Training Session #2 - Simplex Net Procedures

Last week we reviewed our fallback procedures for a single repeater failure.  This week we'll address 
what to do if both repeaters fail.  This scenario would be typical if we had a hurricane, tornado, 
earthquake or other violent natural disaster that disrupts both power and physical structures such as 
towers and repeater sites.  Remember, our repeater sites are less than 3 miles apart and could easily be 
affected by the same disaster.  The benefit of amateur radio is the widely distributed and independent 
nature of our individual facilities.  Each ham has his own "radio site" at his/her home location.  A 
simplex net takes advantage of this distributed topology and employs proven HF communications tactics in 
a Line-of-Sight VHF network.  

Net control, having determined that both repeaters were down, would open the net as usual and then call 
for checkins, either by roll or more likely by suffix blocks.  If he is unfamiliar with the layout of the 
net stations, he may ask that stations indicate during checkin their location, operational status, such as 
"Poor", "Favorable" or "Excellent" and also their willingness to act as relay stations during the net.  
The NCS would accept checkins until no additional stations were heard and then call on selected relay 
stations, in turn, to handle relay checkins from outlying sectors in the valley.  The relay station would 
call for checkins and note callsigns of stations for relay back to net control.  As stations check in they 
may announce that they can hear the net but can't check in directly, or just that they can only hear the 
relay station, or a selected subset of net stations that have checked in directly to the main net.

The relay station would then forward this information to net control.  The NCS would then proceed to the 
next relay station in turn until the affected area has been adequately covered.  Note that you may not hear 
net control during this type of net.  You may only hear the relay station when he calls for relay checkins.  
This is the difficult part of simplex communications...you have to be QUIET even though you can't hear other 
stations on the frequency.  BE PATIENT, eventually some relay station will come up to accept checkins in your 
area.  It may be 5 or 10 minutes past the net opening time before you hear the call for checkins.  That's 
okay, the normal preamble and direct checkins have to be processed first, so if you don't hear the net, or 
do hear the net but your checkin isn't acknowledged, just stand by until an S9 relay comes up on frequency.  
Normally, you'll have a good idea of the net's progress because you'll hear some stations, either those close 
to you or high profile ones, as they checkin.  

Handling bulletins and other traffic in this type of net is a lot more tedious, since the net has to provide 
for ALL the net stations receiving the data.  The listing station may be a relayed station and the relaying 
station must copy the traffic and then pass that traffic to net control.  When he passes the traffic to net 
control, his small "flock" of stations will hear it, but they'll probably be the only ones.  The NCS must now 
reread the traffic for all the direct copying stations and then call on all the other relay stations, except 
the one that listed the traffic, to repeat it to their "flocks" of outlying stations.  In effect, a one minute 
message that would have taken one minute on the repeater may take up to ten minutes, with fills and repeats, 
on a simplex net.  However, the essential component of having a net, the passing of information, will be 
completed under less than favorable conditions.

This may sound like a inefficient way to conduct business, but HF nets have operated this way for a long time!  
You may be only 50 miles from the net control station, but not be able to hear him.  You may hear the relay 
station 600 miles distant and check in through them.  It's just the way propagation works.  With Line-Of-Sight 
communication, we have similar problems due to each station individual situation  regarding topography, power 
and antenna.  We just use the HF net paradigm to accomplish our normal net objectives. 

73,
de N0KIA