[Fourlanders] adjusting takeoff angle

Jim Worsham wa4kxy at bellsouth.net
Sat Jun 16 19:16:41 EDT 2007 

I went by HRO today and picked up a copy of the March/April issue of NCJ.
It is a special issue on 6 meter contesting and it has some very good stuff
in it.  For some further information go to this website
www.arraysolutions.com and check out the stackmatch II.  Pay particular
attention to the BIP (Both in phase) and BOP (Both out of phase) functions.
To summarize, they claim that feeding both beams out of phase by 180 degrees
raises the main lobe of the radiation pattern by approx. 15 degrees while
reducing the gain by only 1 dB.  They also claim that this is very effective
on 6 meters.  The cost of this gadget is around $300 - $400 depending on
options.  We could probably build something that does the same thing for
less for at least experimental purposes.  It would require two DPDT RF
relays capable of handling 750 Watts and a half wavelength of coax.  It just
so happens that I have such a relay that I bought to use as a TR relay for
my 432 amplifier.  I would be willing to temporarily donate it for
experimental purposes in September if someone can help me come up with the
coax and a waterproof container to put it all in.  We will also need some 2
conductor cable and a small power supply and switch in the shack to energize
the relay with to switch the phasing line in.  I will talk to Bob when he
returns from Anguile to see if he can work with me on this.

73
Jim, W4KXY

-----Original Message-----
From: fourlanders-bounces at contesting.com
[mailto:fourlanders-bounces at contesting.com] On Behalf Of S Kosmetatos
Sent: Wednesday, June 13, 2007 11:07 PM
To: rfacres at gmail.com; 'Fourlanders'
Subject: Re: [Fourlanders] adjusting takeoff angle

The March/April Issue of the ARRL's National Contest Journal is devoted to 6
meters. What caught my eye was the reference to an article: "Control of
Take-Off Angles For 6 Meter Es" by K3LC and the cover picture of a 6 meter
array using an Az-El rotator. I picked up a copy at HRO.

The basis for the article is a series of computer simulations comparing a
single yagi being tilted from 0 to 70 degrees and examining the lobes, and
comparing it to a set of stacked antennas with switchable phasing (both
driven, in phase; both driven, out of phase; lower driven, alone; and upper
driven, alone). The article may shed some light on the topic at hand.

The article in the issue by K7BV has some pictures of his four 7-element
long boom yagis in an H frame configuration to accommodate az-el
maneuverability.

I can try to somehow make the articles available if anyone is interested and
doesn't have access to a copy.


Kos, N4NIA


 

-----Original Message-----
From: fourlanders-bounces at contesting.com
[mailto:fourlanders-bounces at contesting.com] On Behalf Of Brian McCarthy
Sent: Wednesday, June 13, 2007 5:06 PM
To: Fourlanders
Subject: Re: [Fourlanders] adjusting takeoff angle

I would advocate a beam for this application as opposed to a dipole.
In another set of emails we talked about the noise coming in from the east
on 6m. By using a beam for the high angle antenna we should have significant
sideways rejection, or at least much more rejection than a dipole toward
that noise source.

What we are talking about here is not much different than the NVIS antennas
used for short range HF communications, but rather than an omni-directional
pattern our first experiment should target the high population areas of the
northeast. Again, it begs for a beam of 3-5 elements.

The distance from W9ICE (EN60vb) to W2SZ/1 (FN32jp) worked out to about 698
miles and W4NH EM85jm to W2SZ/1 was about 727 miles. They are just one
example, but W2SZ/1 ends up being near the beginning of first hop Es and
they are a bit past much of the northeastern high population areas. We want
to shorten up that first hop distance, or at least beef up the amount of RF
injected to the short portion of first hop.

