Opportunity

My son and daughter are playing ice hockey this winter. This means that every Saturday morning I have to get up very early and haul them off to the rink for practice and a game.  It is actually a lot of fun because I love watching them play.  Having played a certain version of pond hockey in my youth, it brings back good memories.

In any case, last week, after they finished their game and changed out of their hockey gear, my son wanted to watch the older kids play.  Thus, we sat down in the bleachers for a few minutes to watch the 12-15-year-olds play against a traveling team.   Most hockey leagues are mixed, that is to say, girls and boys play on the same team.  Not to put too fine a point on it, but the girls can be decerned not only by their ponytails but also the pink stake laces or pink hockey gloves.  I also noticed that the girls seem to play a more cerebral version of the game, which is a joy to watch.

Not soon after we sat down, a fast break play developed at mid-ice.  It was truly a thing of beauty.  A player from the home team intercepted a pass from the opposing team and took off down the ice.  She was followed closely by another player from her own team.  As they crossed the opposing red line, the other team closed in.  I watched the lead player move fast toward the goal and then fake out the goalie, lifting her stick oh so much as she made the shot.  The goalie was completely fooled and dove for the non-existing puck, which was left on the ice for the following player, who neatly scooped it into the goal under the goalie’s leg.  It was over in a flash of white jerseys and pink laces.  I thought to myself; these are kids are great!  You do not have to watch an NHL game to see good hockey and sometimes the so-called “professional” sports are overrated anyway.

Which got me thinking about LPFM.  How many budding journalists, play-by-play announcers, DJs, and presenters are out there waiting for an opportunity to show their stuff?  An opportunity that they may never get because most commercial and many public radio stations are locked into an increasing automation loop.  Locally originated programming is constantly being cut and replaced by satellite-syndicated formats and or out-of-market voice tracking.  It is truly a shame because the strongest leg that terrestrial radio can stand on is localism.

LPFM can be that opportunity to return the radio to its community of license.  It will not be easy, clearly, the rules were written to prevent LPFM from ever competing with commercial or even public radio stations.  Restrictive power levels, odious interference rules, and limited fundraising capability will keep all but true believers and perhaps ignorant souls from attempting for a license.  It will be hard, but not impossible, and true believers will make a go of it.  The October 15th, 2013 filing window will very likely be the last opportunity for community organizations to establish a local radio station.  After that, the remaining spectrum crumbs will be divided between translator aggregators to create ever larger networks of mostly redundant content.

Terrestrial radio may well go through an evolutionary change.  As more and more broadcasters are finding out, once a license is owned, there is a great deal of expense in operating a station.  Things like employees and office supplies can be cut, however; towers need to be maintained, transmitters and antennas need to be replaced periodically, electricity bills must be paid, etc.  The larger the station, the more operating costs are involved.  Another serious economic downturn like 2008 and the crazy train will be off the rails.  The inexpensive-to-operate, volunteer-run local LPFM may indeed be the last radio station(s) standing.  I have heard many decry this type of station as “amateurish” or “not professional.”  Here is what can happen if you give a bunch of amateurs a free hand:

Good stuff.  Big picture stuff.

Nautel Radio Coverage Tool

This is a Webinar video from Nautel about their Radio Coverage Tool:

Highlights of the Nautel RF tool kit:

  • Analyze the proposed transmitter location’s coverage
  • Tower heights can be adjusted
  • Antenna gains can be changed
  • Transmitter power levels
  • Includes Terrain data
  • Includes population within coverage areas
  • Frequency Range 30 Mhz to 3GHz
  • Useful for general broadcast or point-to-point systems

This can be a useful tool for those looking to gauge the realistic coverage of a station in terrain-challenged areas.  It can also be useful for studying STL paths, RPU coverage, etc.

One problem is the power levels and antennas are preset, with the minimum setting of 200 watts into a two-bay antenna.  These settings are too high for use when investigating a potential LPFM.  For that, Radio Mobile Online (which is the engine behind the Nautel RF tool kit) can be accessed directly via www.ve2dbe.com/rmonline.html.  Requires an account, which is very easy to set up.  For most users, FM broadcast band frequencies will not be available, however, 2 meter amateur frequencies (146 MHz) are the default, and for all practical purposes, will model coverage in the FM band (88 to 108 MHz) just fine.

