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| Document ID | 55033 |
| Application ID | wvpxaeNlTBMbnmgouznwCA== |
| Document Description | 8 |
| Short Term Confidential | No |
| Permanent Confidential | No |
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| Document Type | User Manual |
| Display Format | Adobe Acrobat PDF - pdf |
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| Date Submitted | 1999-08-19 00:00:00 |
| Date Available | 1999-10-01 00:00:00 |
| Creation Date | 2001-06-04 10:41:25 |
| Producing Software | Acrobat Distiller 4.0 for Windows |
| Document Lastmod | 2001-06-04 10:41:45 |
| Document Title | 55033.pdf |
| Document Author: | jsoscia |
mun 26 p , RQ/MAWM TECHNICAL MANUAL 1 WATI' VHF AMPLIFIER FOR MX1V SERIES TV TRANSMITTER/TRANSLATOR LARCAN INC. 228 AMBASSADOR DRIVE MISSISSAUGA, ONTARIO CANADA L5T 2J2 ran-none: (905) 564-9222 FAX: (905) 564-9244 Part Ppflp’ififififlh’r‘ Fig VHF AMPLIFIER INSTALLATION Contents: Topic Page General Information ............... Grounding and Ground Loops ‘ Lightning and other Transient Protection ........ Power VWring ............................................................ 29-9 Venuiafion and Air Conditioning ............................................ 29—10 Furs Proteuion ...................................................... 29-11 Unpaddng . , , .......................... A . 29.12 Transmitter Enema] lnianock Connections . 29-12 On Site: First Time Slartup .................... List of Flguros: True Drawing Reference Transminef Intenock Comedians .................................... text pg 29-12 Application Diagram: Transmilter Grounding Principles Application Diagram: Tower and Building Gmunding Puma—29 rev 0 Dec. 12. 1998 294 VHF Amplifier inshilafinn VHF AMPLIFIER INSTALLATION Noles: FUBSS—ZQ m a Dec, 12, 1996 29-81‘ VHF Ampiifier installation VHF AMPLIFIER INSTALLATION IMPORTANT: If you haven‘t already done so, please take the time to read, study, and understand your Exciter manual, and all sections of this manual. You may find overlooked items that may be slgnifiwnt to your installation planning or to the actual work to be done, 1. GENERAL INFORMAHON The economics of manufacturing a transmitter dimtes that much of the lnstallation information in its manual must be non-specific to any particular site, Although most of the following material. which we are presenting as "technical interest” information, is pertinent to higher powered transmitters, some of it is generally applicable to low powered equipment as well We hope that one or more of these suggestions contained herein will pmve helpful to you and provide worthwhile challenge to your imagination and technical ability. One of the keys to a successful installation is meticulous planning and adequate allowances for task times. Allow sufficient time to consider and plan all aspeas of the installation, including the building, whether new or existing. then allow for realistic time spans for the building construction or renovation. equipment transportation and wistallation, and final commissioning. A low powered transmitter naturally will require a very short time span for these activities. while high powered equipment muld require many months, Should you feel apprehensive about planning an ‘nstallation. simply phone or FAX our Applications Engineering Manager who is available and able to guide you. Your consulting engineer is also a good source of information. Betti these persons would be familiar witti teainical aspects of the proposed installation. Applications Engineering support offered by LARCAN includes technical information, recommendations on vendor products when requested, and advice on project task mnsiderations and time span estimation. This assistance is available upon request; simply ask your LARCAN representative. Although general application information (Figures 2 and 3) was included in this manual, it is important that specific system layouts be prepared, and that locations of cabinets and RF equipment such as RF painting or switching equipment, are determined together with the routing of the transmission line, AC power (Mains) feeds and other wiring, grounding (earthing). and ventilation air ducting. Lightning protection should be considered eariy in the planning process, because a good building layout can offer significant benefit. We mention "cabinets" throughout this document. although the TTSlOB and Tissue transmitters were designed as single chassis for rack mounting in a standard 19“ cabinet to be supplied by the customer. This assumption was based. on the antidpated market for the transmitter being for standby or unattended isolated site locations. and that mbinet rack space of about 10‘4" would be available for mounting the amplifier ano exciter or translator. The cabinet ventilation openings should be fitted with air filters, to help the transmitter components remain clean. Alternatively, a tabletop style of cabinet an be used instead if required. Due consideration rmst be given to ventilation, as proper cooling ensures the longest equipment lifetime. Basic cooling information is provided in following Pan 5, but if a hlgher powered transmitter is also on site, we behave that the importance oflhe subject may warrant and justify the hire of an eiqaerienoed air conditioning contractor. Ensure that ambient space is available both in front and rear of all cabinets and other equipment to permit easy access while equipment is being moved around, and to enhance awessibility for future maintenance. A minimum 90 to 100 on (about 3 to 3K ft) of clearance is recommended to allow access for a technician and test equipment, but you may need more clearance for other reasons or for the lifting devices sometimes used during installations. You may wish to consult local equipment rental agencies for dimensions of their available lifting apparatus; the required clearance is one of the "planning" items to be considered. All cabinets should be level. An uneven t'loor surface can distort the sheet metal frames of many cabinets so that door latches will not operate properly. Purses-29 rev 0: Dec. 12 1995 29-1 VHF Amplifier installation VHF AMPUFIER INSTALLATION 2. GROUNDINGIEARTHING Please overlook our typically North American use of the word "grounding“ throughout this text to describe a comedion to earth. and the word "ground” which usually refers to a point of zero voltage, ie. the earth. We are certain. however, that the identiml meanings of derivations of the word "ground” with those words pertinent to "earth“ are universally understood by all broadcasters. That said, we shall proceed. For safety‘ it is important that grounding conductors of adequate size be used to connect the transmitter (and other) whinetts) to the station "technifil ground" point. The metal bulkhead plate through which all circuits and coax fines to and from the tower will pass, makes an excellent techniml ground because “1 will be connected with one or two. 150 mm wide x 1.5 mm thick, copper straps to the tower ground system. Figures 2 and 3 suggest one memod. in which copper bar 75 or 100 mm wide and the same thickness as the floortsle is laid under transmitter and other cabinets for grounding. Each cabinet rock or tabletop cabinet is then connected with 