Posts Tagged ‘FlexRadio’
Welcome to Episode #148 of Linux in the Ham Shack! In this installment, your hosts discuss Art Bell and the radio of kooks everywhere, free newsletters, Linux terminal utilities, FreeDV, FlexRadio, loggers and a whole bunch more. Thanks for listening, and enjoy all the information we cram in your earholes.
73 de The LHS Guys
I’ll be writing a lot in future postings about how FlexRadio’s new 6000 series transceiver technology has influenced my new station’s design. Today’s post will focus on these rigs’ ‘Slice Receiver’ capabilities.
First, however, allow me a digression on 21st Century Radio-Sport a/k/a “Contesting.” There are hundreds of radio-sport events spread across the calendar each year from state QSO (QSO = radio contact) parties to major global events such as the CQ World Wide DX Contests (CQ WW DX, ‘DX’ = long distance radio contact) held across two weekends – one for CW (Morse code) and one for Phone (Signal Sideband = voice) – in the northern hemisphere autumn. The smaller events have a friendly ‘small town’ vibe. On the other end of the scale, the big DX contests are hard fought struggles that test technology, skill and endurance (you try averaging two international contacts via morse code per minute for 48 hours straight!).
The big contests have a multitude of classes to parse the competitors. Single operator, multiple operators with one transmitter, multiple operators with multiple transmitters, high power, low power, really low power (also known as ‘QRP’), assisted and unassisted. You compete against others in your class in your country and in your class on a regional and global scale depending on your ambition.
I mentioned ‘assisted’ and ‘unassisted’ classes in the previous paragraph. This can mean various things but the major source of assistance during a contest is the so-called ‘cluster’, Internet resources that reports what stations are active and on what frequencies. These networks started in the ’80s with hams transmitting short reports of the distant stations they were hearing, generally on the HF (short wave) bands, via the amateur VHF digital networks which were generally local, within a city or region. These were know as ‘DX Packetclusters’ back then and I used to operate a node in Tiffany, Colorado in the ’90s.
These networks later migrated to the Internet, became interconnected and are now global in scope passing literally millions of ‘spots’ (as each report of a station and its frequency is called). DX Summit, based in Finland but with visitors from around the world, has reported over 23 million such spots since it launched in 1997!
One of the challenges of big data is finding actionable useful information shooting out of the digital firehose. The cluster networks go bonkers during the big contests with several spots per second streaming by. This is not always helpful. An operator can be overwhelmed by choice; which station do I try to contact? It’s like getting a restaurant menu with a thousand choices. And with spots being reported from all corners of the planet much of the data is not actionable. A station being heard in say Mongolia might not be making it to your shack in Peoria at that time of day on that particular frequency.
I will manage this onslaught of data by disconnecting from the Internet clusters and generating my own spots distilled from radio signals actually being detected at my station in real time. The data will thus become relevant and actionable. Many stations are already doing this to supplement the Internet spots that every assisted class station sees. K3LR and W3LPL, two giants of multi-operator contesting, are doing this effectively using CW Skimmer software written by Alex Shovkoplyas, VE3NEA. CW Skimmer uses ‘sensitive CW decoding algorithm based on the methods of Bayesian statistics’; in other words your computer listens for Morse code on your radio and tells you who is transmitting and on what frequency. CW Skimmer, of course, is not much use in Phone (voice) contests.
There are several challenges to using CW Skimmer effectively. The first challenge at most stations is receiver bandwidth. Most ham radios can only listen to relatively small segments of radio spectrum at any one time limiting the size of the net CW Skimmer can cast. If a particular contest has its competitors spread out over say 70-kHz and your radio can only monitor 2.8-kHz you are going to miss a lot of the action. So called SDRs (Software Defined Receivers) overcome this limitation and can look at much larger chunks of spectrum at once. An operator using one of these radios (older generation FlexRadios for example) can actually look at a visual spectral display showing where signals are and indicate their relative strength; a CW Skimmer software working with one of these radios can decode and report on the activity of dozens of stations with this set up.
That hurdle jumped, another one looms ahead. If you are monitoring stations on one band how do you know what’s happening on other bands? Most contests are spread across several of the amateur radio bands. Some bands are good during the day, some are good during the night and propagation on all the bands is always changing. Europe might be good in the morning on a particular band , say the 21-MHz (15m) band, Africa in midday and Japan in the afternoon. The general propagation trends are predictable but there are large daily variations in propagation that are not predictable (in other words, what signals are being refracted back to earth and where). Some stations (K3LR, for example) have separate SDRs for each amateur contest band. Other stations (W3LPL for one) uses the QS1R receiver which can listen to several bands at once.
The Flex 6000 series radios listen (via direct sampling, more on that in a future posting) to 77-MHz of spectrum at the same time. That is truly spectacular! With my multiple Flex-6700s (I have two on order and plan on ordering a third unit later in 2013) i will be able to assign ‘Slice’ receivers (each Flex-6700 can have up to eight of these, created in software and 384-kHz) to each amateur band from 1.8-MHz (160m) to 144-MHz (2m) and let them run all the time, during contests and in between. I will have live, actionable intel on what CW (Morse) signals are propagating to Glade Park, Colorado at any given time on all the amateur bands. I will be feeding this data out to the Reverse Beacon Network (RBN) and using it for my own contesting and day-to-day DXing operation. (More on the RBN in a future Blog posting.)
How I plan to keep transmissions on one frequency from overloading and possibly damaging receivers listening – and running CW Skimmer software – on other frequencies on co-located (and sometimes the same) antenna will be covered in a future posting. The Flex 6000 series radios are full-duplex (in other words, they can transmit and receive at the same time) so the listening on the same band I’m transmitting on becomes a possibility but one with significant challenges.
I should point out here that many hams operate without any kind of assistance in contests whatsoever. These are some of the world’s most skilled and motivated amateur radio operators and I admire this type of contesting. However, my personal current motivation is to see where I can go with technology in contesting and amateur radio in general. Assisted, in so many words, but seeking innovation.