By creating a hypothetical LP100 transmitter site, the coverages between the FCC 60 dBu contour and the actual coverage based on terrain can be compared.  This is the FCC 60 dBu coverage contour:

Example contour, LP-100 station
Example 60 dBu contour, LP-100 station

According to the US Census data, this station has a population coverage of; 30,721 in the 70 dBu or 3.162 mV/m contour, 92,574  in the 60 dBu or 1 mV/m contour, and 165,183 in the 50 dBu or 0.316 mV/m contour. Courtesy of REC Network.  The 60 dBu contour is considered the protected area licensed for use by the FCC.

Looking at a coverage terrain map, the picture changes somewhat:

Example coverage map, LP-100 station
Example coverage map, LP-100 station

This is based on predicted receiver location using terrain data; receiver antenna height 1 meter, 90% reliability, minimum signal level 10 µV (20 dBu,  yellow, very good car radios) and 31.62 µV (30 dBu, green, good radios and indoor reception).  Areas to the south and east of the transmitter are shaded by a large hill, thus they show low or no signal on the terrain based coverage map.  UN Population data indicates the yellow has 178,573 and the green area has 72,014 persons.  This map does not take into account co-channel and adjacent channel interference, which there is sure to be.

When comparing the two maps, one can see the coverage holes in the terrain map that are within the 60 dBu contour.  There may also be a slight difference in populations covered because the FCC map uses 2010 US Census data and the Radio Mobile Map uses UN population data.  For general planning purposes, the area shaded in green would be a safe bet on good reception, all other things being equal.

Since the LPFM stations are very limited in their ERP, finding a good transmitter site that will cover the desired area will be key to a successful operation.

Migrating the existing AM stations to former TV channels 5 and 6

This is one of the possibilities that has been bantered about as a solution for the “AM problem.” The theory goes as such; former TV channels 5 and 6 (76 – 88 MHz), which are not suitable for DTV would be an ideal place for the existing AM stations to move.  That represents a 12 MHz chunk of spectrum, which is much more than the current 1.16 MHz spectrum the current AM broadcasting service takes up (.54 to 1.7 Mhz).  An added benefit is that the VHF spectrum does not have the skywave “problem” that the MF spectrum does, thus many more stations could be licensed to the service.  Everyone would benefit, and AM stations would get a new lease on life in the FM band.  The number of stations would increase by several fold, including LPFM, non-commercial, and translators.  AM stations would no longer be burdened with expensive directional arrays or substandard audio quality.

It seems almost too good to be true…

The FCC reportedly promised “take a hard look” at this idea back in 2008.  Four years later, one wonders what has become of it.

A quick search of the existing TV stations licensed to channels 5 and 6 reveals the flaw in this theory.  The FCC has re-licensed many full powered and Low Powered DTV stations to channels 5 and 6 since 2008.

List of full power channel 5 stations:

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
WOI-DTDTLICAMESIA866113.9566CAPITAL COMMUNICATIONS COMPANY, INC.
WGVKDTLICKALAMAZOOMI2478310169GRAND VALLEY STATE UNIVERSITY
WBKPDTLICCALUMETMI760016.4301LAKE SUPERIOR COMMUNITY BROADCASTING CORPORATION
KXLF-TVDTLICBUTTEMT3595910588KXLF COMMUNICATIONS, INC.
KXGN-TVDTLICGLENDIVEMT242871152.4GLENDIVE BROADCASTING CORP.
KHAS-TVDTLICHASTINGSNE4800345217HOAK MEDIA OF NEBRASKA LICENSE, LLC
WLMBDTLICTOLEDOOH1707610155DOMINION BROADCASTING, INC.
KOBIDTLICMEDFORDOR82606.35823CALIFORNIA OREGON BROADCASTING, INC.
KIVV-TVDTLICLEADSD343489.2561KEVN, INC.
WTVFDTLICNASHVILLETN3650422425NEWSCHANNEL 5 NETWORK, LLC
WMC-TVDTLICMEMPHISTN1918434.5308WMC LICENSE SUBSIDIARY, LLC
KCWXDTLICFREDERICKSBURGTX2431623.7412CORRIDOR TELEVISION, L.L.P.
WCYB-TVDTLICBRISTOLVA245529.9743BLUESTONE LICENSE HOLDINGS INC.
WDTVDTLICWESTONWV7059210240WITHERS BROADCASTING COMPANY OF WEST VIRGINIA
WIWNDTLICFOND DU LACWI605719338WWAZ LICENSE, LLC

List of Low Power Channel 5 stations (analog):

