Jim, I'm not sure I have a full answer to your question, but the observation of arcing at the ends of the radials is quite interesting. The arcing can be reduced, as you suggest, by staking the ends
Technically correct, but I don't mind serious non-modeling discussion on this list, away from Towertalk's exceptionally high "noise level." On another topic, are any of you on this list working on b
I'd like to confirm Guy's notes and add my 2 cents on one specific topic. Numerous references purporting to explain common mode currents in feedlines claim that there is a Kirchoff-style split of cu
Howard, At a length of 30 feet, there is no RF "ground" -- it's nearly 1/4 wavelength at 40M and will always be part of any antenna connected to the attic-mounted tuner. If you include the ground wi
Hi Andy, I tried changing wire size on my models of the K9AY Loop and Flag, but did not get the kind of difference you report. With the Flag, I see 2 dB difference between #14 (1.6 mm) and 1" (25.4 m
Allan, Does the coax have two shields -- e.g. is there a shield around the inner dielectric, then the second dielectric, and another shield over that? If so, it's "triaxial" cable with an isolated sh
Welcome Ian, This isn't the most active list around, but its focus reduces the 'noise level' that plagues lists with broader interest. I'll be posting some info on 80M and 160M antennas in 6-8 weeks,
Andy, One of the minor drawbacks of a 4-square is the high angle rear lobe you are seeing. With optimal phasing, you should be able to get a pattern where that rear lobe is down 25 dB or more. This m
Flam, Based on your description and measurements, I am certain that proximity to the tower is affecting the impedance matching. I was able to obtain similar results modeling the tower about 30m tall.
Alan, I made some DXpedition verticals several years ago, and found two things most useful: 1. Pre-set the guy ropes as close as possible to final length. You can calculate using geometry or graph pa
Flam, In 2007, I experimented with larger loops -- same height as the original (about 8 meters), but almost 2 meters more on each side. In theory, the signal increase should have been 2 dB, which is
Comments interspersed... That's a good start. Things are not a total mess! Coupling to "something" is the strongest possibility. It can be the radials as well as the radiator of the Inv-L. I would re
Flam, The signal capture (voltage or current) of a small loop is proportional to the area. Thus, double area is 6 dB. My larger loops had almost 1.25x the area of the "original" loop, so I expected n
Warren, You might check out my article in the ARRL Antenna Compendium V, and perhaps get a copy of US Patent 5,489,914. I don't have any reference material on hand in electronic form. Then if passive
Flam, There will be no problem using two separate reversible-direction loops. The loops are so small (electrically) that there is very little coupling, even when placed close to one another. 73, Gary
Dave, First, take the 10 ohm 'ground loss' resistance out of the model. 48 radials approximately 1/4-wavelength is a low-loss ground. Without it, the 'zero-X' spot is around 36.5 ohms at 3.840 in my
Modeling and building are tightly linked. I would hope that Tony has, or will be, modeling his proposed system ... if not, then Pete is correct that this is not the right forum. However, I prefer tha
There is far too little traffic on this reflector. What some members see as an expansion of its scope may be a good thing. When someone like Tony asks for advice, the appropriate response is to discu
-- I am somewhat behind the curve, using NEC-2 based EZNEC+. I have other programs available to me, but have little time right now with the demands of running an active small business (www.highfrequ
... _____ The limitation Terry notes is another example why I use modeling for a "close estimate" rather than "precise replication" of an actual antenna. In this case, given the scale of the structu