Sounds reasonable. You probably have severe pattern distortion and you can probably detune the tower and reduce it. You simply must add out-of-phase currents in the shunt that are exactly equal and
What you generally want to do is cause an equal and out-of-phase current in the drop wire that opposes radiation from the tower. The only accurate way to do that is with an actual signal strength te
What spacing do you have between the mast and the antenna element, and how tall is the mast Gary? I've never seen that effect either in a model or in real-life antennas. I just checked one random ol
In general you want a modest length of drop wire, something that uses a fairly large capacitor for tuning. The drop wire connects someplace above the point where the system ties to the tower. That k
Any tuner that will hit the correct reactance will do that Billy, as well as any length of coax that you cut to the correct length. When I use my four-square, I detune the tower by open circuiting a
Unless you really know what you are doing with RF layouts, you never want to switch high impedance lines! Finding relays that have good isolation is even more of a problem when impedances are high,
My dislike for doing that comes from years of measuring relays and switching systems. I think people would be amazed at how poor some relays are, and some layouts. While a reasonable RF layout will
I use relays, because it is easier than running a dozen RF leads with potential loose or broken shields to a box that gets moved around. Most small DIP relays are excellent for 1.8-30 MHz. Larger re
Hi Mauri, I have not found a practical way to measure actual antennas except to translate the measurements from a calibrated test bench to a working system. How do you measure actual antennas? Consi
Right you are. Let's see how that repeats over time now that people are catching on to how to optimize the score Earl! 73, Tom W8JI W8JI@contesting.com
Hi Bob, Antennas like that (and the Snake antenna) fall into the class of accidental antennas that are not based on any logical design or thought. They work solely by accident, because of actual flaw
I have not read the article, but why would you see a null in current Tree? When we tuned such systems for BC stations, we would see a *peak* in the loop current through the detuning system at nearly
Good work Tree. Your results parallel what I have seen over the years in BC systems. The reason you see the slight difference is the equivalent series reactance you are creating between the tower and
One more comment. Think of the detuning as the electrical equivalent of a physically-long parallel L/C circuit. If the structure above or below the point where you are detuning is resonant or nearly
Maybe I missed it, but I don't think anyone addressed the insulated elements. The voltage between insulated element and the boom can be very high when you shunt feed the tower. It can also be VERY t
You are thinking of Radio Switch Corp, which is now part of Multitech Industries. Tel: (800) 431-3223 Fax: (732) 409-6695 Beware of one important thing. You actually should test the switch for your
Hi Don, We *always* must use some sort of controlled test to verify theories or predictions, where we can isolate causes. This is especially true when many random variables affect results. Otherwise
Hi Gary, Feedline length only affects signal pickup to a noticeable extent if the shield of the cable is somehow coupled into the system through common mode coupling. If we use transformers without
Hi Don, I doubt it has anything to do with the moon, since the exceptional propagation days from here are totally random with respect to the full moon. As I said before, W1BB initially put forth the
The newer version of the RCS-4 should be better at switching receiveonly signals. It now uses fully sealed relays which are more immune to contact contamination. The older open-frame relays were OK