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
KSCT-LPTXLICSITKAAK153480.0490DAN ETULAIN
K05KFTXLICDILLINGHAMAK7920.160ALASKA CORP OF SEVENTH DAY ADVENTIST
KRDN-LPTXLICREDDINGCA1271790.60KM COMMUNICATIONS, INC.
W05COTXLICSARASOTAFL6699530THREE ANGELS BROADCASTING NETWORK, INC.
W05CJTXLICKEY WESTFL1256420.590JAMES J. CHLADEK
DKHHB-LPTXLICHILOHI12623330KHHB, LLC
WIKY-LPTXLICEVANSVILLE, ETC.IN610360.140ROBERTS BROADCASTING COMPANY OF EVANSVILLE, IN, LLC
K05IVTXLICPARK RAPIDSMN553740.0190RED RIVER BROADCAST CO., LLC
W05BVTXLICSTARKVILLEMS216340.0660FIRST UNITED METHODIST CHURCH
K05LUTXLICJEFFERSON CITYMO1285200.110HISPANIC CHRISTIAN COMMUNITY NETWORK, INC.
K05LYTXLICMOBERLYMO1285600.10HISPANIC CHRISTIAN COMMUNITY NETWORK, INC.
KSXC-LPTXLICSOUTH SIOUX CITYNE12801230VENTURE TECHNOLOGIES GROUP, LLC
K05KYTXLICLINCOLN CITYOR1291902.250MICHAEL MATTSON
K05KXTXLICTILLAMOOKOR1291940.650MICHAEL MATTSON
KRCW-LPTXLICPORTLANDOR351512.70TRIBUNE BROADCAST HOLDINGS, INC., DEBTOR-IN-POSSESSION
K05LETXLICASTORIAOR1291612.50MICHAEL MATTSON
KJIB-LPTXLICCLEAR LAKE CITYTX211840.1030FAR EASTERN TELECASTERS
KLUF-LPTXLICLUFKINTX289370.0940INTERNATIONAL BROADCASTING NETWORK
K05EFTXLICBRADY, ETC.TX100430.0680FOSTER CHARITABLE FOUNDATION, INC.
KTXF-LPTXLICABILENETX1308400.6650KM COMMUNICATIONS, INC.

List of Low Power Channel 5 stations (digital)

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
K05FW-DLDLICGIRDWOODAK7960.0610ALASKA PUBLIC TELECOMMUNICATIONS, INC.
K05ET-DLDLICLIKELYCA82400.250CALIFORNIA OREGON BROADCASTING, INC.
K05CR-DLDLICHAYFORKCA681120.0070TRINITY COUNTY OFFICE OF EDUCATION
K05CF-DLDLICWEAVERVILLECA713810.0150WEAVERVILLE TRANSLATOR CO., INC.
K05FR-DLDLICCROWLEY LAKECA435120.060MONO COUNTY SERVICE AREA NO. 1
K05DQ-DLDLICBURNEY, ETC.CA83140.0450BLUESTONE LICENSE HOLDINGS INC.
K05LI-DLDLICWEBER CANYONCO1308820.00230SOUTHWEST COLORADO TV TRANSLATOR ASSOCIATION
K05GA-DLDLICDOLORESCO614700.00520SOUTHWEST COLORADO TV TRANSLATOR ASSOCIATION
K05JW-DLDLICISMAY CANYONCO614490.00240SOUTHWEST COLORADO TV TRANSLATOR ASSOCIATION
K05MD-DLDLICCRIPPLE CREEK, ETC.CO1678091.50TUCK PROPERTIES, INC. C/O LEE PELTZMAN
WRUF-LDLDLICGAINESVILLEFL42000.30BOARD OF TRUSTEES, UNIVERSITY OF FLORIDA
K05GL-DLDLICCOOLINID535160.0130PRIEST LAKE TRANSLATOR DISTRICT
K05EY-DLDLICTERRACE LAKESID231500.0650GARDEN VALLEY TRANSLATOR DISTRICT
K05BE-DLDLICLEHMI, ETCID587080.0130SALMON TV TRANSLATOR DISTRICT
W05DD-DLDLICST. FRANCISME396520.0970MAINE PUBLIC BROADCASTING CORPORATION
K05GM-DLDLICPLAINS-PARADISEMT527800.0170PLAINS-PARADISE TV DISTRICT
K05AH-DLDLICHOT SPRINGSMT276850.0050HOT SPRINGS TV DISTRICT
K05ML-DLDLICSULAMT1815780.0060SULA TV DISTRICT
K05IZ-DLDLICHINSDALEMT272590.00340HINSDALE TV CLUB
K05MW-DLDLICFERNDALEMT1825480.0240SWAN HILL TV DIST
K05FC-DLDLICLAKE MCDONALDMT167540.0050CANYON TV
K05KK-DLDLICPOPLARMT530120.0370POPLAR TV DISTRICT
K05JU-DLDLICELKONV194010.10ELKO TELEVISION DISTRICT
K05AF-DLDLICMINA/LUNINGNV427020.070MINERAL TELEVISION DISTRICT #1
W05AR-DLDLICBRYSON CITY, ETC.NC538960.0890WYFF HEARST TELEVISION INC.
WTVFLDLICNASHVILLETN3650430NEWSCHANNEL 5 NETWORK, LLC
K05AR-DLDLICROCKVILLEUT709620.0310BONNEVILLE INTERNATIONAL CORPORATION
W05AW-DLDLICCHRISTIANSTEDVI702860.30VIRGIN ISLANDS PUBLIC TV SYSTEM
W05AA-DLDLICROANOKEVA739890.0970WSET, INCORPORATED
K05MU-DLDLICLEAVENWORTHWA1875400.010LEAVENWORTH NON-PROFIT TV ASSOCIATION
KCEM-LDLDLICCHELAN BUTTEWA644550.0030APPLE VALLEY TV ASSOCIATION, INC

