Simulated Surveillance Video Systems
Since the video camera systems are totally psychologic^ -nar s the vrsibMit> and suggestion of vttieo cameras is what deters the thief s des^e to steat. all that is realty needed *s a device mat appears to be a functioning video camera The SSV System provides ihe businessman with ihe same deter rent to crime as reaJ systems at a traction of Ihe cost, because the Cameras and alarm boxes are em^T> .'^e.tromcs -ui t r — crook ^ ton'i kno^ this and SSV Systems are r-* tie mei>
realistic in detail. Some scan back and forth and all have red neon lights They leaiure easy installation, mount on any wail, have metal construction tnrou ghout with «-inkle finish paint all aluminum er.sbarre (thf-stopsJooiagemajtiings and conve^ ootics smuisted coanal catHesnd i plate manu'Acluref s unconditronal ¡^ja'antee. plus warning stAckers included with all orde'E
SVS 900 Scanning camera features 155 degree scanning action. long-He quiet. 1 rpmmotof.only $100 (regularly $119 95i catalog VP0010 SVS-8S0 stationary camera is adjustable to any angle lor fixed view coverage with mounting brackets and hardware, only S50 regular» S53 95'catalog W0011 or go first class with i^e SVS 2000, which has a soit: blue finish with satin mylar trim only $tQ5 (regularly $124 95) catalog <P0012 the stationary version is only S55 (regularly $62.951» catalog •PO013 Alarm bones are only $20 (regularly $24 95| catalog *P0014 and complete your look ot having real survetiiance equipment installed at your business nome or ollice
^ Reader Service—5ee page 226
Dave Ingram K4TWJ Eastwood I 'ifiaxe 1201 South Rte. 1 Box 499 Birmingham AL 35210
Hustler Minibeam: the Mobileer's
Secret Weapon
— two-el beam fits in your trunk
One of the most useful a n d convenient accessories of interest to many amateurs is a fold-down minibeam antenna A portable and efficient gain antenna solves numerous signal radiation problems for traveling amateurs weekend vacation enthusiasts. or amateurs with limited Most mini-
beam antennas suffer two distinct problems which limit their use by today s on-the-go radio amateurs f Ft her they are too ¡arge to be easily transported and quit kIv erec ted by one man or they require a large number of parts to be assembled before each period of use. Consequently, many amateurs merely use simple dipoles or mobile whips for their portable activities.
The Hustler Minibeam was devised to provide a solution to this dilemma
This antenna described in this article provides up to 3 dB forward gain, may he Operated on the 20-, 1 or IOmeter bands, and will fit comfortably in one corner ot an auto trunk The vacationing amateur can unpack, assemble, and erect the antenna in less than fifteen minutes, and the approximate cost of this array can be under forty dollars. This two-element beam also may be operated as a rotary dipole for the 40- or B(J meter amateur bands, if desired.
Theory of Operation
Basically, this antenna is a two-element yagi of reduced proportions. Center loading of each element is provided through the use of Hustler mobile resonators, and most of the beam's aluminum tubing is salvaged from an old CB beam antenna. While this small array may be fed directly with 50-Ghm coaxial cable, a 50-0hm unbalanced-to-balanced balun transformer will substantially improve overall performance.
The requirements for a two-element yagi are relatively simple: The driven element must be Vi wavelength long, and the parasitic element must be either $% longer if it is used as a reflector or 4% shorter if it is used as a director. The close-spacing distance between driven andi parasitic elements should be approximately .15 wavelengths for a reflector and ,1 wavelengths for a director As we have [earned through the use of triband minibeams, however, less-than-opti-mum element spacing is often quite acceptable.
New-Trontcs mobile antennas have proven their outstanding ability through numerous years of service, and this minibeam antenna performs with almost the class of its full-sized counterparts. Band changing is accomplished by exchanging resonators as necessary. Additionally, 40-meter or 80-meter resonators may be used with the driven ele ment proper to afford the rotary dipole option. Resonators used with this antenna are not subjected to the stress of mobile activities, so damaged and electrically restored resonators should work very well in this array.
Rather than adjusting element length for resonance at the desired frequency, the beam's resonators are tuned by moving their tip rods and monitoring resonant frequency with an antenna noise bridge or indicator Once these positions are located, a notch is filed in the resonator's tip rod tor future reference The antenna's driven element may be adjusted for operation by merely tuning for a l-to-1 swr at the desired frequency. Assuming 20-meter res^ onators are employed, the driven element should be tuned to approximately 14,250kHz AsshowninFig 1(a), this equals an approximate length of ^ 84 reet A comparable reflector element will be approximately 5% longer, or 14 48 feet in length. In Fig, l(b)H we find that this length equals a resonant frequency of 468/34.48, or 13,570 kHz. Since this frequency is below the resonator's range, each side of the reflector's elements must be extended slightly, I his is accomplished by varying the screw-stock length for
Photo A J he knock-down Hustler minibeam can be removed from the trunk of a compact auto and be in use on a moment s nonce.
Fq(MHZ)
1/2 wavelength (ft.)
Fig, 1(a). Determining element length.
coarse adjustments and adjusting resonator tip rods for fine tuning While the parasitic element may be adjusted to act as a reflector (lower resonant frequency) or as a director (higher resonant frequency), a slightly higher forward gain will be produced when using a reflector efement
Concept of Construction
Rather than presenting a siep-by-step-dupl ication procedure here, I will describe this antenna in a manner which will allow personal ingenuity and available parts to be used to maximum benefit You can "mix and match" ideas as you like.
The dipole (driven) element should be constructed first, since it may be used independently or as a reference to ensure that the other element is properly adjusted to its respective frequency.
As shown in Fig. 2, the driven element should be insulated from the boom by whatever means you find convenient If you can't sal vage these parts from a damaged CB beam, a short length of PCV plastic pipe may be used. An old boom-to-mast plate may be incorporated for element mounting, and it will serve double duty should you also desire a rotary dipole arrangement for 80 or 40 meters. A section, or sections, of aluminum tubing totaling 5375 inches (the length of the New-Tronics Mobile Mast, MOT or M02) can then be inserted and secured to the PCV piastre pipe.
Each end of these aluminum sections is fitted with screw stock (from any hardware store) which mates with Hustler res-sonators for the desired band of operation. Holes
Fig. 1(b). Determining resonant frequency.
may be drilled through the PCV pipe and aluminum tubing, and sheet metal screws with balun or feed-line connection lugs inserted. In order to ensure portability, my driven element is broken into three sections, each slightly less than 3 feet in length, fcach section is marked at its insertion length, and screw-type compression clamps are used to secure the element when assembled.
The parasitic element, complete with boom mounting assembly, may be secured from an old CB beam. Many of these arrays employ swaged elements which mate perfectly with the screw stock which is inserted in their outer ends. Since these element sections are not insulated from the boom, they may be removed at that point for transportation and rapid reassembly. Each end of the screw stock-fitted sections should be slotted with a hacksaw and fitted with screw-type compression clamps. Approximately 12-to 16-inch lengths of screw stock should then be inserted and the clamps tightened only enough to hold them securely. A final tightening will be accomplished after the efement is tuned to frequency and its position marked with a laundry marker pen. A construction procedure similiar to the above is satisfactory for conventional aluminum tubing assemblies, also.
The boom may be salvaged from a CB beam, or a piece of aluminum shower curtain rod may be utilized As I have (earned from a variety of minibeams marketed rn recent years, several variations of boom lengths may be acceptable l( however, have realized good results using a 6.5-foot
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