Coping/TechnoPrepper’s Notebook: Solar Footlights

My big mission in Life today is to get you to spend $10 bucks at Amazon.

Before you rush off thinking “Oh my God, not another highly polished and monetized website,” rest assured it’s still UrbanSurvival.

But I have an interesting tale of aging, looking at data, and thinking that we’ve been doing in background that I don’t think we have ever really discussed.

I’m 67-years old. Elaine’s age is classified. But there are three or four risks of dying up at this end of the demographic spectrum that I’ve been paying a lot of attention to. Risk of dying from choking. Risk of serious injury from auto accident. Risk of falling down in the shower.

All manageable risks. Eating together, wearing the seat belt, doing the air bag recall, and having a non-skid low entry shower…you know the drill, right?

But this falling stuff? Well that awareness begin creeping into consciousness about couple of years back. A buddy of mine from down the road had come by on his freshly detailed Harley. We had a rum, or three, and got into some discussion about the bike and went outside to look at it.

Oh, it was dark. Can’t see a hand in front of your face dark.

And I completely misjudged the end of the deck. The railings were still one of those “gotta get to it” items on my massively long to-do list.

I went off the edge and while falling I remembered a number of details about how to fall safely…landed on my stomach, head only slightly turned. Six feet down, soft ground, wasn’t too bad, except that it knocked the air out of me and I was dizzy for a couple of minutes.

Lesson: All decks must have railings. Even if only a foot high. That’s plenty high to sprain an ankle when young or break a leg or hip when you “get up there.”

No surprise: The decks at the ranch now have railings around them. Miraculously they appeared shortly thereafter. Until I got them down, I cowered around the house edge of things even in full daylight.

That still didn’t fix the “dark stairs at night problem” for me, however. That went on my massively long to-do list, again.

Until last week.

Had a problem in our recording studio. The rear fill speaker main amp (Alesis RA-100 reference amp) decided to roach the power supply so I needed to crawl around on the floor behind the desk and rack looking for the problem.

So this is where I went to get a flashlight. And then I discovered a collection of half a dozen flashlights over in my office. Big ones, little ones, UV lights, MagLites…waterproof and aircraft lights? I had them all.

Wandering back to the house with an armload I asked the near-genius question “Hmmm…how did all these lights get to my office?” Because you idiot, you haven’t fixed the dark stair problem and you have almost killed yourself THERE TOO, remember?

Oh…yeah….got it.

So I decided to do something about it. I went shopping and found a Solar Powered Motion Sensor Light 12 LEDs Wall Light for Yard Garden Path 2-Pack $19.  I’m in…

Less than 10 bucks per light. I put them in and it took about 10-seconds per light. I didn’t use the small mounting screw that came with them. I went with an inch and a quarter coarse threat sheetrock screw because they have more grip (wider pitch of the threads) and they are slow to rust (which it they did would discolor sheetrock) and which I have used literally by the THOUSANDS around here.

The installation on the stairs gets full sun in the afternoons for several hours (west side of the house). The other one is on a south-facing deck so it gets almost a day’s worth.

The only problem (so far) is that either the cat or the raccoons are coming up the stairs about 3 AM and the light comes on for 30-seconds.

One of these days, I will do something about that:

TnP II: Antenna Tuner School

A right-thinking reader of ours asked me what kind of antenna tuner we use in our robust communications facility.

I decided that since antenna tuners are one of the most misunderstood items in ham radio, a little discussion is in order.

First point: I mainly use antenna tuners for three purposes. These are:

1. Getting and absurdly high voltage standing wave ratio down to something believable. A (V)SWR of 2:1 will lose about 11% of transmitter power. At 3:1 it’s up in the mid 30% range. Depends greatly on feedline length and coax cable quality.

2.But, despite the (wrong) assertion of some hams, this is not dissipated as additional heat in the final amplifier section of a transmitter. It’s more heat loss in the line and tuning components and such. These will cascade fail-back to the amplifier, though. Much better covered in the whole (and damn good) book on SWR and feedlines called Reflections II: Transmission Lines & Antennas.  (Don’t panic at the $114 price tag for a paperback copy…sometimes really knowledge costs something.)

3.I like to use an antenna tuner whenever I operate AM.

Some discussion on each of these points is warranted.

Starting with #1: An antenna SHOULD be matched fairly well to the feedline at its resonant frequency. This can be done using an RF transformer, such as a balun, or it can be done with a matching section of feedline or some other impedance tool like a tuner.

If an antenna is NOT resonant, then yes, an antenna tuner is ideal. Tapped coils work…but having done that in the rain….yeah, tech works!

I’m in the process of getting ready for two antenna projects this fall: A new OCF (off-center-fed) dipole and a 900 foot long wire.

The OCF MAY need a tuner to get close to useful on one band (15 meters where the design is not intrinsically resonant where the ,main bands 80-10 meters is close). And on the Texas Monster Long Wire project, I will use a tuner in order to transform the nominal 50-ohm impedance feedlines coming out of the ham shack to the 600-ohm Zepp Antenna-like open wire feedline in the plan. So much for Case #1.