List of full power Channel 6 stations:

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
WUOADTLICTUSCALOOSAAL7749626395THE BOARD OF TRUSTEES OF THE UNIVERSITY OF AlABAMA
WEDYDTLICNEW HAVENCT135950.488CONNECTICUT PUBLIC BROADCASTING, INC.
WCES-TVDTLICWRENSGA239377.9429.4GEORGIA PUBLIC TELECOMMUNICATIONS COMMISSION
WABW-TVDTLICPELHAMGA2391710.5378.9GEORGIA PUBLIC TELECOMMUNICATIONS COMMISSION
KBSD-DTDTLICENSIGNKS6641431216.8SUNFLOWER BROADCASTING, INC.
KTVM-TVDTLICBUTTEMT1806619.2591.3BLUESTONE LICENSE HOLDINGS INC.
KWNB-TVDTLICHAYES CENTERNE2116211.9221PAPPAS TELECASTING OF CENTRAL NEBRASKA, L.P.
WRGBDTLICSCHENECTADYNY7394230.2392WRGB LICENSEE, LLC
WPVI-TVDTLICPHILADELPHIAPA861634330ABC, INC.

List of  Low Power Channel 6 stations (analog):

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
K06LGTXLICCHUATHBALUKAK628270.0520STATE OF ALASKA
K06LPTXLICCIRCLE HOT SPRINGSAK625290.5480STATE OF ALASKA
KNIK-LPTXLICANCHORAGEAK214920.920FIREWEED COMMUNICATIONS LLC
K06MFTXLICKENAI, ETC.AK214901.440FIREWEED COMMUNICATIONS LLC
W06BHTXLICPHENIX CITY, ETC.AL252070.060GREENE COMMUNICATIONS, INC.
KNJO-LPTXLICHOLBROOKAZ1311620.4750KM COMMUNICATIONS, INC.
KVFA-LPTXLICYUMAAZ1311440.050KM COMMUNICATIONS, INC.
K06MUTXLICBIG BEAR LAKECA6314910BEAR VALLEY BROADCASTING, INC.
KNNN-LPTXLICREDDINGCA1292491.50VENTURE TECHNOLOGIES GROUP, LLC
KLOA-LPTXLICINYOKERN, ETC.CA2858330ROBERT D. ADELMAN
KCIO-LPTXLICVICTORVILLECA115290.990OBIDIA PORRAS
KRPE-LPTXLICBANNINGCA1296510.9990VENTURE TECHNOLOGIES GROUP, LLC
KUHD-LPTXLICVENTURACA679630.9990OBIDIA PORRAS
KBKF-LPTXLICSAN JOSECA1278820.60VENTURE TECHNOLOGIES GROUP, LLC
KEFM-LPTXLICSACRAMENTOCA12799630VENTURE TECHNOLOGIES GROUP, LLC
KXDP-LPTXLICDENVERCO6755230SYNCOM MEDIA GROUP, INC.
WHDY-LPTXLICPANAMA CITYFL13006310CONFESORA PERALTA
WEYS-LPTXLICMIAMIFL603530ALMAVISION HISPANIC NETWORK
WDDA-LPTXLICDALTONGA1311272.50WORD OF GOD FELLOWSHIP, INC.
KESU-LPTXLICHANAMAULUHI13100530CHANG BROADCASTING HAWAII, LLC
WKQX-LPTXLICCHICAGOIL12823930WLFM, LLC
W06BDTXLICPRINCETONIN492430.0140NORTH GIBSON SCHOOL CORPORATION
WDCO-LPTXLICSALISBURYMD13043910SIGNAL ABOVE LLC
WJMF-LPTXLICJACKSONMS2625320KID’S TELEVISION, LLC
KGHD-LPTXLICLAS VEGASNV13002730OBIDIA PORRAS
WMYH-LPTXLICELMIRANY1258190.250VISION COMMUNICATIONS, LLC
WXXW-LPTXLICBINGHAMTONNY1292240.0160JOHNSON BROADCASTING COMPANY, INC.
WNYZ-LPTXLICNEW YORKNY5604330ISLAND BROADCASTING LLC
