This is the 2M slot cube antenna. Posted by 10 months ago. A Surecomm SW-33 swr meter will cost you $30-35 but for another $20 you can. Quad antenna, how to build a quad antenna for ham radio use category is a curation of 85 web resources on, Shrunken Quad, The Cubical Quad is Beautiful, Two portable antennas for 6-meter. Resources listed under Quad Antennas category belongs to Antennas main collection, and get reviewed and rated by amateur radio operators. Many RASON members truly enjoyed last month's collinear antenna. This month I decided to build a 2 meter 5/4 wave antenna. This antenna is unique in that it is enclosed entirely in 3/4' PVC which makes the design a little more complicated. The primary problem is that PVC tubing has a significant velocity factor which causes RF to slow down. On a vehicle with a steel body and roof, the most feasible 2 meter slot antenna design is a pair of square flat plates with spacers to maintain the space between them. The slot ends up being the horizontal space between the plates.
- 2 Meter Slot Cube Antenna Arrl Radio
- 2 Meter Slot Cube Antenna Arrl Amateur Radio
- 2 Meter Slot Cube Antenna Arrl Antenna
- 2 Meter Slot Cube Antenna Arrl Ham Radio
Cubical quad antenna includes:
Cubical quad antenna basicsQuad beam antenna with reflector & director2 metre cubical quad design
The cubical quad antenna lends itself to use at VHF and UHF, and a 2 metre quad or two meter quad is easy to make using a few items that are easy to obtain or may even be available anyway. It should be remembered when considering its use that the quad, when fed at the bottom gives horizontal polarisation.
Construction of the 2 metre cubical quad does not require any specialised tools and can be accomplished using the basic tools available to any radio amateur or short wave listener.
At the outset it as decided to make each element the same size, and then use small electrical stubs to extend or decrease the electrical size of the element. A small short circuit stub makes the reflector inductive, thereby effectively making it longer than the resonant length. Similarly an open circuit stub makes the director capacitive and effectively shorter than an electrical resonant length.
2 metre cubical quad construction
A quad for internal use can be made quite simply by constructing a simple wooden frame. Each element is made up from a cross of available wood approximately 12.7 x 12.7 mm (1/2 by 1/2 inch) wood – it requires tow lengths each, i.e. a total of six for a 3 element 2 metre cubical quad.
The wood is not critical so see what is available and adjust the design to suit. The length of each member of the cross member of the quad is 720mm.
At both ends of each piece of wood a small slot is cut to accommodate the wire. This slot can be cut with a saw, or alternatively it is possible to drill a hole of sufficient size to enable the wire to easily pass through. At the centre cut a section out as shown.
In some ways the slot provides more flexibility because it enables the length of the loop to be altered to tune the 2 metre quad to exact electrical resonance.
The next stage is to join and glue two cross members to make the characteristic ‘X’ of the 2 metre cubical quad antenna. The two small sections removed from each cross member should slot neatly together.
Having completed the mechanical construction of the ‘X’ frames, the wire can be added and brought to a small two way terminal block. The wire should be of a reasonable diameter, typically 12 or 14 SWG is good.
The wire is brought to a two way terminal block and secured in this way. The coax or stub can then be attached to the connections in the terminal block and held securely.
The weight of the coax should not be left to be held by the antenna wire, but the coax should be loped and secured to the boom or the mounting pole.
The stubs should be around 7 or 8 centimetres long – their length is not terribly critical, and can be adjusted. The wires can be around 14 SWG and left to remain parallel under their own strength. The short circuit one can use a single section from a terminal block. The position of this one can be adjusted to give the best performance.
The boom for the antenna is made out of two lengths of 25 x 25 mm wood. If necessary the spacing of the parasitic elements can be adjusted with these two lengths of wood acting as a clamp. However once all the adjustments have been made then all the elements should be firmly screwed and glued to the boom.
2 metre cubical quad summary
Although in many ways this 2 metre cubical quad design is rudimentary, it is nevertheless one that can be build with a minimum of tools and expertise.The antenna can be adjusted to provide the best performance for the particular situation in case, however it should not be used externally as it is not sufficiently robust to withstand the rigours of the weather. However when used internally it has given a good account of itself.
