The Slicer - 2 Meter Antenna for Mobile SSB
This describes a horizontally polarized, omnidirectional, 2-meter antenna suitable for mobile SSB service. It is essentially a Halo antenna fabricated for very low surface resistance for high efficiency and for very low wind resistance. It is a very rugged little antenna.



Halo Half Wave Dipole
Figure 1 shows the original Halo configuration – a half-wave dipole curved into a circular radiator, gamma matched
to 50 Ohm feedline.
Construction
The antenna is made from double sided G-10 copper clad circuit board stock, picked up at a ham flea-market. The rectangular board is trimmed with tin-snips to round the corners a bit, and then the board is etched, top and bottom to remove all of the copper except for a 2″ wide band, both on the top and on the bottom. This is an 8 inch cross section surface (2 X 2″ on top plus 2 X 2″ on the bottom) for the RF to run on. If it were not for edge effects, etc., this would be roughly equivalent to building the antenna from 2-1/2 inch diameter copper pipe. As it is, however, this is still a lot of surface area yielding a very low RF resistance at resonance. I used copper braid from RG-58 to connect the top and the bottom conductors at the edge of the board.
Figures 2 and 3 show the general dimensions of the board. These are not critical – I used what I had, hence the rectangular shape of the Slicer, instead of square, diamond or round. You should use what you like. I have had excellent results with this antenna, working Sporadic E from South Texas into North Carolina and Georgia mobile with 10 Watts. It performs within a couple of dB of my full sized Big Wheel antenna for tropo contacts, and without the need for heavy duty mounting. My wife says it doesn’t look as bad as the Big Wheel (this is a compliment?). The wind load on the antenna comes almost exclusively from the coax – the circuit board edge-on into the breeze is negligible.


Gamma Match
The gamma match could have been etched from the board, but when I first made this antenna, ten years ago, I wanted to play with it a little, so I used a discrete variable capacitor (3 to 30 pF) soldered onto pads on the board. Likewise the gamma rod could have been etched from the board, but I used a piece of #10 AWG wire. These apparently light duty components handle my 100W linear power without a problem – and have for 10 years!
Tuning
Tuning to resonance was accomplished by making the non-etched conductors on the board slightly short, and by soldering a pair of #12 AWG wires at the gap between the ends. Adjusting the spacing between the wires can put your frequency exactly where you want it, and then the gamma match can be tweaked to perfection. Needless to say, an antenna analyzer would be great for this simple tune up, but I found that an SWR meter does the job very well.
Support Mount
Support was designed to fit on top of my Hustler (TM) HF antenna mount. My local hardware store had some brass gas fittings that perfectly matched the threads on top of the Hustler mast. If you have some other means of lifting this antenna above your vehicle, you will need to find your own mounting scheme.
Originally posted on the AntennaX Online Magazine by Bill, W5GVE
Last Updated : 28th April 2024