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@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@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@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
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