Saturday, November 17, 2018

Radio Ops From DN70

The Silicon Graybeard had quite a good post about solar activity and some new theories of predicting future solar activity. While his post concerned a new "Maunder Minimum", and it's effects on the weather, I found it interesting in a different way. We're both interested in the subject because of our mutual interest in Amateur Radio. Hams rely on the Propagation of radio signals to talk to each other. The radio waves from the transmitter travel to the Ionosphere, where they reflect back to Earth, usually 800~1500 miles from where they started. Think of the Ionosphere as being a big Radio Mirror In The Sky, and you'll be pretty close. There are actually several layers of the Ionosphere ( the D, E, and F layers) that reflect radio signals, but we'll just lump them all together for simplicity.

But what "polishes" the reflector? What makes these layers capable of reflecting electromagnetic energy of certain wavelengths? Without going into the Physics of what happens, the answer is charged particles, which is the "Ion" part of "Ionosphere".

And where do these charged particles come from? Well, some come from Deep Space, but the great majority come from our own Sun, and the amount is highly variable depending on where we are in the roughly 11-year Solar Cycle (graphic below from Wikipedia).



The largest spike on the chart represents "Cycle 19", a real whopper, which gave us basically 24-hour propagation below 30MHz to almost anywhere in the world. I wasn't involved with radio at the age I was when Cycle 19 happened, but the Old Timers who taught me the code and Theory for my Novice test had tales that today would sound far-fetched. "Arm Chair Copy" between Chicago and Tokyo with 5 Watts to a dipole on 30 MHz was common, and the few guys who were active on 50MHz told us it was almost as good.

In short, when the Sun is in a "Quiet Period", it doesn't produce the flood of charged particles that it does when it's active. No, or few, charged particles to polish up the old Ionosphere, and radio Propagation takes a big fade.

In the time I've been a Ham, I've seen several cycles come and go, and closely followed the predictions about what the upcoming cycle would be. And I've learned to take most "predictions" with a grain of salt. There are so many models and methods used to generate the predictions that all they demonstrate is that nobody really understands the process....yet. The new method in SiG's post is based on taking the "waveform" produced by the recorded observations, and applying Digital Signal Processing techniques to the data. Since the "waveform" of Solar data is definitely periodic in nature, this treating of historic periodic recorded data as a waveform, and using DSP techniques on it, is definitely new to me. Processing a waveform with DSP like this can reveal many things not evident 'by inspection'. DSP is used to literally "Pull signals out of the noise", and you can recover data buried in the noise by many dB, and get useful information from it.

Perhaps it will lead to a better understanding of the Solar Cycle, with better predictions than we have now.


Fast forward to 2018, and a Little Guy Ham station in Northern Colorado.....

One thing I immediately noticed when I first put up an antenna here was how low the background noise level was compared to Long Beach. In Long Beach, my signal strength meter would read about half-scale, a "7" to a "9", with noise. Power line noise, "wall wart" noise, noise from WiFi routers, cheep TV sets, and a multitude of other noise generators. Here in Northern Colorado, with buried power lines and a distinct lack of large industrial facilities, the meter reads about "1", or maybe "2" on noisy days. This means that I'm a LOT more aware of weak signals that were formerly hidden in the noise.

And with reduced solar activity, we have weaker signals to work with. Not much you can do short of putting up a bigger antenna to capture more signal, or make what ever antenna you have more efficient.

Since I like verticals (yeah, I know..they radiate equally poor in all directions), that means optimizing my installation. The 33' vertical I had up for a while really did work "poorly" because I only had 4 ground radials laying on the ground. To be even minimally "optimized", I would have needed something like 64 of them, and that ain't gonna happen!

It was a noisy antenna, and didn't radiate as well as my BuddiPole. When I set this iteration of the BuddiPole up last weekend, it was 90% of what I wanted; The feed point was about 6' above ground, and both radials were also 6' above ground. This isolates the radials from ground-effects, like soil conductivity and dielectric constant, and gets them close to being in the theoretical Free Space environment. The only things I would improve on is getting it up a bit higher, and adding a couple of more radials, even though everything I've read indicates two is fine.

And it's a much quieter antenna compared to the ground-mounted vertical. This leads me to believe that the 33' vertical would work very well if I had it and the radials 8' in the air, very similar to how I had it installed in Long Beach.

Now I just have to figure out what to use, and get it planted.

11 comments:

  1. Will the lesser noise environment allow you to keep some of the equipment you were talking about getting rid of after your wife nixed a triangle cross-section antenna tower?

    I hope so. Your skills will be very useful in times of a blizzard or other not-good period of time.

    You do have a decent generator or backup power system, right?

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    1. A low background noise level is good *always*.

      The Tower and Antenna Project was going to be my "last grand project", and the main reason I was holding on to certain equipment.

      Since that's most likely a dead project, I'm not sure what I'll do with that stuff.

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    2. And yes, I have a Honda EU2000i generator, a pair of 100 Watt solar panels, a charge controller, and a couple of 100AHr deep cycle "yellow top" Optima batteries. I can pretty much stay on-the-air indefinitely.

      Delete
  2. Around 1959 in Northwest Colorado a kid two years ahead of me in high school communicated daily, by Morse code, with someone in France. Always amazed me. His equipment was bits and pieces he had assembled.

    I had access to a shop and welded up some shelving for his equipment.

    ReplyDelete
    Replies
    1. That would have been during the Great Cycle 19, but even when the sunspots are sparse, Morse code contacts to EU from CO are quite doable.

      My high school buddies were also amazed that I could turn on the radio, hear somebody on the other side of the country, and then "just talk to him".

      Delete
  3. That was a fascinating post and I don't know why but it's inspired me to make a Tesla Coil(!). Also, it reminds me of our old battle, the War on Weather.

    Seems the Sun's against global warming and about to kick off an ice age. Wrap up warm!

    ReplyDelete
    Replies
    1. I built a Tesla coil back in high-school. It was about 6' tall, and I could get 30"~36" discharges from it.

      I "unbuilt" a few months later after it arced into the phone lines, and popped the circuit protectors, mandating a service call from Ma Bell, and the attending bill.....

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  4. This was interesting, even though I know diddlysquat.

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    1. I've been interested in this stuff since I was 10 years old.

      Guess a lot of it stuck with me....

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  5. Good luck, waiting for the pictures! :-)

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    Replies
    1. I should make a banner....."Coming Spring 2019!!".

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Keep it civil, please....