A New Tutorial on Using the RBN

It has been over three years since I last wrote a tutorial for users of RBN spots, and I was amazed when I read the old one to discover how much things had changed.  Here's the current word.

There are two RBN Telnet servers, at telnet.reversebeacon.net port 7000 and arcluster.reversebeacon.net, port 7000.  The intended use of these servers, however, is not to provide spots to end users, but rather to feed spots to AR Cluster and CC Cluster nodes worldwide for "retail" distribution.

To find a cluster node that provides what you want, go to and search by software type. Of course, geography is pretty unimportant these days, with the demise of RF clusters, but you'll want to check to be sure the node you use has Skimmer spots from the RBN as well as the filtering capabilities you want.
 
Both ARCluster Version 6 and CC Cluster provide a choice to users as to whether to include spots from the RBN in the spots they receive.  More importantly, each has its own set of filtering capabilities, with quite different underlying philosophies.  Why filter? Because even on a Monday morning, the RBN typically pumps out more than 120 spots per minute, and during a contest, the flow can be 20 per second average.

If you use a VE7CC (CC Cluster) node, he has already made some decisions for you.  His nodes provide de-duped data, which all by itself will cut the volume of spots by more than 80 percent, and he has done some pre-processing to reduce busted spots.

A complete list of CC Cluster commands is at http://bcdxc.org/ve7cc/ccc/CCC_Commands.htm. The easiest way to set filters is to use the very versatile CC User client program, available from http://www.bcdxc.org/ve7cc/default.htm#prog





Among other useful features, CC User can be used between a cluster node and a logging program, to make it easy for you to manage your filters.

A caution - CC User is usable with DX Spider, CC and AR Cluster version 4 nodes.  It is not compatible with AR Cluster Version 6, which has adopted an entirely new  "Boolean" filter syntax.

The AR Cluster commands are at http://ab5k.net/ArcDocsVer6/UserManual/ArcCmdSummary.htm.  As you can see, the default AR Cluster posture is not to remove duplicate spots.  This offers one important benefit - to use a program such as Viewprop, which relies on spots to and from your area to give you a near-real-time portrayal of propagation, you must have access to all spots of each station.

AR Cluster also has a client program, available at AB5K's web site.  It provides for setting a wide variety of user-defined filters, including duplicate removal if you wish



A feature not found in CC Cluster is the inclusion of CT1BOH's "skimquality" algorithms, which flag verified spots (ones heard by more than 2 Skimmers), QSYing stations (which may occasionally be image spots), and busted spots (based on a complex statistical algorithm.  Here's a sample of the output:





 
Note the spot of OK7FL as K7FL, about 3/4 of the way down - the algorithm not only identifies the spot as a likely bust, but also tells you what the correct call is.  You can filter on any combination of these attributes - for example, so that you do not see busted spots, or QSY spots until they are verified by at least 3 Skimmers.

A beauty of the AR Cluster filtering approach is that you can create compound filter selections to store very complex filtering combinations as a single string.  for example, the Hi-Q button on my N1MM Logger Telnet window above, when clicked, tells the cluster "SET DX FILTER call=n4zr OR (NOT Skimbusted and spotterstate=[MD,PA,VA,NJ,WV, NY,NJ,NC]).  This lets through any spots of my station from anywhere in the world, and lets through both Skimmer and traditional spots from the states listed, deleting any that the cluster believes to be busted.  Here's a sample with the filter in use:



Note that since I did not choose to block the first spot of a new station or a previously-spotted station on a new frequency, spots coded ? and Q come through immediately. 

That's about the whole story.  I hope this encourages more people to use Skimmer/RBN spots for CW, RTTY and BPSK.

73, Pete N4ZR

Finding Your Spots

Want to find spots of your callsign on a particular day, like during the 2 days of CQWWCW?

Bob, N6TV has come up with an easy .cmd script for use under windows, as well as a version for Linux.  you can download them as a zipfile at http://bit.ly/GetSpots.

Use notepad to open the .cmd file, and you'll see that it specifies the filenames of .csv files from the RBN's Raw Data archive.  You can change the filenames to anything you want, add more, etc.  Then put the .cmd file in the same directory as the .csv files you've downloaded.  Run it, specify the callsign you want extracted, and boom, it creates a .csv file in the format [call].csv.  Very neat. 

CQWW CW 2013 - RBN Stats by N6TV

Once again, Bob, N6TV has compiled statistics on the RBN during the 2013 CQWW CW contest.  But as seems to happen a lot to us, the infrastructure isn't up to the task.  In this case, it's the blogspot editor, which can't handle a file this big, so I have put the data out on Dropbox in .pdf form.  You can access the file (and download it if you wish) at this Dropbox location.

