G3TPW CobWebb Antenna for the 14, 18, 21, 24 and 28 MHz Bands
Author and source: http://www.g3tpw.co.uk/
Read more: The CobbWeb AntennaThe main advantages of the CobWebb over other 5 band 14 to 28 MHz antennas are that it is small, lightweight, strong (made from fibre glass), only requires a single support, needs no rotator, gives full size dipole performance on all 5 HF bands (without the end on nulls that straight dipoles suffer from), is fed by a single 50 ohm co-ax cable (via an in built air core choke balun), and most important of all, it produces a pure horizontally polarised signal with a confined electric field. This results in much reduced coupling to nearby conductors, so that losses and interference problems are reduced to the absolute minimum possible.
The CobWebb can be easily mounted on a single 20 foot aluminium scaffold pole, fixed to the wall of the house with a couple of stand off wall brackets. The pole can then be pushed upwards to put the CobWebb up at 30 to 35 feet, or lowered so that it is at roof ridge height, to overcome any possible planning problems!
All the other small multi-band commercial antennas that are available are less than optimum. The “broad band” folded dipoles and verticals have lossy transformers or terminating networks in them. These may provide a fairly low SWR over the full 2 to 30 MHz band, but so does a dummy load! Some trap dipoles have lossy traps and baluns, so that a nice 50 ohm match is produced on all bands. Others have no balun at all, the feeder cable will then need to be a particular length to reduce feeder radiation and provide a match. Doublet Antennas may have some gain on the higher frequencies, unfortunately every 3 dB peak has a 20 dB null in other directions! Other small “magic maths” antennas are available, but their performance is so poor that you can’t even hear them on the bands, to measure how far down they are! The many types of vertical antennas are best avoided, unless you have no neighbours, because of all the interference problems.
The inherent losses and poor radiation efficiency of the mini-beams negates any so-called gain. Remember that if a beam has a gain of 4 dB over a dipole in free space, it will be DOWN on a dipole! It will also only “work” over a very narrow frequency range. A dipole or a CobWebb has a gain of about 5dB over a dipole in free space, (due to ground reflection) or 7dB over an isotropic radiator (7dBi) and will work equally well over the entire band. The CobWebb has no lossy components in it, so there are no power limit problems for the QRO operators. The low loss and consequent high radiation efficiency also makes it ideal for QRP!
The G3TPW CobWebb Specification
Covers all 5 Bands. Gives a low SWR resonance on the 14, 18, 21, 24 and 28 MHz bands. The SWR at the band edges is mainly reactive, i.e. the resistive component is still near 50 ohms, so auto and simple ATUs can match it with low loss. Over 95% radiation efficiency on all bands! Have you ever seen this spec mentioned by other manufacturers?
Omni-directional. Talk to all the world, without the need for a rotation system.
Absolute Minimum of EMC Problems. Vastly reduced interference on both transmit and receive due to pure horizontal polarisation and confined electric field.
50 ohm Single Co-ax Feed. Built in co-axial choke balun to prevent feeder radiation. Standard PL259 plug on end of short lead. Feedbox and resonators all pre-assembled.
No Compromise Performance. Full size half wave dipole on each band, without nulls!
Fibre Glass Construction. Flexible so no metal fatigue problems in windy locations.
Simple Assembly. Fix fibre glass sections together. All screw holes pre-drilled. All elements pre-tuned, just uncoil them and fix to spreaders. No adjustments needed.
Small Size and Weight. Only 2.6 metre (8.5 feet) sides and 6 kg (14 lbs) weight when assembled. 1 metre maximum length parts for low cost world wide delivery.
Easily Erected. “V” bolt fixing to mast of up to 58 mm (2.25 inch) diameter. Can be fixed to 20 foot scaffold pole, which can then be pulled up to the wall bracket with rope.
160 Km/hour (100 mph) Wind Survival. As long as the mast/support can take it!
The G3TPW CobWebb Design
The most important design point about the CobWebb is that it is a completely horizontally polarised, confined electric field antenna, which provides maximum radiation efficiency and the absolute minimum of interference problems. TVI fears have encouraged many people to shy away from the HF bands, in favour of VHF, UHF or 160 metres.
