Antenna steering

[VK2XSO]

I was having some fun with a piece of hardware and my mind was wondering into other topics and thought experiments I have seen over the years.
One of my favourites is the question, "Given a clock, how can you use it to measure the height of a building."
It's not about accuracy, it's about creativity.

So thinking about it along similar lines, I thought this question might create some interesting answers.

Given two 1/4 vertical antennas (or radiating elements) used to form a directional radiation pattern of any kind. How would you steer the beam of radiation ?

Points given for;
- Antenna gain/beamwidth
- Precision of the pointing direction
- Speed at which you can change the direction of radiation
- Bizarre or unique method used to steer the antenna/array.

[VK3YE]

I must admit to finding the clock one interesting so will give that a go.

Assume the clock or watch has numbers around it.

The numbers around it would be 30 degrees apart.

A 30 degree angle with respect to the 9 - 3 line would be formed by running a line between 2 and 7 on the clock.

Assuming the building is an erect block there is a 90 degree angle with respect to the ground.

One could pace away from the building to the location where you need to look up exactly 30 degrees to see its top.

Count the number of paces and estimate the distance.

The other angle would be 60 degrees and a right triangle would be formed.

As we know the angles of all sides and the length of one it should be possible to work out the length of the side opposite the 30 degree angle and thus the building height.

As for the antenna one I'm reminded of what Les Moxon advocated with two loops and open wire feedlines to achieve instantaneous beam reversal.

[VK6ADF]

I must admit to finding the clock one interesting so will give that a go.

Assume the clock or watch has numbers around it.

The numbers around it would be 30 degrees apart.

A 30 degree angle with respect to the 9 - 3 line would be formed by running a line between 2 and 7 on the clock.

Assuming the building is an erect block there is a 90 degree angle with respect to the ground.

One could pace away from the building to the location where you need to look up exactly 30 degrees to see its top.

Count the number of paces and estimate the distance.

The other angle would be 60 degrees and a right triangle would be formed.

As we know the angles of all sides and the length of one it should be possible to work out the length of the side opposite the 30 degree angle and thus the building height.

As for the antenna one I'm reminded of what Les Moxon advocated with two loops and open wire feedlines to achieve instantaneous beam reversal.

Peter,the engineer in you is showing. I would attach a line/string/rope to the clock and lower it to the ground. Then measure the line/string/rope. Height of building then known

Not creative I guess.

[VK6ADF]

I was having some fun with a piece of hardware and my mind was wondering into other topics and thought experiments I have seen over the years.
One of my favourites is the question, "Given a clock, how can you use it to measure the height of a building."
It's not about accuracy, it's about creativity.

So thinking about it along similar lines, I thought this question might create some interesting answers.

Given two 1/4 vertical antennas (or radiating elements) used to form a directional radiation pattern of any kind. How would you steer the beam of radiation ?

Points given for;
- Antenna gain/beamwidth
- Precision of the pointing direction
- Speed at which you can change the direction of radiation
- Bizarre or unique method used to steer the antenna/array.

You don't specify a frequency so....could the vertical radiating element be turned into a vertical dipole and end up with a 2 element vertical yagi , shorting the other radiating element to it's other half to create a reflector or director. Then attach it to a Hills Hoist for rotating. Poor gain and beamwidth but the rest of the points are ticked.

Not really thought too hard about it.

[VK5ZD]

Hi

Re the antennas, mount them, say, 1/4 wavelength apart and vary the magnitude and phase of the signal to each antenna to steer the beam.

Re the clock and building, drop the clock from the top of the building when the second hand is on the twelve. Note where the second hand is in the wreckage thus determining the duration of the fall. Calculate the height of the building (d) using the formula d = 0.5gt², where g = acceleration due to gravity (9.81 m/s²) and t = duration of the fall in seconds.

[VK3BSF]

When the clock strikes nine am on a monday visit the council offices and ask for the building plans to ascertain the height.

For the two 1/4 wave antennae, fix one in a predetermined spot and get your partner (wife) to manually rotate the other around a compasss for beam switching and aiming ...

