. If you'd like to hear what they sound like, I have a few radio meteor recordings and videos at http://tim-tom1.magix.net/ . The MS effect on frequency Radio meteor signal strength and duration vary exponentially with frequency. The higher the frequency the weaker the signals, the shorter the 'ping'. This is why it's easier to make contacts on 6 meters than it is on 2 meters and above. The hourly meteor rate is effected by frequency as well. MS on HF? Radio meteors happen on HF all the time. As long as the HF frequency is below the MUF and the station is within meteor scatter range (1200 miles) it should be possible to use meteor scatter to work that station. This is a great way to make use of a "dead" 10 meter band at night! QSO Time A meteor scatter QSO can take as little as 2 or 3 minutes, but it's not uncommon to wait 30 minutes or more to complete a contact. Meteor rates can suddenly change for the worse one hour only to pick up the next so persistence is key. Which WSJT Mode? The 441 mode is less sensitive than JT6M, but can decode very short pings. This makes it more suitable for meteor scatter on 2 meters and above. Radio meteor reflections tend to last longer on 6 meters so the JT6M mode is more suitable. Mode choice depends on conditons at the time. If pings happen to be longer than usual, use JT6M to take advantage of the sensitivity (JT65 is not suitable for MS). Power / Antennas There are quite a few stations running 100 watts and a dipole on 6 meters with good results. Of course a gain antenna will increase your success rate, but it does show how little it takes to get on the air. The antenna / power 'issue' is more of a factor on 2 meters and 432 so a good size beam (or two) and a bit of power will do nicely. Skeds / Callng frequencies Random meteor scatter QSO's take place all the time, but the majority of contacts are made by sked. The internet meeting place is Ping Jockey http://www.pingjockey.net/cgi-bin/pingtalk . The 6 meter calling frequency is 50260 and 144140 on 2 meters. Tony KT2Q