1.5 mm copper strap or automotive smrter cable to the copper ground bar. The copper bar in turn conneds to the metal bulkhead plate. Alternatively. copper strap can be laid in a grounded overhead noble tray. Indoor grounding conductors must ultimately connect to the bulkhead plate. Consult your electrical code book. or ask your elecme contractor about the minimum permissible ground conductor size, but for broadcast installations a low ground impedance is desirable. so generally the cross Section of each cabinet ground should be the same or larger than the total of its AC wiring cross sedion. All outdoorgrourd comections shown be well bonded using an exafliennic brazing process such as Cadweld'" or equivalent Special precautions should be taken to minimize corrosion where connections are made of dissimilar metals indoor connections can be brazed. silver soldered. or simply bolted together and then tin—lead soldered in the conventional manner. When indoors. don'ttorget that the steelwork, the ventilation system, and all other metallic objects in the building, should also be grounded. It is mandatory that a good low impedance earth ground be provided for the tower. and it is good practice to employ this tower ground for all station ground connections. A system of buried radial conduaors as shown in figure 3. extend'mg outwards from the tower case and from each guy enmor, with their far ends temrinated in several ground rods spaced about twice their length apart and driven into the water table, is considered to be a good ground. The steel rebars and J-bolts in footings should also be bonded to this ground system. Be careful of dissimilar metals, and don‘t blaze anything to the lower legs! Use stainless steel worm gear style hose clamps to clamp copper strap or copper wires to the tower members. A special conductive grease is available to avoid dissimflar metals con'osion. but frequent inspection is necessary. More heroic measures become necessary it the tower footing is located on solid bare rock. These measures would include setting the gromdlng radiate in poured concrete (“midi has surprisingly good conductivity), doping with conductivity-enhancing chemical salts such as magnesium sulphate (Epsom salts are supposed to be less environmentally harmful than others), and using special hollow ground rods that are intended to be driven into holes drilled in the rock, and which are said to bond chemically to the rock and provide excellent grounding. as long as they are kept filled with water or chemical solution. "ULTRA GROUND" rods are available through LARCAN or from our business atfiliate LeBlanc & Royle Telcom Inc The building layout should place the tower, its wiring transmission line, the AC panels and surge suppressor. and the telephone terminations, all near one another so that all ground connections are as short as possible: all indoor equipment should be grounded to the same ‘technicel ground“ which we suggest should be the undead plate. whim will become a good low impedance ground when connected with several 150 mm copper straps to the tower. This single technical ground will provide the basis tor lightning protection of all equipment in the building. Both the power company and the telephone company should also use this same technical ground, otherwise a fightning hit to the tower could easily induce damaging transients that back up through the equipment and out the power or phone line to its own ground connections. Surge suppresors for coax lines and other tower circuits can mount (and ground) on the bulkhead plate. Fuses-29 rev 0» Dec 11 1993 29-2 VHF Amplifier insiaiiarion VHF AMPLIFIER INSTALLATION Many installations in large cities make use of existing tall buildings or spec'fimlly dedicated structures (such as the CN Tower in Toronto, Canada), and grounding for these installations could present a slight challenge. Most tall structures are provided with wide copper straps running from top to base. and grounded at or under the building foundations. The structural steel is also grounded to the same point. The d‘allenge occurs when the structure sustains a lightning hit, because an enonnous voltage gradient will be present from top to bonom. Equipment grounding must be done to one point only, as explained in the next section. Although most audio and video signals around the transmitter plant are of relatively h'ngh levels, it is well to be aware of another planning aspect that should be addressed anyway: this is the possibility of inadvertent creation of one or more "ground loops" of the kind that can induce hum into low level audio circuits. The most common muse of the hum-inducing kind of "ground loop“ is a result of code-approved electrical work in which all wiring is placed inside metallic conduit or raceway, and the conduit is attached to, and in center: with. the grounded structural steelwork of the building. Here is what can happen: 1. The transmitter cabinets are grounded; 2. The electrical service panels are grounded; 3. The conduit or raceway additionally may be grounded through its fasteners to the structural steel; 4. The service panel is connected by the metallic path through a conduit or raceway to the transmitter cabinet. The result is one or more large area single tum loops that have AC induced in them due to the wiring in the conduit but which can induce significant hum currents into low level audio wiring. Suggested treatment for these Ac ground loops, is simply to break each metallic loop by using a short length or non-metallic duct on the end of the metallic raceway. or use a short non-metallic section or a non—metallic coupling in the min of conduit This non-metallic part should be located as near as possible to the cabinet. IMPORTANT: Non-memllr'r: pans used for elecflical work must not be able to burn, nor emit hazardous gaseswhensubjectedmflames. You will needto work outtheexact ground loop treatmentmethod with your electrical contractor. and probably with your local electric-l inspector as well. This grounding treatment is acceptable to most regulatory audiorities in North America and perhaps elsewhere as well. provided that the equipment in fact is grounded through the copper ground conductors, the bulkhead plate, andsotidtowerground Note that this method does require hstallation of a separate dedicated grounding wire inside each conduit for the connection or the isolated ground cannot or each receptacle. wherever rewptacles are used. It is assumed that isolated ground receptacles are available, usually for use in computer rooms and In hospitals. it may be necessary that you and your olefin-at contractor also become technical instructors, in order to reassure your electrical inspector that reduction or ground loops does not irl tact contravene me applicable codes, At the very least you will probably need to prove that all your equipment is indeed grounded, despite the nonmetallic connection of conduit or raceway. Other. less severe. ground loops can result from the outer conductors of coax cables being grounded to the Guests of the equipment at both ends or the cable, and of course these components are also grounded through the cabinets in which they mount LARCAN excher video inputs use a differential connection and are not grounded. so do not contribute to a coaxial cable ground loop. The transmission line, however. is grounded at the tower, at the bulkhead, and at me transmitter. Treatment of coax cable ground loops usually consists of coaxial cable dress in such a menneras to minimize the area presented by the loop. Lowering the line bridge between the building and tmver will indeed reduce the loop area presented by the transmission line. but more importamly a lowered line bridge significantly reduces the energy induced on the center condudor due to a direct lightning hit to the tower. 