Monday, November 22, 2010

What if.... the RBN Telnet server goes down during CQWW?

We are monitoring the RBN Telnet server closely in hopes of discovering what killed it during CW Sweepstakes, but we do not have a definitive answer yet. It is hard to be confident that we have fixed it until it gets hit with the traffic that only a major contest can provide, both in terms of the spot flow and the user numbers. Next weekend will guarantee both in spades, but our object is to provide useful information, not a toy, so we thought it was appropriate to offer suggestions on how to make your RBN spot feed somewhat fail-safe.

The most comprehensive solution is probably to use WintelnetX by K1TTT to merge the spot stream from the RBN with those from one or more of the more prolific individual RBN stations' Telnet servers that are relatively close to you. for example, I might use WZ7I plus the RBN. A downside is that the Skimmer Telnet server does not filter spots, so you must contend with everything the local server sends you and rely on your logging software to cull out the ones you do not want. Of course, you can filter the RBN Telnet server's output, as described in the previous article.

Another, much simpler solution is to configure your logging program for the RBN server and a nearby RBN station's Telnet feed, and keep an eye on the spot flow. It will be easy to tell, at >5 spots/second, when or if the RBN server goes down, and an easy matter to switch.

How do you get the IP address of your nearby RBN station? Most of them are on . We are trying to get those guys whose IPs aren't currently displayed to display them before the contest.

Again, we hope none of this is necessary. See you on the bands!

73, Pete N4ZR

Wednesday, November 17, 2010

What Happened During Sweepstakes?

I'm sure I'm not the only one who got burned by this during the ARRL Sweepstakes - periodically the RBN Telnet server would go down, throwing everyone off, reject connection requests for a few minutes, and then come back on - but unless your client had automatic re-connect capabilities, you might not notice until the spots stopped flowing, and then, if you tried to reconnect, you might or might not get back on..

We (mainly Felipe and Nick, F5VIH) have been studying the logs and configuration details for a few days, trying to figure out what is going on.The spot volume doesn't appear to have been to blame - only 470k spots for the busiest 24-hour day, or about 5.5 per second on average ("only", he says!). Instead, it seems to have been the number of users - we're once again victims of our own success.

There are several potential avenues for fixing this - the best would probably be to adjust the current server's parameters to increase its inbound bandwidth and other capacities very substantially, but that may not be feasible with a Virtual Private Server such as we're currently using. We could get another server, and set up a round-robin DNS so that connection requests are routed to them alternatively. Fine, except that this requires the added server to have a fixed IP address, and if either server gets overburdened and crashes, then half the users would find themselves getting rejected or thrown off until it recovers. A third possibility might be to move the whole thing to another server that we don't share with anyone, and that we can set up for high volume. A fourth, crude solution would be to set up another server with an entirely separate URL, and publicize its availability in the hope that the users themselves will redistribute among the servers.

Anyhow, we're scrambling to figure it out and solve the problem before CQWW CW in ten days' time - please stay tuned.

73, Pete N4ZR

Monday, November 1, 2010

Finally, a "DX Cluster" for Contesters - how to use the RBN in contests

As we approach the big CW contests of the season, I thought that Assisted/Unlimited contesters might appreciate a few tips on how to make the best use of the Reverse Beacon Network's Telnet feed (, port 7000).

As I've said before, the RBN is uniquely fitted to use by contesters, because its 40 or more stations scattered worldwide spot every running station, wherever the station is being heard. Stations are re-spotted every 10-11 minutes if they stay on the same frequency, or immediately if they change frequency more than a few hundred Hz. The result is an all-band snapshot of activity on every band, delivered in real time. Picture that on Sunday afternoon in Sweepstakes, or anytime during the CQWW DX contest. Is 10 meters open? As soon as one station calls CQ, and is heard by CW Skimmer at one or more of the Reverse Beacon Network stations, it will be spotted. You should never have to miss that rare opening again.

Now obviously, the volume of RBN spots will be tremendous, and could easily overwhelm you (or your logging program). The first thing to do, to manage this, is to filter spots at the Telnet node. K4TD, who generously hosts the node, uses DX Spider cluster software. This software lets you set filters with great precision, so that, for example, you can tell the node only to send you spots from a given continent, or country, call area, or even state. I find it most useful to limit the RBN spots I receive to those generated by stations nearby, because I can pretty much count on being able to hear everything they spot.

DX Spider's filter commands are quite different from those used by AR-Cluster. You can either learn the syntax or, as I did, download VE7CC's excellent CC User ( This software translates your wishes to commands and "tells" DX Spider what to do. You do *not* have to use CC User as an intermediate step between the telnet node and your logging program. Instead, once you've set the filters, you can shut it down, start your logging program, and you're ready to go.

Two more hints for operators using the RBN. Most contest loggers have a setting for "packet spot timeout", or something similar, that removes spots from the bandmap when they get too old. Because of RBN's unique re-spotting capability, there is no reason to have the timeout set to more than 15 minutes - if the station is still there, it will be spotted again, and your bandmap won't be clogged with obsolete spots.

And finally, if you want to make sure that you're spotted by the RBN, then once in a while, even if you're running fast, send "CQ" or "TEST" as a part of your end-of-QSO transmission. CW Skimmer isn't perfect at determining which stations are running and which are S&P - it has trouble with runners who only sign their calls at the end of each contact - but this way, you can help it "notice" you.

See you on the air.

73, Pete N4ZR