[RTTY] RTTY Skimmer - DF4UE

[Lee Sawkins]

Hi Phil 

Always nice to work you in the contests. 

I am curious which cluster call you mean when you say you are using "skimmer cluster". Do you mean the RBN or another specific cluster? I wrote the CC Cluster node software, which is used by several very busy nodes. My own cluster node VE7CC-1, has at times has over 1800 local users. I believe the reason there are so many users is that they are pleased with what they receive in the way of skimmer and non-skimmer spots. 

Since I am an active contester, I have tuned my node software to give me what I want to see. A high number of good spots with as few as possible bad ones. 

I check all USA calls against the latest FCC data and drop any that are invalid. Lots of Italian calls have missing first letters, which changes the call to an invalid USA call. JA calls are checked to make sure they are valid format. ie JJ1XX is invalid as JJ1 calls must always be followed by 3 letters. Grid squares and other weird calls are also dropped. 

Users of CC Cluster nodes are not required to enter commands to get rid of bad spots. The defaults are to always eliminate the bad ones. The Time To Live (TTL) of Skimmer spots is 3 minutes on CC Cluster nodes. After 3 minutes, new CQs generate new spots. This is the default. This is done on a per user basis. Having spots persist in a band map for more the 10 minutes is not needed, as they will always be re-spotted if they are still there. 

What surprises me with some bad RTTY spots is that there are letters missed in the middle of calls. I can understand why beginning and ending letters can be lost, but how can the middle ones be lost? Perhaps there is a non printing character detected. If this happens, then the whole call should be discarded, not one letter removed from the middle of it. 

Sometimes I even see duplicate letters in calls. Once again the problem is with the decoding glitching out somehow. 

During the last contest as well as DF4UE generating lots of bad calls, VE3/N2WQ did the same thing. Users of AR Clusters won't see the busted VE3/N2WQ spots, as they don't see any spots at all from VE3/N2WQ. 

Lee VE7CC 


----- Original Message -----

From: "pcooper" <pcooper at guernsey.net> 
To: rtty at contesting.com 
Sent: Wednesday, March 23, 2016 6:01:24 PM 
Subject: Re: [RTTY] RTTY Skimmer - DF4UE 

Pete and the group, 

Agreed, the DF4UE skimmer has loads of partial/wrong calls listed every few minutes. 
I've just had a look at his recent postings, and they contain numerous partials and totally wrong calls, let alone the ones responding to FH/F2DX on 12m RTTY earlier today. 

It would be interesting to note whether he takes your advice, and whether you get a response from him. 

Our local skimmer is making use of several other skimmers, most of which are OK, but I not that N2QT and KM3T both frequently spot me when I am responding to a CQ call. 

I'm running Spotcollector from DXLab Suite by AA6YQ, and I have two windows open, one for the normal cluster, and one for the skimmer cluster, so I can see when I am spotted on either. 
I keep the skimmer cluster going to watch for that first activity from rare DX, and it has served me well. 
I was lucky to get K1N on 10m RTTY, simply because I was in the right place at the right time, and got them before anyone else came on frequency. 
But, I was also spotted by several other skimmer clusters as being on 10m RTTY at the same time. 

Having said that, I wouldn't want to be without access to a skimmer cluster, except I just don't find it that useful in a contest. 

73 de Phil GU0SUP 
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