Mike, Tom, W8JI has a comparison between 1/4 wave and 5/8 wave vertical mobile antennas here: http://www.w8ji.com/VHF%20mobile%20vertical.htm He is comparing mobile antennas but it looks like the 5/8 wave can be 2 db better than the 1/4 wave. Looking at the radiation angle graphs it shows the 5/8 has more gain at lower radiation angles in particular. If you were doing your comparison on long haul contacts it makes sense that the 5/8 would do better.
Bob K6UJ On Sep 6, 2013, at 4:35 PM, Mike Armstrong wrote: > Guy, you aren't reading my emails...... because that question is not > appropriate to the conversation. I am NOT, I repeat NOT talking the > difference between LOCATIONS, but the difference between ANTENNAS AT THE SAME > LOCATION! I am NOT talking about RURAL ANYTHING. That location being on > Gannet Avenue across from the Marina that was LITERALLY across the street > from my house. > > I say again, READ MY EMAIL as your question has absolutely NOTHING to do with > the conversation. The fact that you sent the same email to me after I > answered you tells me that you are not reading what I wrote. I am not being > insulting, but if you don't read ALL of what I wrote, you cannot possibly ask > a valid question or make any statements about its content. If you read it, > you would know that I am not saying ANYTHING about location changes or > differences. OF COURSE a sea water location is better than a rural location. > THAT fact has nothing to do with the comparisons I am making or asking Tom > to discuss. Sorry for the repetition, but I want to make sure that you will > see that, even if you don't read this email entirely. Again, no insult > intended, but it is tiring trying to respond to someone who isn't reading ALL > of what I wrote and jumping to incorrect conclusions as a result. I WILL > tell you the address, if you still want to know, after you have read and > responded to > the content of this email specifically. > > 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 > _________________ > Topband Reflector _________________ Topband Reflector