Sunday, June 3, 2018

For Radio Amateurs Who Drop By

Of course I talk about ham radio, but not much and not often.  The index at the bottom of the right column shows 53 posts before this one with the label "radio". 

Ham radio has been described as "a thousand hobbies with one name" and that's pretty much right on.  There are probably a thousand things to emphasize depending on your interest, from the emergency/SHTF/Tactical radio that is blogged about the most in the places I see, to building your own gear, to uncountable number of technical aspects of the hobby, to experimenting with different modes like Slow Scan TV, fast scan TV, to, well, far too many to mention. 

I've always been oriented to the techy side (surprise?), building gear, writing software, semi-automating my station and so on, with an emphasis on testing the limits of the station.  It's pretty common for someone seeing a ham's station for the first time to say, "how far can you talk with that?".  I've always been interested in testing just how far I can, and always pushing those limits. 

Probably the thing I find the most interesting in radio is propagation - how the signal gets from one station to the other - and especially the ionospheric propagation.  This can turn into multiple pages itself, but the ionosphere is a layer of the atmosphere where the molecules present in the lower atmosphere are ionized by incoming solar radiation, and the air is so rarefied that it takes long times for ions to bump into something that makes them neutral again.  ("Do you think you're ionized?" "Yes, I'm positive") .  The ionosphere, in turn, is characterized as having several layers, with each layer's name changing with height.  The lowest, densest layer is called the D layer, and as we look farther vertically, they go through the E and F layers.  During periods of high ionization the F layer can further stratify into F1 and higher F2 layers.  The ionosphere expands and contracts, getting taller or shorter with incoming solar energy.

In general, the higher layers are active when the sun is overhead, but even then are dependent on the solar energy output which varies day by day, with the solar cycle, with (possible) grand cycles of solar activities and so on.  Generally, the type of propagation that gets hams excited is from the F2 layer, for a simple reason: it's the highest layer, so signals "reflect" from farther up and can go farther around the world. 

There are other types of propagation but tonight I want to talk about one that has been doing phenomenally well lately, called Sporadic E.  Sporadic E has been known for a long time, but "sporadic" in the name is an indication of the toughness of predicting when it will occur.  We know that it's caused by fleeting clouds of sufficient density in the E layer, and that it tends to occur more at certain times of years than others (now in the northern hemisphere).  We know that it tends to form later in the day and linger into the evening; that is, you'd be more likely to find it at 3PM local than 3AM local.  Finally, we tend to observe it on higher frequency bands, especially 28 MHz and up; in the US, 28, and 50 MHz, although it happens on occasion on the 144 MHz band.  Hams have long said that sporadic E clouds form above the tops of thunderstorms - long before mechanisms that could extend the charge into the ionosphere, such as red sprites or dark lightning were discovered. 

The last week or so has brought levels of sporadic E propagation that I've never seen before.  There are websites where hams report other stations they've heard or contacted ("worked"); the one I've been using for years is DXMaps.  This is a screen capture from a few minutes ago; around 7:30 PM EDT, 2330 UTC in the UK and earlier in the morning as one goes farther east into Europe. 
The density of reported paths is so high it's hard to make sense of it, but I call your attention to the long arcs from US into Europe.  In some of those countries it's past midnight, yet they continue to hear and work each other across the continent and across into the US. 

I don't have any real numbers on how this compares to other times in the past, but I've heard and worked more Europeans in the last five days than at any time before. 

What's going on?  We're supposed to be in a solar minimum that's going to impair propagation and make things worse.  A closer look at the DXMaps website shows a list view of reported contacts.  About 2/3 of them are using a rather new digital mode called FT8.  All of my recent contacts with Europe have been using that.  FT8, part of package of advanced digital modes from Princeton University physicist Joe Taylor, burst on the scene last year, and has become the "new hotness" of ham radio modes.  All of the modes in Joe Taylor's software package are run by connecting the radio's audio input and output to your computer, letting the sound card digitize the audio and pipe the samples to the software for processing.  FT8's strength is that it embeds robust error correction and signal processing to allow copying weak signals easy.  Considering it's an offshoot of another program of Joe's designed to help operate moonbounce, usually very weak signals, that makes sense.  Moonbounce or EME (Earth-Moon-Earth) is reflecting VHF/UHF or microwave signals off the moon to allow any two spots on Earth to communicate (if they can both see the moon). 

Clublog, an online service to help hams get confirmations from those stations they've contacted, charts the growth of FT8 vs the most popular modes in log submissions during 2017.  The kicker is that FT8 was barely introduced until about midway through the year.  I had my first few contacts with FT8 last July, when it was still beta software. 

The last digital mode to take ham radio by storm was another "sound card mode", PSK31.  By contrast, PSK31 is a conversational mode (hams call that "rag chewing") with freeform contacts.  Type as much as you want and the other guy will receive - or not.  FT8 is much more structured so more of a contest/fast contact mode.  Each side transmits for 15 seconds alternating with the other station.  When things are working well, a contact can be completed in one minute.  If the messages aren't decoded properly, that can stretch out, but no transmission is longer than that 15 seconds (a small number of characters). 