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HF Skeleton Slot - An antenna system with a difference.
For many years at this QTH I have tried different wire antennas. Not being interested in rotary beams of the usual type, I have always use fixed wire antennas.
Over the years I came to the conclusion that for my particular purposes I needed something with gain that would work in more than one direction.
Having tried vertical beams and phased verticals all hanging from a nylon line, I decided to use the same nylon line to hold up a Lazy H antenna.
The Lazy H works very well of course, Bi-directional, low angle and gain, BUT its a bit too big to rotate to fill in the directions 90° from its broadside line of fire and I don't have the room to put up a second Lazy H.
It was while playing around with this antenna using the MMANA-GAL modeling program that I tried bending the ends of the top dipole down and the ends of the bottom dipole up, still keeping the open wire phasing line between the two dipoles and fed in the center. I eventually ended up with the ends of the dipoles joined together and the horizontal top and bottom parts of the dipoles very much shortened and tried feeding at the junction of the dipole ends, getting rid of the phasing line between the two dipoles.
This arrangement now reminded me of the VHF skeleton slot antenna that I had seen in an old RSGB handbook, but a search on the Internet turned up nothing for an HF version.
More adjustments in the MMANA-GAL program showed that the antenna should perform well on all bands from 30 meters to 10 meters.
To get the low angle take off, the bottom of the antenna needs to be about 15 feet (4.5M) off the ground. It will still work if the bottom is lower but with a higher angle of take off.
I purchased a Pump up mast 50 feet (15m) and a small cord operated rotator. The top horizontal spreader is fixed to this rotator and the whole antenna hangs down from there.
The MMANA-GAL program can be found here.
Below are the dimensions I used for the Lazy-H antenna.
The plot below shows the gain and angle of elevation of the Lazy-H, as computed with MMANA-GAL. The antenna works well but is difficult to rotate.
The photograph below shows the antenna installed at my QTH.
The top spreader is 50 feet above ground. The bottom about 20 feet above ground level.
HF Skeleton slot
The drawing above shows the dimensions of my Skeleton Slot.
It can be easily rotated. It is bi-directional. It has high gain, low angle of elevation, and can work on all bands from 10 to 30 MHz.
Below are the plots of the Slot for the bands 20m, 17m, 15m and 10m.
Below is shown a 'BowTie' version.
It has slightly higher gain and lower angle of elevation.
The corresponding plots are shown below.
This picture shows the bowtie version at GW3RQT(SK)'s
The small marine ply support for the spreaders can be seen in the center.
The short horizontal bamboo in the center is to support the dog bone insulator and the open line feeder together with the vertical wires coming from the four corners.
Alan GW3RQT(SK) uses the same antenna but with smaller dimensions as his mast is only 30 feet high.
It is designed for 15m but works well on all bands from 10 to 20m.The plots are shown below.
He uses spreaders for the diagonals mounted on a rectangular piece of marine ply with U bolts.
The center is then raised to the top of the mast which gives a height of 15 feet from the bottom of the antenna above ground.
2 Meter Slot Cube Antenna Arrl Radio
Constructional details
The antenna is very easy and inexpensive to make. For the sake of clarity, the constructional details are on another page.
Conclusions
The skeleton slot antenna is very cheap and simple to make - mine consists of three bamboo spreaders and copper wire!! It is fed in the middle of the center wire with open wire line which is taken to an antenna tuning unit in the shack.
2 Meter Slot Cube Antenna Arrl Amateur Radio
Results have been excellent and quite a lot of DX has been worked on digital modes using 50 watts even through the odd pile up .. With such a broad horizontal pattern I only need to turn the antenna 90° to get pretty well full coverage of the world . For example with the antenna in a NE/SW direction, stations from K4 down to LU and JA down to VK6.
Have fun 73 Don G3VCG
2 Meter Slot Cube Antenna Arrl Antenna
My e-mail address is here
2 Meter Slot Cube Antenna Arrl Ham Radio