K3PA Reporting from Kansas

Here's another variation on the equipment used by some of the most prolific RBN nodes, from Drew, K3PA:

"As the tradeoff between low band overload and high band sensitivity is so often noted, here is the approach I took.  I wanted to spot 10 bands (incl 6M), and so needed two QS1R units in any case.  I use a 18 foot vertical with a unity gain buffer (a YCCC RX circle amp) for 160 through 15m on the -1 node.  It has reduced sensitivity on 15M and up, due to the antenna design AND the buffer, AND the QS1R.


So, to spot 15/12/10/6, I have a separate antenna, an omni horizontal, basically a clone of a multiband "spider", which we used to call a "squalo" on 6M.  That antenna has a low noise figure, high intercept 16 dB gain preamp on it.  (Homebrew MOSFET type)  It generally hears better than the vertical on those bands.  I let both skim 15M with separate IDs as either can be better on 15.


As a benefit, I believe I have the only 6M node in the central US area.  I'd like to get it a little higher and away from household spurs but it does OK.


Jeff, AC0C is in my immediate geographical area also, and he has a more complicated setup leveraging his main TX antennas as well as an 8 circle and a vertical.  He also skims RTTY.  But no 6 meters there.  His node hears extraordinarily well on 160.  (Ask the east coast guys.)  Similar to me on other CW bands."  

I hope you're finding this series interesting and perhaps even inspiring.  Europe's next. 

73, Pete N4ZR

W3LPL's Solution by Frank Donovan, W3LPL

Somewhat in the same vein as my last post, about WZ7I's RBN node, here is W3LPL's setup, in his own words (warning, this post may trigger severe aluminum-envy):

I use an extremely complex system of nearly two dozen large antennas

feeding a nine port combiner that then feeds a single QS1R.

The secret to the combiner design is my W3LPL band pass filters (Google it). 

Unlike many filters, my band pass filters have approximately 50 ohm

impedance in-band and are high impedance out of band. This characteristic

allows the output side of up to five filters to be connected together to

form a frequency selective signal combiner.

I built a low band combiner and a high band combiner that capitalizes

on this band pass filter characteristic:

     - a 160, 80, 40 and 30 meter combiner, and

     - a 20, 17, 15, 12, and 10 meter combiner.  

The two combiners feed a 3 dB splitter -- operating as a passive combiner --

which then feeds the QS1R input.

A Clifton Labs preamp in front of each of the 17, 15, 12 and 10 meter filters

optimizes QS1R sensitivity on those bands.  Additional bandpass filters at the

inputs of each of the 17, 15, 12 and 10 meter preamps protects them from overload.

This arrangement results in an excellent nine input signal combiner with

one output feeding a single QS1R.

Treating each band independently (they are highly isolated from each

other), these antennas feed each of the nine combiner inputs:

160 meters:  any combination of receiving antennas manually selected

by a K9AY switch feeds the combiner.  The most frequently used receiving

antenna is a 160 meter  W8JI/W5ZN/N4HY eight circle array pointed NE.

80 meters:  any combination of receiving antennas manually selected

by a K9AY switch feeds the combiner.  The most frequently used receiving

antenna is an 80 meter W8JI/W5ZN/N4HY eight circle array pointed NE.

40 meters: two 3 element full size Yagis feed the combiner through a

matching transformer.  The most common configuration is a 3 element

Yagi 200 feet high pointed NE and a 3 element Yagi 100 feet high pointed

at 130 degrees azimuth.  When the 40 meter transmitter is transmitting

during contests, a relay switches the combiner input to any combination

of receiving antennas manually selected by a K9AY switch.  The most

frequently used receiving antenna is a 40 meter W8JI/W5ZN/N4HY

eight circle array pointed NE.

30 meters: a full size 3 element Yagi 120 feet high feeds the combiner,

typically pointed NE.

