Oh-oh. Calendar says it’s time to study up for another doctor’s appointment. No, not the eyes this time. This is the regular blood draw and chat with my doctor. Yep, the one who didn’t like my giving him Ignore the Awkward, the book that outed statins. “I take ‘em” he told me. “I don’t…” I told him.
This trip in he will tell me all about my cholesterol being high and I will go through the family genetics with him…my body was designed for lots of cold weather. Think Scotland and Denmark in cold winters and you get the idea.
But it’s here that our tale really begins.
As you may know, I have a very nice ($1,200 class) treadmill in my office. I also have a window type air conditioning unit that keeps the office at about 68F.
The crackpot theory?
Walk on the treadmill until just on the verge of breaking a sweat, about 15-minutes…and the knock off for a while; long enough to cool down.
Rinse and repeat.
After a couple of cycles of this, my consigliere called to report his new ham radio antenna had not come in yet…and we got to talking about my crackpot diet idea.
“You can actually go about an hour between bouts on the treadmill,” he offered. What followed was a discussion of how long the body would continue to burn calories at the higher metabolic rate from exercise. He figured once an hour ought to be about right.
I was thinking about half-hour breaks in-between, but this longer break idea was an easy sell: Less walking.
So I will be on this regimen for a while as I ready for my next “medical adventure.”
Something you might want to think about, though, is the underlying idea of “heat cycling” as exercise.
There was a study some time back that showed people who lived in the South tended to be more obese (or amply packaged, your call) because of air conditioning. The theory of the article was that lots of calories are burned either by heating or cooling the body, but few are burned when the temp is always “just right.”
Oops. Off to the machine again…I feel cool and it has been an hour.
The Science of Ham Radio, Prepper Wire Antennas
The next project for the weekend was double-checking I am making the right decision for a low band (*3.5 and 7 MHz band) ham radio antenna.
\This is actually more along the lines of prepping than playing, because for reliable communications (in the event of an actual emergency) you will find it very useful to know about two kinds of antennas. One is a classic “vertical” antenna, which will work fine on 20 meters and up through VHF. But on the low bands, two very popular antennas that give a good account of themselves are simple wire antennas…which is good stuff to know.
One choice is to put up that we talked about recently the RadioWavz fan dipole which, unfortunately, is still on back order from GigaParts.com. You can build one yourself fairly inexpensively, or, like me you can order from Gigaparts and wait for a fair bit of time, or order direct from RadioWavz. That’s more money, but time is…well, I’m kind of busy with eyes lately, so waiting IS and option for me.
The curse of ham radio is that no decision on equipment or antennas is ever perfect…but where there’s a will, there’s software.
So I fired up the antenna modeling program (EZNEC 6.0) and decided to model how the 80 meter performance of the RadioWavz dipole ought to be. Down low to the ground when the tower is down, 32 feet up, more or less, the dipole doesn’t develop much directivity…and the pattern (viewed from overhead) looks something like this: just slightly out of round.
I don’t know how much low band antenna shopping you have done, but there is another antenna that has captured my imagination: The “Carolina 160 Windom.” This is essentially a longer off-center fed (OCF) dipole antenna. A dipole is fed in the middle while an OCF is fed about 31-32% in from one end.
If you live on a small lot in the city, you can likely forget the OCF for 160-meters. They require about 265 feet, although people do get good results with up to a modest dog-leg to fit larger property. Antenna farming is one of the real benefits of living in the outback. The fan dipole is much shorter, on the order of 130 feet, or so, and again, up to a modest dog-leg is acceptable.
A number of people make the bigger OCF’s, and they tend to get good reviews, so here comes Mr. Modeling, again.
A little study of the 80 meter performance suggests the OCF antenna actually performs a wee bit better than the dipole, but only in two directions. Down low I’d have to take care that the major lobes would go where I wanted them, which by luck won’t require playing Paul Bunyan.