WMBO-LPTXLICWESTVALENY143190.30METRO TV, INC.
WNNY-LPTXLICAUBURNNY413641.450RENARD COMMUNICATIONS CORP.
WMTO-LPTXLICWANCHESENC1278020.60RAY H. LIVESAY
WLFM-LPTXLICCLEVELANDOH669930VENTURE TECHNOLOGIES GROUP, LLC
K06NITXLICTHE DALLESOR1291530.250MICHAEL MATTSON
WRTN-LPTXLICALEXANDRIATN12585820RICHARD C & LISA A. GOETZ
WPGF-LPTXLICMEMPHISTN2384830GEORGE S. FLINN, JR.
KRGT-LPTXLICRIO GRANDE CITYTX579990.040CTV BROADCASTING, LLC
KFMP-LPTXLICLUBBOCKTX12973430VENTURE TECHNOLOGIES GROUP, LLC
KXIT-LPTXLICAMARILLOTX13008930GEORGE CHAMBERS
KBFW-LPTXLICARLINGTONTX12788730GERALD BENAVIDES
KZFW-LPTXLICDALLASTX531630DFW BROADCASTING, INC.
K06PBTXLICUVALDETX673030.990SUPER RADIO, INC.
WDCN-LPTXLICFAIRFAXVA2045030SIGNAL ABOVE LLC
K06OATXLICEAU CLAIREWI1291390.90MARCIA T. TURNER D/B/A TURNER ENTERPRISES

List of Low Power Channel 6 stations  (digital):

Call SignServiceStatusCityStateFac IDERP (kw)HAAT (m)Licensee
K06OR-DLDLICSEWARDAK1688660.30SEWARD MEDIA PARTNERS, LLC
K06AE-DLDLICPRESCOTTAZ352740.50MULTIMEDIA HOLDINGS CORPORATION
K06HN-DLDLICGUNNISONCO256110.060GUNNISON COUNTY METROPOLITAN RECREATION DISCRICT
K06HU-DLDLICASPENCO567040.0060PITKIN COUNTY TRANSLATOR DEPARTMENT
K06GW-DLDLICNEW CASTLECO231590.0050ROCKY MOUNTAIN PUBLIC BROADCASTING NETWORK, INC
K06NT-DLDLICDOLORESCO1308810.00520SOUTHWEST COLORADO TV TRANSLATOR ASSOCIATION
K06NG-DLDLICSARGENTSCO1269290.050GUNNISON COUNTY METROPOLITAN RECREATION DISCRICT
W06AY-DLDLICLEBANONKY704980.30GARY WHITE
K06FE-DLDLICMILES CITYMT357260.10MMM LICENSE II LLC
K06AA-DLDLICBROADUSMT531670.0880POWDER RIVER T.V. BOARD
K06AV-DLDLICWOLF POINTMT733760.0190WOLF POINT TV DISTRICT
K06NV-DLDLICWHITE SULPHUR SPRINGSMT217100.060MEAGHER COUNTY TELEVISION DISTRICT
K06JC-DLDLICCHADRONNE479770.0660NEBRASKA EDUCATIONAL TELECOMMUNICATIONS COMMISSION
K06KR-DLDLICCRAWFORDNE479910.0280NEBRASKA EDUCATIONAL TELECOMMUNICATIONS COMMISSION
K06PG-DLDLICLAUGHLINNV116870.30CLARK COUNTY SCHOOL DISTRICT
K06KQ-DLDLICMANHATTANNV141260.020COUNTY OF NYE
K06MK-DLDLICELKONV193800.10ELKO TELEVISION DISTRICT
K06HT-DLDLICELYNV591290.0530WHITE PINE TELEVISION DISTRICT # 1
K06NY-DLDLICRYNDONNV1287500.0620ELKO TELEVISION DISTRICT
W06AJ-DLDLICFRANKLIN, ETC.NC538840.1930WYFF HEARST TELEVISION INC.
K06NS-DLDLICCHILOQUINOR82680.1930CALIFORNIA OREGON BROADCASTING, INC.
K06PM-DLDLICBEAUMONTTX1288360.30ROGER MILLS
K06JA-DLDLICCEDAR CANYONUT97120.0150CEDAR CANYON TV