20 meters: three six element Yagis feed the combiner through a matching

transformer.  The most common configuration is a 200 foot high Yagi

pointed at 120 degrees and a pair of stacked Yagis pointed NE.  When

the 20 meter transmitter is transmitting during contests, a relay switches

the combiner input to a four square receiving antenna typically pointed NE.

17 meters: a 5 element Yagi 120 feet high feeds the combiner, typically

pointed NE.

15 meters: three seven element Yagis feed the combiner through a matching

transformer.   The most common configuration is a 200 foot high Yagi pointed

at 120 degrees and a pair of stacked Yagis pointed NE.  When the 15 meter

transmitter is transmitting during contests, a relay switches the combiner input

to a four square receiving antenna typically pointed NE.

12 meters: a 5 element Yagi 130 feet high feeds the combiner, typically

pointed NE.

10 meters: three eight element Yagis feed the combiner through a matching

transformer  The most common configuration is a 200 foot high Yagi pointed

east and a pair of stacked Yagis pointed south.  When the 10 meter transmitter

is transmitting during contests, a relay switches the combiner input to a

four square receiving antenna typically pointed south.

What It Takes by Wes Cosand, WZ7I

The following article was contributed by Wes, WZ7I, one of the longest-running RBN node-ops at 10 years and counting.  As you know if you follow such things, Wes is one of the most prolific spotters as well.  The number of spots and the SNRs his station produces are proof of how well it works. Here's how he does it:

Pete, N4ZR, emailed recently asking if I would describe the antennas and equipment that generate the data sent to the RBN.  I feel awkward doing this because I’m a biochemist, not an engineer, and I certainly am not presenting this as an optimal receiving station.  Rather I’m describing the current state of the jumbled mess that evolved in my basement.  If you promise not to laugh, here is a snapshot.

When I started contributing to the RBN  ten years ago my priority was to make it possible for the “rag-chewing” ham to know when his friends were on the air and to allow the casual DXer to find CW contacts.  I used a HyGain “HyTower Jr” wire-loaded vertical, the Clifton Labs 11dB Norton preamp, and when it became available, the QS1R and Skimmer Server.  The HyGain vertical with 32 radials worked pretty well on the wet ground in the woods and I was proud of how the neatly the equipment was laid out on my bench above.

But as the number of RBN nodes in the northeast US began to grow it seemed like just another contributing omnidirectional receiving station didn’t add much value.   It also bugged me that Dave, K1TTT, could hear stuff on his vertical that I couldn’t.  I had discovered that reading brought me more joy than operating so my transmitting antennas were sitting idle.    Over a period of years I began to use the transmitting antennas for skimming. 

I didn’t have much luck using power combiners to feed the input of the QS1R with multiple antennas.  I know other operators more skilled than I  have had marked success using this technique. I attempted to balance the noise from my HF beam with my “shorty forty” using attenuators and preamps but I never got it to work.  So when the Red Pitaya became available with two inputs I saw that as a marked advantage.  I’ve still had to be cautious because in my hands the isolation between the inputs is not great.  Perhaps I should limit my comment to say I often destroyed the sensitivity of the RP when I attempted to combine antennas. 

Here is a diagram of the three antennas I’m currently using to generate the HF spots on the RBN:

The QS1R and the low band CW / RTTY Red Pitaya each have a PC dedicated to them running the following software

·         Skimmer Server

·         CWSL

·         RTTY Skimmer

·         CWSL_SSBWave (or HDSDR)

·         Virtual Audio Cable

·         RCKskimmer for PSK31/63

·         WSJT-X for FT4

·         Dimension 4 for timing

The FT8 Red Pitayas have Pavel Demin’s FT8 receiver / decoder and the “upload-to-RBN” software from  Björn, SM7IUN.  I find this solution robust and quite sensitive. 

In the earliest days of RTTY skimming I embarrassed myself with RTTY spots that were off-frequency so now the frequency of the  QS1R is disciplined by a GPS unit from Leo Bodnar.

The Sommer antenna is 30 years old and may have faulty components now.  Its performance has always been better on 20 meters than 17, 15, 12 and 10 because on 20 it has a five element closely-spaced log periodic covering the band.

