In 1963, I was lucky enough to attend a presentation on antennas, given by Lew McCoy, W1ICP (SK). He introduced me to an antenna which I immediately built and have used whenever it has made sense to use, for almost 50 years now.
Interesting enough. L.B. Cebik, W4RNL (SK) also wrote an interesting article entitled "If I could only have one antenna". He chose the same antenna. (Although I like this antenna, I would have chosen the LAZY LOOP instead.).
In on the air (or on the net) discussions, you often hear people speaking of the optimum feedline length. There is only one useful answer to this, and it was put forth by Lew in his presentation:
"The feedline must be long enough to reach from the feedpoint of the antenna to the connection of the matchbox in the shack."
The reality is, you use this length but sometimes have to add a little extra feedline to avoid certain problem lengths. More on this, later.
Over the years I have used this antenna in various forms at 50+ different QTHs. I played a bit with the lengths of the legs and made some interesting (gut feeling) discoveries:
FOR SMALL BACK YARDS, try building this antenna half size. You will be surprised to see how well it still works on all bands except 80m. It will still work on 80m, but the effeciency will begin to drop off as the antenna gets smaller than 26m overall length.
To save even more space, erect this antenna as an inverted-vee antenna. For instance, an inverted-vee with 2x 8.5m legs (28' legs) requires only about 16m (50') of horizontal space, yet it is an outstanding performer on 40 through 10m and will still load and work on 80m. Using x2 6.5m legs, it fits in an even smaller space.
As high as possible, which for most people is typically 10 to 15m (30 to 50 ft.). Even if it is as low as 10 ft. (ca. 3m), it will still work, but you won't be breaking many DX pileups at that height.
The best thing to use is a non-metalic pole. You can use wood, but a 10m (33') wooden mast is pretty heavy. You are much better off using a heavy duty telescoping fiberglass pole such as the 12m (40') pole sold by Spiderbeam. See: http://www.spiderbeam.com/gate.html﻿
With a matchbox, and of course as good of a matchbox as possible. There are lots of different kinds of matchboxes on the market, deploying several different kinds of technology.
For 1000+w, it can get real dangerous trying to find a solution which does not burn your lips each time they touch the mic, or burn your fingers each time they touch the metal of the key. You will get the best results if you use a symmetrical matchbox, rather than an asymettrical matchbox with a balun.
Interresting, I got different results in different situations.﻿ So even if two people appeared to try the same method, they may very well have experienced different results. Part of the reason of course, is that they are not really the same. Perhaps the feedline length is different, etc.
EINSTEIN WAS NOT COMPLETELY CORRECT: Sometimes you do get different results when you try something again, especially if the second try is at a different QTH. ALWAYS expect the possibility of different results!
FIRST: Before you do anything to the antenna, be sure your matchbox is designed to handle the power level you are working with. If it is, then proceed as described below.
For PORTABLE installations, it depends on how much I really even need that band. Sometimes the best thing to do is just not work that band. If it is a contest QTH and 40m arcs or sparks inside my matchbox, I have to address the problem.
First, I reduce the output power of my transmitter. I have often seen where my matchbox would arc at 100w but run perfectly well without arcing if I reduced the output power (for just that one band) to 80 watts.
If that does not work, or it is not an acceptable solution, adjust the feedline as described under PERMINANT installations below.
For PERMINANT installations, I want my antenna to work with full power on all bands. After all, that's part of the reason I chose "this" antenna. It is supposed to be an ALL BAND antenna.
The length of the feedline should be changed by approximately 1/8 wavelength on the band that is incurring problems. Since it is probably not possible to shorten the feedline and still reach the shack, we need to lengthen the feedline. The 1/8 wavelength is a "ballpark" number and not critical.
Example: 40m is arcing. 1/8 wavelength on 40m is approximately 5m long. Don't forget to apply the Velocity Factor. The VF for openwire feedline is usually about 0.9. The length of additional feedline needed is: 0.9 * 5m = 4.5m. This is about 15 ft.
Add about 13 to 17 feet more feedline to your existing feedline. You may add this inside of the shack or outside of the shack. If you add it outside the shack, be sure to weather-proof the connections.
After adding the feedline, check the SWR on ALL bands. Sometimes changing the feedline length fixes one band but causes problems on another.
With a little bit of trial and error, you will always find a length which works on all bands without arcing inside of your matchbox.
First tie a rope to the pulley, Then fasten it to the pole using the rope. The Spiderbeam 2mm Kevlar rope is perfect for this task.
(Note: normally there would be a clamp where the strap is shown and the strap goes above the clamp.)
Using a metal clamp to fasten the pulley is even more dangerous because it not only adds weight, it can also damage the thin wall of the pole.
A pulley is often used with a metal mast to enable easy raising and lowering of the wire antenna. This is necessary because it is so difficult to raise and lower the mast.
With a fiberglass pole such as the Spiderbeam 12m telescoping fiberglass pole, the pole itself can be raised and lowered by just one person within 2 minutes, or 5 minutes when using the accessory clamp set. As such, a pulley brings little added value.
and to use a 7mm nut driver instead of a screw driver for tightening or loosening the bolts on the accessory clamps. This combination enables raising and lowering the pole quickly as described above.
Assuming this is something you must only do a few times during initial adjustment, why even bother with the extra cost, weight and work of using a pulley?