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The Amateur Amateur: Any-Bounce

12/21/2009

Gary Hoffman, KB0H
Contributing Editor

"Other than the ionosphere, have you ever deliberately bounced your signal off of something in order to improve your propagation?" That was the question asked during one of our recent ARES nets.

I was surprised that most of the net participants responded "No." Since there were so few "Yes" replies, the net controller went ahead and asked what the respondent had used to reflect his signal. I will tell you the answers later.

We all know about the ionosphere, of course, as it was a significant feature in our license exams. We learned about the MUF (Maximum Usable Frequency), the D, E, F1 and F2 layers, gray-line propagation and all manner of technical atmospheric stuff. Some of us have to reduce all that to cartoon images so that we can understand it. My own take is that there is a demi-god up in the sky named Iono. Like most of us, he's awake during the day and asleep at night. When he's awake, he's hungry, and his favorite dish is your HF radio signal.

Walking on the Moon

My own early HF experiments consisted of a lot of snack food for Iono. Those few crumbs that escaped him went, well, I don't know where they went. At the time I was trying to reach my brother Chris, K1KC, in Atlanta; I live in St Louis, Missouri. Those of you who do a lot of DXing will realize right away that my vertically polarized signals went right over my brother's head and likely wound up somewhere in the Caribbean. So my first attempts at bouncing a signal weren't particularly fruitful.

I haven't tried DXing since then, though I occasionally do hear distant stations. I use the HF bands, but mainly to send and receive signals locally. That's another kind of bounce called NVIS (Near Vertical Incident Skywave). The signals more-or-less go straight up and bounce right back down (assuming that Iono doesn't get them). It's a very handy technique for getting signals over hills and such, so it is a favorite of ARES groups.

None of the participants during that ARES net appeared to have done moonbounce or meteor scatter. Of course, neither had I. While those techniques seem like really cool ways to propagate signals, I would have to categorize them as "esoteric" (translation: not for everyone). Don't get me wrong, I would really like to try moonbounce someday, but it would take an awfully long time to acquire the technical knowledge -- and necessary funds. By and large, that puts the date that I'd be ready to give it a try somewhere beyond the end of my life span. Sigh.

The Gateway Arch

Going back to the ARES net again, one of the participants had a rather interesting -- though not terribly surprising -- answer. At least, it wasn't particularly surprising if you lived in St Louis. This fellow, who worked downtown, had carried on an extended conversation on 2 meter simplex with someone who was in his vehicle and driving south. The reason they were able to communicate for a long period of time was that they were bouncing their signals off of the Gateway Arch.

The Gateway Arch is a 630 foot tall stainless steel structure that sits at the edge of the Mississippi River. It can be seen from many places around St Louis County. And it makes a dandy RF reflector.

And it's not just hams that do so. A number of local television stations use the Arch as a "passive repeater" when beaming microwave signals from their remote vans back to their studios.

I may have bounced my own signals off of the Arch, though I haven't done so deliberately.

I can't quite see the Arch from my home in Florissant, which is a suburb of St Louis. But I do know that there are spots in Florissant from which the Arch can be seen quite clearly. I've mentioned in the past that I live on the north face of a hill, and that most of St Louis County lies to the south of me. Even with a tall mast that allows my antenna to just barely peek over the hill, I have a difficult time reaching stations to the south of me via simplex. Yet for some reason, I'm able to reach many stations in south St Louis City, even though they are eclipsed by that blasted hill.

My best guess is that my transmissions are hitting the Arch and bouncing back into the south part of the City. If anything is reflecting my signals, the Arch is the best candidate. You just can't beat that stainless steel.

The Spirit of St Louis?

Yes, I was one of the net participants who said that I'd used something other than the ionosphere to deliberately bounce a signal and improve my propagation. But no, it wasn't the Gateway Arch. Here's the story:

Back when my wife Nancy and I first got our licenses, we used both handheld and mobile transceivers to communicate. Mostly we did so during the evening commute home from work. In those days, we had very cheap glass-mount antennas on our cars.

Propagation from our cars was awful. Even over level terrain, it seemed like we couldn't communicate much beyond 1 mile. As you might have guessed, the problem was the glass-mount antennas. We've since made a number of improvements and our mobile communications have improved dramatically, but I wanted you to understand how things were when I tried my little experimental bounce.

One afternoon I was at home, waiting for Nancy. I knew that she was probably on the road and I thought I'd try contacting her. I didn't have a roof-mounted antenna in those days, so all I could do was stand in our back yard and try to reach her using my handheld transceiver. It was a long shot at best.

But surprise-surprise, Nancy did hear me, at least marginally. And likewise, I could hear her, but just barely. I cursed our rotten antennas and looked around to see if there was a ladder nearby -- or anything else that might give me a little altitude.

I didn't see anything that I could climb, but I did spot a commercial airliner that had just taken off from the airport.

The word "bounce" popped into my head. And so, just on a whim, I tilted my hand held transceiver back until it was perpendicular to the airliner. I keyed up and called Nancy again.

She responded and said that I was coming in much better. I could hear her much clearer as well. There was a certain pulsing to our signals (Motorboating? Picket-fencing?), but we were able to converse just fine.

Naturally, that lasted only until the airliner passed out of sight, but it was such a neat feeling that I had figured out that I could bounce a signal off of that airplane. It was a real Eureka! moment.

There was one more person on the ARES net that night that had a signal-bounce story to tell. He said that he'd once bounced a signal off of a fellow ham's wheelchair. He didn't elaborate, and the net controller was afraid to ask. But it does show that hams can be quite innovative when it comes to propagating their signals.

Editor's note: ARRL member Gary Hoffman, KB0H, lives in Florissant, Missouri. He's been a ham since 1995. Hoffman says his column's name -- "The Amateur Amateur" -- suggests the explorations of a rank amateur, not those of an experienced or knowledgeable ham. His wife, Nancy, is N0NJ. Hoffman has a ham-related Web page. Readers are invited to contact the author via e-mail.



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