100 to 130 cm (3-4 it) above grade is the suggested maximum bridge height, Fumes rev tx Dec. 12. 1995 294i VHF Amplifier installation VHF AMPLIFIER INSTALLATION 2. GROUNDINGIEARTHING (continued). The Canadian Broadcasting Corporation, through is Engineering Headquarters group. maintains its own standards for equipment design and installation and has published many of these tor the information of its suppilers. The CBC specification 'Technical PowerDisIlibr/flon and Grounding Standards, ESS—124'and CBC drawing 45753 which indicates the grounding practices followed in its installations. are highly recommended. Upon request LARCAN can provide you with a copy of these CBC documents. Although we try to amid touting any particular vendor or product. we have no hesitation in also recommending two publications from the PonPhaser Corp. phone 1-800-325-7170 or (702)-782—251 1. FAX (702)-782-4476, in Canada. their rap is SINCLABS INC. tel (905)-841-0624. FAX (905)-727-0861. One is ”The GROUNDS mr Lightning and EMP Protach'on, Second Edition“ by Roger R. Block; this text published by PolyPhaser is well worth the small price asked. harming/EMF and Grounding Solufions' is the curent FonPhaser mtalog of gromding materials and lightning surge suppression devices. The catalog is free. Both of these publications are recommended reading for anyone planning a ground system. 3. LIGHTNING AND OTHER TRANSIENT PROTECTION - a "mortal: A large proportion of mefollowing information which is oflered about lightning. was taken from a booklet entitled 'LIGHTNING PROTECTION for RADIO TRANSMITTER STATIONS" published in 1985 by NAUTEL. which is a Canadian manufacturer of AM transmitting equipment; other intomtatidn came from the PolyPhaser catalog and from lhe'r textbook ”The GROUNDS for L'gltming & EMP Pmlecu'on. Second Edifion'which we recommend highly as worth Its modest purchase price for anyone planning a ground system. We would like to thank the people at both NAUTEL and PotyPhaser, and we hereby gratefully acknowledge their ocrmibutions to the state otthe art The real-world environment of transmitting equipment is one where periodic lightning storms may ocwr and wuss antenna. tower, and power line strikes. The actual incidence varies widely with geographic location and is also attested by ml topography, the height at the tower. and routing of the incoming power and wlephone lines. Unless precautionary steps are taken. such strikes could muse transmitter damage. partiwlarly to the final amplifiers and to the AC line rectifiers associated with them. Oirmajoraraa ofconcem is with the lightning strike caused by discharge ofenergy from an electrically charged cloud to ground. Mod eledrical storms are localized. short in extent. and caused by localized air heating and convection. A less common but more troublesome type of storm is the frontal type caused by the meeting of warm-moist and ccld-dryair masses, escorting up to several hundred miles. The weather office people in the us. and Canada. and esewhere. publish naps sated "isokeraunic charts“ which indicate the mean annual number or days having thunderstorms; these are shown as contours which in North America will vary from C = 1 for northem Canada. all the way to C = 100 for central Florida, (In equatorial regions worldwide. C is even higher. In some parts of Atria, C = 150. and in South America in the Amazon basin. 0 = 200). The average numbernf lightning strikes per square mile per year may be deduced froth these contours by multiplying the C number by 0.37. For localized convection thunder-stems. the strike incidence is about 7591: of the frontal storm incidence, perhaps due to more frequent cloud-te-doud discharge occurrences. A grounded (antenna) structure of “H" feet height is considered by some authorities to essentially cover an area ot9rrH‘ squaretaet (a radius approximately three times its height). and strike incidence within that area at a site where frontal storms predominate, will be approximately C x 0.375 M2 x 10“. Piraeus rev 0' Dec. 12, 1993 29-4 VHF Amplifier installation VHF AMPLIFIER INSTALlATlDN The foregoing leads us to speculate that a 500 foot tower in central Florida (or its equivalent in another region), in contour 100 and with frontal storms, wil be struck an average of 9.4 times a year, and for the Canadian prairies in contour 20 with summertime convection stomrs, a 500 toot tower would receive an average or 1.4 hits per year. More important the "lightning attractiveness" of the tower depends on the SQUARE of its height if the tower is situated on top of a hill or mountain, "H" Will be increased by the hill or mountain height, and becomes approflnately equivalent to the antenna EHAAT. in practice, dimension "H" is slightly higher than the antenna elevation, because a metal lightning rod will be installed for protection of the topmost strobe or incandescent beacon, which is usually located above the antenna. A tightn‘ng strike begins with a local ionization of the atmosphere edited a “step leader“ whichjumps at a velocity about 150 11 per 1 ps inuernent every 4960 us. It can be assumed that during each don-nant 49 ps interval, this leader builds up its voltage to cause ionization for the next 150 it. and then tinds its next step. within an imaginary hemisphere of 150 ft radius. Since it is postulated to be within a hemisphere, the step leader geometry can be such that a horizontal strike to a tower inn oomr anywhere higher than the 150 ft point above average terrain, so side mounted panel or STL mimwave antennas can be just as vulnerable as top mounted slot or tumstile designs, Fortunately, the STL antenna is often flanked by metallic guy writes. thus has somewhat better protection, but guys that happen to be located in front of the panels of the main antenna are usually fiberglass to avoid distortion of the radiation pattern. Imagine a large ball 300 ft in diameter, rolling around in all directions; wherever it touches a grounded object, can become a point of attachment for a lightning hit. (From this, we can infer that coaxial ”grounding kits" will be required at least at the 150 fl point on the lower, attrequent intervals above that. and most definitely at both the base ofthe tower and the bulkhead plate in the building wall). The retum (main) stroke of a lightning strike is diaradarized by a rapid rise and hearty exponential deny of current essentially from a high impedance source comprised of a long length of ionized air. Presumably. the inductance at this air path determines the rate of rise of the arr-rent, and the air path resistance detem'lines the current peak value and its decay rate. Obviously the current peak value will varyfrom strike to strike. and