Fw: [TowerTalk] Take-Off Angles: N6BV's Book "All the right Angles" Reply DE K0FF
Ken Hirschberg
calav@flash.net
Fri, 07 Jul 2000 09:40:55 -0700
Hi all-
Yes, there are systems available to do this, but cost is beyond the reach of
most amateurs. The last one I saw commercial literature on used three
orthoganal loops; hardware plus software was about $35K. (15 years ago) A
contester's dream machine! If anyone has a serious interest, I'll dig for some
details.
Regards, Ken K6HPX
K0FF wrote:
> Subject: Re: [TowerTalk] Take-Off Angles: N6BV's Book "All the right Angles"
> Reply DE K0FF
>
> The question was has anyone actually measured the incoming angles on HF.
>
> I can't do it with precision on HF, but regularly measure arrival angles on
> 6Meters with a stacked array of four 6 elements in a 25 foot "box" and have
> elevation as well as height control: 0-90 elevation , 12-85 feet height. .
> Fascinating results comparing different types of propagation vs the arrival
> angles. Been studying this for a few years now. Most data is directly
> transferable to 10M because of both the F2 and Es type skip there as well.
> On HF (20M especially) all I can do is compare antennas at different
> heights (each on different towers that are adjustable in height), and
> because of the TOA characteristics of each, you can expect a huge
> difference, or no difference at all depending on the takeoff angle of each,
> the type of propagation and distances involved. Basically here we are
> dealing with reflections at different F layer heights, but more importantly
> it's just the "angle of incidence equals the angle of reflectance" rule.
> Sometimes it's not just the incorrect placement of the main lobe at fault,
> it's the deep notch just above it. If the wave angle arrived down that
> notch, an otherwise great antenna can suffer a 30 dB penalty.
> Take daytime , stateside signals and look at them first on the tribander at
> 50 feet, and then the monobander at 100+ feet and you see little or no
> difference on the S-Meter. Comeback that night and listen to AP2's 9N's,
> VU's etc at S - 5 or 6 on the monobander, and indiscernible on the
> tribander. You would seriously think the coax was cut.
>
> Referring to 6M again where the results are crisply demonstrated, a tall
> antenna will be beat almost every time by a short antenna on Sporadic Es
> (seems to arrive at 13-18 degrees, no matter what distance is involved). On
> pure F2 propagation which seems to favor the 5 degree area or even lower,
> the taller antenna wins hands down by a huge margin (measured 6 S units
> already). One thing that's pretty unique to 6m is an E link into an F2
> event, like TEP. Last year for example I worked several VK4 stations by this
> method, and even though the distance was great, the path required a high TOA
> at my end at least. Same goes for the spring and fall equinox opening to
> South America.
>
> On HF there is a multiplicity of propagation types available at any one
> time, and the matter becomes very complex when world-wide contacts are
> discussed. Overall, my experience is that lower antennas (therefore higher
> angle TOA) will equal or even better the stacked arrays when working the
> same hemisphere, all other factors being equal. The tall, or stacked array
> have access to low angle not represented on the pattern of the lower mounted
> (therefore high angle) antennas, and will have a shot to the opposite
> hemisphere that is staggeringly better. Old timers will remember one of the
> first stacked 20M arrays, at W0SYK. Bill had a pair of Telrex 6 elements on
> a homebrew rotating 125 foot pole. We weenie stations would ride him hard
> when we beat him in pileups to the Carib,. or South America, He just
> snickered though when he was the only station even to hear the Asians over
> the pole that night!
>
> I submit that the propagation issues involved are way to complicated for any
> single antenna to handle. My approach as a radio-scientist (amateur of
> course) is to keep all the different antennas on separate feedlines so that
> the effects of each can but compared and studied.
> If I were a DXer, I would have 4 Monoband Yagis stacked and fed in phase,
> one above the other with the bottom one at one wavelength and the others
> stacked at least on 5/8 centers above that.
> If on the otherhand I was primarily a contester, I would undoubtedly go with
> stacked multiband antennas, one above the other, maybe two or three of them,
> and have independent rotating controls for each.
> A ragchewer, a net operator, a traffic handler, a field day enthusiast would
> all chose different antennas more suitable for their needs. Just as on 2
> Meters there is a big difference in design of a system for EME, M/S, Tropo.
> Understanding and defining the needs at hand are the first step.
> The charts showing the different arrival angles of various propagation modes
> and the extremes of distances allowed per hop have been in the ARRL books
> for years, but I'm afraid they have evaded being the general topic of
> conversation in most QSOs.
>
> After studying this effect on 6M for the duration of this cycle, I will
> then break up the box, and reconfigure it into a Diamond, with 2 horizontal
> and 2 vertical components, and then be able to properly look into polarity
> rotation.
>
> Confused? Don't be - there is no one answer.
>
> note; all observations mentioned were done with multiple antennas, well
> distanced apart, and on a coax switch or relay box for A-B-C comparisons.
> each observation was accomplished by dozens or hundreds of switching cycles
> to average out any errors caused by QSB etc., before any conclusions were
> drawn. There is an assumption of reciprocity between TX and RX.
>
> Geo>K0FF
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com