Six meter skimming has been a source of frustration to me because I have no experience operating on the band.  After multiple failures I have a system that has been stable for a couple weeks … chuckle.  I have a stack of two PAR electronics OA-50 dipoles mounted on the side of the tower feeding a tower-mounted ARR P50VDG preamp through an Alpha-Delta surge protector.  About 170 feet of Davis Bury-Flex runs to the basement where it goes through an additional surge protector.  The 12 volts for the preamp runs up the tower in old RG-213 with the shield well grounded at the top.  Currently I’m using a dedicated Red Pitaya and a copy of Skimmer Server set to “Aggressive” filtering.  In addition this computer has the CWSL / HDSDR / WSJT-X stack for FT8, FT4, and MSK144.  I would welcome anyone’s suggestions about how I might improve the sensitivity and, especially, the robustness of the system.

After watching the sensitivity of FT8 I am intrigued. I would like to try operating the mode and if I ever get my HF transceiver back from the repair shop I’m planning to turn off the skimming system during the weekdays and get on the air, at least for a time.  But I plan to be back on the RBN during major contests.

CQWW CW scores and Stats 2016-18

The following are thanks to Bob, N6TV, who provided all the detailed spot numbers to supplement my summary figures.

I thought you'd be interested in summary statistics from the last 3 CQWW CW contests:

2016 spots       2017 spots     2018 spots
6,065,160        7,007,314      8,388,796

Selecting only "CQ" and CW spots (no beacons), and only on the six contest bands 160-10m, the spot counts are a bit smaller, but the trend is the same:

6,033,385        6,971,208        8,341,035

More details follow, summarizing unique callsigns spotted, per continent and band.  This obviously includes many busted callsigns, but they don't affect the obvious trends.  "CO" is the Continent of the DX station (not the skimmer):

No real surprises: unique callsigns heard on 10m have dropped dramatically, while unique calls heard on 160m and 80m are way up.