73, Pete N4ZR

Crunching the Numbers

One of the potential benefits of the RBN has been the use of our archive for studies of propagation, but a barrier to that has been the difficulty of importing and managing all that data.  Now Stephen, WD5EAE has developed a technique for importing some 240 million RBN spots into PostgreSQL.  You can read all about it at his web site.

Already doing propagation analysis with RBN data?  We'd love to hear about it!

Using the Funcube Dongle Pro+ with CW Skimmer

by Gabriel Sampol, EA6VQ

reproduced with permission of the author from

http://www.dxmaps.com/funcube.html  

Editor's note: The Funcube Dongle Pro + is a tiny and relatively inexpensive receiver that plugs into a USB port and is capable of 192-KHz coverage between 150 KHz and 1.9 GHz.  Because it does not blank out US cellular telephone frequencies, the DP+ is not legal for use in the United States.  For interested readers elsewhere, you can read more at the maker's website.

 

I got a Funcube Dongle PRO+ with the idea of setting up a secondary Reverse Beacon receiver for 28 and 70 MHz bands.  To my disappointment the current version of CW Skimmer (1.8) does not support this device so I have spent some time investigating how to make it work.

First of all I noticed that CW skimmer was recognizing it and it was receiving if I configured it as a Softrock with a 192 kHz Sampling Rate.

However, the frequency received had nothing to do with the value of  "LO Frequency, Hz". There was an offset all over the band.

I then realized that the shown frequency had to do with the last frequency set in the Funcube by another SDR program (SDRsharp) that I had used just before, so it was a matter of setting the right frequency with a program that supports the Funcube and setting that same frequency in CW Skimmer.
With this simple two-step procedure you can satisfactory use the Funcube Dongle PRO+ with CW Skimmer, and of course also use it for the Revese Beacon Network thru Aggregator.

This is an example on how to set the LO frequency to 28095 kHz, to cover the lower portion of the 10m band.

1. Download the FCHID (FCD+ Frequency Control Program) program for Funcube, place it in the CW Skimmer folder (for instance) and run it.  Set the frequency to 28095.

2. Set the LO Frequency to 28095 also in CW Skimmer, as shown in the first image.
And that's it.  You will be receiving the 27999 to 28191 kHz band and the frequencies shown in Skimmer will be correct.
No need to say that if you want to receive another band you will have to repeat both steps.

---

Well, now that I had it working I wanted to go one step further and find a way to switch bands automatically, so that I could monitor several bands sequentially. In order to it I obviously had to find a way to programmatically change the frequency in both, FCHID and CW Skimmer.

In order to change it in FCHID I developed a small program that uses Windows API calls. I called it ControlFCD and it accepts a frequency in kHz as a command line parameter (For instance "ControlFCD 28123" will change the Funcube frequency to 28123 kHz in FCHID).  No need to say that FCHID must be running when executing ControlFCD.

For changing the LO Frequency in Skimmer I didn't find a better way than changing this value in the CWSkimmer.ini and restarting the program so that i takes the new configuration file.  Instead of modifying the ini file I opted by creating different copies of the original file, each of which with the desired value of frequency, and copying then later over the CWSKimmer.ini.

Finally, I made a simple VBS to control the whole process of starting all the programs and automatically managing band changes at certain times. You can download this VBS as a sample and the ControlFCD program for your convenience.

Important: Download and use these programs at your own risk. They work fine for me on Windows XP, but you may need to modify the VBS for your own use and you will need some basic programming skills for this purpose. They are also likely not to work in later version of Windows, without changes. I can't provide you support about them.

Testing Spot Quality Filters

It's been a busy and rewarding couple of weeks.  Sometimes, I'm quite overwhelmed by the willingness of hams to invest large amounts of time and intelligence in advancing our hobby, not for any personal gain but simply because they care and enjoy what they are doing. 

This is one such case.  The AR Cluster V6 Telnet server at the RBN has just been replaced with a beta version that provides quality scores for each RBN spot, as well as filters enabling users to apply those scores to limiting the spots they receive.  Note that if you don't set any of the new filters, the node will continue to function as it always has, except for the addition of a validity code as part of the comment on each RBN spot.  All existing filters will continue to work as before.  The full story is at <http://www.ab5k.net/ArcDocsVer6/UserManual/ArcDx_CT1BOH.htm>.

Special thanks to CT1BOH, who did extensive analysis of RBN data and developed the innovative algorithms being used, and to AB5K, for the hard work of coding and testing the filters for incorporation in this new version of his cluster software.

During the beta period, users will see a set of new tags in the comment field of spots coming from the RBN ARC6 Telnet server.  These will not be a feature of the finished version, so software that relies on a particular format in the Comment field of spots will not have to be modified.  Users will see the quality tag, but in order to filter using them, the node they are connected to must be running the beta server software as well.  Users can test with the RBN node at arcluster.reversebeacon.net, port 7000.  Node sysops who want to try the beta are encouraged to contact AB5K.