New stations often begin operating on HF using an end fed wire or a vertical antenna, a recipe for disaster, sometimes even on QRP. After starting in this way and getting involved with various EMC problems, it is often found that planning permission for a horizontal antenna is refused. You can’t really blame your neighbour for being concerned. If that small inconspicuous vertical or simple wire antenna causes so much trouble, what would it be like with the proposed mast and special horizontal antenna? The fact that the use of horizontal polarisation, particularly if it is from a confined electric field antenna like the CobWebb, would probably cure the breakthrough problems is very difficult to explain.
During experimental work on a 5 band beam, using full size resonators on each band, it was noticed how well the driven element worked by itself. It also became obvious that a full sized dipole, up in the clear, worked far better than the multi-band minibeams!
The CobWebb is a full size half wave dipole on each of the 5 amateur bands, 14, 18, 21, 24 and 28 MHz, for maximum performance. There are no lossy traps, stubs or loading coils, so there is no reduction of radiation efficiency on any band. Each dipole is bent round to form a horizontal square, to make the antenna omni-directional. Thus no expensive rotator is required. Each resonator looks like the “square halo” that is often used on VHF, for SSB mobile work using horizontal polarisation.
The parallel but anti-phase “sides” of the antenna cancel the radiation that would normally be wasted as high angle radiation from a straight dipole and fill in what would otherwise be the nulls off the straight dipole ends. The resulting omni-directional pattern has many advantages over antennas with directional effects. Unless an antenna with nulls in it’s response can be rotated, it will be found that certain parts of the world will be very difficult to contact.
The five “squares” are made from white PVC covered multi stranded copper twin cable which is supported by a horizontal cross, made from white fibre glass. Each element is folded and tapped for impedance matching, so that the antenna looks like 50 ohms on all 5 bands. The small size ensures minimum windage and the low weight means that TV type brackets and masts may be used for supports. There are no aluminium elements to corrode and cause high resistance joints, or snap off in the wind.
The antenna is fitted with a co-axial choke balun at the common feed point, to prevent any current from flowing down the outside of the co-axial cable feeder. This balun is absolutely vital, to prevent any radiation or pick up of signals by the feeder. EMC problems can be just as bad as with verticals if this balun is not exactly right.
The electric fields of the CobWebb are confined because the high impedance ends of each element are only a few inches apart. This reduces the coupling to nearby objects so the antenna does not need re-tuning for operation at different heights and locations.
Other Multi-band Antennas for the HF bands
The Horizontal End Fed Wire
This is the simplest and cheapest antenna of all. It will require a very good ATU to tune it up though! Very high voltages may be present at the feedpoint, dependant on the exact length and frequency in use. You will probably need to use a so called kilowatt ATU, when using 100 watts, to avoid arcs on the ATU tuning capacitors. Severe interference problems are common. The antenna is obviously unbalanced with respect to earth, so vertically polarised radiation will occur. This radiation will be either off the vertical feed wire connecting to the end of the horizontal span, or from the earth lead if the wire comes straight into an upstairs “shack”. RF in the shack problems often occur, RF feedback, RF burns to the operator if any metal is touched, and general EMC problems normally restrict these antennas to QRP operations. There is an obvious radiation hazard when using this type of antenna. The local field strengths produced can be way above the maximum permitted safety levels.
Doublet
Any long wire can be fed at it’s centre with a tuned open wire feeder. This should maintain balance to prevent vertically polarised radiation off the feeder and subsequent interference problems. Whenever a twin feeder system is used though, the antenna itself must always be exactly electrically balanced and symmetrical, any slight lack of symmetry will cause feeder radiation, with the dreaded vertical polarisation. It will require a high quality proper balanced ATU i.e. not an unbalanced one with a toroidal balun transformer added on the output! (The balun will only work efficiently over a limited range of impedances) As with any long wire antenna, the polar diagram will contain many deep nulls, in which directions communications will be difficult. This more than negates the few dBs of gain that doublets have on the higher frequency bands.
Note Large spaced open wire feeder should not be used in the shack, or anywhere where people or animals may be able to come into close proximity with it. The fields will not cancel in line with the feeder (they only cancel broadside to the feeder), unless the distance is many times the wire spacing. Unless the small spacing twin is used, the RF radiation problems in the shack can be almost as bad as those with end fed wires.
G5RV
This antenna is very cheap to make, but because it is only resonant on one band, it requires a very good ATU to tune it up on all the other bands. It is really too long to give consistent results in all directions on the higher bands, the polar diagram becomes very “petal” shaped with many deep nulls. It is far better to convert it into a doublet antenna and use open wire feeder all the way to a proper balanced ATU, rather than to use co-ax cable for part of the feeder. The SWR on this antenna is very high on all the bands (except 14 MHz, where it is only about 2:1 at resonance), so the use of co-ax can cause very high losses. The ribbon feeder normally supplied with commercial G5RVs is very poor mechanically, if it swings in the wind it breaks quite quickly.
