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Text File | 1988-08-17 | 22.5 KB | 529 lines

************************************************************ (C⌐ 3▒ JU╠ 88 Eriπ Gustafson 201╕ S« Avenidß Planeta Tucson¼ A┌ 85710 DPL╠á DeriveΣ Datß Carrie≥ Detec⌠ (DCD) Fo≥ Filte≥ BaseΣ anΣ Singlσ Chi≡ Modems INTRODUCTION Iµá yo⌡á havσá ß TN├ whicΦ use≤ eithe≥ thσá AMD791░á o≥á thσ ì TCM310╡ singlσ chi≡ modem¼ o≥ ß TN├ whicΦ use≤ ß modeφ baseΣ ì oε audi∩ filter≤ likσ thσ PK-232¼ yo⌡ caε vastl∙ improvσ thσ ì DC─ performancσ oµ you≥ modeφ fo≥ packe⌠ radi∩ use. Thesσá singlσ chi≡ modem≤ werσ originall∙ designeΣ fo≥á lanΣ ì linσá use«á Thσ designers¼á wh∩ haΣ n∩ ideß tha⌠ thσá chip≤ ì migh⌠á onσá da∙á bσ applieΣ t∩ ßá radi∩á system¼á madσá somσ ì assumption≤á abou⌠á thσ incominτ signa∞ tha⌠ simpl∙á d∩á no⌠ ì appl∙á t∩á thσ radi∩ environment«á Thσ datß carrie≥á detec⌠ ì functioεá fo≥ theφ wa≤ no⌠ nearl∙ s∩ critica∞ ß functioεá oµ ì thσá modeφ a≤ i⌠ i≤ fo≥ u≤ oε ß bus∙ packe⌠á radi∩á channel« ì Fo≥ thσ intendeΣ purposσ oµ thesσ chips¼á therσ wa≤ expecteΣ ì t∩á bσá onl∙ ▓ station≤ involveΣ oε an∙ ▒ channe∞ a⌠ ▒á timσ ì anΣá thesσ station≤ werσ connecteΣ b∙ ß nicσá quie⌠á twisteΣ ì pair«á Unde≥á thesσ circumstances¼á thσ Carrie≥ Detec⌠ (CD⌐ ì functioεá buil⌠ int∩ thesσ chip≤ i≤ entirel∙á adequate«á Iε ì thσá packe⌠ radi∩ environment¼á thσ buil⌠ iε C─ functioεá i≤ ì nex⌠ t∩ useless. Sincσá ╔á can'⌠ makσ thσ samσ defensσ fo≥ thσá designer≤á oµ ì filte≥á baseΣ modem≤ specificall∙ intendeΣ fo≥ packe⌠á radi∩ ì froφá thσá beginning¼á ╔ won'⌠ tr∙ t∩ speculatσá abou⌠á wha⌠ ì drovσ thei≥ desigε decisions. Thσá circui⌠á presenteΣ herσ wil∞ allo≈ you≥ TN├ t∩ bσá useΣ ì witΦá unsquelcheΣ audi∩ thu≤ avoidinτ thσ unnecessar∙á dela∙ ì oµ thσ squelcΦ circui⌠ founΣ iε typica∞ VH╞ F═ radios« Thi≤ ì circui⌠á als∩á provide≤ severa∞ othe≥á importan⌠á beneficia∞ ì characteristic≤ fo≥ thσ DC─ system. First¼á sincσá thσ assumption≤ useΣ wheε thσ TN├á softwarσ ì wa≤á writteεá depenΣá oε DC─ representinτá thσá presencσá o≥ ì absencσá oµ ß datß carrie≥ oε thσ channel¼á i⌠ i≤á importan⌠ ì tha⌠á thσ DC─ circui⌠ bσ ablσ t∩ distinguisΦ ß datßá carrie≥ ì froφá noisσá o≥á othe≥ noε packe⌠ signal≤á t∩á ßá reasonablσ ì degree«á Thσá DC─ circuit≤ whicΦ simpl∙ detec⌠ thσ presencσ ì oµá AN┘á typσ oµ signa∞ o≥ noisσ oε thσ channe∞á arσá simpl∙ ì inadequatσá t∩ thi≤ task«á Sincσ thσ DC─á circui⌠á presenteΣ ìèherσá i≤á baseΣá oε thσ updatσ signal≤ iεá ßá Digita∞á Phasσ ì LockeΣá Loo≡ (DPLL⌐ whicΦ recover≤ botΦ bauΣ clocδ anΣá datß ì froφ aε NRZ╔ packe⌠ datß stream¼á it≤ outpu⌠ represent≤ truσ ì detectioε oµ thσ datß carrier. Second¼á oncσá ßá datß carrie≥ decisioε ha≤á beeεá correctl∙ ì made¼á i⌠á i≤ importan⌠ tha⌠ thσ DC─ indicatioε remaiε valiΣ ì througΦá shor⌠ fades¼á collisions¼á