I operate portable only and usually throw up an EFRW or linked dipole for 40-30-20 on a summit.
I’m planning to build a 40m horizontal delta loop and 20m bobtail to experiment with a bit of gain and low takeoff angle to attempt to work DX stations using low power. If it works well and the setup is easy enough, I’ll bring it to a summit.
Here’s one example - Long distance between supports high enough for a 40m bobtail.
This park is near my house in Vancouver, Canada and the gain will point to the US and down into South America.
To keep things simple, I envision using my arborist throwline to place the wire, running the rope over the limb and back down, then use a few feet of shock cord to keep tension and allow for branch/tree movement where I tie off. Long lengths of cord (150+ft) are the only downside I see.
The antenna wire I have on hand is DxWire from SotaBeams. It’s got 130lb tensile strength and weighs 4grams per meter. My insulators will be cutting board cutouts for the corners/guying points.
Questions:
What size paracord are you using for non-permanent installation of long/large wire antennas? Should I go with 95 cord (95lb test) or 275 cord (275lb test).
Is there another rope/cordage you recommend? I want to get it right before I order 1000ft.
Any recommendations for wire that is cheaper than DxWire in case I want to build an 80m loop?
What other wire/tree based antennas offer gain over a high dipole that could be setup on a summit?
Well, Mike, how much power are you intending to run??? I built my half-square which is two thirds of a Bobtail, out of 26 gauge teflon wire and support it with thread, that is, 40 pound test non-stretch fishing braid. This has essentially no weight, no wind resistance, and has never ever broken.
The other approach is “What’s cheap enough that I can leave it behind without tears” We use “brickie’s twine” for Field Day. That probably does not translate into Canadese, but it is the stuff bricklayers use to get a straight line when bricking a house. General contractors use it when sting-lining a cement foundation, too. On the wire side, following the “cheap is best”, I’ve hade good success with electric fence poly-cord (usually 6 fine strands of steel wire in it). In VK, it runs $37 for 500 mtrs, delivered.
I used a 40m delta loop at home made from DX Wire between trees and it was reasonably effective. The DX wire worked well for a semi permanent installation and survived several Storms slung between trees, but I found it quite hard not to kink the wire which dramatically reduces its strength. It is also very nearly invisible in woodland which is good for hiding my antennas from any nosey neighbours but bad for trying to find the end of the wire… So my take on this - I would use DX wire for a longer stay than a sota activation, but I would use something cheaper, more visible and field repairable for a SOTA antenna. ( This is just an opinion based on by use at home with the antenna in a similar arrangement - up trees attached with a throw-line support ). PS New chasing antennas are a 230ft Doublet, and a DX commander which most days seems to have the edge over the loop. For local contacts the doublet seems to have lots of NVIS and the vertical seems to be better for DX. Most of our summits don’t have trees so my summit antennas are based on a mast… 73 Paul
PPS Impressed with your dog on the summit, mine (Woody) unfortunately takes an active interest in the activation joining in with the QSO with one chaser reporting that I had a problem with modulation as it sounded like a dog barking…
I have an endfed for 17/30/60m with traps that is just under 30m long. At the end of the wire is a mason’s cord about 15m long to pull the wire over a branch.
The wire is 0.14mm² (27 AWG) and the cord is 1.2mm, the cord should have a strength of 45kg.
Since I carry everything on the summits, I want it to be light. So far I have not had any problems with it.
I often just take a stone, tie the cord to it and throw it over a branch. Because everything is so light, the stone does not need to be large to pull the weight over the branch.
My wire is yellow and the cord is neon yellow - so it is easy to find in the undergrowth.
All my endfed are made of this material and have been through many activations.
There is gain and gain Mike. Tree mounted aerials can work very well indeed.
Do you want low angle gain (better for working DX) or high angle gain for closer in? Basic antenna theory. I wouldn’t be prepared to go to as much trouble using trees to support antennas such as bobtails, vee beams or even a rhombic (!) on a summit.
However, I have considerable experience in using tree mounted antennae in my home station. The presence of the tree does not significantly impact on what can be achieved on the HF 30-160m bands.
I’ve used tree mounted aerials in every QTH I have lived where there have been trees. Maybe in some cases, just to tie off the end of an inverted vee or a dipole etc. In my current garden I am fortunate to have a 40 feet mature beech tree supporting three pole/wire mounted antennae. The tree is climbable so it is possible to mount fibreglass poles in the top of it using a mixture of velcro straps and large cable ties. My three antenna set up for the 30m-160m bands works quite well. I have an Off Centre Fed dipole for 80m-30m, a full size quarter wave for 80m with the same common coax feed via a 1:2 UNUN, going to a 160 meter inverted L. So In the top of the tree I have three poles protruding (see pic). The 80m quarter wave and 160m quarter wave inverted L are fed from a connection box under the tree (see pic) which houses the incoming coaxes and the 1:2 UNUN. From the box at ground level I use two 18 SWG insulated machine (very cheap - 2.5mm OD) radiating wires which go up into the top of the tree where they enter the inside of two 10m HD fibreglass fish poles. The 80m quarter wave vertical tops at at 64 feet. The 160m inverted L has the wire fed out from the top going to my house where it is terminated at a height of 28 feet. I have around 2000 feet of buried radials under my lawn, and one 350 feet radial above ground around the garden borders.
