Topband: Are stacked verticals feasible?

[Mike Armstrong]

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 <olinger at 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 <armstrmj at 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" <w8ji at 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
>