Tower and masts may afford a top mounted omnidirectional vertical as well as end-mount yagis, or even room for a 6meter horizontal yagi.
Attics can afford multiple high frequency yagis and maybe a 1/4 wave ground plane for 6meters. Attics are best for high frequencies however because in-house noise tends to make 6meters deaf and sometimes even 2meters is impacted.
Roof mounts with room for only one omnidirectional vertical can still have multiple radio links by using a multi-band antennas.
Tree mounted antennas can be positioned in several ways, hung from a rope, top-of-tree placement, side-arm placement.
Side-arms are great for short yagis and omnis designed to be mast or tower mounted.
Rope hung antennas must usually be omnidirectional verticals, though with a little ingenuity a yagi may also be suspended.
This 446Mhz antenna is about a foot tall for 446mhz and cost about $6 in parts, not counting the coax cable. The parts cost more than that but yielded half a dozen antennas.
There is no problem hanging this from a tree. On 2m and 6m the materials for the ground plane might need to be stiffer than what you can get away with for 440.
This antenna was constructed using 10AWG solid ground wire ($22 for 50 feet on Amazon) and a SO239 chassis connector.
KC3IBN is using this antenna for a 1.5 mile TARPN point to point link near Danville, PA. The other end of the link is a Comet GP-15 tri-band vertical whose 6m side is also a packet link.
Another really cheap antenna is a Corner Reflector.
The Corner Reflector has been a common design since before World War II because it is really simple. Building one for low frequencies would be almost impossible but for 440 it is really quite simple. The antenna has the advantage that if built with an eye toward simplicity it has more gain and directionality than any other antenna with as few parts. You could take the above quarter wave ground plane, drag its ground radials straight down and then build a reflective screen out of copper foil or chicken wire and then place that screen behind the antenna from the perspective of the direction you wish to aim. Here is an article from a 1940 edition QST magazine. qs11-40-kraus.pdf on building these antennas. Keep in mind while reading this that you are interested in the simple antenna, not a great antenna! An outdoor worthy corner reflector for 146Mhz could cost hundreds. But an attic worthy corner reflector for 446Mhz could cost $20 and take almost no precision.
The plans for my first corner reflector:
The reflector panels consist of two 2' x 2'10" frames built out of 1x2 pine. I bought 25' of 3' tall galvanized steel screen fencing from Home Depot and cut out a 6' length. Then I built the two frames, one on each end of the 6' screen, leaving a 4" gap between the two so the screen could fold. The angle between the panels is 90 degrees. Then I put horizontals on the top and bottom of the reflector to hold it rigid. I ran a 1x2 rail forward and back from the focus and then taped or tie-wrapped a vertical between the two front-back rales. I taped a 1/2wave dipole, fed in the middle with coax, to the vertical and ran the coax back through the middle of the screen.
N3LTV discovered that the best place to mount the dipole is about 11" from the screen.
Pay attention to the spacing of the frames at the back by the corner. You want the two frames to be close to exactly parallel at the back. You also want the two reflector panels to be vertical when testing and when screwing down the horizontals.
When I built mine I used #8 hardware to screw the horizontal members to the frame so I could take it apart and move it to the attic.
The corner reflector worked about as well as a 6 element cushcraft 440 yagi.
|Mast mounting is very common in our Central North Carolina group.
One common method is to use a 1.5" inside diameter or greater heavy steel pipe of 20' length or so and then bolt a 10 foot 1.5" TV mast on the inside of the pipe.
There are several pipe suppliers in the region.
The nice thing about this arrangement is that it gets you above the roof of your house or out-building without climbing and provides mounting for VHF yagis and a vertical.
It may also be used free-standing with three guy ropes tied to heavy trees (use eye bolts at the 6' level of 40 year old trees, for instance).
Expected costs for the assembly are about $75 for a 28' tall mast.
If you are interested in going the heavy pipe and TV mast route to make a 28' mast, put out a query on the TARPN yahoo group and somebody will set you up.
The example shown to the right used a 5' TV mast in the top of a 20' tall 2.5" steel pipe.
This is the AARON node and supports an 11 element 433Mhz horizontal yagi and a 2 element 50.99mhz MOXON yagi.
|Click to Embiggen|
Another solution is to use a push-up mast. This company sells push-up masts up to 38' high for $150: 3 Star Inc.