Vee Beams and Rhombics
Great, if you have got the necessary real estate! Radial terminated Vee beams and/or Rhombics, with switching to beam to any part of the globe. Shack in the middle of the 10 acre site, which is a Polynesian island, with only local girls for company! Ahh, this is paradise, but would you bother going on the air? Dream on!!
Log Periodics
Too big and low gain for the size. Note the CobWebb has a “gain” of 7 dBi.
Trap Dipole
Trap dipoles use tuned circuits to isolate sections of a dipole, such that electrically it looks like a half wave dipole (with a low impedance feedpoint) on each band. Four pairs of traps would be required for a 5 band dipole. If the inverted “V” configuration is used, then the feed impedance should be about 50 ohms. However the traps act as loading coils on the lower frequency bands, so the antenna becomes shorter than normal. This should reduce the radiation resistance of the antenna on the lower bands. The radiation from an antenna is determined by the product of current and length. If the length is reduced then, for the radiated power to remain the same, the current must be increased. The increased current for the same power must mean that the voltage will reduce. The shorter length should therefore cause the feed impedance to be much reduced. This should cause the SWR to increase, if it does not the traps must be lossy!
Trap Vertical
This is in effect half of a trap dipole, fed against ground. They can give a good match, but being on the ground the signals will be attenuated by surrounding objects, particularly on the higher frequencies. If your ground has poor conductivity results will be very poor. Verticals can be elevated, using either radials or extra traps. They can then work very well, as long as you don’t have any neighbours. In an urban environment the EMC problems can be chronic.
All vertical antennas suffer from another problem. They require good conductivity soil for many wavelengths around them to compete with horizontals. Even verticals that do not use a ground connection i.e. vertical dipoles or ground planes etc. can still be as much as 8 dB down on a horizontal dipole antenna, due to reflection losses. The difference between sea water and very poor ground is up to 9 dB for a vertical antenna, but only 1 dB for a horizontal.
The Magnetic Loop
This is really just a short dipole that is bent and end loaded with a variable capacitor. There is no magic involved in the way it works, a standard “electromagnetic wave” is produced from them, as per any other antenna. It is not producing magnetic waves with special immunity to “Electric Field Interference”. It does have a confined electric field so that near field “capacitive” coupling to surrounding conductors will be reduced. There will be some reduction in performance on the lower bands, a well designed 5 metre circumference loop will normally work over the 14 to 28 MHz bands with a 50% efficiency on 14 MHz.
To keep the efficiency this high, the loop will have to be made out of large diameter copper or aluminium, NOT co-ax!! The resultant high “Q” will mean that the loop will have to be continuously re-tuned, as the receiver is tuned round the band. The remote control system that is needed to do this can be quite expensive, also the tuning capacitor will have to stand many thousands of volts, even when only running 100 watts. For high power operation a vacuum variable capacitor is normally used, which is very expensive.
A loop standing on the ground in the vertical plane will radiate a vertically polarised signal. The ground will absorb/reflect the horizontal component straight upwards. The vertical component at low angles to the horizon i.e. that required for DX operation, will have a sharp null in the response broadside to the plane of the loop. This can be useful for reducing interference, but it does mean that the loop will need a rotation system.
To prevent low angle signals from being absorbed by surrounding objects i.e. shrubs, fences, trees, houses and the myriad of conductors around the QTH, it is obviously far better if the loop antenna is mounted up in the air. If it is mounted about 30 feet high then the horizontal radiation will be able to be used for low angle DX operation. The loop can then also be mounted in the horizontal plane to eliminate the vertically polarised radiation, and so reduce EMC problems.
The small diameter loops made from co-ax or flat bar give very poor performance. They don’t need retuning as often as you tune round the band, because they are low “Q”, the problem is that most of your transmitter power will be dissipated as heat!
The main advantage of the loop antenna is it’s continuous frequency coverage over the entire spectrum, by remote controlled re-tuning. This is ideal for military users etc. but against this is the cost, especially if you only wish to transmit on the amateur bands.
