The answer to this one comes in several parts. Your antenna is composed of a "pole" (the up 40 and out 20) and a "counter-pole" (your elevated loaded radials). Power is DRIVEN into BOTH of these necessarily. Contrary to a dipole (where pole and counter-pole are identical and opposite, and both intended to radiate), usually on 160 the counter-pole is designed to accept power and then give it back dissipating or radiating as little as possible. The design and efficiency of the pole and counter-pole are separate issues, and from my reading of your post (however accurate or not) contain rectifiable problems for either in your case.
If the counterpole (raised radials, buried radials, counterpoise) is already well designed for very low loss and very low radiation, it will not figure much into the performance of the pole portion of the antenna. Let's first consider the pole by itself. If the pole is a wire that only goes up 40 and out 20, on 160 the current will be zero at the end of the out 20 wire, and some current level related to power at the feed and a pretty low feed resistance at the feedpoint. Looking at a graphical representation, current will nearly linearly reduce in amplitude going from the feed to zero at the end. With the power related to the square of the current, the first thirty feet of wire will be responsible for radiating 86% of the power. The highest current will be closest to the ground creating the highest possible ground field losses for that power and length of wire. And since the highest possible current will be at the feed, therefore the highest possible current will be going into the counterpole, creating the highest possible counterpole ground field loss for that power, for that counterpole design and length of radiator. In your design the feedpoint is only 40 degrees from the current zero at the end of the wire. If instead we do something folded-wire at the end of the out 20 wire to get the feed point at 110 degrees from end-of-wire, then the current max will be in the middle of your radiating wire and current almost evenly distributed over the radiating wire. This will reduce feedpoint current to 0.59 times previous value, and multiply true feed R by 2.86. Given that most ham radial systems are NOT dense or or not uniform, the effective series resistance of the radial system is often fairly high compared to commercial radial systems. The radial system's effective series resistance is often in the same range as the radiator's radiation resistance, sometimes greater, and a large portion of drive power is lost in the ground. Multiplying the feed R, by moving the current max off the bottom and up the radiator, lowers the current that has to be driven into the counterpole, and lowers I^2*R losses in the ground. The COMBINATION of a 5/16 wave single wire folded counterpoise (FCP) AND top-loading the vertical can make a very large difference. Either one has been known to make a large difference. And since an FCP is so much more compact than other counterpole alternatives, that aspect may allow you to improve your vertical radiator run. To create a 70 degree top-load, take a 104 foot wire, run it out west 26 feet, then parallel back to the center, then out east 26 feet, then parallel back to the end insulator at the center. This will look very much like a 52' folded dipole without a feedline. You just take the top of the up 40 out 20 main vertical wire and attach to one side of the folded dipole feedpoint. Leave the other side of the folded dipole feedpoint open and insulated as the end of the overall wire. The top load folded dipole can have the ends droop down 45 degrees, like an inverted vee folded dipole, without any ill effects. The radiation from the top load tends to cancel out. 450 ohm open wire ladder line would be ideal for this. Use of the 360-400 ohm PE sheathed "450" window line (Wireman #554, etc) MAY have some loss associated with its use. I have no data on that. Use of Wireman #554 with a threaded center third conductor for FCP construction did prove lossy. The top load WILL be carrying the same current at the FCP but will not have the threaded third wire in the center. FCP construction and material details for the required isolation transformer may be found at w0uce.net/K2AVantennas.html People ARE making significant improvements in 160 performance on building lots once deemed too small for 160, and absolutely too small for radials. In general, use of a 70 degree reduced or no radiation top-load will elevate the current maximum to an optimum height for any vertical size up to 110 degrees. It's chief advantages are to 1) reduce ground field induction losses, and 2) improve low angle skywave radiation. I have finally figured out ways to make this visible at least in NEC4 based models. 73, Guy. On Thu, Feb 2, 2012 at 1:31 AM, kd1ia <[email protected]> wrote: > HI all, I have had a rocky relationship with TOPBAND that has never really > blossomed. My QTH is small about 1/4 acres. Only two tree's and NO towers > allow. Now that has not stopped me. I have WAS on 160m (took 10+ years) > and a splattering of countries. But I will go on to my problem. I am just > NOT heard. I can hear great with my selection of antennas (resonant on 160m > I have a inductively loaded INV L vert about 40ft 20ft horiz (home brew by > the insane mind that is my own with 4 elevated radials also loaded like the > radiating element) A Cushcraft ma160v with about 40 radials on the groud. A > Alpha delta dxa with about 50 radials on the ground. These radials are all > random ranging from 1/16 to 1/4 wave. ) The verticals make great contest > antenna for stateside as the cushcraft is resonant from about 1.800 to 1.825 > and the Inv L flat from 1.820 to about 1.850. > > This all aside I can hear like I'm running a receiving loop or even a small > beverage (had a nice one at an old qth back in the 90's) but I cant seem to > be heard. I can put 1kw++ into these antennas but still no luck most of the > time. For example I have been calling the HK0NA tonight on 1.833/4 he is s9+ > on 1000d and I am not even getting a ?? > > Other than the WARC band and my eternal quest for a bigger signal on > 20/30/40m I am happy with my antennas. Though I admit I am always > experimenting and have a separate operating position just for experiments and > the rare guest op. > > Well if I'm just crazy then so be it. I've been banging my head on this > problem. > > Any suggestions would be welcome. I an willing to direct email larger > descriptions and even pictures of what I am working with... > > Caveats: I wasn't born yesterday, But, I do believe in magic. sooo Other > than buying out all my neighbors and putting up some big antennas lets try > and be constructive.. (that is unless ya wanta give me themoney to buy out my > neighbors 8) ) > > de John ko1h > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