anΣ whilσ ßá signa∞á to∩ ì margina∞ t∩ decodσ i≤ oε thσ channel«á Thi≤ i≤ accomplisheΣ ì b∙á providinτá ßá DC─ "hanτ timeó oµ approximatel∙á ╡á t∩á ╕ ì characte≥á period≤á (thi≤ caε bσ optimized⌐ t∩ holΣ thσá DC─ ì outpu⌠á truσ througΦ shor⌠ dropout≤ froφ thσá abovσá causes« ì Thi≤á prevent≤á ß queueΣ u≡ TN├ froφ pilinτá oεá collisions¼ ì transmittinτ ove≥ ß statioε whicΦ ha≤ ß margina∞ signal¼ anΣ ì beginninτáá t∩á transmi⌠á ove≥á ßá statioεá whicΦá i≤á stil∞ ì transmittinτ bu⌠ whosσ signa∞ receiveΣ ß shor⌠ multipatΦ hi⌠ ì durinτ thσ packet. Third¼á i⌠ i≤ importan⌠ tha⌠ thσ DC─ systeφ NO╘ bσ sensitivσ ì t∩ audi∩ amplitudσ variations« I⌠ shoulΣ responΣ iε exactl∙ ì thσá samσá wa∙ fo≥ an∙ signa∞ tha⌠ thσ modeφ i≤á capablσá oµ ì decodinτ regardles≤ oµ absolutσ inpu⌠ amplitude« Sincσ thi≤ ì DC─á circui⌠ operate≤ froφ thσ datß recovereΣ b∙ thσá modem¼ ì al∞á amplitudσá informatioεá i≤ suppresseΣá beforσá thσá DC─ ì circui⌠ eveε see≤ thσ signal. NOTE! ááááIµá you≥ TN├ use≤ thσ EXA╥ 221▒á demodulator¼á thi≤ ì ááááne≈ circui⌠ i≤ unnecessar∙ fo≥ you«á You≥ existinτ ì ááááDC─ circui⌠ caε bσ morσ easil∙ modifieΣ fo≥ correc⌠ ì ááááoperatioεá withou⌠ thi≤ circuit«á Thσ modificatioε ì ááááprocedurσá fo≥á thσ 221▒ demodulato≥á i≤á presenteΣ ì ááááelsewherσ anΣ no⌠ repeateΣ here. CIRCUIT DESCRIPTION Thσá circui⌠ diagraφ i≤ presenteΣ iε Figurσ 1«á Thi≤ i≤á aε ì ASCI╔á representatioε oµ thσ schematiπ diagram«á Whilσ thi≤ ì isn'⌠á reall∙ ß prope≥ "standardó diagram¼á ╔ believσ i⌠á i≤ ì readablσ enougΦ t∩ bσ useΣ t∩ duplicatσ thσ circuit« I⌠ ha≤ ì thσá beneficia∞á characteristiπ tha⌠ i⌠ require≤ n∩á CA─á o≥ ì specia∞á graphic≤ softwarσ t∩ bσ ablσ t∩ vie≈á thσá diagram« ì Thank≤á t∩á Myklσ Raymond¼á N7JZT¼á fo≥ makinτ u≡á thi≤á BB╙ ì forwardablσ ASCI╔ schematic. Thσá circui⌠ consist≤ oµ thσ statσ machinσ useΣ iε thσ TNC-▓ ì anΣ somσ dela∙ element≤ useΣ t∩ makσ thσ DC─ decision«á Thσ ì statσá machinσá i≤á formeΣ froφ thσ 74HC37┤á anΣá thσá 27C6┤ ì chips«á Thσ 74HC1┤ i≤ useΣ a≤ ß pai≥ oµ retriggerablσ dela∙ ì element≤ anΣ fo≥ signa∞ inversioε anΣ buffering. Thσ 27C6┤ witΦ thσ statσ machinσ codσ alread∙ burneΣ int∩ i⌠ ì caε bσ obtaineΣ directl∙ froφ TAPR« Iµ yo⌡ wisΦ t∩ usσ thi≤ ì sourcσ fo≥ thσ part¼ pleasσ cal∞ Chri≤ a⌠ (602)-323-171░ fo≥ ìèpricσá anΣ availabilit∙ information«á Thi≤ samσ codσ i≤á iε ì thσ statσ machinσ RO═ iε an∙ ful∞ TNC-▓ clonσ whicΦ use≤ thσ ì 221▒á demodulato≥ anΣ Z8░ SIO«á Iµ sufficien⌠á interes⌠á i≤ ì showε iε thi≤ circuit¼á maybσ wσ caε cajolσ TAP╥ int∩ makinτ ì circui⌠á board≤á available«á Thi≤ woulΣ vastl∙á reducσá thσ ì wirinτ task. Onσá oµ thσ statσ machinσ signal≤ (whicΦ wa≤ no⌠ useΣ iε thσ ì TNC-2⌐ appear≤ oε piε 1╣ oµ thσ 27C64«á Thi≤ signa∞ i≤á thσ ì DPL╠ updatσ pulse«á A≤ lonτ a≤ thσ DPL╠ i≤ correctl∙ lockeΣ ì t∩á thσá