There was a mythbusters episode about this... they mocked up a shower in a lightning test lab where they could do huge (though not quite lightning-energy) arcs. If I recall, it "killed" their dummy p
Good god! Guess it's concrete encased and small diameter... but whoa. Did you hook a big bottle up? Dan _______________________________________________ _______________________________________________
variable depending on the additives included. I've used it for all sorts of antenna applications and not had a problem, but I've never stressed it more than using it for end insulators on a dipole w
I dunno, some of us still use manual tuners. I like to have a bunch of antennas that each exhibit low SWR in my favorite parts of the bands on a switch. I'm an incurable band hopper when I'm operatin
Bob, Added some servo controlled gearmotors. I wrote it up at http://www.n3ox.net/projects/servo if you care to check it out. 73, Dan _______________________________________________ _________________
I think the implicit assumption throughout this thread is that you're comparing a coax fed dipole that you trimmed to be resonant at 3850kHz with a coax fed dipole that you just put up after cutting
Along those lines, jackite.com has 31' fiberglass poles for sale, about $55 apiece. I built a ~65% size 40m dipole with 2 20' rods and a loading / matching coil in the middle that works rather well.
With regard to perfect ground/saltwater verticals are affected much more than horizontals. The pattern of a horizontal dipole over usual soil and over saltwater isn't very different. Once you're up o
I feel like I've seen some kicking around the lab here (lots of plasma research being done in the building). They're high voltage RF connectors, 50 ohm impedance. If you've got both genders, throw 'e
http://www.cebik.com/wire/cut.html ... ok so that's just about the pitfalls of cutting formulas. I think probably that you could scale up a wire model. A 5 inch conductor is about 0.0015 wavelengths
Is there any lightning protection difference? I would think the radial system could come up to higher potential in a strike if insulated. Of course, you shouldn't be relying on your ground radial sys
Peter, Don't have them put up the wire at all. Get some of the best, most sunlight and water resistant rope you can. Make it big, much stronger than what you need for the antenna. Run it in a loop bi
The SDS chucks and bits can be used with a much harder hammering action... plus they only bother putting them on serious pieces of gear. The difference ends up being night and day... SDS-equipped ham
J-poles are somewhat sensitive to their surroundings and can be sensitive to the feedline details... but if you're just looking for 2m FM, as long as you can tweak it a bit on-tower you shouldn't hav
Well, there are beam bending formulas for distributed loading... the windload of the structure itself is nonnegligible, but it's a simple beam so it's straightforward to analyze. Take the formula for
Red, By my calculations the drag on pretty much any antenna element is going to be turbulent, and certainly so for a tens of miles per hour wind. The kinematic viscosity of air is around 1.3*10^-5 m^
*snip* In other words, it's not safe to put this tube up unguyed. The Array Solutions Big Berthas seem to have a pretty substantial stepped taper to them and appear to be a couple feet in diameter a
I've successfully dipped some homemade traps with my MFJ unit, but I'm with Bill... just hook up the tower-as-shunt-fed-antenna to the analyzer port and find the resonance that way. Dan _____________
I don't know much about shunt feeding towers, but more top loading is an efficient way to go. Sounds like you wouldn't need a whole ton of it to get down to resonance on 160, but I guess you already
The Armstrong rotating method can be FAST. Nothing like good old muscle-brain feedback to start and stop a large inertial load quickly without breaking anything. I guess I'm thinking specifically of