Anyone got an idea for a simple way to flip a light weight 2m yagi from horizontal to vertical polarization?
I used to do it by mounting the boom in a sleeve and attaching a couple of stand offs that were attached to a rope. That worked well but I can't use it in my new situation.
I am thinking of a stepper motor, or maybe a solenoid-activated push rod - press zee button in the shack and it flips - or am I being too flippant?
My thoughts relate to the basic Yagi design. Whilst in theory the idea should work, one needs to consider the characteristics of the Yagi being used. Presumably one is looking for good performance on the lower end (144.000 to say 145.000 MHz) when horizontally polarised, and likewise for the FM segment (146.000 to 147.975 MHz) when vertically polarised.
You say "lightweight" Yagi, but of what boom length?
Unless the Yagi is say a OWA design for an appropriate frequency to give coverage across the entire band, you are unlikely to achieve coverage across the band with a single Yagi. One possibility would be to build effectively 2 Yagis cross polarised on the same boom, as implied by Alan VK3DXE. The horizontal Yagi would be designed for the lower segment for SSB/CW/WSJT use, whilst the vertically polarised Yagi would be for the FM segment of the band. In that case, it would be appropriate (IMHO) to use separate feedlines for each individual Yagi.
Whichever you decide to go, good luck & let us know the results.
Consulte the old WIA handbook written sometime in the err ... 70's.
It has an example which isn't too hard to construct.
It's a simple lever on a rope system.
It can be improved with a pulley reduction system so that the mount can be stiffer (using greased clamps) but easy to crank at the bottom of the pole/tower.
If the system is on a rotator, then any twist in the rope can impede it.
But if you need to go modern or electric controlled, then just mounting a cheapy rotator on its side makes the task easy. But even cheap rotators are +$150. (The chinese haven't worked out how to clone them yet).
But the best and cheapest is to buy a small satellite actuator. They're about $25-$30 and they are very easy to set up. construct your antenna in it's sleeve as you had intended using some pipe clamps to hold it in place. Attach a lever arm off the boom of the yagi so the actuator arm mounts on the end of it.
The other anchor point of the actuator is attached to the pole or cross arm that you have mounted the yagi on.
Some of the actuators have mechanical limit switches in them. So all you need is a 12V supply and a switch for V/H and run the actuator into the limit switches.
If the actuator doesn't mechanical switches, it will have a potentiometer. A simple circuit using transistors and a relay is enough to create electrical limits.
I use a hinged arrangement on my 6m, 2m and 70cm yagis for my field day setups for two reasons : (1) polarisation change; and (2) it is easier to set up on the masting pole because the yagis remain horizontal when the mast is leaning over during assembly and when upright for use.
I put photos of the arrangement on my web site at http://www.vk4adc.com/web/index.php/fie ... iques.html a couple of years ago and those same yagis have been used for almost all field days since. In essence, it is a normal "door-style" hinge pop riveted to an aluminium plate about 100mm square and that plate is bolted to the boom via the original u-bolt holes. A second 100mm square plate has the original u-bolt plus v-block and that is fixed above the yagi onto the masting pipe. I use a silver nylon rope attached to the end of the nearest element via a short length of conduit (with a hole in it's end) to pull the yagi vertical.
The 2m yagi is flipped from horizontal to vertical for FM contacts and the design is such that the yagi plus feeder system (T-match without peaking capacitors plus 1/2 wave coax balun) is wide enough in frequency so as to still provide a good match ( < 1.5:1) across the whole 2m band. Normal gamma matches don't usually have quite as wide an SWR bandwidth, but the fundamental yagi design itself is a very important factor.
Your local satellite dealer has them.
Heaps of satellite dealers around these days.
I'm not sure of where some are in VK4, but the yellow pages or as suggested ebay will sort you out.
They also make for a cheap satellite antenna setup.
Using a normal rotator for azimuth and using a satellite actuator for elevation.
They are ideal for any turns of less than 120 degrees.
VK4WDM wrote:Anyone got an idea for a simple way to flip a light weight 2m yagi from horizontal to vertical polarization?
I used to do it by mounting the boom in a sleeve and attaching a couple of stand offs that were attached to a rope. That worked well but I can't use it in my new situation.
I am thinking of a stepper motor, or maybe a solenoid-activated push rod - press zee button in the shack and it flips - or am I being too flippant?
73
Wayne VK4WDM
an electric window acuator will do the job , cheap from the wreckers and works fine
One thing I would say is satellite actuators are designed for all weathers and living outside. Electric window mechanisms from cars are not. Plus there are so many types... cantilver type, and a sort of coarse threaded bowden cable type. We take them out of cars when we put lexan windows in when they are built into rally cars. If it was my antenna, I wouldn't fancy one of these things moving it. If it was shielded from the elements in an attic, maybe...
I have decided to put horizontal and vertical elements on the same boom as suggested by several posters and do the same for 70cm. Then I will use a satellite actuator for elevation as suggested by Trash so I can use the setup for both terrestrial and satellite work. (I have never done anything with satellites - never even heard one. Something else on my retirement "bucket list."
