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ANTENNAS ( AERIALS ) 1 THE ANTENNAS AT MØMTJ I currently use four main antennas: 1/ A trapped Inverted L for 80m and 40m fed by RG213 coaxial cable to the LDG Z-11 Pro antenna matching unit in the shack. This can be used on all bands from 80 through to 10 metres. The support post is installed at the bottom of the garden with the end of the antenna wire being supported by Dacron rope that is attached to a pulley on a pole at the apex of the roof. more 2/ A trapped dipole for 20m and 10m. This is fed by 75 ohm twin feeder to a 1:1 balun then on to the AMU via RG213 coaxial cable. Although it was initially installed horizontally, it is now installed with one leg supported vertically on a 7 metre fibreglass 'Sota' pole with the other leg supported horizontally about 2 metres above the ground. A rather unorthodox arrangement for a balanced dipole, but it seems to work ok, it looks much neater than a horizontally slung dipole and offers a more omnidirectional radiation pattern. more 3/ A compact Inverted L for the 160 metre band - Top Band - shortened with a loading coil. more 4/ A Watson W-2000 collinear antenna for 6m, 2m and 70cms. This is fixed to the top of a 10m telescopic aluminium mast that I push up whenever it is required. more Inverted L Antenna for 80m and 40m (and some other HF Bands from 80m to 10m)  The basic layout of the Inverted L Antenna (Practical Wireless) The first antenna that I installed was for
HF. I decided on an Inverted
L that incorporates a 7MHz trap so that it can be used on both 7MHz (40
metres) and 3.5 MHz (80 metres).
The design of this Inverted L is well known and a good design has been published previously in Practical Wireless by Len Paget GM0ONX. It is based on one half of the famous W3DZZ trapped dipole antenna. It can be made entirely from scratch as a DIY project, or the 7MHz trap could be purchased commercially as a ready made item, or whole antenna can bought as a complete kit from Tony Nailer, G4CFY, at Spectrum Communications. I opted to buy the 7MHz trap from Spectrum Communications, as I already had most of the other materials required - rope, egg insulator, plastic box, and some good aerial wire. The Spectrum Communications trap is solid and well made and 'potted' to protect against the elements. This antenna is tuned for 40 metres and 80 metres, but the VSWR is acceptable on several other bands being in the region of 2:1 to 5:1. The designer anticipated that this antenna would be usable on five of the H.F. bands. I have found that with the use of the Antenna Tuning Unit it can be used on all of the H.F. bands. However the polar radiation pattern may very well be less predictable on bands other than the intended 40 and 80 metres, and it may well be less effective than might be desirable - but it does work! The antenna is in the back garden, while the shack (radio room) is in a bedroom at the front of the house. It is fed by a 30 metre length of RG213 coaxial cable (it is not possible to use twin feeder for this type of antenna as the Inverted L is an UN-Balanced aerial, whereas Twin Feeder is BALANCED). With this length of cable I estimate the loss in the feeder alone to be about 1dB at 7MHz. The feed point of the aerial is located at the base of a 16 foot high wooden pole near the bottom of the garden. The horizontal top wire returns to a fibreglass pole installed at the apex of the roof.  Photograph
showing
the wooden support post and termination point of the Inverted L antenna
The post is coloured green with green fence treatment to mast it somewhat. I have also placed it near the bush to provide further camouflage.  The low loss RG213 coaxial cable runs from the shack at the front of the house up into the loft and exits into the back garden down the rear wall, through some garden hose to offer some protection along the flower bed to the bottom of the garden where it is connected to the base of the Inverted L antenna.
 The Inverted L antenna - lower section now nicely camouflaged. The wooden support post is some 6 metres long.  The photograph above shows the Dacron ropes
supporting the ends of the Inverted L and Dipole antennas are held in
place at the top of the fibreglass support mast by a pulley - one
pulley for each
support rope. This facilitates rapid lowering of either antenna for
adjustment or replacement. This
photograph also shows a second
rope and pulley system that was originally used to support the 20m
dipole and is now used for the top band inverted L wire aerial.
I needed a good reliable knot for securing ropes when installing wire antennas and have found the Bowline to be one of the most useful, it is strong and easy to tie. A Bowline will not slip in any circumstances and, usefully, the more load that is put on it, the tighter it gets.  The Bowline Knot A Bowline can be used to tie two ropes together and should be used to tie a support rope to a pulley, dipole centre and other antenna items. It's
important to use the correct knot for the job when fixing up wire
antennas. I find the Bowline is a very
useful for fixing end, egg and dog-bone insulators to the ends of the
wire and/or ropes. The Round Turn & Two Hitches, Anchor Bend
and
Buntline Hitch knots are very good for tying a rope to a pole or a
mast. 'Animated Knots' will show you how to do them:
http://www.animatedknots.com  Photo showing pulley fixed to the top of the wooden support post and the aerial support rope that it holds in place.  The
Spectrum
Communications Trap
View
of trap showing
that the joints have been thoroughly sealed against the weather with self amalgamating tape and silicone sealant.  Just for good measure I sealed the internal side of the machine screw that forms the connection terminal against the weather with Watson sealant putty.
