Guy, I was right across from the small marina you see. The difference I am talking about is the difference between a 5/8ths wave vertical and a quarter wave vertical in the same place. I am not talking about the difference between a vertical next to the sea as compared to a vertical in Arizona...... two different comparisons and I am thinking you are thinking the latter..... :)
I was responding to Tom saying that a 5/8ths wave doesn't work well on 160, when a ground mounted 5/8 worked so much better than a quarter wave in the same place (relatively speaking). I had both operational at thr same time and would detune them when I used the other...... Again, I was wondering if Tom could explain why it is such a crappy antenna on 160, but a great antenna (when compared to a quarter wave at the same location) when it is on 20 meters. NOT the difference between two antennas in two different geographical locations...... :) Mike AB7ZU Kuhi no ka lima, hele no ka maka On Sep 6, 2013, at 13:38, Guy Olinger K2AV <olin...@bellsouth.net> wrote: > Mike, could you kindly supply the address on Iroquois Point? If it's in the > area I'm looking at with Google Earth, the answer why the difference is > pretty plain, and points to why such a difference vs. a 160m vertical on > rural terra firma. > > 73, Guy. > > > On Fri, Sep 6, 2013 at 1:30 PM, Mike Armstrong <armst...@aol.com> wrote: >> Oh, I didn't address one comment you made, Tom...... 5/8ths are dogs on 160? >> Really? That is odd in the extreme to me. I had incredible success with a >> ground mounted 5/8 on 20 meters while I was stationed in Hawaii. I was >> rather space limited, so I could only go up and a tower mounted beam was a >> "no fly zone" in that particular situation. So, I decided to try the 5/8ths >> wave vertical and its performance was nothing short of spectacular when >> compared to a 1/4 under the same circumstances. Not to malign the simple >> 1/4 wave, but the 5/8ths performance improvement went way beyond what I >> would have expected...... and my expectations were certainly reasonable. My >> thinking was that lifting the major current node a bit above ground would >> probably be an improvement and, to my surprise, that was an understatement >> in the extreme. >> >> I wouldn't want to overblow the results, but I simply couldn't believe how >> well the antenna performed on 20. To be sure, I was on Oahu out in Iroquois >> Point housing, which is well situated with regard to the sea (you are >> basically ON the water in almost all directions). Additionally, I had 60 >> radials underneath the thing, spread evenly around the base (in straight >> lines, no bending). So it was definitely an ideal vertical location. But >> the difference between it and the quarter wave was what truly surprised me >> (with all else being the same.... sea water location, number and length of >> radials, etc). To hear that it doesn't translate to 160 is really a >> surprise to me...... Tell me more, assuming you did any kind of study into >> why it didn't seem to work well. I am as interested in why something DIDN'T >> work as I am in why it does..... If for no other reason than to save a few >> bucks and alot of time.... LOL >> >> Mike AB7ZU >> >> Kuhi no ka lima, hele no ka maka >> >> On Sep 6, 2013, at 9:25, "Tom W8JI" <w...@w8ji.com> wrote: >> >> >> Fully understood. I wasn't referring to the usual collinear antennas >> >> sold by "comet" or anything of that nature. I am referring to the >> >> stacking arrangements used for ops like moonbounce, etc. As far as the >> >> design theory (and practical application) goes, I have a reasonable >> >> amount of schooling and experience (been active since 1966..... he he >> >> he). Just so you realize I am not referring to the often (always?) false >> >> gain claims made by manufacturers for their antenna designs. >> > >> > ........but this is verticals, and not a narrow BW like a long Yagi. The >> > narrower the pattern of a cell in the stack, the wider minimum useful >> > stacking distance becomes. >> > >> > Also, for 160, antennas are near earth. Earth spoils everything. A 160 >> > antenna at 260 feet is like a two meter antenna at 3.25 feet above ground. >> > >> > >> >> All I was saying was, "yes, it is possible and is done" when speaking to >> >> vertical stacking. As far as stacking what we would call "ground plane" >> >> antennas (quarter wave vertical element against elevated radials), the >> >> only example I have seen with any regularity is done aboard some Naval >> >> vessels (stacked/phased, if you will, horizontally on a yard arm). I >> >> "think" I have seen the same thing at airports, but I cannot tell for >> >> certain that they are phased arrays or just happen to "look" like they >> >> are related. Understand that in all cases to which I refer, including my >> >> own, I am speaking of phased arrays, which I believe is what we are >> >> talking about as well. I may have misinterpreted the question to some >> >> degree. >> > >> > This is 160. The distance ratio for the same behavior on two meters is >> > 80:1. If we look at: http://www.w8ji.com/stacking_broadside_collinear.htm >> > >> > we see **freespace** short dipole stacking distances, between current >> > maximums, is 0.35 WL for 1 dB stacking gain. This is for freespace. That >> > means the current maximums have to be .35*160 = 56 meters apart **if** the >> > elements are in freespace. They have to be even further apart if near >> > earth, because the earth reflection already compresses the vertical >> > pattern. I'd guess, for 1 dB stacking gain over a ground mounted vertical >> > (ignoring ground losses), we could move the lower current maximum to about >> > 50 meters above earth and eliminate the upper element. That would pretty >> > much be a vertical dipole. If we wanted to get 2-3 dB gain, we'd probably >> > need 300 feet of height and an inverted groundplane at the top. >> > >> > For 160, is it is a useless endeavor at normal heights. >> > >> > Making matters worse, 5/8th wave verticals are dogs on 160. Been there, >> > done that, used them. A 1/4 wave vertical, or something up to maybe 200 >> > feet, is actually better. They have never worked well here, they never >> > worked when I used broadcast towers, and when W8LT used them in 160 >> > contests they were also pretty weak. >> > >> > The whole thing is a waste of time on 160. Even if someone could run a >> > vertical collinear with useful gain, it would just kill their signal by >> > focusing it at too low an angle for 160, while nulling more useful angles. >> > >> > 73 Tom >> > >> > >> _________________ >> Topband Reflector > _________________ Topband Reflector