statistical probability based on empiriml data indimtes a median vale (5096 of all lightning strikes) of 18,000 to 20,000 amperes, while the pulse decay length to halfits peak arnplimde also has a probability distribution range from 10 us to 100 us, with a median value of 40 us. There is also a 5% probability that the peak current can reach 30,000 amps, and a 1% probability that it can attain 120,000 amps. A onee-ina-lifetime monster peak current of 350,000 to 400,000 amperes is also statistically possible, maybe once every 10,000 hits. The current pulse median rise time to peak amplitude, is of the order of 5 ps. The ignoring strike consists of a discharge from a charged cloud into the semiinfinite reservoir which is called "ground" or "earth". Unfortunately, at the surface of our planet an ideal terminal connecting to the ideal ground (earth) is rarely if ever available; practical terminals will connect to it via a finite impedance having both resistance and inductance. ranging from a few ohms to a few hundred ohms. This implies that it an impedance of, say. 10 ohms to the ideal ground is what you have, then an average lightning hr of 20,000 amps will deliver200 kV acres the 10 ohms, and it is obvious that this must be prevented from reaching the equipment Considering the magnitudes of the lightning stnke currents, it is mandatory that the best possible earth ground system available should be used, as we stated in the previous section on Ear-thing and Grounding, above. if the tower ground is connected via other wiring (eg. grounding radiate, and the power and phone lines) to remote grounds, a substantial part of the strike current can flow to these remote grounds, therefore the real oonnaction to ideal ground becomes a parallel combination of all possible ground pains. Pumzs rev 0: Dec. 12, was 296 VHF Amplifier lnflallation VHF AMPLIFIER INSTALLATION 3. LIGHTNING AND OTHER TRANSIENT PROTECTION - a tutorial: (continued). A single technical ground point for the equipment minimizes the bad etleots of a lightning strike. because although the hit may raise this redinical ground to 200 kV above the iron core of planet Earth, everything else on site connected to this same ground point is also raised equally to 200 kV, thus no damage is done. For installations in typical large o'ty downtown locations. this is the only way of dealing with the enormous voltage gradients that can be developed over the height of a tall structure, When the transmitter is installed on the top floor of the tall building by itself and fed with microwave or other STL, there is no real problem. When the studios and offices are lomated on a lower floor of the same building, and the standby plant is in a vault in the basement, during a ightning strike their technical grounds will be at a considerably lower voltage than that of the tediniwl ground of the transmitter. In this situation you will need surge suppressors and plenty of isolating fen-ite torolds to ensure the lightning goes down the ground strap and not down your signal and AC wiring. lf coax video and twisted pair audio feeds seem less than desirable, you may wish to contemplate, evaluate, and use the complete isolation offered by fiber optics. For discussion purposes, a median lightning strike don be considered to be a near-exponential unidirectional pulse of 20,000 amperes peak amplitude. lasting 40 microseconds to hall-amplitude. For obvious reasons, it is impossible to exactly duplicate a lightning strike in the laboratory, so various working standards groups such as the lEEE in the electrical equipment industry have derived a repeatable, similar unidirectional pulse definition (ANSI 062.1) which Implies that a "standard“ last power line transient (not necessarily lightning) has an 8 ps rise time, and a half amplitude time of 20 us. This "8 x 20" definition appears frequently in MOV vendor information data sheets. There is also another common definition, based on a 10 ps rise and a half amplitude line of 1000 us (10 x1000), which is used by the MOV vendors as their standard to rate the energy dissipation of their devices. The peak pulse extent of20.000 A can be used for estimating the size of surge suppressor required on the Ac mains: Assume that the suppressor contains MOV devices that clamp the transiem to less than 500 V above ground for a 115-04 15 V mains. therefore the energy dissipated will be the mathematical integral of a needy exponential waveform which starts at time t = O and builds linearly to an instantaneous peak power of 10 Megawatts (20,000 amps x 500 volts) in the first 5 ps, deaeasing it 40 ps exponentially to half amplitude, eventually denying to zero. The answer is in Joules. which is the Si name forwetts x seconds. Vendors of MOV surge suppressor devices have published simplifying algonthrns for this integral. They assume that a lightning hlt has a two part waveform, and the answer is the sum of two equations of the from K x V x l x t where K is a constant oonesponting to the evaluation of the integral of the part of the wavefom't being examined, V is the clamp vmgs of the MOV. l is the peak err-rent. and t is time in seconds. The first part of thewavehas K=0.55c>itsenergyis0.5x500x20000x5x10‘ =25J¢whilethssecondpartK=1Asoite energy is 1 .4x 500 x 20000 x 40 x10‘ = 560 J. Adding the two. gives us 585 Joules. Multiple lightning current pulses during single hits are fairly common. so the energy number should be multiplied by another 5 or5 when you decide on your surge suppressors. For tall building installations, you may Wish to multiply the energy number again, because the multiple ground paths available at gade level installations are not present here except for the building stmeral steel and copper mp grand, and niostprmablylneAC mains The mains therefore would carry a larger proportion of the strike current. and the suppressors should be appropriately chosen for higherpeak current. The entire basis of lightning protection is that the strike airrent should never be allowed to blast through the equipment, but paths should be provided for this current to go around it instead. These paths are provided through property grounded (to your single tediniml ground) transient surge suppressors installed on all incoming wires, even iffor aesthetic reasons they all arrive underground. These fincoming wires" include AC mains. other power circuits, and signal, telephone. and remote control drcuits entering the building from the outside wodd, and from the lower. Pueeszs rev 0. Dec. 12. 