The OCFD is coax fed from the ground with RG-213 coax up to a 6:1 Balun at the top of an HD fibre glass swaged pole at 45 feet AGL. The OCFD works quite well on 60m band, and is better match via an ATU there than the 80m vertical and 160m inverted L are. I’ve had this arrangement up since 2017.
It is built to work DX but it also functions well for chasing SOTA. I don’t use these antennas on the higher bands as I have antennae for those bands that exhibit more gain than those mounted in the tree for use on 20/17/15/12/10/6m.
I do use builders string line for portable antenna anchoring when desperate - the missus is a carpenter & not sure if she notices her stringline getting shorter and shorter.
But I would not recommend it. It is terribly prone to tangling (seems to be designed to tangle) compared to normal light weight tent guy rope which is my usual material. It is also very stretchy so you have to tension out all the stretch to use it. The breaking tension is also not great.
@G4IPB - Thanks. I hadn’t considered that DXWire can be tough to work with.
The dog picture isn’t on a summit - it’s in a campground. He’s almost 15 and doesn’t make it up the hills anymore. He was thrilled to be in bed.
If I’m chasing, I’ll still be portable, so I’d like to be operating in less than 30 mins.
@G4OBK - Looking for low gain. Part of the challenge is seeing if I can come up with design that is deployable on a summit. There are a couple good ‘chaser’ parks near me to try a larger/higher than a dipole up 6m or an EFRW up a tree. I love the look of that tree. I’m in an townhouse and can’t put up a permanent antenna from my QTH.
@ZL4NVW - I won’t use builders string. I don’t think it will slide through the canopy well. I’ve ordered 1000ft of 80lb .8mm kevlar kite cord…about $30 canadian, shipped.
@DL6GCA - That is pretty close to my current approach. I take an arborists throw weight and get it up a tree, then I pull the weight back up to the top of a branch, connect my antenna, and let the weight drop to pull my antenna up to tree. I never have to worry about tangling the antenna because it doesn’t pass through the tree.
The last two issues of Radcom (Vol 99 No 7 and 8) have featured the half-square antenna for 20m, showing that the full wavelength halfsquare has a broadside gain of 2.6 dBi (but with the disadvantage that it becomes directional so there is significant loss off the ends) and a reasonable performance in low angle radiation. I am experimenting with the end-fed version using a 49:1 matching transformer, this also gives good gain on 21 and 28 MHz and operates as a low dipole on 7 MHz. In my case this is a chasing antenna which can be installed at the far end of my long garden, end on to the houses to reduce reception of radiation from appliances, the need for two masts makes it less useful for treeless summits! To get full benefit I intend to get a good low loss coax but with RG58 feeding a temporary lashup it looks promising.
The 40m full wave loopI had was an excellent receive antenna and consistently had lower noise than anything else I was using, however in the arrangement I had it could not have been very efficient as it was usually a few dB down on transmit compared with anything else I used. This could have been due to the run of coax from the remote matching transformer…
Gain of the half-square is said to be essentially similar to a two element beam, but there is a difference. It’s take-off angle is unusually low, so it will be most effective for long haul communications and when low angles are being propagated. - fred
On a day to day basis you are probably right Phil. Where these things can be worthwhile is on things like the EU<>VK days when you can erect something like this and leave it pointing at where there should be DX and it should help. Of course people work lots of interesting stations on those events with often quite mundane antennas but having one of these could give you an edge. You’d probably want the 1/2 square and 1/4GP as well so you have the DX direction and general coverage sorted. That’s 3 poles to carry and starts to sound more like a team event
@G8ADD. I’m planning to also use a 49:1 to feed it from the bottom.
@G4IPB. I’m running max 60 watts, but a short run of coax. Was the loop horizontal or vertical?
@KT5X. I’m looking for the low take-off angle to be able to work DX.
@G3CWI. The bobtail curtain is 5+ dBi, also with a low takeoff angle. I if it’s bottom fed from the center, I think I can get away with two support points.
@G40BK. Most of the time I’m going to throw a line in a tree for an EFRW or EFHW when activating. When chasing portable I’d like to experiment with different designs since I’ve can’t operate from home.
@MM0FMF. Agreed that if I’m on a summit it’s a special occasion or overnight camp to go to the effort to set it all up. If it helps get an s2s to EU or VK/ZL, totally worth it.
@K6EL. Do you have a pic or description of the webbing boom? I’ve thought about a 3 element inverted V yagi when each element is secured with tent stakes in the V position. Also considered forming the elements into a triangle with small gap between the ends of the radiator to minimize the width of the beam.
We use “brickie’s twine” for Field Day. That probably does not translate into Canadese, but it is the stuff bricklayers use to get a straight line when bricking a house. General contractors use it when sting-lining a cement foundation, too. On the wire side, following the “cheap is best”, I’ve hade good success with electric fence poly-cord (usually 6 fine strands of steel wire in it). In VK, it runs $37 for 500 mtrs, delivered.
