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How to get spotted

Making the Most of the Reverse Beacon Network

By Pete Smith, N4ZR

The RBN team has been in business since 2009, but we still get lots of questions about how to make it work best for you – particularly from contesters. Herewith, an attempt to clarify things, at least a little.

The basic question is "how do I get spotted as much as possible?" Fundamentally, you must send one of the key-words: TEST or CQ (FD, SS, NA and UP also work in appropriate settings), as well as enough repetitions of your own call (more on that below). These don't necessarily have to be in one transmission, because the way VE3NEA's CW Skimmer works is to "watch" literally hundreds of decoders, each 50 Hz wide, across a band. Each decoder is 256 characters "deep", and with each new transmission newly decoded characters are added and the oldest characters are dropped. What that means, as a practical matter, is that you don't have to meet Skimmer's requirements in any one transmission, so long as you don't change frequency enough to confuse the software.


Figure 1

 

 

 

Skimmer at work, decoding hundreds of signals at once

 

 

 

 

 

 

 

 

 

 

 

 

 

Skimmer at work, decoding hundreds of signals at once.

Skimmer's callsign requirements are simple enough and are derived from the need to avoid grabbing call-sign-like text out of innocent conversations. Depending on how common your callsign is, Skimmer may want to "hear" two, three, or four repetitions of the call before it will be spotted. It uses a "three-character pattern file" harvested from years and years of spots, as well as semi-annual revisions to keep up with new callsigns. Here's a sample:

+ 4U1@
+ 4U1@@
+ 4U1@@@ 
  4U1@@@@
  4U2#@
+ 4U2#@@@
  4U2@
  4U2@@@

A basic pattern consists of the first three characters of a call. Everything thereafter is denoted by either numeric (#) or alphabetic (@) wildcards. If a pattern appears on the list, but without a "+", it means that Skimmer must "hear" it three times (again, in 256 characters in a row) before it accepts it as a callsign. If it has a "+",  meaning that it is judged to be very common, it must be heard twice. On the other hand, if the pattern doesn't appear at all, Skimmer requires 4 repetitions.

The last ten years have seen a rash of single letter suffixes, many explicitly granted for contesting purposes, as well as exotic prefix/suffix combinations for various commemorative purposes. The RBN has tried hard to keep up with this trend by amending the pattern file semi-annually.

 How important is this?  That depends. Experiments with a common (+) call in the weekly K1USN CWTs while running assisted show that, as you'd expect, it takes two brief 1X1 CQs to begin getting spots. A less common callsign (no +) will take 3 quick CQs, and one that is not listed will require 4. 

CW Skimmer is pretty forgiving, but to be optimally copied by the RBN, particularly in QRM and QRN, make sure your CW is good. Any errors here may manifest themselves as mis-spots. Use a memory keyer or your logging software, if feasible, to be sure of this. As remote operation becomes more and more common, be on the lookout for Internet latency and other conditions that can affect your CW. Above all, avoid using half-spaces right before or right after your callsign. Again, taking CWTs as an example, TK and TW prefixes are all too common, because Skimmer may copy the T in CWT and run it together with the real callsign.

One topic contesters frequently ask about is using the RBN for antenna comparisons. This is easy and can be very useful. The only necessary trick, in order to complete the comparison as quickly as possible, is to QSY 300 Hz or more between transmissions. Otherwise, if a node has spotted you during your first transmission, it will ignore you until 10 minutes have passed.

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