1995 29-6 VHF Amplifier installation VHF AMPLIFIER tNSTALLATION For any nearordirect lightning h'n, the tower wiring is "incoming" to the equipment in the building. You need the best possible ground at the tower to ensure that most of the current from the hit goes to ground at the tower, and much less goes to ground at the suppressors where the lines enter the building. Series indumnoe should then be instatled on the equipment side of each and every circult (between the suppressor and the equipment) to provide enough isolating impedance that the transient is forced to choose the easier path through the suppressor, instead of through the equipment The minimum inductance needed can be oaludated from the basic indudanoe expression V = L dildt where V = the suppressor damping voltage, and dildt = peak amps/risetime; when we rearrange this equation and plug in some numbers, L = 500V x 5ps/20,000A = 0.125 pH. Two or three ferrite toroids have been empirically proven to provide adequate inductance for lightning isolation when placed over each circuit, and in practice they limit the current to much lower values than 20.000 amps. The induaanoe of a toroid can be measured. or calwleted from the vendor‘s data shoes. Suitable fen-lie toroids are offered by TDK FairaRite, Siemens, and Ferroxcube Typical TDK part numbers are H5C2-T52-72-10, which is 2" ID. and H5C2-T74-90-13.5, which is 2p" IDr Equivalent ferrite toroids from other warms could also be used iftheirsizes are adequate TDK‘s H5C2 material has a high permeability |rK of about 10.000. high saluation B,value of about 4000 gauss, and moderate Curie temperature of about 120°C. Other tenites as used in swrtchmode power supply transformer applications should wont as well. except that their 14 values are usme much lower so more toroids would be required. The TDK toroids cited have AL values about 5000 to 6000 nHIN‘. suggesting about 5 to 6 pH each toroid. Please note that we specified "each drouit“. not ~each wire". The operating current flow through each wire can easily saturate the magnetic path through the toroid. Place the toroid over the whole circuit instead, and the operating currents magnetic fields cancel each other. leaving the toruid to do its job. For lowpowered stations using typically RG-214 or semi~flexible Heliax'" or other ts" line, there are plenty of suitable fen-ite toroids on the market For higher powered lnstallao‘ons, when toroids that are large enough to fit over larger transmission lines are not available, it is suggested that 1" lengths of steel pipe or steel eledrical conduit, insulated from the line and from each other, are worth trying and may work almost as well. They should be provided with an air gap (a single out with a hacksaw) to avoid saturation. You might want to measure the inductance and loss at say, 2.5 MHz, of a single wire mreeded through one of these gapped greet rings, and compare it with the measured indudanoe of a ferrite toroid. Don't forget that ALL conductors and their sheathing or shielding extending up the tower are ”incoming" for a lightning strike; they need suppressors and inductances. The outer conductor of every coaxial cable or transmission line, or the metallic sheath of mineral mutated or other mulficonductor cable should be bonded (grounded) to the tower at frequent intervals to reduce probability or jacket puncture from the voltage gradients that could be developed between the cable and the tower. and these ‘outers and sheaths” definitely must be grounded to the tower base and to the building wall bulkhead plate. Rigid line is usually bonded to the tower with a metal strap or a line hanger placed every few flanges. mineral insuated noble sheathing is bonded with metallic fasteners. and plastic insulated cables must also have a metallic sheath. Flexible line or sheathed jacketed cable is stripped of about 1" to 1'15" of its jacket at frequent (60-80 ft) intervals, a ground strap is connected to the cable outer conductor, then a spatial polymer tape is used to reseal and waterpmofthe jacket Grounding kits contain all the materials required. Broadcast antenns are usually grounded to the tower. so create few problems. Other antennas. such as some designs used for two-way radio, may connect directly to the center ccnduflors of their cables and are insulated from ground. In any event, the center conductor of any coax, or conductors inside sheathing, can have high voltage induced in them due to a direct hit on the tower. For coax lines up to 3b" size. gas filled coaxial transient suppressors having good energy ratings and low VSWR are available from PolyPhaser, and for mulb‘conduacr cable there are also suitable suppressors offered. We don't intentionally wish to tout any particular vendor, but these products are highly recommended. Piraeus rev 0: Dec. 12, raga 29-7 VHF Amplifier installation VHF AMPUFIER lNSTALLA'HON J. LIGHTNING AND OTHER TRANSIENT PROTECTION - a tutorial: (continued). Coaxial line and other tower circuit surge suppressors should be mounted on and grounded to the bulkhead, which must be well grounded (that means low inductance as well) with at least two, 150 mm x 1.5 mm copper straps to the tower ground system. Any bends in these straps should be as gradual as possible. Be sure that all ground path impedanoes are as low as possible, and try to arrange the SUppressor locations and their grounding oondudors so that personnel mnnot come in contact with them during a thunderstorm. This indudes placement of grounded security fencing around the tower base, the line bridge, the bulkhead, and the guy anchors. Heavy copper wire or strap connecting to multiple groundlng rods around the foundation of the building, and including one ortwo of the tower ground radials, will help to equalize voltage distribution and the strike cunents underground. All suppressors and equipment ground connections, however, should be made to the bulkhead plate which is bonded to the tower ground system. Commeru‘al "surge suppressors“ designed to connect to AC mains and other lines, are available in various ratings of volmges, currents, surge currents. and Joules. Some of these may contain MOV devices and ferrite toroids integrated together. which may be worthwhile because the ten'ite provides the necessary impedance between the suppressor and the equipment and avoids the need for souro'ng at least two large loroids that will lit overthe (ourlarge conductors needed by the typical 3 phase AC power service entrance Other designs use air core inductors to avoid possible saturation of ferrite material from sumessive unidireuional lightning hits. At least one other brand includes high powered adive filter circuits. Be sure to devote sortie of your time to investigation of the various suppressors available to suit your applirzlions (you will indeed have several appllcations on site) before your decision is made. It is not a good idea to go without suppressors, or without isolating impedanoes between the suppressors and the equipment because there would then not be a controlled path for the lightning energy to follow, thus it is possible that the next hit could find an easier path through the PA module cirwit components. power supply realfiers, or power transformer insulation, and these items can become quite expensive. Generally, gas protector devices are useful on drums having relatively low voltage but higher source impedance, as in telephone and signaling systems. With special gases, they can be reflective on 5D 0 lines, especially where the transmitters VSWR protection shots on the RF momentarily dun‘ng the arc. AC power line source impedances are much too Iowfor gas filled protector devices to lunction property, because once an an: begins there, the gas plasma remains ionized long enough that the nextAC halt wale conducts, then the next, etc. resulting in extremely high oun'enttlow through the gas. Surge suppressors using MOVs worn best for AC power circuits. The tower itself must have sutfioienlty low ground impedance mat a major