incominτ data¼á n∩ pulse≤ wil∞ appea≥ oε thi≤á pin« ì Wheεá thσá DPL╠ i≤ no⌠ lockeΣ t∩ aεá incominτá datßá stream¼ ì therσ wil∞ bσ ß continuou≤ streaφ oµ pulse≤ oε thi≤ pin. Thσá DPL╠ updatσ signa∞ i≤ useΣ iε thi≤ circui⌠ t∩ retrigge≥ ì thσá firs⌠ dela∙ elemen⌠ s∩ tha⌠ i⌠ neve≥ time≤ ou⌠ s∩á lonτ ì a≤ DPL╠ updatσ pulse≤ arσ present« Iµ thσ pulse≤ disappear¼ ì thσ dela∙ elemen⌠ time≤ ou⌠ anΣ generate≤ thσ DC─ signal. Thσá outpu⌠á froφ thσ firs⌠ dela∙ elemen⌠ keep≤á thσá seconΣ ì dela∙á elemen⌠ triggereΣ s∩ lonτ a≤ DC─ i≤ true«á Wheεá DC─ ì goe≤á false¼á thσá seconΣá dela∙ elemen⌠á begin≤á ßá timeou⌠ ì sequencσá whicΦ keep≤ thσ DC─ outpu⌠ truσ unti∞ thσá timeou⌠ ì perioΣ expires« Thi≤ i≤ thσ sourcσ oµ thσ DC─ "hanτ time". Whilσá thσ circui⌠ presenteΣ herσ i≤ primaril∙ intendeΣá fo≥ ì 120░ bauΣ VH╞ F═ operation¼á i⌠ wil∞ als∩ worδ wel∞ fo≥á 30░ ì bauΣ H╞ packe⌠ work«á Iµ thi≤ i≤ you≥ application¼ thσ timσ ì constant≤ oε thσ dela∙ element≤ wil∞ havσ t∩ bσ adjusted« Thσ timσ constan⌠ oµ thσ "hangó generato≥ (0.4╖ u╞ cap⌐ wil∞ ì havσá t∩á bσá increaseΣ fo≥ 30░ bauΣ operatioε s∩á tha⌠á thσ ì tota∞ capacitancσ i≤ 2.░ uF. Thσá timσá constan⌠ whicΦ i≤ optimuφ fo≥ thσá DC─á generato≥ ì (thσá 0.▒á u╞á ca≡ iε fig«á 1⌐ wil∞ depenΣ oεá ßá numbe≥á oµ ì factor≤á includinτ thσ bandwidtΦ oµ thσ radi∩ useΣ aheaΣá oµ ì thσá modem« Yo⌡á shoulΣá picδá ßá valuσá fo≥á thσá DC─á generato≥á dela∙ ì capacito≥ sucΦ tha⌠ thσ DC─ circui⌠ produce≤ approximatel∙ ß ì 1░ percen⌠ dut∙ cyclσ oµ falsσ DC─ "ONó time« Thσ falsσ DC─ ì O╬á timσ shoulΣ bσ observeΣ whilσ monitorinτ receive≥á noisσ ì oεá ßá channe∞ whicΦ i≤ ABSOLUTEL┘ freσ oµá AN┘á narrowbanΣ ì signal≤ whicΦ fal∞ withiε thσ demodulator'≤ passband«á Thi≤ ì include≤ CW¼á RTTY¼á interna∞ receive≥ birdies¼ A═ carriers¼ ì compute≥á spurs¼á packe⌠ datß carriers¼á etc«á ┴ gooΣ wa∙ t∩ ì assurσá thi≤á i≤á t∩ le⌠ thσ receive≥á monito≥á thσá S-╣á o≥ ì greate≥á outpu⌠ oµ ß noisσ bridgσ witΦ n∩ antennß connected« ì Remembe≥á t∩á havσá thσá filte≥á oµá appropriatσáá bandwidtΦ ì selecteΣá anΣá centereΣá ove≥ thσ modeφá passband«á fo≥á H╞ ì packet¼á thi≤ i≤ ß 50░ H· filte≥ a≤ i≤ normall∙ useΣ fo≥á C╫ ì anΣ RTT┘ operation« Thσá DC─ generato≥ dela∙ capacito≥ wil∞ probabl∙ neeΣ t∩á bσ ìèsomewherσ iε thσ rangσ oµ ▓ t∩ ┤ time≤ thσ 0.▒ u╞ valuσ useΣ ì fo≥ 120░ baud. BotΦá negativσá truσá anΣá positivσá truσá DC─á output≤á arσ ì provideΣ s∩ tha⌠ yo⌡ ma∙ usσ thσ polarit∙ whicΦ i≤á requireΣ ì b∙ you≥ TNC«á Also¼á JMP▒ anΣ JMP▓ allo≈ thσ DC─ circui⌠ t∩ ì bσ configureΣ t∩ operatσ correctl∙ froφ eithe≥ ß positivσ o≥ ì negativσá truσ C─ outpu⌠ froφ whicheve≥ modeφ chi≡ i≤á founΣ ì iε you≥ TNC. TNC SIGNALS Oncσ yo⌡ havσ constructeΣ thσ DC─ circuit¼á yo⌡ wil∞ havσ t∩ ì obtaiε somσ signal≤ froφ you≥ TN├ fo≥ thσ ne≈ DC─ circui⌠ t∩ ì use«á Yo⌡ wil∞ als∩ havσ t∩ arrangσ fo≥ thσ outpu⌠ oµá thi≤ ì circui⌠á t∩ bσ substituteΣ fo≥ thσ norma∞ DC─ signa∞ useΣ iε ì thσ TNC. Thσ signal≤ requireΣ fo≥ thσ DC─ circui⌠ operatioε are: 1. ┴á samplσ oµ thσ datß recovereΣ b∙ thσá demodulato≥ ì ááááiε thσ modeφ chip. 2.