      ----- Unique Callsigns Spotted (Contest Bands, CW Only) -----

                    Sat 2018-11-24 to Sun 2018-11-25

CO       160        80        40        20        15        10  Callsigns

-- --------- --------- --------- --------- --------- --------- ----------

AF        91       224       390       326       107        18        747

AS       358     1,276     2,053     1,860       614       139      4,211

EU     2,814     7,486     9,268     7,732     2,011       500     18,536

NA     1,368     3,536     6,080     5,360     1,264       260     10,695

OC        58       205       434       314       180        43        794

SA        61       181       506       409       227        71        979

-- --------- --------- --------- --------- --------- --------- ----------

 6     4,750    12,908    18,731    16,001     4,403     1,031     35,962

      ----- Unique Callsigns Spotted (Contest Bands, CW Only) -----

                    Sat 2017-11-25 to Sun 2017-11-26

CO       160        80        40        20        15        10  Callsigns

-- --------- --------- --------- --------- --------- --------- ----------

AF        51       181       382       315       150        31        736

AS       278       995     2,069     1,790       857       174      4,033

EU     2,472     6,456     8,252     7,282     2,888       582     16,884

NA     1,029     3,027     5,441     4,954     2,242       351      9,810

OC        39       160       395       366       241        68        830

SA        38       151       439       427       334       102        982

-- --------- --------- --------- --------- --------- --------- ----------

 6     3,907    10,970    16,978    15,134     6,712     1,308     33,275

      ----- Unique Callsigns Spotted (Contest Bands, CW Only) -----

                    Sat 2016-11-26 to Sun 2016-11-27

CO       160        80        40        20        15        10  Callsigns

-- --------- --------- --------- --------- --------- --------- ----------

AF        72       198       380       283       187        38        721

AS       336     1,034     1,810     1,580       941       192      3,859

EU     2,328     6,055     8,252     6,794     2,769       424     16,397

NA       942     2,854     5,805     4,992     2,407       629     10,242

OC        56       165       408       339       226        80        801

SA        37       135       433       450       340       133        992

-- --------- --------- --------- --------- --------- --------- ----------

 6     3,771    10,441    17,088    14,438     6,870     1,496     33,012

          ----- RBN Spot Counts (Contest Bands, CW Only) -----

                    Sat 2018-11-24 to Sun 2018-11-25

CO       160        80        40        20        15        10      Spots

-- --------- --------- --------- --------- --------- --------- ----------

AF    15,593    36,483    79,021    63,762    15,656       175    210,690

AS    24,030   128,898   261,471   226,674    44,441     1,320    686,834

EU   463,532 1,584,499 1,991,227 1,125,628    84,692     5,477  5,255,055

NA   101,063   334,043   780,059   578,128    54,580     1,475  1,849,348

OC     1,277    10,115    54,842    24,160    15,603       781    106,778

SA     7,842    25,550    91,598    59,816    46,874       650    232,330

-- --------- --------- --------- --------- --------- --------- ----------

     613,337 2,119,588 3,258,218 2,078,168   261,846     9,878  8,341,035

          ----- RBN Spot Counts (Contest Bands, CW Only) -----

                    Sat 2017-11-25 to Sun 2017-11-26

CO       160        80        40        20        15        10      Spots

-- --------- --------- --------- --------- --------- --------- ----------

AF     5,564    27,190    66,725    43,193    27,563       281    170,516

AS    13,572    79,866   208,233   192,258    71,311     2,122    567,362

EU   425,055 1,300,986 1,524,636   877,328   173,114     6,168  4,307,287

NA    61,374   267,777   586,855   481,603   147,872     2,912  1,548,393

OC     1,985     7,273    38,288    35,035    24,908     3,088    110,577

SA     5,367    19,258    87,759    73,867    75,820     5,002    267,073

-- --------- --------- --------- --------- --------- --------- ----------

     512,917 1,702,350 2,512,496 1,703,284   520,588    19,573  6,971,208

          ----- RBN Spot Counts (Contest Bands, CW Only) -----

                    Sat 2016-11-26 to Sun 2016-11-27

CO       160        80        40        20        15        10      Spots

-- --------- --------- --------- --------- --------- --------- ----------

AF     3,707    28,790    52,069    40,234    32,630       781    158,211

AS    19,534    87,860   185,402   181,616    86,490     3,132    564,034

EU   334,503   994,353 1,273,844   762,900   144,365     3,109  3,513,074

NA    41,966   193,588   501,163   489,021   164,511     9,749  1,399,998

OC     1,813     7,092    31,513    29,049    22,972     2,279     94,718

SA     6,657    21,670    81,711    99,800    80,176    13,336    303,350

-- --------- --------- --------- --------- --------- --------- ----------

     408,180 1,333,353 2,125,702 1,602,620   531,144    32,386  6,033,385

ContestSpots.awk by N6TV

2018-12-21 02:02:29 UTC

RBN Developments October 2017

Recently a friend suggested that FT8 was probably making a dent in
activity on the RBN and taking away from CW in general.  Out of
curiosity, I compared last week on the RBN (weekdays only, to avoid
contest activity) with the corresponding week in 2016, and was pleased
to see that the volume of RBN spots in 2017 was up about 8.4 percent
compared to the corresponding week in 2016.

Maybe growth would have been stronger if FT8 and WSPR had not been
introduced, but for a mature system near the bottom of the sunspot cycle
I think the continued upward trend is encouraging. The same week in 2016
was down 12.1 percent compared to 2015, which looks more like what I
would have expected this year.

I don't want to suggest that this is the last word.  I did not take into consideration 
the fact that the number of regularly-active RBN nodes increased year over
year during those two years.A much more accurate metric would to count the 
number of unique CQs reported by the RBN; I didn't do that.  Bottom line, though - 
the RBN is pretty healthy.

