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Antennas

What antennas you use depends largely on the mounting positions available at your station. I can think of several broad categories of antenna sites.

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. 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.

Really cheap antennas

For packet stations where line of site is assured or very short distances are involved, (a mile or two?), consider home-brewing a quarter wave ground-plane or building a corner reflector for indoor/attic use.
dylan_440_ground_plane_crop_x400

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.

Article about 1/4 wave ground planes is here: SO-238-Ant

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.

Here is a photo of my first hack corner reflector. It's hanging in N3LTV's attic.
corner_reflector_n3ltv_attic

Masts and Mounting Structures

Tree mounting is discussed later in this page.

Mast mounting is very common in our Central North Carolina group. One common method is to use a 2" inside diameter or greater schedule 40 (really heavy steel) pipe of 20' length or so and then bolt a 10 foot 1+1/4" EMT Conduit 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.

The example shown to the right used a 5' TV mast in the top of a 20' tall 2" I.D. 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
aaron_node_nov2017_x400

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 top 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.

Yagis

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.
hygain_vb_25fm_i6_08205 higain_vb_25fm_yagi

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.
arrowantennas_220_and_440_i6_8206
arrowantennas_220_and_440_i6_8205

More TADD node pix. Click on the image to see a few more images and descriptions.
Antennas shown are:
  • Hygain VB-25FM 2m yagi,
  • Arrow 220-5s 220Mhz yagi,
  • Arrow 440-5s 440 yagi, and
  • MFJ 1532 tri-band vertical.

The white pole in the middle was the mount for an experimental antenna, now removed.
2016_n41598crop__x400

Fin NC4FG's Arrow 440-5s antenna shown with a Kenwood UHF mobile radio and bar stool for scale. . arrowantennas_440_s5__i6_08267x564

AES Ham Radio sells Comet, Cushcraft, Diamond, High Gain, Elk, M2, and MFJ yagi antennas

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 which I consider to be rather expensive! The a430s10 is made for 432Mhz and is out of its useful frequency range in the 440 to 450 FM band. It works great at 433 to 434Mhz. There are 8 in the network as of November 2018 including CHRIS, FFVC, TADD, ADAM, VON, GREG, AARON and BILLY nodes. The nice thing about having a link at 433Mhz is that it is easier to keep it from interfering with repeater operations or another link in the 440Mhz range.
The a144s5 seems to work quite well -- As of November 2018, six were in use, horizontally mounted, at TADD, TILL, DOUG, and GREG nodes.
The Diamond beams 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 433Mhz 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 supported by TK805d and Maxon SD125 plus many other commercial surplus radios.
 Diamond A430s10 mounted horizontal at AARON node
a430s10_i6_08263proc_x360

Here is the Diamond A430s10 mounted below a GP15 at the SKIP node. The A430s10 is shown in vertical mode with the KB430 side-arm accessory:
a430s10_and_gp15_i6_08199cr

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:
2015_davis_node_i6_05300sca 2015_davis_node_i6_05275sca

Antennas In Trees

The local network has seen 3 different methods for placing antennas in trees. These are: Tree to Tree dipoles are not generally very high gain but for 6m, where it is somewhat harder to get high gain, a dipole may be adequate. Furthermore, trees can support a 6m dipole at a decently high elevation above ground. The rope hung antenna is the easiest for achieving altitude and is somewhat subtle, an important feature when in an HOA community. The side-arm gives great versatility and permits yagis to be mounted.

Tree to Tree dipole

Below is a photo of NC4FG's tree to tree 6m dipole hanging about 15 feet above his mast mounted yagis. The technique for hanging a dipole usually involves sling-shots or other projectile throwing devices covered below. The dipole is suspended from its ends by ropes. One rope goes to one tree and is tied down. The other rope goes through a pully on a second tree and then drops to a weight which holds the dipole mostly straight. The reason for the pulley and the weight is that the two trees will move independently and you don't want your dipole ripped in half.
The cost of a tree to tree 6m dipole is about $35 for a W2DU-VHF balun, about $5 for wire, $3 for two insulators, $10 for a pulley, $4 for two eye hooks, $20 for 150' of rope?, and about $50 for RG8X coax.
fin_node_with_yagis_and_wire_dipole_7203x700

Side Arm Antenna

Don't get killed. I'm not an expert in tree health.
If the antenna is omnidirectional, the side arm has to put the antenna a large fraction of a wavelength away from the tree. For 6meters you'd want the antenna about 12 feet from the tree.
If the antenna is a yagi, you can aim the yagi directly away from the tree in which case the reflector could be almost against the bark. If the antenna is aiming across the tree, then you again want to space it out a large fraction of a wavelength from the tree. For 440Mhz, 70centimeters, you could have it 2 feet from the tree and the antenna would be nearly perfect.
In this photo, KE4VNC, has the antenna about 18 inches from the tree and the antenna worked as desired. billy_tree_sidearm_uhf_4596mc
The mount Billy is using is a Rohn WN24d which costs about $70.

Antenna in the Attic

Antennas can be installed in the attic. This is not ideal for several reasons: Household noise at 2m and 6m make those bands hard to use. Metal wire, ducting and other equipment in the attic will affect antenna performance. However, sometimes it's all you are going to get.