Mini-beams
These antennas are a very big compromise. They generally only cover the 14, 21 and 28 MHz bands, because of interaction effects with 18 and 24 MHz. A reflector resonance for 28 MHz will act like a director resonance for 24 MHz, a reflector resonance for 24 MHz will look like a director resonance on 21 MHz etc. etc. The result is a very expensive trap dipole! The gain that they are supposed to have is only over a very narrow bandwidth. They are very difficult to set up, most people just give up and feed them with an ATU. They need to be rotated, not because of a good front to back ratio, but because of the nulls off the ends of the dipoles! They are often rated for high power use, presumably what this means is they don’t actually catch fire when used with QRO, because they certainly get very hot!
Broad Band Verticals
These antennas use most of the applied power to produce a low SWR reading. The fraction of power that is radiated can still produce some DX QSOs on the higher frequency bands though, it’s amazing what you can do with QRP on HF! If the guy with a 100% efficient antenna is getting a 59 plus 20 dB report, then the guy with the 1% efficiency will still get S9!! On the lower frequency bands these antennas are very good dummy loads!
It always amazes me that if a 100 watt rig was only putting out 10 watts, most amateurs would be very upset, yet they will use a 10% efficient antenna and be quite happy. The reason is, of coarse, they can’t measure the radiation efficiency but they can measure the power/SWR. Many radio amateurs seem to think that a low SWR means that all the power is being radiated, so you cannot really call the producers of these antennas “Con Artists”, they are merely producing what the radio amateurs say they want! They are even quite good for lack of TVI and general EMC problems, as they radiate such a small amount of the applied power!!! Caveat Emptor!
Broad Band Terminated Dipoles
These antennas also use most of the available power to produce a low SWR reading on the lower frequency bands. On the higher bands they only use about half of the power for this purpose, so about half of the power is actually radiated! Unfortunately, on these higher frequencies, the antenna will have lots of lobes and deep nulls as per a standard doublet antenna. The military have used this type of antenna in the past, because of its ease of matching over a wide continuous frequency band, but it really is just a waste of power to use it on the amateur bands.
Crossed Field Antennas
These antennas don’t work! A little knowledge is a dangerous thing! The co-ax feeds radiate a little power, because they don’t have proper baluns on them! The metal bits radiate a little power because they are metal and have a small amount of RF current flowing through them! One guy on the internet has even offered a $10,000 dollar reward to anybody who can demonstrate one working! The so called “antenna design experts” who invented and patented the CFA have not claimed their reward!!! A short length of wire and a parallel tuned circuit ATU will work much better! It’s a classic case of somebody inventing a theory and then trying to make the facts fit the theory!!
Parallel Connected Dipoles
These antennas work very well. The dipoles need to be spread out so that the high impedance ends of the shorter ones are not affected by the longer elements. They can be arranged “maypole” style round a central support, so that they can act as guy wires as well as antenna elements. When arranged in this way the feed impedance will be about 50 ohms so they can be fed with 50 ohm co-ax, via a choke balun. This system works very well when out portable, the only problem is the vertically polarised radiation off the ends. This radiation fills in the nulls off the ends of each dipole, so that no rotation is needed but it can cause the dreaded interference problems.
These antennas really need to be horizontally polarised for minimum EMC problems, but they then need a 75 ohm feed. They can be double gamma “T” matched to 50 ohm co-ax, as long as an effective choke balun is used. This is in fact what the G3TPW CobWebb antenna is! The dipoles are each bent into squares, so that they can be supported by a single horizontal fibre glass cross, rather than having separate supports for all ten dipole ends. Bending the dipoles into squares also eliminates the dipole end nulls, resulting in an omni-directional radiation pattern. Another major effect is that the electric field of the square dipole will not couple into the ground, or any other nearby conductors so losses are much reduced.
Verticals and EMC (Electro-magnetic Compatibility)
Whilst we have all heard that vertical antennas cause interference problems, I suspect that most people don’t fully appreciate why. I certainly didn’t, until I investigated the TVI problems that I had with my original 5 band vertical design. In fact I always used to say that verticals cause TVI because they put out such good signals at the low angles that we need for DX communication! It was only when I discovered that my vertical was causing lots of EMC problems with my neighbours, whilst my horizontal half wave dipole antenna at 30 feet was not causing any problems at all, yet giving a better signal in Australia, that I realised that it was the vertical polarisation that was to blame.