These are the quality tags:

? - Not yet verified.  The first and/or second identical spot of the same station, including erroneous spots of callers 
V - Valid, meaning that at least three identical spots (call and frequency) have been posted by Skimmers worldwide
Q - QSY?, meaning that it is the first and/or second spot of a station on a new frequency, where spots of that station were previously verified. Sometimes, this will be a legitimate QSY, but the tag may also indicate an I/Q image of a good spot.
B - Bust, based on whether a new spot is enough like ones already seen and tagged Valid, except for a difference in the callsign.  This is based on a really clever applied math concept called the Levenshtein distance.  Google for more info.
. - Unique, meaning that there are only one or two stations currently spotting stations in a given country.  Will often change to V if more stations spot it, but in the meantime you won't miss that P5 because only one RBN station heard it.

You can filter so that you get only Valid spots, or so that you can block all busted spots, or so that you get no Q spots until they are verified (so I/Q images will not come through).  You can even tell the cluster node to let through spots with a "." tag, so you don't miss the really rare one who is only spotted by one or two stations.  Full info and examples at the URL above.

I do not assume that this is the last word on improving RBN spot quality.  Beta means beta.  Please experiment, see what you think, and let me know.  One particularly fruitful line of inquiry would be to compare the arrival time of unfiltered spots and spots that have been judged Valid, to note instances when an apparently legitimate spot doesn't get through or is judged to be a bust, or when a bust is not caught. 

In this connection, in testing we have noticed that sometimes a Busted call will be mistakenly judged Valid, because there are more busts than good spots in a time window.  Often, this seems to be due to spacing errors (RN4ZR for N4ZR), frequent omission of portable designators by ops (N4ZR instead of P5/N4ZR), and PTT cutting off the first dit (E4ZR for N4ZR)  

Please send your comments/reports to me, and I'll see to their onward distribution.  Do not send them to this reflector!


73, Pete N4ZR

6 Meters and the Power of the Reverse Beacon Network

by Paul Carreiro, N6EV

The Reverse Beacon Network has evolved to become a powerful tool with quite a few Amateur Radio applications, mostly on the HF bands.  Antenna comparisons; spotting contest and DX stations; checking to see where your transmission is being heard; and seeing which bands might be open to particular parts of the world at any given time are just a few examples of the RBN’s usefulness.  The RBN also provides a very unique opportunity for real time propagation awareness on VHF, and in particular on 6 meters.

“The Magic Band”

6 meters is known as the ‘Magic Band’.  It got this nickname in part because of the wide range and transitory nature of its propagation modes. F2, Sporadic-E, Transequatorial, Tropospheric, Back Scatter, and Meteor Scatter are all propagation modes regularly observed on the band, often at the same time or in combination!  The power of RBN’s ever-listening ear, combined with the existing constellation of active beacon stations, enables an awareness of 6 meter band conditions unheard of before now.    

In the case of sporadic-E, the added path information helps more than just those operators geographically close to the RBN node and spotted station.  The center of a sporadic-E path is generally where the ‘E Cloud’ resides.  As a result, operators around the spotted path are alerted to probable centers of sporadic-E ‘cloud' activity.  This allows them to anticipate additional paths that share the common 'cloud' center; or even connect multiple ‘cloud’ centers into multi-hop paths.

RBN and 6 Meters in Action

Here are a couple of excellent examples of 6 meter propagation as shown on the 6 meter maps at dxmaps.com.  Often, RBN spots (green callsign paths on the map), particularly of beacons, are some of the first to show up, indicating the start of a sporadic-E opening.

Note how the intersection of the paths clearly locates the sporadic-E cloud area.  Dxmaps.com also offers a real time EMUF map view showing the upper cutoff frequencies for each sporadic-E center of activity.

Of course, it works in Europe too.

The Reverse Beacon Network coupled with DXMaps.com equals fantastic real time 6 meter propagation awareness!

Unique Issues for 6 Meter RBN Nodes

You’ll note in the maps above that some of the spots in both Europe and the U.S. were derived from active beacons.  In order to spot beacon stations on the band, Skimmer must be configured to pass all callsigns, not just CQing stations.  However, disabling this filter opens up the possibility of Skimmer falsely spotting a callsign it decodes from digital spurs created by consumer electronics that seem to be prevalent on 6 meters.  The callsigns of these false spots often contain lots of dits (e.g. EI5I, ES5I, EE5E).  

 A situation can also arise where Skimmer decodes not only the callsign of the station being heard, but also of the unheard station being worked.  This is the result of the heard station sending the unheard station’s callsign repeatedly in an exchange.  This is common on HF too, but would be considered a particularly unhelpful false spot on 6 meters as the propagation path between the RBN node and the unheard station does not exist.