portion or the fightning energy goes to ground at the tower base or guy anchors, and only a small amount then needs to be dissipated in the suppressors. Locating the line bridge between the tower and the building as low as possible (1 mew or 3 to 4 ft above grade is suggested) will result in lower induced energy into all suppressors, and at the same tints. the extra line needed indoors to reach from the top at the transmitter cabinet or patch panel, down to the bulkhead plate, will add desirable isolating inductance. Many types of protedion devies are eveiable at a wide range of prices, but even the most expensive protection is extremely economical when compared with potential costs of affair loss of revenue, and/or the costs of rebuilding or replacement of the equipment being protected. You may also wish to oonsult with your power utility company engineers: their extensive experience with Iighming and grounding would certainly qualify them to be able to advise you about these same subjects, and a phone call or FAX to the PonPhaser people might also prove worthwhile. PolyPhaser numbers: Phone 1-800-325-7170 or (702)-782-251 1; and their FAX is (702)-7824476. Puaeezs rev 0- Dec. 12 1993 29-8 VHF Amplifier Installation VHF AMPLIFIER INSTALLATION 4. A FEW WORDS ABOUT POWER WIRING: This transmitter requires a single phase power source. The transmitter power supply is a switd'ier type with autoranging AC input allowing it to operate in the ranges of 90 to 135 V or 180 to 270 V. Typical measured power consumption at black. amplifier only, is 200 VA at 49% PF for the TTSlOEl, and 285 VA at 49% PF for the TI’SSGB. The exciter, mough, needs its primary taps set for appropriate line voltage, which must be within 110% ofnominal. Taps are at 100. 120, 130. 200, 210, 220, 230, 240, 250, and 260 V. The standard design allows the transmitter to operate Iine-to-neutral from single phase 100 to 130 V. For operation in typical 50 Hz regions. where a 380 V or 416 V mains is available, the transmitter also would be connected to operate line—to-neutral. Line to neutral in 380 V 3 phase mains is 220 V, and in 416 V 3 phase mains, line to neutral is 240 V. Optionally (with added fuse 1F2) it can be operated line-to-line when used as a standby at a site where 208 V 3 phase power is available. or from single phase 1150—1 15 V power. All switcher power supplies use a large input filter capao'tor, which is the reason for the poor power factor. "Power factor“ is based on measurement of zero crossings of input voltage and input current, and 100 times the cosine of these ziero crossings angular difference is the powerfactor in percent As the switcher operates, the filtercepan'tor recharge current occurs in narrow high current peaks, so the wrrent zero crossings obviously don‘t ooho‘de with the voltage zero crossings Furthermore, at stamp, ttie oapao'tor has no stored merge and takes a large inrush current for the first few AC cycles to bring its stored marge up to a value emugh for the supply to operate, Time delay fuses or circuit breakers are therefore necessary on me power line feeding the transmitter. Vendor spedtied voltage peak inrush current is about 55 amps, For standard line-to—neutral operation, a fuse 1F1 is provided; for the TTS10B this fuse is 7 amps slow blow, and for the TTSSOB the fuse is 12 amps slow blow. For the power source, we suggest that a slow trip breaker of 15 amps, rated for motor starting service, should be satisfactory, Even at lowest voltage the TTSSOB transmitter and its exciter together should draw less than 5 amps, so a 15 amp breaker is adequate. For optional line—to—line operation, the transminer is fitted with two fuses, 1F1 and 1F2. A sinusoidal output, Ac voltage regulator is recommended so that the exciter AC irput remains within its t10% limitation, especially at sites where line voltages fluctuate widely. Regulators having variable transformers that work a buck-boost connedion to the mains, provide sinusoidal outputs thus are the best regulators for the purpose. One small tradeoft is that some variable transformers are motor driven, thus may seem slow in correcting extremely wide variations in mains voltage. For most situations. rriost ofthe time, the mains voltage variafion rate is slow enough that this is not of oonoem Motor driven regulator response speed is not usually aitioel, but there is one situation for this type of regulator that should be kept in mind: Many power failures are preceded by an abnormally low mains voltage with consequent highest omit from the regulator, and upon restoration of power the output of the regulator will therefore be at its maximum torthe length offime required forthe regulator to respond. To make matters ivorse, often the restored incoming mains voltage will be well above normal for several seconds. A power surge of extremely high voltage thus can be applied to the equipment There is a solution to this regulator response problem: The regulator should be specified to have battery badarp, a DC servo amplifier and DC motor driving the variable transformer, and controller anangements such that it will reset itself to its LOWEST output voltage DURING a power failure, The result will be that upon restoration, the output voltage will begin at its lowest value. This will avoid equipment overstress. Selling of the regulatorfor light regulation will cause it to correct often for small incoming voltage Manges, which may rennin increased bnish wear in the variable transfomiens). Some regulators which have no brushes use special transformers in which two coils move in relation to each other. The original designs of these variable transformers came from General Electric and were called “lnduclrol' regulators, wees—2s rev 0: Dec. 12, 1993 29-9 VHF Amplifier installation VHF AMPLIFIER INSTALLATION 4. A FEW WORDS ABOUT POWER WIRING: (continued). Another compaan design of regulator made use at a large number at thyristor devices to switch taps on a transformerwinding. and would require at least two AC cycles tor its oontroiiercireuit to decide which tap needed to be swiwhed. with the result that small spikes were inherentty part of the regulated output. The 175108 or TTSSOB and its Exciter have good intemal regulation for wide extremes (nominal 11096) of incoming line voltage, but other on-site equipment may not be as tbrgiving ot poor line regulation, and a voltage regulator is a desilabte awessory. ifthe site mains voltage extremes are greaterthan10% variafion, a voltage regulatorthat has wide range input voltage spedfimtions, should be considered mandatory. 