Brian
NX9O

On 6/13/07, Rogers, Ron <RR124640 at ncr.com> wrote:
> Well, a dipole would certainly create a high angle and probably result 
> in bi-directional results in a shorter range. We just heard a similar 
> presentation at the VHF conference about box array, closer-in range, 
> antenna work which stimulated this other discussion and coincided with 
> my experience at W9ICE.
>
> But, the goal of the elevated directional antenna experiment is to be 
> able to create a concentration of RF, in the direction and angle you 
> want, so you have some sort of control of a calculated touch down.
>
> We had no problem with the elevated Cushcraft at W9ICE with 1500 watts.
> Just so no one stands around it or touches it while transmitting !!
>
>
> Ron Rogers
> Eng. Prog. Mgr.
> Elec. Payment & Wireless Sys.
> NCR Corp.
> 770-623-7690
>
>
> -----Original Message-----
> From: fourlanders-bounces at contesting.com
> [mailto:fourlanders-bounces at contesting.com] On Behalf Of Sherman Banks
> Sent: Wednesday, June 13, 2007 1:34 PM
> To: 'Fourlanders'
> Subject: Re: [Fourlanders] adjusting takeoff angle
>
> How about a simple dipole antenna?  Something that can take full power 
> so we can switch the amp from the stacked beams to the high-radiation 
> angle antenna easily?
>
> -----Original Message-----
> From: fourlanders-bounces at contesting.com
> [mailto:fourlanders-bounces at contesting.com] On Behalf Of Rogers, Ron
> Sent: Wednesday, June 13, 2007 1:18 PM
> To: Paul Yeager, ABR(R), REALTOR(R); Fourlanders
> Subject: Re: [Fourlanders] adjusting takeoff angle
>
> Hi guys,
>
> For those that weren't on the mountain to hear our discussions about 
> this 6 meter antenna experiment, here is some history.
>
> This W4NH idea started between myself and NX9O a few weeks ago when I 
> was discussing a 6 meter experiment that we tried at W9ICE in EN60 
> with our frustrations of not being able to score 6 meter contacts into 
> eastern PA and NY where some key population densities were. Brian 
> picked up on a fact real quickly and pointed out that the areas being 
> targeted by W9ICE were the same areas targeted by W4NH and, in fact, 
> were about the same distances.
>
> A quick calculation of our W9ICE easterly take off angle and E-layer 
> reflective result showed our first touch-down point to be out in the 
> Atlantic ocean somewhere. So, one of the final W9ICE contests we 
> simply put a Cushcraft 5 element beam on the ground and pointed it in 
> the desired direction, then propped it up to about 45 degrees and had 
> a coax switch back at the station to switch between our 2 antennas.
> The result was that we started harvesting more close in contacts (500
> miles) using the antenna pointing upward. It appeared that the 45 
> degree angle off the E-Layer (un-enhanced) shortened the first touch 
> down point to about 500 miles out.
>
> Now, if you add up what we use on Soco Bald on 6 meters (5500'
> elevation, stacked 5 element beams, and tight vertical plane take-off) 
> theory says this is actually detrimental to our desire to put the 
> 18,000 Watts ERP into the high population areas (or even hear the 100 
> watt stations calling you) within 500 miles of our location. In fact, 
> it would suggest that the incident angle to the E-Layer would be even 
> further out, thus even a longer distance to first touch down point.
>
> If you take a quick measurement of the shortened 500 mile radius from 
> W4NH desired by us, that would include New York, Philly, Cleveland, 
> Chicago, St. Louis, Jacksonville, etc.
>
> If you could view the 6 meter log Sunday evening when there really 
> wasn't any wild sporadic "E" openings taking place, the suggestion was 
> made to point the 6 meter beams to the W-NW after they had been 
> pointing to the N-NE, what did we see started happening ?
>
> We actually started scoring contacts in the DN & DM grid 
> areas.......yep, about 1200 miles out. That's why some of us suspicion 
> we may be overshooting the upper east coast population density using 
> too high of gain antennas at such a high altitude.
>
>
> For the elevated antenna experiment we already have a beam lined 
> up......a Cushcraft 5 element beam not being used right now. We don't 