Compact
Antenna for Top Band
A Shortened Inverted L for 160 Metres
Despite the dreadful noise on top band caused by modern electronic gadgets and the difficulty in accommodating a necessarily large aerial in a small garden, I was keen to try to get on to top band. I experimented with some different ideas during 2009, some of which are shown on this page. Eventually I settled on the design shown below. It is an Inverted L type aerial, shortened by the use of a loading coil. It uses a fibreglass telescopic fishing pole to allow it to be easily lowered out of sight when not in use. Read more here>  uses a fibreglass telescopic fishing pole to allow it to be easily lowered out of sight when not in use Read More Here > VHF - UHF Vertical Co-Linear Rather than make my own antenna for VHF (2 metres / 144 MHz) and UHF (70 cms / 430 MHz), I cheated and bought a commercial item, the Watson W-2000. The W-2000 also, rather usefully, covers 6 metres (50 MHz) too. The W-2000 is 2.5 metres long and enclosed in white fibreglass with three radial elements at the base. Unfortunately I have nowhere practical to install a separate mast for the VHF / UHF antenna, so this has to be mounted on top of a 33 foot (10 metre) high telescopic aluminium mast in the back garden. The base of the mast is placed in a handy metal sleeved hole that was already present in a small wall in the garden. Very fortunate indeed! The antenna is connected to the radio via the very low loss Westflex 103 coaxial cable. The cable is left in place permanently, running from the shack in the front bedroom, up into the loft and out of a small hole in the back of the house, down a drain pipe into the back garden. From there the aerial can be connected as an when required: When VHF or UHF operation is required I have to connect the coaxial cable to the Watson W-2000, fix it to the top of the telescopic mast, which is very quick using two V bolts and 4 wing nuts, put the mast in the hole and raise it to a good height. I tend to extend it so that the bottom of the antenna is at about 24 feet in the air, the height of the apex of the house, so it is in fairly clear space. A VHF and UHF aerial needs to be as high as possible since at these frequencies communication is essentially local and 'line of sight' - unless heightened propagation conditions, such as Sporadic E or a Temperature Inversion is prevailing at the time. Even at 24 feet the mast is a bit wobbly, so I tie it down using three nylon guy ropes.  The
Watson W-2000 on to of the extended telescopic pole. Now about 8 or 9
metres high.
  Watson
W-2000
on Telescopic Mast at the lowest position
KNOTS FOR SECURING WIRE ANTENNAS I have found the Bowline, Round Turn & Two Hitches, Anchor Bend and Buntline Hitch to be some of the most useful. The Bowline I find most useful for fixing end, egg and dog-bone insulators to the ends of the wire and/or ropes. The Round Turn & Two Hitches, Anchor Bend and Buntline Hitch knots are very good for tying a rope to a pole or a mast. More at Animated Knots.com: http://www.animatedknots.com I know that if I use the correct knot that the these parts of the antenna will be as strong as possible. OTHER ANTENNAS Our good friend in Australia Felix Scerri, VK4FUQ, uses Inverted V antennas but also highly recommends the Quad Loop style antenna for HF work. These are well worth investigating, and you can read more here: Antennas 3 with more antenna ideas on Antennas 2 and Antennas 4 and the Links Page here and here Links to further reading: Introducing The All Band Doublet: http://www.cebik.com/content/edu/edu6.html N.B. Create a free account at http://www.cebik.com The All Band Doublet - http://www.cebik.com/wire/abd.html The ALL Band HF Doublet on Ham Universe - http://www.hamuniverse.com/hfdoublet.html Multi Band Dipoles Compared - by ARRL on QST and DX Zone: http://www.arrl.org/tis/info/pdf/9611073.pdf http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=7499 PDF Document - The W3DZZ Antenna - http://www.users.icscotland.net/~len.paget/GM0ONX%20trap%20dipole.pdf (**!!! But don't use coaxial cable with a 'choke balun' at the centre of the dipole! Use twin feeder with the Choke Balun at the other end. Less power loss.!!!***) See Practical Dipole Antennas Compared: http://www.qsl.net/ta1dx/amator/practical_dipole_antenna.htm Practical Antenna For 160 Metres - http://www.iw5edi.com/ham-radio/?a-practical-antenna-for-160-metres,32 http://www.ik1mnj.net/id202.htm More: The website of GM0ONX http://www.gm0onx.co.uk/ The Inverted L - PDF document: http://www.users.icscotland.net/~len.paget/5%20band%20Inverted%20L.pdf Adding Top Band To The Inverted L - PDF Document: http://www.users.icscotland.net/~len.paget/Inverted%20L%20adding%20top%20band.pdf The All Band Inverted L - http://www.antennex.com/preview/archive3/ltv.htm 
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Mike Smith - MDS975.co.uk © 2003 - 2009
M0MTJ
Amateur Radio; Ham Radio; Radio; Transceivers; HF; VHF; UHF; Data Modes; Morse Code; RTTY; PSK31; SSTV; FSTV; Amtor; Sitor
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