After I wrote the eleven points about MSK144 and the Perseids David, GM4JJJ added another. I will re-post it here:-
Might I add a number 12 bulletin point?
In MSK144 there is a checkbox marked 'sh'. This allows a short-format message format to be used.
The user guide explains:
For operation at 144 MHz or above you may find it helpful to use short-format Sh messages for Tx3, Tx4, and Tx5. These messages are 20 ms long, compared with 72 ms for full-length MSK144 messages.
It also makes plain that on 50 and 70 MHz sh is not useful as the pings are of much longer duration anyway.
What is important to remember is that on 144MHz, you need to know if the other station is using sh or not, failure to use the sh setting if he is using sh will result in no decode even when a strong burst is received.
Another point is that if sh is used, there is a greater chance of false decides, so once you have detected the other station it is best to use RIT to get your RX frequency as close to his transmitter frequency as you can and then narrow FTol.
Thanks for that David.
|"Sh" is accessible by clicking a box. SWL mode is for listening to the Sh messages of others|
I might even add point number 13.
13) Think about AGC?
On the face of it, AGC should be turned off, especially on 2m metres. Meteor scatter pings are short events and they tend to be shorter the higher you go in frequency. AGC will cut your receiver gain as soon as a ping is detected, and therefore seems like a bad idea for a mode which depends on momentary signals. You receiver gain may remain lowered as the ping trails off, and thus you might miss the weakest part of a vital ping.
In practise I find that this is not an easy decision to make. Using my IC-7100 and IC-7300 the initial AGC action is very deep. However, the recovery time is adjustable and you can make it very fast indeed. At the fastest setting the response is good and it seems to help in some cases.
I would therefore suggest that it might be a good idea to try the AGC on and off for trial periods. To some extent it will depend on your rig. Slow acting AGC is almost certain to be detrimental, but fast AGC might work depending on the equipment. If in doubt, I would suggest turning it off.
I am a bit worried that listing 13 points makes meteor scatter with MSK144 look very difficult. It is not difficult. Why not try it and see?
Just because the Perseids are over, there is no need to wait for another shower to try meteor scatter propagation.
About 40,000,000 kg of material collides with the Earth every year. Whilst during a shower the particles may be bigger and there may be more of them, this is still only about 4 times the average for a normal day. When I say bigger, maybe golf ball sized, rather than the size of your thumb nail or smaller. But even a speck of dust can produce an ion trail as it falls to Earth and compresses the atmosphere in front of it, producing heat, light and ionisation as it progresses. Either the "burned up" particle is reduced to a speck of material which falls gently through the lower atmosphere, or, more likey for the ones that interest us, they are vapourised entirely by the intense heat.
Any object large enough to remain a significant size and reach the Earth's surface is called a meteorite. If we are ever going to be on the receiving end of a large meteorite then, believe me, the effects it might have on radio propagation will the be the last thing we are interested in. So the small ones are our main interest, and they fall all year round.
Is random meteor scatter a reliable method of communication? Take my QSOs with Henning, OZ1JXY. Since 2014 I have worked Henning by meteor scatter 61 times, at all times of the year and at all times of the day. That is reliable meteor scatter communication over a fairly short distance - 732km. During the same period I have worked Henning only two times on Es and once each on aurora and tropo. Anyone who suggests that meteor scatter is confined to a few days of the year needs to look at the performance of that link (not even a sked, all of it random answers to CQ calls).
|OZ1JXY blasting in on FSK441 on 1 October 2016, outside a recognised meteor shower|
The Perseids shower is formed by the Earth crossing the dust trail left behind by a previous pass of the Swift-Tuttle comet. As we pass through the path of the comet we cross the material it left behind. Thus we have a predictable event to take into account. Random meteor trails are not as dense, but they are capable of producing surprising results for the amateur. And they occur almost all the time if you have the patience to wait.
Given the many advantages of MSK144 over previous formats, I am surprised to see so many stations on 2m still using FSK441. I will not go into the reasons for this, but they are just plain stupid. The justification used by one or two of these people is keeping MSK144 off the table for the rest of us.
For many operators, all they do is follow the pack, which in this case means sticking with FSK441. Nevertheless, for the few operators who drive this piece of numb-skullery, the basic object of resisting the spread of MSK441 is their belief that changing mode will damage their success. It won't.
There is a sort of meteor scatter neurosis which develops amongst operators. I know, I have had it too. The other station seems never to have heard you, though you can hear them (or vice versa, it doesn't really matter which). Therefore, the fault is clearly your antenna, their antenna, the software, your sound card, the phase of the Moon, ..., perhaps this new mode will reduce my QSO potency. This is human nature, given the characteristics of a mode that depends on tiny wisps of signal. But, meteor scatter communication depends on probability. You are waiting for a randomly timed event to happen. The gaps between hearing the other station are --- random. Who'd have guessed it? There is no need to blame your rig, or MSK144 for it, nor anything else. Mind you, when you are sitting there waiting for a signal, you might think of everything under the Sun.
Here the Perseids produced a few interesting contacts here.
6m MSK144 - LX1JX, S59A, SM6A, and SO3Z
4m MSK144 - DF1AN, DF3XZ, DF5VAE, DJ9YE, DK5YA, DK6AO, DL4KUG, DL9YEB, GD0TEP, OH7TE, ON4FI, OK1DIG, OZ1JXY (of course - twice), OZ1MFP, OZ6GH, PA3ECU and YL2CP,
2m FSK144 - SM2CEW and SM7THS
With 6m squares now being less sought after by me (I already have quite a lot), I have been looking for new ones and not calling ones I have. On the other hand, most of the 4m contacts were from stations hunting out my square, IO85. I do not think that I live in a rare square on 6m, especially as it has Edinburgh City in it. However, on 4m there are not many active operators, hence it is more in demand.
With 2m I stood out for a while by sticking to MSK and working no-one as a result. I had a few QSOs on FSK but that was it.
Two new countries for me were provided by LX1JX on 6m and YL2CP on 4m. Many years ago Jack, LX1JX (JO30, 843km) was my first LX station on 4m (on FM!) but it has taken a while to track him down on 6m. YL2CP (KO27, 1674km) had to have a lot of patience to work me as we had a number of attempts over two days. Because YL have only recently gained 4m he was much in demand and had to keep switching to other stations who kept calling him. We did it in the end though.
All this talk of meteor scatter has made me think about how reliable it is, and how unreliable Es has been for me this year. I must look all that up and see if I am imagining it.