I didn’t bother with modeling the 22’ vertical section used to feed the OCF, though I doubt it would have created many “magical effects” on it’s own. But let’s see what happens on the 40-meter (7 MHz) band when we have a modeling contest between the OCF and the dipole – OCF first:
You see? This is more like it OCF is exhibiting some gain. Let’s go back to the 40 meter dipole and see how it looks in comparison:
So how do you compare the antennas? Damn tough question because of one other set of comparisons the antenna connoisseur would have to look at: What is the antenna’s take-off angle when viewed from the side?
Take-off Angle matters greatly as it will define how far you can talk, to some degree. Imagine there is a shimmering reflector of radio waves that moves up and down, day and night, which reflects different radio frequencies depending on time of day (and season, too). This is called the ”F-2 Layer of the Ionosphere.”
The key part of the Wikipedia entry on the F-2 is this:
The F2 layer exists from about 220 to 800 km above the surface of the Earth. The F2 layer is the principal reflecting layer for HF communications during both day and night. The horizon-limited distance for one-hop F2 propagation is usually around 4,000 km. The F2 layer has about 106 e/cm3. However, variations are usually large, irregular, and particularly pronounced during magnetic storms. The F layer behavior is dominated by the complex thermospheric winds.
And yes, this is why ham radio types are always looking at geomagnetic conditions.
So back to the practical prepper problem with antennas: If you want to be able to talk across the country, you would ideally set up an antenna which would have a reasonable low take-off angle toward the horizon. Those vertical antennas used by AM broadcast stations bounce across the country at night (when the reflective frequency of the F2 layer comes down to the broadcast band).
The dipole offers a fairly simple take-off angle and it’s ideal from ranges from local out to a thousand miles, or more.…From the side, it looks more or less like a big ball of energy most of which is going into the area between straight up and 45-degrees above the horizon.
This is why I recommended the fan dipole for my friend Robin. It will have the highest probability of getting a signal down here – even in the daytime – on 40 meters.
But let’s say the mission was different that a high-reliability 300 mile hop. What if I want5ed to set up an antenna that would reach out to Europe with greater consistency? The Carolina Windom 160 has a couple of very attractive lobes down closer to the horizon…
As a practical matter, both are great antennas. But then, too, so is a simple quarter wavelength of wire helt vertically into a tree of some height. This kind of antenna, however, is severely limited in performance by the amount of ground radials you can sick out. Purists actually order special grounding plate accessories from www.dxengineering.com in order to make solid connections for 20-60 radial wires.
But back to what I said about no antenna being perfect: My history teacher back in high school, the late gentleman (circa 1965) had a marvelous Hy-Gain High Tower antenna. This is a 53-footer that you can still find at MFJ Enterprises, last time I looked.
My teacher put in as many ground wires as he could sneak into his back yard and he was able to talk quite literally all over the world. But more often than not, the dipole I was using at the time, up a mere 40 feet on a piece of 4” diameter aluminum irrigation pipe, would “out talk” his signal anywhere closer than 250 miles, or so. Out past there? I’d be left in the dust.
The takeaway from all this is simple:
For regular prepping use, a single band dipole is fine, a fan dipole for multiple bands is better, and other antennas like the Carolina Windom 160 may offer better performance, but the asterisk there it is will depend on direction and whether you’re working DX (distance) where the low take-off angle can really help.
Most important of all, though, is getting an antenna as high and ‘in the clear’ as you can. Go back and read our noise hunting detective notes and you’ll be well on your way to an enjoyable time on the HF radio bands. No voice on HF until you upgrade to a General class license, though there are Morse code areas of several HF bands. This is how to learn propagation and code at the same time, though code is not required any longer…damn shame that, but dumbing down America is “progress” they tell me…
If you want to dig further into the OCF dipole, Buxcomm has a very long and detailed article on design and history and they make OCF’s for a number of resellers, some of which are private branded. The long page/ebook is here: http://www.buxcomm.com/windom.htm
Damn, time to get on the treadmill again…
Write when you get rich,