It is obvious that vertical antennas will couple more power into nearby vertical conductors than horizontal antennas will. This causes much loss of radiated signal and also causes many EMC problems. If more RF energy is being coupled into a vertical TV feeder co-ax cable, then TVI is going to be more lightly. Interference will also be picked up from the TV, producing an increased background noise in your receiver.
However I was not convinced that this was the whole story. My neighbours portable radio was also clobbered by the vertical but completely clear when I used my horizontal! The portable radio could be oriented in any plane, with no effect on the amount of interference received.
Tests with a calibrated field strength meter showed that the field strength levels near the ground were very low from the horizontal antenna, and very high from the vertical antenna! The field strength meter needed to be up at a height of about 20 feet before the field strength readings from the horizontal antenna were similar to those from the vertical. Reports from Australia showed the horizontal to be 3 dB stronger though!!
The susceptible portable radio was substituted for the field strength meter. It became obvious that the ground was effectively “shorting out” horizontally polarised signals. It was found that at low heights the power fed into the horizontal antenna needed to be about 100 times (i.e. 20 dB) greater than that fed into the vertical antenna, for the same interference levels at a given distance.
It was realised that if any electronic device with an EMC problem is mounted close to the ground (in terms of wavelength) then it will not receive horizontal polarised signals very effectively. Up to a height of about a quarter of a wavelength the ground will act as a reflector, so that horizontally polarised signals will only be received from higher angles. Below a height of about an eighth of a wavelength the ground will also provide a lossy dielectric path for the horizontal electric fields, and thus tend to short them out and/or dissipate them. Thus the ground will protect electronic devices from horizontally polarised electromagnetic fields. Vertically polarised fields will however be received very well, even if the susceptible equipment is actually sat on the ground.
I decided to concentrate all my efforts on the design of horizontal antennas, to avoid all the hassle of TVI, HI-FI and telephone breakthrough etc. I thought that it would be very anti-social of me to market a vertical antenna that would subject lots of radio amateurs, and their innocent neighbours, to EMC problems that could be avoided by the use of the correct polarisation. Thus the CobWebb concept was born!!
G3TPW COBWEBB F. A. Q. s (Frequently asked Questions)
What is a CobWebb antenna and what is it’s gain?
It is a very efficient horizontally polarised omni-directional antenna for the 14, 18, 21, 24 and 28 MHz bands, with a gain of 7 dB over an isotropic radiator (7dBi). Note that this is the same as a standard dipole, although a straight dipole will have sharp nulls off each end. A standard straight dipole has a gain of 5 dB over a dipole in free space! I notice that the specification of my standard large 3 element tribander says that it has a gain of 8.5 dB over a dipole in free space. This means that it has a gain of 3.5 dB over a dipole at the same height!
How does it work?
Technically the CobWebb is 5 separate full size dipole antennas, each bent into a square. This makes it very small (only about 8 foot square) but it is still full size! It has 5 separate double gamma tee matches to match each element to a common 50 ohm co-axial feeder, and has a built in air cored co-axial choke balun, to prevent feeder radiation.
What is the secret ingredient. Why does the CobWebb work so much better than other antennas?
Simply because it radiates all the power fed into it, and it also radiates in an omni-directional manner so there are no nulls. There are no lossy ferrites, traps or loading coils to heat up, and each element is full size and made from 84 strands of 0.2 mm diameter pure copper wire with a plastic covering.
The confined electric near field (caused by the high impedance ends of each dipole being close to each other) also ensures that the antenna does not couple to other electrical conductors i.e. telephone wires, power cables, television antennas or even the ground and lossy di-electrics such as trees and buildings. Thus the radiated power is not absorbed by nearby objects, it is all radiated into free space. Breakthrough and noise pick up are also reduced to an absolute minimum and the ground conductivity and height do not affect the antenna tuning.
What is the maximum power that can be fed into it?
Nearly all the power fed into the CobWebb will be radiated, so the antenna will not heat up and so limit the power rating. There are no ferrites used so no intermods are produced. It has been tested with 3 kilowatts of RF, above this level there could be a problem with corona discharge sparking at the ends of the elements as the air is ionised!
How is it constructed?
A single horizontal fibre glass cross supports all 5 elements. The feed-box is on the end of another solid fibre glass rod, such that the feed is in the centre of one of the sides of the squares. Each rod is secured with “U” bolts onto a 0.25 inch thick aluminium plate. Another similar plate allows the antenna to be fixed to a vertical mast of up to 2.25 inches in diameter, with the “V” bolts provided. Plastic covered “figure of 8” section 84 strand copper conductor is used for the elements, which are secured to the fibre cross by the unique G3TPW system to prevent pre-mature breakages!