[VK6MB]

When I dropped the watch from the top, the second hand broke off

For the antenna you could use a VDA - http://www.dxing.eu/vda.html

73 Mike VK6MB

[VK2VHF]

When the clock strikes nine am on a monday visit the council offices and ask for the building plans to ascertain the height.

Make that 9.10am, so they can make their coffee.

[VK2XSO]

Re the antennas, mount them, say, 1/4 wavelength apart and vary the magnitude and phase of the signal to each antenna to steer the beam.

Now that's a creative answer. You haven't been too specific but I interpret it like having two transmitters used, one connected to each antenna.
Easy to control the phase and amplitude of each with relation to the other. This is typical of SIMO configuration.

I had expected somebody to suggest mounting the two elements on a boom or a plate and mechanically turning them. It's an obvious answer, but simple and not too complex.

Another obvious answer is to vary the lengths of the coax, either by switching fixed lengths in and out, or having a sliding trombone kind of coax.
I can think of many others but I haven't mentioned them because I'm trying to encourage others to think about them.
The antenna elements themselves are rather trivial, and you can configure them however you like. Placing them like a dipole is fine, though you may consider each antenna element can itself
be a dipole if you so wish. They can be dipoles, yagis, dishes or discones. Though this doesn't enable a level playing field, when compared to other ideas, they'll just be considered to be generic 0dBi radiating elements.

---

One of my favourite clock answers was to place the clock on the ground in direct sunlight beside the building.
Measure the shadow of the clock and then that of the building and the height of the clock scaled will give you the height of the building.

[VK4GHZ]

One of my favourite clock answers was to place the clock on the ground in direct sunlight beside the building.
Measure the shadow of the clock and then that of the building and the height of the clock scaled will give you the height of the building.

I like the logic involved, despite the potential margin of error introduced.
It does offer some backwards compatibilty with noisy ye old analogue clocks though!

[VK2AVR]

I had expected somebody to suggest mounting the two elements on a boom or a plate and mechanically turning them. It's an obvious answer, but simple and not too complex.

Fine for VHF+, but it would be quite entertaining to see somebody with an enormous lazy susan for 2 x 40m verticals

Another obvious answer is to vary the lengths of the coax, either by switching fixed lengths in and out, or having a sliding trombone kind of coax.

Considering the beamwidth of a 2-element array though you could probably handle 360 degree coverage with only a few phasing combinations:

1) elements fed in phase - you would get 2 lobes in opposite directions perpendicular to the plane of the array
2) elements fed out of phase (via coax phasing harness) - you would get a lobe off the end of the array
3) elements fed out of phase (reversed) - a lobe off the opposite end of the array

90 degree steps would pretty much cover it, without too much complexity.

[VK6MB]

Fine for VHF+, but it would be quite entertaining to see somebody with an enormous lazy susan for 2 x 40m verticals

This http://www.dxing.eu/vda.html can be rotated for 20m, for 40m you would have to use the 28m Spiderbeam mast

73 Mike VK6MB

[VK2JDH]

One of my favourites is the question, "Given a clock, how can you use it to measure the height of a building."
It's not about accuracy, it's about creativity.

.

Assuming old school clock with hands.

Set the stopped clock's minute hand to 52 min 30 sec past the hour
Start pacing from the base of the building in 1 M steps ( thats about average ) and keep the clock level
When the line through the minute hand points the the top of the building the number of steps is the how high the building is.

[VK2XSO]

I should clarify to the readers that these are thought experiments.
The frequency is basically irrelevant. We might consider a 5 element yagi at 10MHz in free space behaves just like a yagi at 10GHz.
Steering the 10MHz with a massive theoretical rotator is much the same as steering the 10GHz one with a tiny little one.

The same can be said for the clock. There is no description as to what this device is, or how you must use it. That's the point.
It can be an hour glass or a cesium beam.
So another of my favourite examples is to use two clocks, that one to the top of the building and the other is placed at the bottom.
The delay between the two clocks is a function of the height of the building.
One might even take into account the relativistic effects of gravity for a more precise answer.

---

The answers with regard to the steering the antenna don't have to be physically easy to achieve or practical. They just have to be theoretically feasible.