5. VENTILATIONIAIR CONDITIONING INFORMA‘HON At black level with full aurat power. the maximum amount of heat is generated by the RF amplifier This heat is removed by forced convection from the heatsink. A bunt-in blower pushes air through the heatsink, from which it is exhausted into the transmitter room. Care must be ialoen that the specified maidmum transmitter ambient temperature of 45°C is not exceeded at any time. The RF average power output delivered to the transmission line is almost 7 watts et black level with aural on, when the TTStOB transmitter is operating at its rated peak visual and 10% aural output. Subtracting this 7 W amount from the (200 VA x .49 PF) = 98 W ofAC power input, gives us the heat generated by all stages in the transmitter: about 90 W total. Add the 100 W exoiterpower input to this, and the total is about 190 Wt'or the transmitter on the air. Likewise, the TTS5OB defivers average power of 35 wads RF in the line and takes about (285 VA x AS PF) =140 w of AC power input. which generates about 105 watts of heat. and with the endter = 205watts of heatwhen on the air. These equipment heat amouns do not include the heat dissipated by input and monitoring equipment, or other sources or heat in the room. Due to the complexity of the entire discipline of “heating, ventilation and air ooncfitloning” (HVAC). it is recommended for best results that the services of an experienced air conditioning contractor/engineer be engaged for the design and implementation of your bulldog air conditioning or ventiiafion system. This is perhaps more important at shared sites using a single tower. such as for two-way radio, cell phone, telco. and/or other uses. such as in small communities where a studio Instanafion may be in the same building. Forbudgehty purposes, you may wish to perform this estimating exero‘se: Assuming a transmittersite only (no studio facflities), outdoor ambient temperature of 40°C, typically windowless concrete block walls, uninsulated precastcone'ateroot', andoveralt tflmensions tsttxzottx 11 it, itwouldprobablyrequireabout2‘bto 3tons of refn‘geration to keep the building habitable tor an inside emblem of 20° to 25°C without equipment. This is equivalent to maybe 9 kw of heat. and equipment heat load adds to this, at a rate of 3413 BTU per hour for every kilowatt of heat. whim works out to about 0.3 ton of refrigeration required to remove each kilowatt of heat. Ti‘lereare120008TU perhourinatonotret'rigerstion. Tiansrrimer heat is spedfied above, but the rack equipment and lighting loads are mspeoifted. Simply total the imut povnrtorthis other equipment, since you can safely assume all its AC input gets convened into heat Add the transmitter and exciter to this, add the result to the 9 kW for the building, multiply the total kW number by 0.3. round the result up to the next integral number. and that is your approximate tonnage. Reference to mail order catalogs (Sears, etc) indicates approximately the price per halt-ton for a 5000 BTU window mount air conditioner. We don't recommend window mount air conditioners because they are not designed torunattended continuous duty and they are difficult to service, but the catalog list price is a start. This price per halt-ton must then be multiplied by two and then by your integral number of tons. The result of this math represents a continuously running system; multiply again oy two for main-alternate. MSG-29mm Dec121sse 29-10 VHFAmpiifierlnstaJlafion VHF AMPLIFIER INSTALLATION The resulting total gives you an approximate equipment cost. less installation. Your air conditioning contractor should then be asked for an official estimate, including installation and warranty. 6. FIRE PROTEC‘HDN Some persons may lhink that the folowing material is totally overdone for a low powered transmitter site; indeed. many such sites are in remote regions or the country and would probably sustain far more damage from forest fires than from fires originating in the equipment or elsewhere inside the building. Nevertheless, you may find something of technical interest in this part. even though some of it may not be relevant to you, Transmitter Interlock connections are on TEE-3 and TBZ-4 on the back of the amplifiier chassis. These connections form a series path for “Enema Interlock #1" “Midi enables the transmitters control circuit, including its blower. Because the air is simply exhausted to the room. in use of fire the current of air from the transmitter may fan the Harries. so it is desirable that the blower be stopped. A fire alarm system should be able to be ananged to provide a set of normally closed dry contacts to connect into this interlocking circuit n is recommended that this be done, Other alarm system contacts may also be needed for various purposes separate from the transmitter. These extia alarm system contacts may be needed to shut dorm other air systems in the building, to close air dampers and fire doors, and to enable activation of automatic firefighting apparatus, if provided. One extra set of dry contacts should be made available for reporting of the fire through the remote control. Building designers once thought that a fire alarm system needed only to trip the main AC breakerto the building. whidi would automatimlly stop all tans and blowers. As long as the fire is prevented from spreading by ensuring all blowers are stopped and air dampers closed. and fire doors are closed, there is no reason that AC cannot remain on. to keep fighting available for evacuation of personnel. For installations where the transmitter is located on top of a tall building, the main AC should never be able to be tripped by a fire alarm, because doing this can also stop elevators full of people, sometimes between floors. Fire alarm systems for these situations should be engineered by spedalis’ts. It is assumed that itan emergency alternator is installed at the station, it is located in either a separate building, a fire proof vaultwith its own separate ventilation. or in its own enclosure. and is fitted with its own fire protection systems. so the above air system considerations would not apply to it Specific building codes may apply to it though, particularly regarding its fuel supply. It is well to check with your fire diief. fire marshali's office. and/or building inspector for applicable code requirements. The transmitter plant. particularly those using higher powered transmitting equipment represents too large an investment to neglect its fire protection, especially for unattended sites having ditficult access. Investigation of available fire alarm and fire fighting systems should be canted out as early in the design process as possible. and well before final design commitment. Your local fire chief or fire marshall's office may be helpful sources of advice during planning of your installation. Even if the site is normally unattended. it must be mandatory that any automatically activated fire fighting system can be disabled whenever personnel are working in the space protected by the system. Most systems for use with eledrical apparatus. depend on the high pressure discharge of carbon dioxide, halogenated hydrocarbons such as Halon". carbon tetrachloride, or other equally deadly extinguisher gases into a closed equipment room: this puts a fire out by displacing all oxygen. Obviously, the design must be fail~safe, because when personnel are worta‘ng in the room, they must never under any circumstances be exposed to a risk of system malfirnction which could be fatal. Check this out; it‘s important. FUESB-ZB rev 0: Dec 12. 