I know some number of hams drop by and read this.  If you're interested in 6m Sporadic E, get that radio on.  If you haven't worked FT8, it's a bit complex to get started with, but if you can run PSK31 you have all the hardware you need.  Sound card to radio. 


  1. I should probably put up something for 6 Meters. I've had antennas for 6 before, but only got in on one really good band opening, and it was amazing. A friend loaned me an Antenna Specialists 1/4-over-5/8 vertical, and with my FT-847 and 50 Watts, I was getting "30 Over" reports from the East Coast.

    I have FLDigi and WSJT-X on this laptop. I installed them a few weeks ago when I hooked up my my SignaLink USB to my Elecraft K2. Made a couple of QSO's to verify they work together properly.

    If you're on 20 Meters during the week, look for NI6BB doing digital stuff. My replacement as Station Manager there is huge on digital stuff.

  2. 36-year ham operator here, RF engineer for a living, so yes, I love the technical stuff. I must have worked a dozen FT8 stations this afternoon on 10 meters using what I assume was a Sporadic E opening. European and South American stations were booming in, and I was even able to work stations close by (<500 miles) in the states. Interesting stuff.

    Love the blog, SiGB. Radio, electronics, CNC, guns, politics, love your take on it all. Been reading you for years.

    1. Cool - good to know. I never bought that idea that RF engineering would go extinct as "the A/D gets attached to the antenna", (I mean, seriously, they have like a 35 dB NF) but it's a world of quiet at the former employer.

      Yeah, FT8 has gotten extremely popular on HF. I hear it all the time, all bands. Seems really popular on 30m. There will be not much activity below 10.120 in the CW portion, or up in the RTTY portion, but the FT8 segment is elbow to elbow.

  3. I'm waiting for a decent open source crypto radio to appear, which does local communications and telephone quality voice. Possibly one based on gigabytes of key material. Pick a byte offset into the key based on your transmitter's clock/calendar, and broadcast that offset in the clear at the beginning of the transmission. Then there's no back-and-forth like SSL which doesn't work many-to-one, and receiver clocks don't have to be synchronized much at all. The key generator could be a camera watching bubbles percolate up through spinning overlapping wheels in an aquarium.

    Governments everywhere ban technology of military utility, no matter what their dead-letter founding documents say. The shepherd does not approve of the sheep carrying guns, otherwise wool and mutton would be difficult to harvest.

    1. Well, the ethos of "open source" is that if you think someone ought to write something, you're probably that someone.

      I know very experienced engineers who turn pale and change the subject if digitally-encoded voice comes up.

      The key to that is getting a codec (coder/decoder) that's understandable and doesn't make everyone sound like Mr. Tudball. Most voice codecs are licensed products that you're not likely get without spending a fair amount of money. With FreeDV available now, maybe that's not an issue, but I sure don't know.

      This is as far from anything I've done as you can get in a box and still have it called a radio. So everything I'm saying here is "as far as I know" or "from what I hear".

      If you want to send a small number of messages to a group or one member of a group, any digital mode would work. FT8, PSK31, RTTY, anything. As would open, unencrypted voice. The coding is done with preset codes.

      Ever heard of numbers stations and one-time pads? One time pads are unbreakable codes.

    2. Make your own. Seed an open-source 256-bit AES generator algorithm with whatever one-time-pad you want. Use to encrypt your data Send it over a cheap Part 15 radio transmitter of whatever kind you want (WiFi, etc). Do the reverse at the receiver. Boom, not even the NSA can hack that.

  4. You may find this interesting or totally off topic. One evening, perhaps 8 pm in the winter, I drove to high point near a ski area in Anchorage Alaska. I was listening on the CB and talking too when I connected with someone in Southern California. Nothing special about my setup, out of the box cheap CB radio and a whip antenna on the rear bumper. Strange.

  5. Anon 1054A, by itself, that's cool but not really surprising because CB'ers work "skip" all the time. It used to be considered illegal by the FCC but that was long ago. Without knowing the year and solar cycle it's hard to know if that was F layer skip or E layer skip.

    CB is just a few hundred kHz below the bottom of the 10 meter ham band - they used to call CB 11 meters. (Meters in ham speak is a rough correspondence to the frequency.) When the sunspot cycles are in our favor, you can work anywhere in the world on 10meters. I used to consider Australia, New Zealand and the entire western pacific rim as easy targets for ham radio from Florida.

    I know Alaska is often cut off from the rest of the world by aurora activity, so it's kind of a special case. Maybe it's harder from Alaska than I'm thinking.

  6. During Cycle 19, my Ham friends in the Midwest were working Japan using 5 Watts on AM Phone on 10 Meters.

    When 10 (and 6) are "open", you can really get some good DX.

    1. There'll never be another Cycle 19 in our lifetime. This is probably as good as it's going to be for awhile.

    2. I think you're right. I've seen predictions that sunspot activity should pick up by about 2030 but others saying this minimum will last longer. I think that since nobody alive has ever seen the sun with this level of activity, and none of today's instrumentation quality was available even a century ago, it's not something predictable with any confidence.