Consider this answer. The transmission line to each radiation element can be stretched. Now you're all thinking of me stretching a piece of RG58 like a rubber band
If the wire is elastic then it can be stretched and contracted at will causing variation delay to each element. It doesn't have to be coax. The transmission line can be anything you like, it can be open wire.

It's not too practical to stretch wire in the real world, but it does provide insight into subject. I might suspect that some F calls or non technical readers might be reading this thinking about or learning how antennas can be steered, though technical without mechanically moving the radiating elements.

I haven't excluded mechanical options from experiment because such restrictions also restrict creativity.
The funny answers are often the most interesting.

[VK2AVR]

This http://www.dxing.eu/vda.html can be rotated for 20m, for 40m you would have to use the 28m Spiderbeam mast

That looks like a great antenna, but unfortunately it's 2 x 1/2 wave elements so not *quite* in keeping with Trash's specifications. Although, Trash.. if it's a thought experiment and "the frequency is basically irrelevant" does that mean we can use this 20m rotatable vertical and consider that it has 2 x 1/4 wave elements on 40m? We're just using it on the wrong band.. silly us!!

Jokes aside, both the clock and antenna problems have been thought-provoking discussion. Well done Trash

[VK2XSO]

The radiating elements can be anything you like. If 1/2 wave floats your boat, then that's ok.
Like the frequency the antenna type itself is basically irrelevant. They can be reduced to an equivalent isotropic radiator to level the playing field.

Think about all the things you can change that will change the amplitude, timing, position and the phase of transmitted signal at each radiating element.

[VK2GFR]

My head is hurting Trash,

But how this for the height of the building....
Assume your finger is say 20mm wide, apply a scale to that and add more fingers to the Horizontal plane.
The more fingers, the more the multiple of scale increases proportionately.

So, if 20mm (one finger)= 10mtrs (at 50mtrs distance away) then the height could be extrapolated into a guesstimation of variables dependent on the size of your finger.
Simple! Eh? But you might just run out of fingers, that's where many friends are most welcome to attend your height party.

As for the antennas... a slinky style feed might just be the answer.
But the mechanics to "push-me-pull-you" of the cable feeder might induce polar patterns adverse to the required application.
But then again you only asked for a theoretical approach and I am no Big Bang expert.

[VK2XSO]

How would you use a slinky as a form of transmission line ?
(I can think of a couple of methods, but we'll use your brain for this exercise.)

Nobody has suggested using a hybrid yet ??? (which is actually the answer which wins out for simplest solution but not the most entertaining).

[VK3YE]

How about a series of vertical plastic pipes with conductive salt water (or better still mercury) forming the elements?

Controlled by valves (not the glass type) and pumps.

The height of the mercury columns and which pipes were filled with it would determine operating frequency and directivity.

[VK4TS]

Trash - assume we are going to fix the verticals - there are three variable components that can be adjusted pretty easily.

The phasing between the antennae, the length of the antenna and the ground plane.

If we take out length of the antenna there is a simple two element reversible beam using just a modified three way switch. Using 135 degree line you can reverse directions of the array - the switch needs to leave the unused coax open circuit - this will provide inductive load to the unused vertical causing it to drop frequency and act as a reflector - the opposite is also true - - Combining the feeds will create a broadside array Need to use 1/4 75 ohm that will again be close to a four square in performance without the front to back side interference is cut down of course. You will need to design some relays to make it all work or experiment with the feedlines so you can easlly switch the 75 ohm in and out - in practice you may find it easy enough just to leave it in line..most modern rigs will handle the mismatch.

The fourth option would be to ground one element and the other would act as an omni direction radiator. At our contest station we use a 40m four square and we have the option to switch it to an omni antenna - it is very effective to have the four basic directions plus omni..

So with a three way switch two elements will have the performance of a four square in two directions -

From VK4 with the Asian QSM I would be inclined to be broadside to the USA to null Asia and then have the gain towards EU SP LP and SA SP.

The other item that is not adjusted often is the ground plane Consider a ground mounted vertical with two radials = very high lobe with a lot of radials= low angle...if you can adjust the ground plane you can adjust the take off angle..