A push-up mast is shipped with several pipes inside each other with a guy-wire/guy-rope attachment point at the top of each of the pipes. The tope of each pipe also provides a tightening ring for the pipe mounted inside. The user would stand on a step-ladder and push up the thinnest pipe to its maximum extension, then tighten the ring for that pipe. Next the 2nd thinnest pipe is pushed up to its maximum extension and its hardware is tightened. Some of these masts have five pipes inside each other. This provides up to 38' of mast, shipped in a single box of about 10' long.
Hy-Gain end-mount 5 element vertical 2m yagi, VB-25FM.
Gigaparts has the VB-25FM for about $54
The left photo is from the TADD node. The right is from the FIN node.
Arrow Antennas makes and sells a decent end-mount yagi for 220, and for 440Mhz.
They also have a center mount (horizontal) 2m yagi and 6m yagi.
Here, from the TADD node, are the 220-5s 220Mhz antenna, mounted horizontal in this case, and below it is the 440-5s 440Mhz Arrow antenna, mounted vertical.
|More TADD node pix.
Click on the image to see a few more images and descriptions.
Antennas shown are:
The white pole in the middle was the mount for an experimental antenna, now removed.
Gigaparts has very competitive prices.
If you have a rigid mount available, end-mount Yagis are much nicer than the multi-band omni antenna. In some cases, height is better than gain, but gain sure is nice.
Diamond makes a pair of good working yagis, a144s5 and a430s10. They cost about $55 each. They are each equipped for horizontal mounting. For vertical mounting you need a side mount bracket / side-arm. Diamond sells this as an accessory for about $25! The a430s10 is made for 432Mhz and is out of its useful frequency range in the 440 to 450 FM band. It works well at 433.1Mhz. There is one in use at the AARON node site in Knightdale. The a144s5 seems to work quite well -- One is in use at the DAVIS node in Apex, but he had to buy the side-arm.
The a430s10 may be assembled in about 2 minutes without tools. If you have a link which can use a yagi on each end and can be supported by 435Mhz radios, this may be the way to go.
One notable feature is that the antenna tuning is fixed. It takes no time at all to tune it, because you can't. The A430s10 is good for the 433.1 to 433.9 Mhz frequency range.
Diamond A430s10 mounted horizontal at AARON node
Here is the Diamond A144s5 mounted below several HF and VHF antennas at the DAVIS node.
The HF beam is not as close to the 2m yagi as it looks. The HF beam is very long.
The A144s5 is shown in vertical mode with the KB144 side-arm accessory:
You need to have Hard hats, Fishing line, Plumbers string (bright colored), Ropes, Pully, Gloves to grip rope. 5" long 3/8" ScrewEye, Shooter, Shooting device, Weight, Tape, Tie wraps. Coax on roll, pipe to support the coax roll.
This process involves physical manipulation of objects which have real weight and which if allowed to fall on an unprotected head or face could be hazardous. Take appropriate precautions! Especially be aware of falling branches.
First you need to put a fishing line over the tree or over the appropriate branch.
Use a slingshot or tennis ball cannon with a tennis ball or a fishing sinker.
Once you get a string over the tree appropriately, you need to use the fishing line to pull a plumbers string over the tree.
At this point put your hard hats on and take appropriate caution.
Your coax should be on a spool about 20' away from under falling branches and the spool should be supported through a pipe or pole. Don't hurt your coax or your fingers.
Use the plumbers line to pull 550 paracord or equivalent. I like the Synthetic Textiles 770 pound stuff myself.
Pull the 550 over the path of your string, and through an eye bolt screwed into the tree at the 6' level.
Tie a marine pulley appropriate for 550 paracord to the paracord such that it can be pulled up the tree by tugging on the rope coming down the other side of the tree or branch. Tie the 550 paracord into a loop (call this the "loop paracord").
Put another paracord (pully paracord) through the pully and tie that to the coax at the bottom of the antenna. I did that by wrapping the pully paracord around the coax several times and then I taped it, and then tied at the bottom of the antenna and then tied again at the top of the antenna.
The idea is that the strain of holding the coax weight is on the rope and not on the antenna's coax connector.
Now drag the pully up into the tree (falling branch hazard here!) by pulling down on the loop rope coming back down the tree.
Tie off the loop rope by making a bow of it and then knotting it through the eye bolt.
Use the pully rope to pull the antenna slowly up the tree while standing out of harms way!! (EXTREME falling branch hazard here) while your buddy stands well back out of falling branch range and makes sure the coax is unrolling properly.
Walk back a couple of dozen (more) yards. Take a photo of your work. Now you can think about taking off your hard hats.
Austin 144/220/440 antenna 80' up in tree
Click to zoom in