Looking through this data, particularly the digital licenses which were granted since 2009, one an only assume that the FCC has, by de facto, nixed this idea if it ever considered it at all.

The unitless coefficient of Zorch

Zorch is a term used to describe an over voltage or over current condition that usually leads to catastrophic failure, e.g. the power supply was zorched by lightning. There is also a quality to radio signals that defy and exceed theoretical definitions for service contours or power density.  That is quality defined as:

Zorch (adj): The ability of an RF signal to be received in unlikely locations; outside of predicted service contour, in steel structures, underground facilities, tunnels, etc.

It brings to mind the saying, “antennas are not amplifiers and amplifiers are not antennas.”

ERI circularly polarized 2 bay antenna
ERI circularly polarized 2 bay antenna

During the earlier stages of FM broadcasting, there was a notion that costs could be reduced by increasing antenna gain and reducing transmitter size. While theoretically, ERP (Effective Radiated Power) is ERP, broadcasters soon learned that high gain antenna, low TPO (Transmitter Power Output) installations lacked building penetration and had other reception issues.  Realizing that there is a trade off between antenna bays, transmitter power output especially in difficult reception areas, a great debate occurred and continues on what the optimal system is.  The answer is, it depends on the receiving environment.

Where this technical detail can be really important is with lower powered FM stations; Class A and LPFMs to be exact.  They are already battling against bigger stations that have tens or even hundreds of times  more power.  Certainly an LP-100 station has it’s work cut out for it.  The choice of antenna is perhaps one of the most important technical decisions to be made.  Choosing the right balance of antenna type, antenna gain, antenna height and transmitter power output can greatly influence reception reliability and thus coverage area.

A good study of this quality can be had by looking at various LPFM installations:

Station ERP (watts) Antenna Type Antenna Gain (power) TPO (watts)* Coefficient of Zorch
100 1 bay vertical 0.92 127 0.1
100 1 bay circular 0.46 253 0.4
100 2 bay vertical full 1.98 58 0.15
100 2 bay vertical half 1.40 83 0.2
100 2 bay circular full 0.99 118 0.5
100 2 bay circular half 0.70 166 0.7
100 3 bay circular full 1.52 77 0.46
100 3 bay circular half 1.01 115 0.52

*Includes 100 feet of 1/2 inch foam transmission line, Andrew LDF4-50A, loss of 0.661 dB  at 100 MHz, or 0.859 power gain.

Stations should try to get the transmitting antenna as high up as permitted without reducing ERP.  In other words, the FCC allows 100 watts ERP with 98 feet Height Above Average Terrain (HAAT) radiation center in their current LPFM rules.  Being lower in height will reduce the coverage area.  Going over 98 feet HAAT will cause the station’s power to be reduced, which will lower the coefficient of zorch accordingly.  Therefore, getting as close to 98 feet HAAT, which is different than 98 feet above ground level in many places, will net the best performance.

If a singular polarization (horizontal or vertical) is desired, vertical polarization should be chosen, as most mobile reception is by a vertical whip antenna.  For best reception performance, a circularly polarized antenna will work best, as receiver antenna orientation will not effect the signal reception.  A circularly polarized antenna has better building penetration and multi-path characteristics.  The FM broadcast circularly polarized antenna in not a true circularly polarized antenna, it is actually unpolarized.

The use of a multi-bay antenna has the effect of focusing the RF radiation outward, perpendicular to the element stack, thus limiting the radiation directly up or down from the antenna.  This is more pronounced with one half wave spaced antennas, which may be an environmental consideration in heavily populated areas.

Thus, the best coefficient of zorch for an LPFM station would be a circularly polarized, 1/2 wave spaced, 2 bay antenna.  This antenna would have some gain over a single bay antenna, take up less room on a tower than a full wave spaced antenna, offer good RF protection performance for the general public living and working under the antenna, reduce wasted upward radiation and offer good building penetration for the ERP.  It would require a slightly larger transmitter and more electricity, but that trade off is well worth the effort.