1993 29-1 1 VHF Amplifier mailman VHF AMPLIFIER INSTALLATION 7. UNPACKING Caretulty inspect each package as it rs received, for possible shipping damage. Claims for damaged equipment must be tiled with the oam'erwithin seven days of delivery or the daims will not be accepted. Unless specific contractual arrangements for title, FOB Iowtion, eta have been made, generally the delivery or the equipment to the carrier by LARCAN lNC. constitutes transfer of title to the customer. and it is therefore customer responsibility to ensure that any such claims are prornptty filed direcliywlth the earner. Check the equipment received against the shipping list. Should there appear to be a stripping error or if reptadement equipment must be ordered due to transportation damage, notify your LARCAN representative as soon as possible. It consmrction or renovation work at the transmitter site is not complete by the time the equipment is received, repaok all equipment items after their inspection and store them in a dean, sate, dry area to avoid harm to any of the equipment. Repaddng for storage should be performed in sum manner to prevent access by mice and other small animals which can damage wire coverims. Construdion debris sum as plaster dust metal filings, and other abrasive contaminants entering the equipment an also muse damage. When the construction work is complete, the area should be cleared at all dirt and debris, and vacuumed thoroughly before the equipment is installed. Plain concrete floors should be seated ortrted to prevent surface dustfrom being drawn into the equ‘pment. When minmlafionwkisoompleta. thearea should again be mated otalldebris and vacuumedonce more, before any at the equipment is initially tumed on, Check for loose screws and connections, and tighten where necessary. . Finally, before powering up, be certain that all tools surplus and scrap installation materials, stray hardware, stray “blobs" of solder, ends art from wires. stripped wire insulation, and other trash, are completely removed from inside the mrnets. 8. TRANSMITTER EXTERNAL INTERLOCK CONNECTIONS: RF PATCH PANEL: ' ' (m mill] - . ANY LINK p/s CONT ACTOR ”RE ALARM EXT |NTK | Figure 1: 173108 and TTS5OB Transmitter Intertook Connections. Purses-29 rev 0: Dec. 12, 1993 29—12 VHF Amplifier rumination VHF AMPUFIER INSTALLATION We wil be the fist to adrrill-rat marry people think ‘imedooldng” is overdoing itfor such low powered equipment, lheretore we have shown dashed line jumpers 1 and 2 (or you to use in lieu ofirrterlooks. Just in case you DO need intertocks. such as when the amplifier is a driver for a high powered linear, know this: All intertodrs are low energy, 12 VDC. and laments are in the order of about 250 miliamperes. Connections shown are functionally compatible with interlocks for other LARCAN transmitters, as follows. Normally-closed contacts from the building fire alarm system should connect to "Ext lntartock 1" (1TBZJ5.4) whidt will shut down the whole transmitter. including its blower. This fire alarm comer: could cannot: in series with any patch panel and dumrrry load interlock wiring, or it wiring can be made easier, the petal panel and dummy load intertodcs could oonnect for convenience to “Ext Interlock 2‘ (tTB26,6) as shown. Transmitter operation is identical from either, the only dinerence bemeen these interlodwx 5&9 363: «1133,- .E Tmmzm I .4aDoo 4for at amplifier 2 an DSZE-SLZ-DCIZV RELAY 2 FORM 5 LATCHING xzvnc 1 EA DSZE—S-DCIZV Remy 2 FORM c 340mm” 12VDC 1 EA “5052—2000 DIODE said-rune see 17436503 or 1115711 2 2A up]. Ic om Isou'roa 1 Di mass" Ic OF A"? DUAL 2 EA mussp Ir: TIMER see 555 1 m "use: m, 48 VDC mm" 1 EA chncr Ic +12 vom' REG 1 2A Mcnztcr 15 +24 vom' REG 1 EA HDL‘J FUSE 3A 250V GLASS 1 BA HDL 1/4 ruse 1/u 250V cuss for control ps 1 EA Mil-IWGIES {c as m 1 FA "255598 TRANSISTOR PM? as" was» 2 FA Hsc154x Tuemzsroa z n mszu Ic RF m in He preamplifier only 1 EA axzosu szm‘oa nmtcrrm (control board fuse) 1 FA 5115394342 TRANSISTOR H‘ch DUAL er Polite m 1 EA PU598-35 rev 0: Del: 12, 1996 35—9 VHF In! Dlflex Beale TX Mzim VHF POWER AMPLIFIER at HEATSINK ASSEMBLY 1. RF Power Amplifier a HeaNnk Assembly 300189961 - GZ - G3: (continued). Most LARCAN exciters produce their best linearity at or near their maxrmum rated output levels, and often the overall system gain is sufficient to result in overdrive of later stages of the transmitter. The transmitter or translator lineup may therefore include an in-line attenuator between the exciter and the preamplifier, to prevent overdrive from certain models of excitermodulator. This is especially true for the 10 watt system, because in our basic ransmltter family a 10 watt amplfiier ls simply a Iightty driven 50 watt amplifier, and a 50 watt amplifier is likewise a lightiy driven 250 watt output stage running without its driverIlPA, (Our 250 watt transmitter lineup needs an additional IPA to get enough drive to the identical final stage that is used in the 50 watt end 10 watt lineups). 2. RF Preamplifier 10A1453G5 (Low Band) and 10A145354 (High Band): Figures 2 and 6. This preamplifier design originally appeared in the aural/sound section 01 a dual RF chain transmitter which operaEs two single RF chains in quadrature and therefore requires phase and gain control of the input to each chain. The same anopulated cit-om board is used tor-the present application, morefore has the pads and holes for the components which perion'ned the adjustment of RF gain and phase in the parallel systems. In a single chain transmitter such as the present one under discussion, there is no requirement for control of RF phase nor consequently its components; they are therefore removed and wire jumpers substituted. In the Low Band preamp, the 50 0 input cable is matched by C5. which uses the inductanw of the traces on the PC board to form a low pass matching network, and fed to amplifier U2 whose output connects through a table to the PA U2 is a linear amptr‘fier designed originally for use as a wideband mble system trunk amplifiert Cable amplifiers are nominally 75 ohms in and out but the MHW6185 is capable of a good match with 50 ohm source and load. C12 and the lead inductance of a CA2885 when used as U2, perform output matching to 50 0. C12 is not present in a board using an MHW6185 for U2, The gain of uz is spec'd as 18 dB. and allowing a few dB ortosses, the gain ofthe Low Band preamp is 14 to 16 dB. RF power FETs operated in High Band amplifiers exhibit about 6 dB less gain than they do in Low Band. so an additional amplifier is necessary to make up the ditlerenoe. The High Band preamplifier therefore consists at In the High Band preamp, the input is matched by C5 and the PC trace inductance which togethertonns a low pass matching network and the signal is red to an additional preamplifier stage U4, whose output appears as the input of U2, which in turn leads the board cumin cables The spedfied gain oftype MWA330 in the U4 position is 6 dB, and a type MHW6185 orCA2885 (U2) is 18 dB. Atede oflcsses existon the board, some effective gain otthe High Band preamp board 10A145GG4 is about 20 to 22 dEt At the output or U2, a match to 50 fl is provided by C12 and the device lead inductance, which together create a low pass matching network in boards where a type CA2885 cable amplifier is used; conversely a type MHW5185 device charaaeristics give it a wideband match to 50 0 therefore no special output matching is necessary, and C12 is not present U3 is a voltage regulator providing +24 V to the preamplifier stage(s), Fuses-32 rev 0: Dec. 12, 1998 1322 PA s Heatsink Assembly
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