I’ve not seen any of your adverts for ages. Why don’t you advertise the CobWebb more?
The last time we advertised in a magazine was in 1993! The CobWebb was last reviewed in a magazine in 1996 though. It is interesting to note that the magazines always asked us if they could review the CobWebb, we never had to ask them!! Of course the reviews in the magazines were very good adverts, but they only last for a month or two. We find that the 750+ antennas that we have sold are the best long lasting advertisements, literally being broadcast to the world every time somebody says, “And the antenna here is a CobWebb”.
So are your antennas sold purely by word of mouth?
Most of our sales do come from people who have received personal recommendations from existing users. However, the interest is mainly generated when people hear stations using CobWebbs doing so well on the bands. The recommendations are normally received when the enquirer is trying to find out our address/telephone number!!
This is, of course, a scale model made specially for your lectures. How big is the full size antenna?
No, we only have full size CobWebbs! We don’t need a scale model of the CobWebb because it is so small. I must admit that even I am still amazed when I look at a CobWebb and realise that though it is so small IT IS STILL FULL SIZE!! A 33 foot dipole is a much bigger beast than a square with 8 foot 6 inch sides!
Can two CobWebbs be used as a beam?
Yes, but only by phasing them, i.e. they both have to have separate feeders. Parasitic elements will not work because the CobWebb does not couple to other nearby conductors! The maximum gain obtainable is less than 3 dB over a single CobWebb and of course a beam rotator is needed. The phasing adjustments needed to provide optimum directivity across all the bands are quite complex and the phasing unit becomes expensive and difficult to operate. If you increase the antenna height by 50%, then the DX signals will increase by more than they would by phasing 2 antennas!
I’ve heard that different antennas suite different locations. Will the CobWebb work at my QTH?
YES! The ground conductivity for many wavelengths around an antenna will affect its performance. Vertical antennas that use a ground connection can be as much as 20 dB down on a dipole. Verticals that do not use a ground connection i.e. elevated feed vertical dipoles or ground planes etc. can still be as much as 8 dB down on a horizontal, due to reflection losses. The difference between sea water and very poor ground is up to 9 dB for a vertical antenna, but only 1 dB for a horizontal
.
The CobWebb is not affected as much as other antennas by trees, buildings, power lines, TV aerials feeders and telephone wires etc. The poorer or more cluttered that your QTH is, the better the CobWebb will perform, compared with other normal ants, including a straight dipole!
These are the reasons why CobWebb antennas so often out perform other antennas, they are not affected by the nearby environment so THEY WORK AT ALL LOCATIONS.
How do I mount it?
The CobWebb can be mounted on a vertical pole of up to 2.25 inches in diameter. It can be added to existing antenna installations such that the mast goes straight through the CobWebb. A 20 foot scaffold pole makes an ideal mast, this can be fixed to a wall with a couple of stand off brackets.
Do I need planning permission for it?
Most people don’t bother to apply, if they are just mounting a CobWebb on a 20 foot pole. The pole can be slid down through the brackets so that the CobWebb is below the roof ridge height. This meets the standard “not above the roof ridge” planning restriction; it can then be gradually pushed up to the optimum height of 33 feet!
Will it stand the high winds at my QTH?
CobWebbs are in regular use in the Falklands and on Ascension Island. They have stood up to gales that have destroyed many other antennas. Most of the breakages that have occurred have happened when either the mast has come down, or the antenna has been dropped. Even then the antenna can be quickly and cheaply fixed because the short 1 inch diameter fibre glass joining tubes break, and the antenna simply folds up. These joining pieces can be easily changed in a just a few minutes. If the wires do get broken they can be repaired with choc block screw connectors or crimp connectors, or we can supply new wires.
How does the CobWebb minimise the chance of TVI and breakthrough problems?
The pure horizontal polarisation and use of a choke balun reduces the chance of breakthrough to the absolute minimum possible. The confined electric near field (caused by the high impedance ends of each dipole being close to each other due to being bent into squares) also ensures that the antenna does not couple to other electrical conductors i.e. telephone wires, power cables or television antennas.
Are there any complicated adjustments to be made during installation?
None at all! The CobWebb is not detuned by nearby objects, including the ground, because of the confined electric field. Thus the CobWebb can be pre-tuned and matched during production, so that it works at any QTH and any height!