The steps to help eliminate false spots for a 6 meter RBN node are relatively simple.

1.    Turn ON Skimmer’s Aggressive Call Validation – this forces Skimmer to decode the callsign more times in a row before it is announced.  It also puts a higher weighting to callsigns in the Watch List (see next item)

2.    Populate the Skimmer Watch List with a list of callsigns of known beacons and other stations heard on the band operating CW.  With aggressive call validation active, any call in the Watch List will be validated more quickly.  A good source for this is the current World Wide 6 Meter Beacon List maintained by G3USF, stripped of all the text except the callsigns.  In addition to beacon calls, you can add the calls of CW ops worked or spotted from your location.  This way subsequent spots are validated quicker.  The Watch List can be managed easily as an external text file with a text editor.  Include comment text to help organize the list into sections.  Cut and paste into Skimmer when updated.

3.    In Aggregator, under the Spot Filters tab:

     a.    Enable the filter to eliminate callsigns that look like grid squares.  Many beacons send grid squares identifiers which are occasionally misinterpreted by Skimmer as callsigns.

     b.    Enable the filter to not send VHF+ callsigns with 1dB SNR or less.  Many of the digital spurs on the band are close to the noise floor.   Typical false spots with lots of dits show up with 1dB SNR
.
     c.    If you have known digital spurs that repeatedly are the source of falls spots you can populate those frequencies in the bad frequency list and click the appropriate filter to not spot those frequencies.

     d.    If you have persistent false spots from partial callsigns, or incorrect beacon call signs (usually from poor automatic beacon CW spacing), you can add those bad callsigns to the bad callsign list and click the appropriate filter to eliminate them.

4.    Monitor the 6 meter spots from your RBN node on a regular basis.  Look for false spots and analyze if any adjustment in filtering is necessary.  You can also collect additional spotted callsigns to include in your Watch List.

5.    Update the beacon callsigns in your Watch List to represent exactly what is spotted and/or sent over the air.  Many beacons send a call suffix of /B not represented in the G3USF list.

6.    Keep your Skimmer and Aggregator software up to date.   Features, filters and algorithms are improved and added from time to time.

Performing these few steps will eliminate most of the false spots typically reported by new RBN nodes on 6 meters.

6 Meters Needs Your Help!

We need additional 6 meter RBN nodes in North America!  Europe currently has much better RBN node coverage on the band and as a result enjoys very good early warning of 6 meter openings.  At the moment a handful of full time and part time nodes are in operation in the continental U.S.  We could really use additional coverage in the Mid-west, Gulf, Plains and Western states (is that all?!).  The more diverse and plentiful the nodes are the better.  It’s summer time.  And that means sporadic-E season is upon us.  Activity on 6 meters is hot.  So now is the time to set up a 6 meter RBN node!  If you have a QS1R coupled with Skimmer Server, consider giving up one of the lower frequency bands in favor of 6 meters from mid-May through August (sporadic-E season) each year.  Softrock offers a single band VHF SDR kit at a reasonable price, making it a good choice for a full time 6 meter RBN node.

6 Meters for the Uninitiated

For those not familiar with the 6 meter band layout, CW activity can be found between 50.000 and 50.126 MHz.  International beacons are found between 50.000 and 50.060.  The U.S. beacon band runs from 50.060 to 50.080.  Point-to-point CW QSOs are found between 50.080 and 50.100.  The DX window, which includes CW activity, runs between 50.100 and 50.125.  50.125 is the U.S. SSB calling frequency.  Some CW ops often call CQ on the SSB calling frequency (an accepted practice) to drum up activity when there aren't many signals on the band.  

In Skimmer, configure the 6 meter CW band limits between 50.000 and 50.127 without any beacon band annotation.  Depending on available bandwidth, your 6 meter RBN should concentrate on 50.059 to 50.127 (in the U.S.), and if you have the available bandwidth, run Skimmer between 50.000 and 50.127. Note: Even if you can run 192-KHz bandwidth, the default Skimsrv.ini file has the 6m CWSegment set to 50.0-50.1 MHz.  You'll need to edit that line to 50000000-50130000 before Skimmer Server will decode above 50.1 MHz.

Antennas for a 6 meter RBN node don’t need to be elaborate.  Even though the vast majority of weak signal work (CW/SSB) on 6 meters is done with horizontal polarization, a vertical works well for skimming and has the advantage of the omnidirectional pattern.  I’ve used a simple Cushcraft Ringo Ranger for my 6 meter RBN node the past three years with great success.  A halo for omnidirectional horizontal polarization is commercially available and is also easy to build.  If you don’t have a 6 meter-specific antenna, the use of a preamp is advisable.

Contact me, the RBN team or Mark, N2QT, who also operates a full time 6 meter node, if you need help setting one up.

73 – Paul,  N6EV