AM Coverage Mapping & Prediction (4th Report by Pedrosa)

AM COVERAGE MAPPING & PREDICTION C

What are Coverage Maps? Coverae !a"s are desined #o indi$a#e #he servi$e areas o% radio $o!!ni$a#ion #rans!i##in s#a#ions. Ty"i$a''y #hese !ay (e "rod$ed %or radio or #e'evision s#a#ions) %or !o(i'e #e'e"hone ne#*or+s and %or sa#e''i#e ne#*or+s. ,$h !a"s are a'#erna#ive'y +no*n as "ro"aa#ion !a"s. -or sa#e''i#e ne#*or+s) a $overae !a" is o%#en +no*n as a %oo#"rin#.

What are Coverage Maps?  These !a"s are dra*n sin enineerin da#a %ro! #he -CC -edera' Co!!ni$a#ions Co!!ission/. The $overae "a##ern %or ea$h AM s#a#ion is (ased on #he standard groundwave feld strength pattern) #he requency o the station) and the ground conductivity o the local area.

Distant Coverage: 0i#hin #his area) #he sina' o% #he radio s#a#ion !ay (e *ea+ n'ess yo have a ood $ar radio or a ood s#ereo *i#h a ood an#enna. 2o !ay no# (e a('e #o re$eive #he s#a#ion a# a'' on *a'+!ans or o#her "or#a('e radios.

Local Coverage: 0i#hin #his area) yo sho'd (e a('e #o re$eive #he radio s#a#ion on a'!os# any radio *i#h !odera#e'y

Fringe Coverage: 0i#hin #his area) #he s#a#ion1s sina' *i'' (e very *ea+. 2o !ay (e a('e #o re$eive #his s#a#ion i% yo have a very ood radio *i#h a ood an#enna) (# i#1s "ossi('e #ha# in#er%eren$e %ro! o#her s#a#ions !ay "reven# yo %ro! "i$+in " #hese s#a#ions a# a''.

AM Antenna Patterns AM radio s#a#ions *i#h one #o*er #rans!i# #heir sina' *i#h e3a' s#ren#h in a'' dire$#ions. These s#a#ions have a $ir$'ar) or 4non5dire$#iona'4 an#enna "a##ern. AM s#a#ions #ha# have !ore #han one #o*er $an "re$ise'y #ne #heir an#enna "a##erns #o a very s"e$i6$ sha"e. The n!(er o% #o*ers) #he s"a$in and orien#a#ion o% ea$h #o*er) and #he "hase and ra#io o% #he sina' #ha# is sen# #o ea$h #o*er a'' $o!(ine #o $rea#e an an#enna "a##ern #ha# !ih# 'oo+ hear#5sha"ed $ardioid/) "ean#5sha"ed) or sha"ed 'i+e a 7) 8) or !'#i5'ea% $'over.

Ground Conductivity  To a 'are deree) AM radio sina's are a9e$#ed (y #he e'e$#ri$a' $ond$#ivi#y o% #he rond over *hi$h #hey #rave'. :iher rond $ond$#ivi#y *i'' ena('e AM radio sina's #o #rave' %ar#her. The eo'oy o% #he ;ni#ed ,#a#es varies rea#'y %ro! one area #o ano#her) and #his a9e$#s #he $ond$#ivi#y o% #he ear#h. ,ea *a#er has a !$h hiher $ond$#ivi#y #han #he rond) so AM radio sina's *i'' a'*ays #rave' !$h %ar#her over sea *a#er #han over 'and.

How accurate are these aps?  These !a"s are enera#ed sin #he sa!e da#a and !os# o% #he sa!e a'ori#h!s #ha# #he -CC ses *hen #ryin #o "redi$# $overae o% radio s#a#ions and in#er%eren$e *i#h o#her near(y radio s#a#ions. :o*ever) #here are !any %a$#ors #ha# $on#ri(#e #o radio re$e"#ion. One of the biggest factors is your radio < so!e radios *i'' "er%or! !$h (e##er #han o#hers in #ryin #o "i$+ " dis#an# radio s#a#ions.

How accurate are these aps?

Other factors include interference from radio signals (on$in o9 near(y (i'dins !'#i"a#h in#er%eren$e/) in#er%eren$e %ro! o#her s#a#ions on near(y %re3en$ies) or in#er%eren$e %ro! near(y e'e$#ri$a' e3i"!en# in yor area.

Very mountainous terrain, or very nontypical geology can also aect radio signals . I% yo1re on a !on#ain) yo !ay (e a('e #o "i$+ " radio sina's !$h %ar#her #han indi$a#ed on or !a"s. Li+e*ise) i% yo1re in a va''ey) yo !ay have #ro('e re$eivin !any s#a#ions.

How accurate are these aps?  At night, AM signals can bounce o the ionosphere and travel great distances. This !eans #ha# a# nih# yo !ay (e a('e #o "i$+ " an AM s#a#ion %ro! hndreds o% !i'es a*ay. I# a'so !eans #ha# a# nih#) AM s#a#ions #ha# are hndreds o% !i'es a*ay !ih# in#er%ere *i#h s#a#ions $'oser #o yor area.