Looking ahead to the big DX contest weekends, Felipe made a change in
the data flow at our server this week to sharply reduce the number of
operations that need to take place after spots are received from RBN
nodes and before each individual spot is sent out. We are hopeful this
will improve the server's reliability and handling of large volumes of
spots, as well as reducing the delay in their being posted on retail
servers around the world.

Feedback would be appreciated. ARRL CW Sweepstakes will probably be the
first major test.

Beacons Revisited - a checklist

The recent initiative by the beacon folks at the NCDXF to spur competition among RBN nodes to copy all of the NCDXF beacons has prompted me to review our documentation of how to spot these beacons.  This checklist should help you set up your node to receive these beacons. You must do each listed step, or it will not work.

1.  Make sure your Skimmer or Skimmer Server is set up to cover the beacon frequencies. See this earlier blog post for the details.  Remember, you need to set both the frequency coverage and the CW decoding segments in order for Skimmer/Skimmer Server to do their thing.

2.  Create a watch.lst file containing the calls of all 18 beacons.  Details here.  Store it in the correct place.

3.  Set your Skimmer or Skimmer Server (on the Telnet tab) so that it does not send only CQ spots.

Once you have done these things, you're ready to spot the NCDXF beacons.  The Aggregator knows the callsigns, and will automatically append the NCDXF tag before sending the spot on to the RBN "mothership."

The RBN and the Solar Eclipse - Coming August 21

On August 21, 2017, from 1400 to 2200Z, operators of RBN nodes will have a unique opportunity to contribute to scientific understanding of the ionosphere.  That time-frame straddles the period when the solar eclipse will be visible across North America, and is also when the Solar Eclipse QSO Party will be run.


The RBN's unique contribution, in North America but also worldwide, is to provide as many data points as possible during the 1400-2200Z period.  In order to do this, two departures from our normal practice are needed:

1.  It is desirable for science to have much more frequent spots of stations active in the QSO Party than could be produced with the standard 10 minute respot interval. To this end, Alex has provided for adjustabilty in this respect in the current versions of CW Skimmer, CW Skimmer Server and RTTY Skimmer Server.  By adding a single line to the .ini file for your skimming software, you can adjust the respot interval anywhere from the original 10 minutes down to zero.  In the latter case, every repetition of a station's callsign will be reported (provided of course that the station includes CQ or TEST at least twice in each transmission).

2. The RBN archive is not the best source of the scientific data we hope to produce, because the timing is relatively imprecise (nearest minute).  So check your Skimmer computer for a file titled "spots.txt" , which will be found in C:\users\[your username]\Appdata\Roaming\Afreet\Products\Skimsrv.  The spots.txt file gives the time when a spot is actually made, to the nearest second. Regrettably, there is no comparable file in CW Skimmer. For Skimmer ops, your data are welcome too, even if still on a 10-minute scale - after all the eclipse period is hours long!


If you have been operating your node for a while, this file will be quite large - all that we need is 1400-2200Z on the 21st.  You can use a text editor to extract the part we need.  Look on the HamSci web site for the address to send your data to - it will be posted very soon now.

HamSCI is also looking for recordings of digital I/Q data from Skimmer receivers made during the duration of the Solar Eclipse QSO Party. This will allow HamSCI to replay and analyze recordings from specific receivers in greater depth following the contest. HamSCI will be publishing guides shortly on how this can be done with the QS1R or Red Pitaya and CW Skimmer Server, or with any SDR capable of sending data to CW Skimmer using its built-in recording function. Note that this will consume significant hard disk space - up to about 4GB per hour per band. The data will be accepted for upload after the contest.

If you're interested in putting your node to work on this project, you're still lacking one thing - the magic formula to put into your Skimsrv's ini file to generate more frequent, "granular" data.  Email me, and the secrets of the universe will be revealed.



I'm doing it this way because I want to have some reasonable confidence that people won't start using shorter interval settings with the RBN servers outside the eclipse period.  Even one Skimmer can make a big difference in this regard, and we will not hesitate to block anyone's spots from the RBN server if they violate this rule outside the eclipse period.

So c'mon - it'll be fun!