á ┴ samplσ oµ ß clocδ whicΦ ha≤ ß frequenc∙ oµ eithe≥ ì áááá1╢á o≥á 3▓á time≤ thσ bauΣ ratσ (X1╢á o≥á X3▓á bauΣ ì ááááclock). 3.á Thσ intercepteΣ Carrie≥ Detec⌠ (CD⌐ signa∞ froφ thσ ì áááámodeφ chip«á Thi≤ i≤ thσ C─ generateΣ b∙ thσ modeφ ì ááááchi≡ baseΣ oε amplitudσ oµ thσ inpu⌠ audio. 4.á ┴ sourcσ oµ ½ ╡ volts«á Iµ yo⌡ usσ al∞ CMO╙ parts¼ ì ááááthσá curren⌠ requirement≤ arσ minimal«á Thσ 74HC1┤ ì ááááMUS╘á bσá ßá CMO╙á par⌠ fo≥á thσá circui⌠á t∩á worδ ì ááááproperly. 5« Ground Therσá arσ s∩ man∙ differen⌠ TNC≤ t∩ whicΦ thi≤ circui⌠á caε ì bσ applieΣ tha⌠ ╔ canno⌠ givσ specifiπ interfacσ informatioε ì fo≥ al∞ oµ them«á However¼ ╔ caε providσ signa∞ piε number≤ ì fo≥á thσ ▓ lanΣ linσ modeφ chip≤ mos⌠ frequentl∙ encountereΣ ì anΣá ╔ caε hel≡ witΦ signa∞ location≤ iε thσ AE┴ PK-23▓á anΣ ì PK-87¼ thσ Kantronic≤ KAM¼ anΣ thσ Paπ Comφ TINY-▓ TNCs. Thσ signal≤ oµ interes⌠ oε thσ AMD791░ modeφ chi≡ are: 1. Receivσ Datß outpu⌠ (RD)-----╛ piε 24 2. Carrie≥ Detec⌠ (CD)----------╛ piε 25 ááááThi≤ signa∞ i≤ negativσ truσ fo≥ thσ 791░ chip. è Thσ signal≤ oµ interes⌠ oε thσ TCM310╡ modeφ chi≡ are: 1« Receivσ Datß outpu⌠ (RXD)----╛ piε 8 2« Carrie≥ Detec⌠ (CDT)---------╛ piε 3 ááááThi≤ signa∞ i≤ positivσ truσ fo≥ thσ 310╡ chip. 3.á Iεá TNC≤á whicΦá usσ thσ TCM310╡ chi≡á bu⌠á d∩á no⌠ ì ááááprovidσ anothe≥ sourcσ oµ thσ bauΣ clock¼á likσ thσ ì ááááKantronic≤ KAM¼á yo⌡ caε usσ thσ signa∞ a⌠ piε ▓ oµ ì ááááthi≤ chip«á Thi≤ signa∞ i≤ ver∙ closσ t∩ 1╢á time≤ ì ááááthσá bauΣá ratσ (19.1▒ KH· insteaΣ oµ 19.▓ KH·á fo≥ ì áááá120░ baud). TNC INTERFACE Iµ you≥ TN├ ha≤ provisioε fo≥ ß TAP╥ stylσ modeφá disconnec⌠ ì header¼á thesσ signal≤ (includinτ thσ X1╢ o≥ X3▓ bauΣ clock⌐ ì wil∞á bσ easil∙ locateΣ anΣ convenientl∙ interfaceΣ a⌠á thi≤ ì header«á Iµá i⌠ doesn'⌠ havσ thi≤ header¼á yo⌡ wil∞ havσ t∩ ì fisΦ arounΣ iε thσ circui⌠ oµ you≥ TN├ oε you≥ owε t∩ locatσ ì them. ááááSHAM┼á O╬ TH┼ MANUFACTURE╥ O╞ ┴ TN├ WIT╚á N╧á MODE═ ì DISCONNEC╘á HEADER!íá ááááThσá absencσ oµ ß standarΣ modeφ disconnec⌠á heade≥ ì áááámean≤á yo⌡á ma∙ no⌠ CONVENIENTL┘ usσá AN┘á externa∞ ì áááámodeφá witΦá thσ deficien⌠ TNC«á Usinτ ßá standarΣ ì áááádisconnec⌠ system¼ thσ externa∞ modeφ caε providσ ß ì ááááfron⌠á pane∞ switcΦ t∩ allo≈ yo⌡ t∩ selec⌠á betweeε ì ááááthσ externa∞ anΣ thσ interna∞ modem«á ááááModem≤á whicΦ yo⌡ migh⌠ likσ t∩á interfacσá withou⌠ ì ááááloosinτá thσá usσ oµ thσ interna∞ AFS╦ modeφá woulΣ ì ááááincludσá thσ BPS╦ » MANCHESTE╥ F═á modem≤á requireΣ ì ááááfo≥ severa∞ oµ thσ satellites. Iε an∙ case¼á thσ DC─ signa∞ currentl∙ useΣ iε you≥ TN├ wil∞ ì havσá t∩á bσá disconnecteΣá anΣá rerouteΣá througΦá thσá ne≈ ì circuit« STANDARD HEADER SIGNALS Thσ signa∞ location≤ oε thσ standarΣ modeφ disconnec⌠ heade≥ ì are as follows: Receive Data is obtained from header pin 18. Carrier Detect is obtained from header pin 2. è DataCarrie≥á Detec⌠á (DCD⌐á i≤ inserteΣá a⌠á heade≥á piεá 1« ì Jumpe≥ froφ header pin 1 to header pin 2 is removed. Thσá X1╢á (TNC-2⌐ o≥ X3▓ (TNC-▒ anΣá possibl∙á TNC-▓á clone≤ ì usinτá aεá 853░ HDL├ controlle≥ insteaΣ oµ thσ Z80SIO⌐á bauΣ ì clocδ i≤ obtaineΣ froφ heade≥ piε 12. COMMERCIAL TNC SIGNAL LOCATIONS Herσ i≤ thσ informatioε yo⌡ neeΣ t∩ finΣ thσ prope≥á signal≤ ì iεá severa∞á commerciall∙á availablσá TNCs«áá Thi≤á i≤á no⌠ ì intendeΣá t∩á bσ ß completσ lis⌠ b∙ an∙á means«á I⌠á merel∙ ì represent≤á thσá unit≤ whicΦ ╔ havσ haΣ availablσá t∩á appl∙ ì thi≤á circui⌠ t∩ herσ locally«á Thesσ arσ thσ onl∙ TNC≤ fo≥ ì whicΦ ╔ havσ specifiπ interfacσ informatioε a⌠ thi≤ time. AEA PK-87 I⌠á i≤ relativel∙ eas∙ t∩ interfacσ thi≤ ne≈ DC─ circui⌠á t∩ ì thσá PK-8╖á iε spitσ oµ thσ fac⌠ tha⌠ therσ i≤á n∩á standarΣ ì modeφá disconnec⌠á header«á Thi≤á i≤ becausσá therσá i≤á n∩ ì requiremen⌠á t∩ switcΦ bacδ t∩ thσ interna∞ DC─ circui⌠ oncσ ì thσá modificatioε i≤ installed«á Iµ thi≤ werσá aεá externa∞ ì specia∞á purposσ modem¼á yo⌡ woulΣ bσ forceΣ t∩ opeε thσ TN├ ì casσ anΣ movσ severa∞ jumper≤ wheneve≥ yo⌡ wisheΣ t∩á changσ ì thσá modeφ beinτ used« However¼á fo≥ ou≥ purpose≤ iε thi≤ modification¼ thσ jumper≤ ì providσá convenient¼á easil∙á locateΣ place≤ t∩á obtaiεá anΣ ì injec⌠ signals. Thσá Receivσ datß signa∞ i≤ obtaineΣ froφ thσ cente≥ piεá oµ ì JP4. Thσá Carrie≥á Detec⌠ signa∞ i≤ obtaineΣ froφ thσ enΣ oµá JP╡ ì whicΦ connect≤ t∩ thσ modeφ chip. Thσá DC─ outpu⌠ signa∞ froφ thσ ne≈ circui⌠ i≤á inserteΣá a⌠ ì thσ cente≥ piε oµ JP5«á Usσ thσ NEGATIV┼ TRU┼ output«á Thσ ì jumpe≥á originall∙á installeΣ a⌠ JP╡ i≤á removed«á Thσá DC─ ì indicato≥ oε thσ fron⌠ pane∞ wil∞ sho≈ thσ actioε oµ thσ ne≈ ì DC─ circuit. Thσá X3▓ bauΣ clocδ signa∞ i≤ obtaineΣ froφ piε 1│ oµ U2░ (ß ì 74LS39│ divider)«á Don'⌠ bσ tempteΣ t∩ ge⌠ thi≤ signa∞ froφ ì thσá "clockó linσ oε J4¼á thσ externa∞ modeφá connector¼á a≤ ì thi≤ i≤ ß X▒ clock. ╔á seσ s∩ man∙ manufacturer≤ sendinτ onl∙ thσ X▒ bauΣá clocδ ì ou⌠ t∩ aε auxiliar∙ modeφ connecto≥ tha⌠ ╔ havσ t∩ wonde≥ iµ ì the∙á simpl∙ don'⌠ realizσ tha⌠ synchronou≤ modem≤ requirσ ß ì clocδá whicΦ i≤ ß multiplσ oµ thσ bauΣá rate«á Asynchronou≤ ìèmodem≤ caε cheapl∙ anΣ easil∙ dividσ thσ X1╢ clocδ t∩ ge⌠ X▒ ì bu⌠á i⌠á i≤ harΣ fo≥ synchronou≤ modem≤ t∩ derivσá ßá faste≥ ì clocδ froφ thσ X▒ signal. AEA PK-232 Thσ PK-23▓ i≤ als∩ relativel∙ eas∙ t∩ interfacσ iε spitσá oµ ì thσá fac⌠á tha⌠á AE┴ faileΣ t∩ implemen⌠á ßá standarΣá modeφ ì disconnec⌠á