2018-11-26

Meteor Scatter

Introduction

The Meteor Scatter tips and tricks described here are based upon more than 35 years of active MS operation. A lot of it has to do with IARU recommended Meteor Scatter Procedure that may seem hard to understand at first glance. Thus the following topics are described:

• IARU recommended Meteor Scatter Procedure
• Timing issue
• Good behaviours
• Bad or invalidating behaviours
• Operating frequency
• WSJT mismatch
• WSJT single tones
• QSO examples

One remark though on the issue of the IARU recommended Meteor Scatter Procedure is that many individual web pages and programs try to explain or interpret the IARU recommended Meteor Scatter Procedure and sometimes these are not updated. In order to avoid all this do only accept the original nothing less than that.

Meteor scatter procedure

The IARU recommended Meteor Scatter Procedure (MSP) can be found at the IARU webspace (warning: PDF file!) here.

Timing issue

IO and JO stations use second period 98% of the time when working outside the "IO-JO Box." Stations working another station "inside-inside" or "outside-outside" the "IO-JO Box" agree on this on a case by case basis and choose a frequency that is far away from the activity centre. This is in line with the principles recommended by the IARU, MSP 4.4.4, and more than 35 years of operation.

Good behaviours

Bad or invalidating behaviours

Bad behaviours or actions that will invalidate an MS QSO attempt, according to the MSP, are:

• Bad behaviours
  • Using messages that does not comply with the MSP
    The QSO partner expects you to follow the MSP. If you do not you reduce your chance for a successful QSO
• Invalidating behaviours
  • Talk back revealing QSO information, MSP 4.4.9
  • Talk back requesting information to be send, MSP 4.4.9
  • "Continuing" a half finished QSO. There is no such thing as continuing a QSO in the MSP. Every attempt must be uninterrupted, MSP 4.4.5
  • Changing the sent report, MSP 4.4.8.3

You may also take a more dubious approach to the MS procedure here.

Operating frequency

The IARU recommended MS random, i.e. CQ, frequencies are:

• 50 MHz
  • SSB and CW: 50,200 MHz
  • MGM: 50,370 MHz
• 70 MHz
  • SSB and CW: 70,250 MHz
  • MGM: 70,270 MHz
• 144 MHz
  • CW: 144,100 MHz
  • SSB: 144, 200 MHz
  • MGM: 144,370 MHz
• 432 MHz
  • SSB, CW and MGM: 432,370 MHz.

Due to the fact that you are likely to find a lot of non meteor scatter traffic on the bands, e.g. many SSB stations can be found up to 144,370 MHz, I recommend that you always pick a frequency according to the below list:

• 50 MHz
  • SSB and CW: 50,200 → 50,210 MHz.
  • MGM: 50,370 MHz → 50,399 MHz.
• 70 MHz
  • SSB and CW: 70,250 MHz → 70,260 MHz.*
  • MGM: 70,270 MHz → 70,299 MHz.*
• 144 MHz
  • CW: 144,103 MHz → 144,150 MHz.
  • SSB: 144,190 MHz → 144,210 MHz.
  • MGM: 144,373 MHz → 144,399 MHz.
• 432 MHz
  • SSB, CW and MGM: 432,373 MHz → 432, 380 MHz.

* Note: Each country may have very different 70 MHz band frequency allocation(s) thus only the available segments can be used and as a consequence meteor scatter traffic may take place almost everywhere.

QSO examples

Motto: "If you do not know why the IARU Region 1 VHF Committee Meteor Scatter procedure is the way it is do not change anything. When you know why it is the way it is, you also know not to change anything."

Below are a number of meteor scatter QSO examples based upon the IARU Region 1 VHF Committee recommended Meteor Scatter Procedure.

1. Standard sked QSO - example 1.
2. Random QSO - example 2.
3. Another QSO example - example 3.
4. A QSO that gets "out of sync" - example 4.
5. Random QSO with CQ QSY (CQ 394) - example 5.
6. A QSO where one of the stations has made his own type of messages - example 6.

Keep in mind that it is the same information that has to be exchanged in a sked and in a random QSO.

Why Is The MS Report Sent Twice

In the IARU recommended Meteor Scatter Procedure the signal report is sent twice in stead of just ones. Why is that?

Exchanging information over meteor scatter is all about probability and patience. Let us look at a couple of examples given the QW1XYZ and OZ2M call signs are used. Keep in mind the procedure stipulates that both call signs have to be received in full. Furthermore a shorter message will be received more often increasing overall probability.

Table 1: Comparison of character probability versus the number of times the signal report is sent.

When sending the report ones the probability for each characters is the same and given the fact that all characters have to be received it makes a lot of sense. Unless ...

...

We cheat!

Some possible reasons:

• R: The report is needed twice to make sure it is correct.
  Q: Hmm, perhaps true but what about the rest of the characters then. Don't they deserve the same accuracy?

• R: The callsigns are known already therefore only the variable part has to have higher accuracy.
  Q: Hmm, but then it is cheating isn't it?

WSJT

WSJT is a very useful piece of software acknowledged by many radio amateurs through out the world. Unfortunately there are some slips in the way WSJT deals with the IARU recommended Meteor Scatter Procedure.

Signal report

The signal reports suggested by WSJT in the "Rpt" column does not comply with the IARU recommended Meteor Scatter Procedure. Thus you should not use one of these when entering the "right report" into the edit box. The correct reports are shown below:

Please note that "1" is not used in the report.

Standard Operating Procedure/MS Procedure

Another mismatch is the WSJT Standard Operating Procedures, evoked by pressing F5.

In brief words and in same style as WSJT the IARU recommended Meteor Scatter Procedure can be written like:

Start by sending both calls (Msg 1)
If you have received:
... his call or own call or parts of one them send calls and report (Msg 2)
... both calls complete and report send calls and R-report (Msg 3)
... both calls and R-report send RRRR RRRR own call (Msg 4)
... RRR, the QSO is complete! But you may respond with 73 own call (Msg 5)

You can also download the complete IARU recommended Meteor Scatter Procedure here.

A trick that you may apply when working on the random frequency is to change Message 4 into "RRRR own call" or "RRRR own suffix" if your call is long, as this will make it easier for the receiving station to identify who is sending the RRRs. But do not waste reflections and probability on transmitting the receiving station's call when sending RRRs.

WSJT single tones

In IARU Region 1 the Single Tone Messages are not used. So a decode and subsequent display of such a message is irrelevant.

See also Meteor Scatter above for a discussion of compliance between WSJT and the IARU recommended Meteor Scatter Procedure.

Bo, OZ2M, www.rudius.net/oz2m