               

Notes on installing horizontal yagis in an attic

  • Look for horizontal pieces of metal that are within 6' of a horizontal antenna.
    Vertical pieces aren't that much of a problem to a horizontal antenna
  • Any metal that is 30" or longer that is within 6' of a 2m antenna is worrisome,
    but horizontal 1/4 wave pieces of metal are likely to be a problem (19 inches or longer on 2m, 7 inches or longer on 440) for a horizontal antenna.
    In a UHF 440 installation, the distances are much smaller since the wavelength is one third of 2m.
  • There should be no furnaces or big ducts in the direction the antenna is aiming.
  • Anything behind the antenna is ok. in front of or above or below or left or right is more of an issue.
  • The coax feed should drop straight down from the feedpoint on a horizontal antenna. Not go horizontal at all. On a vertical antenna the coax should go left or right from the antenna and then wrap around the back of the antenna.
  • Coax should go straight away from the antenna for at least a half wave (or straight up for a half wave) but running the coax parallel to the boom is also ok, depending on where on the driven element the feed point is located. Best is to go straight down or up as far as practical before curving it to run straight back to behind the antenna.
  • Look for sharp bends or kinks in the coax. The coax should be straight or gently bent.
    Coax lengths of > 50 feet or so should only be done with LMR400 or better coax.
  • Use N connectors for UHF 440 antennas.
  • Make sure you get a compass alignment OUTSIDE the house, and figure out where the beam should be aimed relative to the house, then go inside and point it correctly. The compass can be badly affected by metal and AC wiring inside the house so don't trust the compass while inside the house. This includes cellphone devices! Double check the angle used in the attic because almost everybody gets confused going into and out of the attic.

Note the image below. The coax is properly run down and out the back of the antenna.
My only complaint was that the metal duct was big and close enough that it could change the pattern.
Watch that any metal straps or wires going through the antenna are insulated.
Oddly enough, that strap holding the duct is not going to hurt the antenna pattern because it is perpendicular to both the elements and the boom, so long as it isn't metal on metal contact with the antenna, it shouldn't affect the pattern.
Doug is going to move the antenna to the left 9 inches or so which should make it better.
n3ltv_attic_diamond_a144s5_pipe_problem

               

Rope Hung Antenna

Hanging an antenna from a tree is a great thing, but you have to make sure the branches aren't right near the antenna or your antenna's performance will be compromised. The best omni antennas I've found for tree-hanging at a TARPN node are the Comet GP-15 tri-band vertical, and the Comet CX-333 tri-band vertical. Each are $160+shipping or so from
GP-15 R&L Electronics
GP-15 Ham Radio Outlet
CX-333 at R&L Electronics
CX-333 Ham Radio Outlet
The big disadvantage of each of these tri-banders is that they have ground radials and requires extra special care if hanging it from a tree. A second disadvantage of the GP-15 is that it is finicky about nearby foliage. Don't hang it such that there is foliage within 10 feet horizontal from the vertical radiating element. It wants to be hung below a long horizontal branch. The 6m performance is also expected to be weakened by close proximity to foliage. In practice the foliage should be kept a half wavelength or more away from the antenna.

Below is a tree-hung GP-15 whose base is 85 feet off the ground. Cost including 100' of JefaTech LL400 and 200' of rope was about $350.
$170 (antennna) $110 (coax) $6 (connectors) $50 (rope) $15 (pulley)
The iphone lens perverted the scaling as the car looks taller than the antenna though the antenna is 10 feet tall.
2015_i6_04896x700

Antennas which do not have ground radials include the Ed Fong tri-band vertical and the Austin Suburban Quad or Triband verticals. Both of these antennas perform as vertical dipoles, i.e. no gain to speak of.

Below is a 3 element 6m yagi hanging from a tree. This required a branch which was fairly heavy, fairly long, and was the first branch on that side of the tree.
The antenna, in this case, has 9' long elements and is about 6' boom-length. There is an 8' aluminum mast onto which the antenna is mounted. The mast is hung from the top and the coax is taped to the mast. This forces the masting to be vertical. The antenna, which is both balanced and light-weight, will then stay horizontal. The direction of the antenna is controlled by a very lightweight string tied to one end of the boom and to a tree or other object away from the antenna, mostly horizontal.
The advantage of hanging the antenna from a tree, instead of placing it on a mast on the house, was that the noise level caused by electronics and LED incandescent replacement bulbs is much reduced by being located away from the house. 2016_n41611crop_x700

Below is a Comet CX-333 144/220/440 tri-band vertical mounted to a 6' mast with a PAR antennas 6-meter stressed MOXON antenna mounted below. The MOXON is a 2 element beam directional antenna. The two antennas are fed into an HF + VHF diplexer to combine the two antennas onto a single coax. In the ham shack there is another HF + VHF diplexer. The VHF side is then fed into a tri-band 144/220/440 triplexer. This single antenna system provides antennas for four different ham radios simultaneously and is fed with one run of coax.
The total cost of this system including 200' of JefaTech LL400, 200foot of Synthetic Textiles rope, and 3 used triplexers and diplexers from eBay was about $650. The average of a new antenna system for a TARPN is closer to $90 per radio.
This one was $160 per radio but this one is away from household noise, is 20' higher than the house, and isn't visible to the casual observer.
The real flaw in this kind of system, compared to one mounted on a mast, is that the ropes and trees compete to wreck each other. Between squirrels eating the ropes and tree bark growing over the ropes, this is higher in maintenance than something on a mast. Expected life of this system is four years without major work.
cx333andMoxon_modified_3835_x700
quad_plexing_4698x700

Installing the rope-hung antenna

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.

Getting Started
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.
2014_03_22__rope_tied_to_coax_i4_0388
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 antenna and roll of coax -- the hard hats are out of picture. We just posed for this picture after lunch and before we pulled the antenna up.
Austin antenna and coax roll_i4_0388

Austin 144/220/440 antenna 80' up in tree
Click to zoom in
Austin_antenna_in_tree__i4_0390ed

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