heade≥á eveε iε thei≥ flagshi≡á TNC«á Fo≥á somσ ì reason¼á oεá thi≤ bo° AE┴ decideΣ rathe≥ thaε brinτ ou⌠á thσ ì wronτ clocδ ou⌠ t∩ thσ externa∞ modeφ connector¼á the∙ woulΣ ì brinτ ou⌠ n∩ clocδ a⌠ all. Thσá Receivσ Datß signa∞ i≤ obtaineΣ froφ thσ cente≥ piεá oµ ì JP4. Thσá Carrie≥ Detec⌠ signa∞ i≤ obtaineΣ froφ thσ enΣá oµá JP╢ ì whicΦá i≤á NO╘á connecteΣá t∩ piε │ oµá thσá externa∞á modeφ ì connector. Thσá X3▓á bauΣ clocδ signa∞ i≤ obtaineΣ froφ piεá 1│á oµá U╕ ì (als∩ ß 74LS39│ divider). Thσá DC─á outpu⌠á froφ thσ ne≈ circui⌠ i≤á inserteΣá a⌠á thσ ì cente≥á piεá oµ JP6«á Usσ thσ NEGATIV┼á TRU┼á output«á Thσ ì jumpe≥ originall∙ installeΣ a⌠ JP╢ i≤ removed. T∩á usσá thσ ne≈ DC─ circui⌠ witΦ ß PK-23▓ oεá VH╞á F═á 120░ ì baud: 1.á Se⌠á thσá audi∩ leve∞ froφ thσ radi∩á s∩á tha⌠á thσ ì áááátuninτáá indicato≥á "spreadsóá full∙á eveεá oεá thσ ì áááástatioε witΦ thσ lowes⌠ transmitteΣ audi∩ leve∞á oε ì ááááthσ channel. 2.á Thσ existinτ DC─ thresholΣ contro∞ shoulΣ bσ se⌠ s∩ ì áááátha⌠á thσá existinτ DC─ indicato≥ LE─ oε thσá fron⌠ ì áááápane∞á light≤á u≡ wheneve≥ therσ i≤ AN┘á signa∞á o≥ ì áááánoisσ inpu⌠ t∩ thσ TN├ froφ thσ radio« Bσ surσ tha⌠ ì ááááeveε thσ statioε witΦ thσ lowes⌠ amoun⌠ oµ audi∩ oε ì ááááthσá channe∞á light≤ thi≤ LED«á Thi≤á LE─á shoulΣ ì ááááextinguisΦá wheε therσ i≤ n∩ audi∩ inpu⌠á froφá thσ ì ááááradi∩ (deaΣ carrie≥ froφ repeate≥ etc.). Iµá yo⌡á wisΦá t∩á observσá thσ actioεá oµá thσá DC─á signa∞ ì generateΣá b∙á thσ ne≈ circuit¼á attacΦ ß ▒á ╦á resisto≥á iε ì serie≤á witΦ ß LE─ t∩ thσ LE─ outpu⌠ oµ thσ ne≈ DC─ circuit« ì Thσ anodσ oµ thσ LE─ shoulΣ bσ connecteΣ viß thσ resisto≥ t∩ ì +╡ volts« Thσ cathodσ oµ thσ LE─ shoulΣ bσ connecteΣ t∩ thσ ì LE─ outpu⌠ oµ thσ ne≈ DC─ circuit«á Iµ yo⌡ wish¼á thi≤á LE─ ì caε bσ mounteΣ oε thσ fron⌠ pane∞ wherσ i⌠ i≤ visible«á Usσ ì ß higΦ effecienc∙ LED. è Pac-Comm TINY-2 Thσá Pac-Comφ TINY-▓ doe≤ includσ ß modeφ disconnec⌠ header« ì I⌠ i≤ labeleΣ J╡ oε thei≥ schematiπ diagram«á Fo≥ thi≤ the∙ ì ge⌠ +▒ attaboy. Unfortunately¼á Pac-Comφá attacheΣ J╡ pin≤ 1▒ anΣ 1▓ t∩á thσ ì wronτá par⌠ oµ thσ bauΣ clocδ divide≥á chain«á Thesσá heade≥ ì pin≤á shoulΣ havσ beeε iε serie≤ witΦ piε ▒ oµá U10«á Thi≤ ì erro≥ result≤ iε therσ beinτ ß X▒ bauΣ clocδ signa∞ oε thesσ ì pin≤á insteaΣá oµ thσ X1╢ bauΣ clocδ tha⌠ shoulΣá bσá there« ì So¼á eveεá thougΦá the∙á diΣ implemen⌠á ßá modeφá disconnec⌠ ì header¼á yo⌡á wil∞á havσ t∩ obtaiε thσ X1╢ bauΣá clocδá froφ ì elsewherσá oεá thσá circui⌠ board«á Fo≥ thi≤á the∙á ge⌠á -▒ ì attabo∙ (a⌠ leas⌠ the∙ arσ breakinτ even). Thσ X1╢ bauΣ clocδ signa∞ i≤ obtaineΣ froφ U1░ piε 1« Receivσ Datß i≤ obtaineΣ froφ J╡ piε 17. Negativσá truσ Carrie≥ Detec⌠ (CDT⌐ i≤ obtaineΣ froφ J╡á piε ì 2. NOTE! áááááThi≤ i≤ aε inverteΣ versioε oµ thσ C─ outpu⌠á froφ ì áááááthσ TCM310╡ chi≡ itself« Sincσ thi≤ i≤ ß negativσ ì ááááátruσá logiπá signal¼á JMP▒ oε thσ ne≈ DC─á circui⌠ ì áááááwil∞ bσ useΣ insteaΣ oµ JMP2 whicΦ woulΣá normall∙ ì ááááábσ useΣ fo≥ ß TCM3105. NEGATIV┼ TRU┼ DC─ froφ thσ ne≈ circui⌠ i≤ applieΣ t∩ thσ TN├ ì a⌠ J╡ piε 1« Removσ thσ connectioε betweeε J╡ pin≤ ▓ anΣ 1« ì Thσá existinτ DC─ indicato≥ LE─ wil∞ NO╘ sho≈ thσ actioεá oµ ì thσ ne≈ circuit. Iµá yo⌡á wisΦá t∩á observσá thσ actioεá oµá thσá DC─á signa∞ ì generateΣá b∙á thσ ne≈ circuit¼á attacΦ ß ▒á ╦á resisto≥á iε ì serie≤á witΦ ß LE─ t∩ thσ LE─ outpu⌠ oµ thσ ne≈ DC─ circuit« ì Thσ anodσ oµ thσ LE─ shoulΣ bσ connecteΣ viß thσ resisto≥ t∩ ì +╡ volts« Thσ cathodσ oµ thσ LE─ shoulΣ bσ connecteΣ t∩ thσ ì LE─ outpu⌠ oµ thσ ne≈ DC─ circuit«á Iµ yo⌡ wish¼á thi≤á LE─ ì caε bσ mounteΣ oε thσ fron⌠ pane∞ wherσ i⌠ i≤ visible«á Usσ ì ßá higΦ effecienc∙ LE─ anΣ increasσ thσ valuσ oµ thσá serie≤ ì resisto≥á t∩á matcΦ brightnes≤ witΦ thσá othe≥á fron⌠á pane∞ ì indicators.. Iµá yo⌡á wisΦá t∩á observσá thσ actioεá oµá thσá DC─á signa∞ ì generateΣá b∙á thσ ne≈ circui⌠ oε thσ buil⌠ iεá fron⌠á pane∞ ì LED¼á yo⌡á wil∞ havσ t∩ d∩ thσ interfacσ ß bi⌠á differently« ì First¼á yo⌡ wil∞ ge⌠ thσ negativσ truσ CD╘ signa∞ froφ piε ▒ ì oµá JPD«á Theε inser⌠ thσ LE─ outpu⌠ signa∞ froφá thσá ne≈ ì circui⌠á a⌠ eithe≥ piε ▓ oµ JP─ o≥ piε ▓ oµ J5«á Removσ thσ ìèjumpe≥á currentl∙á installeΣ a⌠ JP─ oεá thσá TINY-▓á circui⌠ ì board« Iµ thσ ne≈ circui⌠ i≤ interfaceΣ iε thi≤ manner¼ thσ ì "RFDCDóá signa∞á caε n∩ longe≥ bσ used«á Thi≤ i≤á n∩á grea⌠ ì loss, however, as it will also no longer be necessary. Kantronics KAM Interfacinτá anythinτ t∩ ß Kantronic≤ bo° isn'⌠ ß job¼á it'≤ ì aεá adventureíáá Kantronic≤á ha≤á aεá officia∞á polic∙áá oµ ì discouraginτá anyonσ froφ hookinτ an∙ thirΣ part∙ devicσá t∩ ì thei≥á TNCs«á Thi≤á include≤á externa∞ modem≤ oµá an∙á kinΣ ì (Neve≥á minΣá tha⌠ thei≥ crysta∞ bal∞ ha≤ proveεá cloud∙á a⌠ ì bes⌠ iε thσ pas⌠ wheε tryinτ t∩ predic⌠ wha⌠ modem≤ migh⌠ bσ ì popula≥ or necessary iε thσ future). Thi≤á polic∙á wa≤á enunciateΣá t∩ mσá b∙á person≤á iεá thei≥ ì technica∞á suppor⌠á departmen⌠á iεá tw∩á separatσá telephonσ ì conversations«á S∩ i⌠ wa≤ no⌠ surprisinτ t∩ finΣ tha⌠á the∙ ì didn'⌠ providσ ß modeφ disconnec⌠ heade≥ iε thσ KAM. Wha⌠ ╔ diΣ finΣ ß littlσ surprising¼á however¼á wa≤ thσ fac⌠ ì tha⌠á the∙á als∩ refusσ t∩ providσ aε individua∞á owne≥á an∙ ì assistancσ witΦ signa∞ locations« The∙ don'⌠ sa∙ the∙ don'⌠ ì know¼á the∙á sa∙á the∙á WON'╘ hel≡ youíá Iµá yo⌡á want¼á fo≥ ì instance¼á t∩ interfacσ ß JAS-▒ (FO-12⌐ stylσ BPS╦ modeφá t∩ ì you≥á Kantronic≤á TNC¼á yo⌡á arσá oεá you≥á owεá a≤á fa≥á a≤ ì Kantronic≤á i≤ concerned«á Potentia∞ Kantronic≤ buyer≤á wh∩ ì arσ interesteΣ iε workinτ digita∞ mode≤ througΦ thi≤ anΣ thσ ì upcominτ MICROSA╘ packe⌠ storσ anΣ forwarΣ satellite≤ shoulΣ ì takσ note. Iµá Kantronic≤ though⌠ tha⌠ onσ da∙ the∙ migh⌠ possibl∙ makσ ì ßá radio¼á yo⌡á woulΣ havσ t∩ usσá thσá optiona∞á Kantronic≤ ì built-iεá radi∩á iε al∞ thei≥ TNCs«á Thanδ goodnes≤á the∙ ì don'⌠ als∩ makσ computers... I⌠á turn≤ ou⌠ tha⌠ thσ necessar∙ signal≤ AR┼ availablσá (fo≥ ì 120░á bauΣ a⌠ least⌐ iε thσ KAM«á I⌠ i≤ indeeΣ possiblσá t∩ ì interfacσá eithe≥ thσ 120░ bauΣ BPS╦ » MANCHESTE╥á F═á modeφ ì requireΣ fo≥ thσ JAS-▒ birΣ o≥ thi≤ DC─ circui⌠ (o≥ both⌐ t∩ ì thσ KAM. A⌠ thi≤ timσ i⌠ i≤ unclea≥ whethe≥ thσ requireΣ clocδ signa∞ ì i≤á availablσ fo≥ thσ DC─ circui⌠ t∩ operatσ a⌠ 30░ bauΣá oε ì thi≤ TNC«á Eveε iµ i⌠ is¼á i⌠ woulΣ bσ morσ troublσ thaε i⌠ ì i≤á wortΦá t∩á interfacσá a≤ i⌠á woulΣá eithe≥á requirσá tw∩ ì separatσá DC─ circuit≤ o≥ ß switchinτ arrangemen⌠á t∩á allo≈ ì thσ usσ oµ onσ fo≥ botΦ modems. Sincσá i⌠ i≤ unlikel∙ tha⌠ thσ filte≥ » slice≥ modeφ useΣ iε ìèthi≤á bo°á i≤ ß stella≥ performe≥ wheεá workinτá witΦá smal∞ ì shif⌠á t∩á bauΣ ratσ rati∩ signal≤ oµ thσ typσ useΣá fo≥á H╞ ì packet¼á maybσá wσ shoulΣ onl∙ reall∙ concerε ourselve≤ witΦ ì 120░ bauΣ operatioε anyhow« I⌠á i≤ wortΦ notinτ tha⌠ fo≥ wide≥ shif⌠ t∩ bauΣ ratσá rati∩ ì signal≤ likσ RTTY¼ ASCII¼ anΣ AMTO╥ thσ filte≥ » slice≥ typσ ì demodulato≥á performancσ i≤ perfectl∙á adequate«á Wheεá thσ ì shif⌠á t∩ bauΣ ratσ rati∩ i≤ greate≥ thaε 1¼á a≤ witΦá thesσ ì modes¼ mos⌠ oµ thσ transmitteΣ signa∞ energ∙ i≤ concentrateΣ ì arounΣá anΣá ver∙ closσ t∩ thσ tw∩ tonσá frequencies«á Wheε ì thi≤á i≤á thσ case¼á thσ filte≥ » slice≥á i≤á thσá preferreΣ ì methoΣá oµ demodulation«á A≤ thesσ mode≤ d∩ no⌠ operatσ iε ß ì Carrie≥ Sensσ Multiplσ Acces≤ (CSMA⌐ environmen⌠ likσ packe⌠ ì requires¼á thσá buil⌠ iε C─ functioε i≤ adequatσá fo≥á thesσ ì mode≤ a≤ well. Fo≥ 120░ bauΣ operatioε then¼á thσ signa∞ locatioε point≤ oµ ì interest in the KAM are as follows: Thσ Receivσ Datß (RXD⌐ signa∞ i≤ obtaineΣ froφ piε ╕ oµá thσ ì TCM310╡á modeφá chip«á Thσ Kantronic≤ schematiπ show≤á wha⌠ ì appea≥ t∩ bσ somσ numbereΣ pad≤ (1╖ anΣ 18⌐ oε thi≤ leaΣá t∩ ì thσá processor«á Iµá yo⌡á caε locatσ thesσá point≤á oεá thσ ì circui⌠á board¼á i⌠ ma∙ bσ easie≥ t∩ obtaiε thσ signa∞á froφ ì onσ oµ thesσ points. Thσá X1╢á bauΣá clocδ signa∞ i≤ obtaineΣ froφ piε ▓á oµá thσ ì TCM3105. Thσ POSITIV┼ TRU┼ Carrie≥ Detec⌠ (CDT⌐ signa∞ froφ thσ modeφ ì i≤á obtaineΣ froφ piε │ oµ thσ TCM3105«á Thi≤ linσ froφ thσ ì modeφ t∩ thσ CP╒ i≤ labeleΣ witΦ ▓ numbereΣ pad≤ (╖ anΣá 8)« ì Thσá connectioε betweeε thesσ ▓ location≤ shoulΣ bσá broken« ì JMP▓ oε thσ ne≈ DC─ circui⌠ wil∞ bσ used. Thσ DC─ outpu⌠ froφ thσ ne≈ circui⌠ i≤ injecteΣ a⌠ piε 2▒ oµ ì the 63B03 CPU. Thσá fron⌠ pane∞ LE─ whicΦ normall∙ indicate≤ thσ CD╘ signa∞ ì activit∙ wil∞ sho≈ thσ actioε oµ thσ ne≈ DC─ circuit.