Wow. At last the heat is backing down and the radio season is here. When the bands go through their change from summer to winter.
Generally – in he northern hemisphere – in the summer, the higher radio bands like 20-meters are open a lot of the time. But, the “old boys nets” in the early morning (and late nights) on the low bands (80 and 160 meters) tend toward much higher noise levels. Static.
Every year around this time, thousands of hams begin thinking about antenna projects to support whatever their specialized interests might be. Low bands – 80 and 40 meter optimizations probably lead the list.
This week, I decided to put up (“fly”) the new double-sized W5GI “Mystery antenna”. It’s big but it does some great things. Like give some gain on the 40-meter band – prime X (long-distance) Morse and digital modes over winter.
80-meter antennas are a worthwhile endeavor – especially if you like AM – in which case the 3.885 MHz national calling frequency is a good place to listen. As I’ve explained before, AM (amplitude modulation, but also called “ancient modulation) involves a carrier frequency on which two “sidebands” of audio have been impressed. The other popular voice mode on the low frewuency ham bands is single sideband (SSB) and involves equipment that nulls out the carrier and one of the sidebands. This means much more “talk power” for a given power level, but it requires the now suppressed carrier be recreated locally to understand the signal. This is done with a beat frequeny ocillator (BFO) which is best applied to a product detector, although the AM-friendly diode detectors can be OK until they overload. At which point it sounds god-awful. Anyway, all baseline stuff.
In general, the higher you can get an antenna, the better it will work – with one exception. Daytime, on the low bands, propagation is easiest with “near vertical incidence skywave” [NVIS} propagation. That’s because during midday periods, you want to squirt as much signal straight up so that the ionosphere provides something akin to backscatter. Which is thought of (in the micrwave frequency range) as “troposcatter.”
Putting Up a Beast
The “double W5GI is about 200-feet long. Step outside with me and we will take down the old off-cnter-fed dipole (OCFD) and we’ll put this bad boy up.
I used of of our drones, hauling some 30-pound test SpiderWire fishing leader, up over a couple of tall trees. The west tree, I maneuvered the line into the highest notch I could, like so:
And on the east side, it went into this tree because the tallker one on the right, I still have plans for…
The eastern tree is easy to get to, but the west one has a short trail to it through the brush:
The “downhaul” is attached to the tree with an inch-and-a-half stainless steel eyebolt. You use these so that when the tree is harvested (somewhere in the future) you will be able to remove the metal, so the tree doesn’t cause an accident for a sawyer or a mill.
Sharp eyed antenna inspectors will see two lines are tied-off here. One is the “bitter end” of the line (we buy paracord in 1,000 foot spindles – we use a bit). The one up and to the right is the antenna end.
After Elaine helped get the low parts clear of a storage building and the other clear of the solar panels, that left nothing but the center feedline to connect to coax.
There’s nothing serious inside the PVC, the center of the coaxial line goes to one side of the ladder line while the outside (shield) goes to the other. There’s about 50-feet of twinlead and yes, this is why higher is better.
With a 40X digital zoom setting, the top looks like this:
The line running off to the right is the center raising halyard – and it doesn’t look like the usual “going up” because I set it to get the antenna as far away from the tower as possible. Towers tend to absorb energy so good practice is to keep antennas 4-6 feet from anything grounded.
Out at the ends, one the west side that eye bolt holds the line and on the east side a convenient fence is used as the tie-off point:
Decoding the numbers:
- This is the line that goes up to the tree top (tension on the antenna)
- The “bitter end” is tied off.
- Even though it looks like a mess, this whole rats nest can be strung out straight in a minute, or so.
Putting up bigly to hugely antennas is easy with you “get creative” with your lift. Drones are one of the best ham radio inventions ever.
Still to come this winter: Trying to decide whether to put up the 80-meter double bazooka or the 20-meter optimized W5GI. The final antenna for this winter will be a very long (246 foot on one side) off-center fed dipole.
This one will run north-south because OCFDs tend to be end-firing, depending on height over ground. This one will be fed with 450-ohm ladder line, too and should give good enough performance that (with luck) Hank might be able to hear it out in Hawaii.
We shall see…
Still Ahead Today
Lawn more spindle has been replaced – so that’s back in service and calling to me for a trim. I put off going to Lowes to get the rest of the wood and stair stringers for the deck, but the good news is all the computer issues have been nailed now…
Weekends and working with your hands is a good thing to get used to…you never know how long civilization will remain “civilized.”
Write when you get rich,
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