Apologies to all for delay in response. Losses related to ground and close dielectric materials remain the single monster gorilla in the room for improving TX performance of vertical antennas.
Setting aside content on k2av.com relating to the FCP, the other issues in that web page’s "Loss List" section apply to any inverted L, e.g. not having a tree inside the bend, avoiding proximity to dielectric materials, quality of whatever counterpoise, etc Simply having the RF current maximum on a vertical wire at the ground, largely diminished at the top, is a loss issue, unless the in/on ground radial system is EXCELLENT. If you are considering beefing up your radial system in stages, then by definition your radial system is NOT EXCELLENT. You already know the deficiencies, those are what you haven't done yet and plan to do, sometime. The net effect of a collection of radial system deficiencies separating you from EXCELLENT will be at minimum over Midwest USA magic super dirt. Ground losses move in the direction of catastrophic as ground quality deteriorates from super to average, to poor, very poor, junk, awful, to unbelievably bad. The vast majority of the country has ground quality that will make you pay if your radial system is NOT EXCELLENT. If you have that magic, super 30 millisiemens dirt, you can do anything and get away with it. Please do not tell us, just keep it to yourself. We already have enough things to make us jealous or feel bad. Enjoy all your good results with schemes that blow up in ordinary places. I have no problem with your good fortune, I just don't want to be reminded over and over how poor NC dirt is for RF. But please do not offer shortcut low-band advice, because you have no idea what awful results your scheme might get in 2 millisiemens North Carolina dirt, or even worse in the barely covered-over rubble that sometimes passes for dirt in urban and some suburban building lots, or in historic areas that have been built over previous ruins for thirteen centuries, places where the skeletons of ancient kings have been discovered buried in medieval church ruins found under current-day parking lots. The enemy of a vertical radiator is loss. Specifically, 1) dielectric loss, RF exciting increased electron energy levels without electron movement between atoms and 2) resistive loss, RF inducing current in conductive but resistive materials. Dirt usually has both. Further and worse, UNLESS there is net field cancellation at the radial wire or below (outcome of an EXCELLENT radial system), dielectric material within a few millimeters of radial field conductors INCREASES dielectric loss. RF fields at the feedpoint are huge, especially where a self-resonant vertical radiator meets in/on ground radials. Radial deficiencies will be costly close to vertical wire meeting counterpoise, further multiplied by the "poorness factor" of the dirt underneath. That is one of the gains of an elevated counterpoise, getting high fields away from the damnable dirt where an EXCELLENT on/in ground counterpoise just ain't possible. Another way to reduce the fields at the ground is to quit using the length of the vertical aerial wire as a cheap way to provide tuning for matching to coax. If (on 160) you use an 88' foot wire as a start for the L's horizontal, you will move the current max to 1/16 wave down from the bend in the L. You will have done two good things, 1) reduced the feedpoint current, hence also the RF field at the base, reducing the power loss by the square of the field reduction, 2) put a fairly uniform current on the *entire* vertical wire, further reducing takeoff losses in trees, buildings, etc, by having a much larger percentage of the total takeoff energy high enough get to sky without encountering ANY dielectric losses. How long to make the vertical wire? As long as you can while still sufficiently avoiding dielectric and conductive materials. Losses from higher current on a shorter vertical wire are outweighed significantly by gains moving the feedpoint up in the air away from dreadful ground losses only otherwise mitigated by EXCELLENT ground radial systems. There are also questions about the efficiency of ground radials on top of typical root content of "woodsy" locations. Roots are high loss dielectric materials. Controversial, but an EXCELLENT *elevated* radial system in the woods is going to outperform radials on ground. Buried radials in the woods outright dismissed by many as impractical at best. The usual killer reason for abandoning or not adopting non-resonant improvements to move current maximum well up on the vertical wire? Desiring low SWR without tuning apparatus at the base of the vertical wire. From the "Taming the exasperating Inverted L" section on k2av.com: **An Efficient Self-resonant Inverted L is NOT a natural 50 ohm antenna** Not even close. Think 20 to 35 ohms. Varies with dimensions and environment. **Lower SWR does NOT predict improved performance** A dummy load has perfect SWR, and at 100% loss is a worse antenna than a light bulb. 73, Guy K2AV PS: How much wire does it take to be an EXCELLENT radial field? Has to be dense, full size all around, uniform in all directions. There are a lot of hams who have had the space and actually done that, put down an EXCELLENT radial field, and are definitely getting EXCELLENT results. Just remember that "merely decent" radials over typical poor ground can evaluate to "disappointing." On Tue, Dec 18, 2018 at 11:07 AM Todd Goins <[email protected]> wrote: > > Hi Gary, > > Thanks for the help. I got the new wire in place roughly as you described. > It is a few feet lower to give good clearance from the anchoring branch. > > It doesn't work very well. Last night it was much poorer on receive and > transmit than my existing 43' vertical setup. I'm not sure what to think. > Maybe the light of day will reveal a clue, but it was fairly quick and easy > to construct and kinda tough to mess up but who knows... > > I'll put an analyzer on the feedpoint this morning and see if it looks out > of whack. I was expecting it to be a least a little better but it clearly > wasn't. > > 73, > Todd - NR7RR > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