> need anything fancy, and certainly DON'T need a lot of gain and 
> directivity for this experiment.
>
> It's light enough for the Yaesu 5400 AZ-EL rotor and we already have 
> the mounting figured out......IF we want to do it that way in Sept.
>
> But, the initial plan in Sept. was to simply use the Cushcraft, set 
> its ass on the ground, point it toward FN21/31 (or EN51-61), then 
> point up toward 45 degrees, and held there by a inverted "V" wooden 
> frame made from 2X2 lumber or even wooden step ladder. I have 100' of 
> Beldon 8214 coax and a 2 KW antenna switch to handle the power.
>
> We just think it would make an interesting experiment for W4NH to try.
> Who knows. If the theory pans out and validates a few assumptions to 
> us, it would make a nice case study to present at an upcoming VHF 
> conference.
>
> Anyhow, enough rambling about theories for now..........
>
>
> Ron
> WW8RR
>
>
> -----Original Message-----
> From: fourlanders-bounces at contesting.com
> [mailto:fourlanders-bounces at contesting.com] On Behalf Of Paul Yeager, 
> ABR(R), REALTOR(R)
> Sent: Wednesday, June 13, 2007 1:28 AM
> To: Fourlanders
> Subject: [Fourlanders] adjusting takeoff angle
>
> Ron WW8RR points out that our high-gain stacked beams are likely 
> striking the ionosphere quite some distance away, due to their low 
> takeoff angle.  Ron further suggests that this is causing us to miss 
> closer in stations that we might be able to work, if could arrange a 
> higher takeoff angle.  (Ron - please let me know if I have misstated 
> something here)
>
>   I see two obvious ways to change the takeoff angle.
>
>   1) Mount anntenna(s) on an az-el rotator.  This seems pretty simple, 
> but when one considers the details, it becomes a bit complex 
> mechanically.  How does one mount a horizontally-polarized yagi on an 
> az-el rotator?  The only way I can see is to mount it on a rather long 
> "boom", rotated by the elevation rotator.  The boom needs to be rather 
> long to avoid interaction between the antenna and the tower/rotator, 
> and may need to be fiberglass or other non-conductive material to avoid
> degrading the performance of the antenna.   This will also place quite a
> side load on the rotator and tower, unless the boom is extended to the 
> side opposite the rotator with a counterweight.
>
>   Alternatively, we  might extend the antenna's boom, then add a right 
> angle to the rotator.  This increases the load on the elevation 
> rotator considerably, unless a counterweight is added.
>
>   See what I mean about mechanical complexity?
>
>   2) Using a similar antenna arrangement to the one we used for the 
> contest, adjust takeoff angle by adjusting the phase between the two 
> antennas.  Mechanically, this is no more complex than the current 
> arrangement.  Electrically, it's quite more complex.  Not rocket 
> science, but certainly more complex than a single feedline running to 
> a splitter feeding both antennas.
>
>   We could do something as simple as selecting upper/lower/both yagis, 
> or get more complex and switch sections of feedline in and out to 
> actually change the phase.  Two switchable sections of feedline would 
> give us 4 choices of takeoff angle - in-phase pluse three different 
> phase delays.
>
>   Anyone have any idea how to model phase vs. takeoff angle for out 
> pair of yagis?  Speaking of modeling...  how about takeoff angle vs.
> "skip distance"?
>
>   I suggest that we test the concept using a lightweight 6m yagi, like 
> the 4 element Comet I have, mounted on an az-el rotator, either during 
> the September contest or at some time between now and then.  This 
> would give us an idea of whether or not the concept is viable, and 
> what sort of adjustments to takeoff angle are necessary.  Once the 
> concept is validated, we could construct a "phasing system" to use 
> with our pair of yagis.
>
>   So... what do y'all think?
>
>   73 de W4SKI
>
>
> Paul Yeager, ABR(r), REALTOR(r)/Broker Accredited Buyer Representative 
> Mountain Fever Real Estate
> 828 400 9442 (cell)
> 828 926 2545
> 888 926 2545
> 828 926 3860 (fax)
> paul at mtnlist.com
> www.mtnlist.com
>
> What is ABR(r)?  Find out at http://www.rebac.org 
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