Case #2 is a little different problem: Remember that high SWR (reflected power) MAY cause component heating. On modern radios, there is something called an SWR-foldback circuit designed to reduce power output of the radio so reflected power (back into the final amplifier area components) doesn’t “let the smoke out.”

That said, as a practical matter, if the antenna has an SWR of under 2.5 to 1, you are not likely to get into power fold-back.

And modern solid-state radios tend to have modest antenna tuners built-in. While they won’t go into 600-ohm end-fed Zepps and the like, they will do fine with a 3:1 SWR which you cut for use at the other end of the band.

This gets us to Case #3…and this harks back to my days in my teens when I was a real broadcast engineer before moving into news.

When you listen to an AM radio station, you can actually HEAR how good the antenna tuning is by listening on a high quality radio.

Some AM stations just don’t sound as LOUD as others, even when your Nems-Clarke field strength meter tells you they are very close in terms of millivolts per meter.

What’s going on it often a bad antenna phasor design or adjustment.

A phasor is the box (or series of boxes on multiple tower/directional AM) stations that provides for antenna tuning.

Let’s look into apparent loudness on two antennas. One will have an improperly designed or adjusted phasor, typically a Pi-section type. The other will have a T-type filter. (L type or T type, got it?)

For convenience, we will use an example at 1,000 KHz – smack in the middle of the AM dial.

Pause for a second right here: We know that AM stations impress audio on the RF carrier.

If you could whistle (or use your signal generator) to make a 5,000 cycle / 5KHz whistle, you will create sidebands from the central carrier frequency.

When you tune across the signal, with constant tone modulation we see a lower sideband at 995 KHz (1,000 KHz carrier-5KHz tone), then the carrier itself at 1,000 KHz, and last the upper sideband at 1,005 KHz which is the carrier PLUS the 5 KHz tone.

OK…so this has what to do with apparent loudness, assuming the station is modulated at 100%?

Well, if the phasor uses a high Q tuning circuit, or if the engineer habitually tunes to one side of carrier or the other consistently, then what happens is either the upper, or lower sideband can be reduced. Oh-oh…there’s our drop in apparent loudness. A minutely reduced high end on one sideband. But you would never notice until you tune and listen super critically.

This is oftentimes what differentiated the classic power-house rockers like KJR and KFRC and KHJ. They either had low Q (which means quality or “peakiness”) of their phasors, or they had engineers who understood how this phenomena works and used it to their advantage.

My friend Hank, a broadcast engineer in Hawaii (and elsewhere) has seen the same thing:

“Some personal experience:  The quest in my AM radio days was to get the AM common point (transmitter match point) to have a symmetrical impedance curve on each side of the carrier frequency.  Some old systems were terribly non-symmetrical, affecting one sideband more than the other, and sounded horrible!  There were designs that added a T-network to rotate the phase so the match point was symmetrical, and chosen to add as much power to the sidebands as possible for ‘loudness’.”

As a practical matter, it doesn’t matter a hill of beans on a wideband/low SWR antenna. But if you are in an emergency communications mode, the AM with wide bandwidth is NOT your friend. Don’t waste your time.

On 80 meters at night? Well in this circumstance a minor change in apparent loudness can be delivered so careful adjustment of a tuner might be something you could get interested in.

Or, not.

But since our reader was kind enough to ask, and since I wrote a good bit of the SGC SmarTuner manual years and years back (’97?), I do have some opinions about them.

For loading up ANYTHING? Any of the computer-controlled tuners/couplers are grand.

But will you get a good signal out on the air?

For that, my friend, there is nothing like big solid copper, a huge ground system (seawater is great, so are railroad tracks) and something that is resonant…with a tuner, or without.

Two other Antenna Notes:

Even if you are operating with a short feed line from your radio to the antenna, say 10-25 feet and a reasonable SWR then cheap coax is fine. Here, since both the beam and the wire antennas are about 130 foot runs, we use Times Cable LMR-400. Look at the difference in losses and you’ll see why.

Second point is on wire antennas, I always over-build. The OCF dipole antenna I will putting up will be using 19-strand #10 wire with insulation.

I run a little bit of power (two 3-500Zs is a little?). While conventional wisdom says #12 wire is fine, I have seen a dB or two from nearly identical antennas  (*shorter than quarterwave, 10 meters), one from #18 and one from #12 at the 100 watt power level. Bum wire? Maybe.

But think for a minute about the voltage and current nodes on an antenna. Ever work out the peak current at 1.5 kw? And remember, the actual “snapping out” of RF is at the axis crossing point which gets us into a long discussion of the physics. In addition to the OCF, I will likely be putting up an 80-meter dipole with (not kidding here) #6 wire.

I know what theory says, but sometimes there’s a little offset from real life experience on this stuff.  On receive, there is no difference.  On transmit, however, 7 strand 14 gauge will never give the power handling and superior bandwidth (lower effective q) as big wire like 19-strand 10.  Area counts for skin effect.

I’ve always want to have one of those crushing loud signals on the band: “California (or Texas) Kilowatts” they’re called. The FCC regs state PEP (peak envelope power). They don’t limit hams on ERP (effective radiated power) and if you’ve got the real estate….ahem….

Hell-built for stout, or rip it out.

Write when you get rich…

George@ure.net