[VHFcontesting] How to order

N1BUG paul at n1bug.com
Wed Jan 24 06:21:41 EST 2018

> What makes it tough to work MS, besides depending on random meteor shower
> activity, Is that MSK144 uses only one Audio carrier freq of @1500 Hz(
> USB). So its designed more for one station at a time to make a contact.
> (FT8 allows multiple contacts at a time).

That's not entirely true. I have personally been involved in making 
meteor scatter contacts on 50.260 MSK144 when there were a dozen 
meter scatter QSOs proceeding quite well there at the same time. I 
have done this successfully both as a low power and a high power 
station. The developers explain this better than I do, but I don't 
have a link to their explanation handy. Basically, we are making use 
of TDMA (Time Domain Multiple Access). The many short pings and the 
rapid fading of longer bursts on meteor scatter allow success even 
though everyone is transmitting and listening on the same frequency. 
This is because the pings (and fades) happen at different times on 
different paths (even paths with only a slight difference). Since we 
only need a few milliseconds of signal to get a message through, the 
chances are good we can do so even with many other QSOs proceeding 
at the same time.

If the problem is that you have more than one strong station who you 
hear direct (and constantly), then you have a problem if they are 
not all on the same sequence. The only solution there would be to 
try to make an agreement with those stations so that you are all 
transmitting on the same sequence.

> High powered stations that set on the 50.260 Freq calling CQ for more than
> 20 times in a row on MSK144, Like I saw Sunday, Does not let other lower
> powered uses have a chance to make any contacts.
> Both stations are usually on the Odd sequence and would be transmitting the
> same time, thus the higher power stations could be covering up the lower
> power station to a distant station.

Collisions do happen, but many times I have been able to receive a 
low power station and a high power station in the same (distant) 
grid square in the same period. It is true that I hear more from the 
high power station than the low power station, but the lower power 
station sneaks through in one of the quiet slots (which may be an 
instantaneous fade of the high power station). It's really quite 
amazing how this works! It's even easier when they are not in the 
same grid, as the paths become more diverse and the probability of 
suitable time slots for a decode increases.

Of course, the lower power you run, the more difficult it becomes. 
Isn't that the nature of contesting, and in fact, of ham radio itself?


More information about the VHFcontesting mailing list