Cobra 148 GTL 148 GTL 148 GTL Manual de servicio Pagina 1

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5Now, we can convert binary to HEX very easily:-8 4 2 10 0 0 0 = 00 0 0 1 = 10 0 1 0 = 20 0 1 1 = 30 1 0 0 = 40 1 0 1 = 50 1 1 0 = 60 1 1 1 = 71 0 0 0

6If we always split the binary codes into groups of four, the conversion remains easy:- 8 4 2 1 8 4 2 1 8 4 2 1 1 0 0 1 1 1 1 1 0 0

7The position of channel 23 is odd and the effect is as if the channel switch goes ---26-23-25-24--, so this arrangement in most FCC and European rigs

8PRACTICAL CONSIDERATIONSWhich Eprom?The smallest Eprom currently available is the 2708. This is actually obsolete and has thedisadvantage of requirin

9Transistor InverterIf the codes require the 9th pin always to be a "1" or always a "0" then there is no problem.We connect that p

10 1 0011 1011 1 0000 0101 0 1100 1111 0 1001 1001 0 0110 0011 1 0011 1010 1 0000 0100 0 1100 1110 0 1001 1000 0 0110 0010 1 0011 1001 1 0

11In the foregoing table each bit of the 9 bit code has a value according to its position fromleft to right, for instance:- 256 128 64 32 1

12Operating VoltageOne point which is MOST important is the operating voltage of the Eprom. All thosecurrently available require a supply voltage of 4

13Input VoltageThe voltage applied to each input should not exceed the supply voltage or damage willeventually result. If the voltage from the channel

14Switch CodesBefore you begin a conversion you should ALWAYS use a voltmeter to determine theswitch codes for every channel. Don't rely upon a b

IITHE CB EPROM DATA BOOKThis book is provided, by Lou Franklin and Martin Pickering, for FREE download inPortable Document Format from the following w

15Output VoltageThe output voltage from an Eprom can be a problem and will often be less than 3.5 voltswhen the Eprom outputs are connected to a PLL.

16Practical ExamplesThe Cobra 148 on 10 metersSo much for the theory. Now suppose you want to carry out an actual conversion of a CBradio to the Ameri

17So we need to switch in four diodes to add these bits to the appropriate inputs of the binaryadders. The end result will be codes of 241 to 241+45 w

18code in Eprom Eprom locationChBinary "N"Code HEX Dec Switch code HEX40 1 0 0 0 1 1 0 0 0 18 280 1 1 1 0 1 1 3B39 1 0 0 0 1

19Eprom Codes 0 1 2 3 4 5 6 7 8 9 A B C D E F 000** ** ** ** ** ** ** ** ** ** ** ** ** ** ** F1001F2 F3 ** F4 F5 F6 F7 ** F8 F9 FA

20Channel Switch CodesThe codes from the channel switch don't matter, as mentioned previously, since they serveonly to SELECT the LOCATION in Epr

21ChOld Loc. 5 4 3 2 1 0 5 2 4 1 3 0 New location40 3B1 1 1 0 1 1 1 0 1 1 1 12F39 3A1 1 1 0 1 0 1 0 1 1 1 02E38 391 1 1 0 0 1 1 0 1 0 1 12B37 381 1

22The MB8719 used in Uniden ChassisThis PLL is unusual in having only seven programming pins but an internal inverter whichmakes it work as if it had

23ch<...Eprom Contents...> Eprom location401 0 1 1 1 0 1 13B 3B391 0 1 1 1 0 1 03A 3A381 0 1 1 1 0 0 139 39371 0 1 1 1 0 0 038 38361 0 1 1 0 1 1

24Rigs which use an 11 MHz crystal can not be modified so easily as the range of MB8719divide ratios is not sufficiently large. It is necessary to cha

IIICONTENTSINTRODUCTION ...1SIMPLE As A B C D E F ...

25If, however, a conversion board can be fitted which uses the MC145106P IC then therange of "N" codes is greatly extended and permits the s

26LOC. EPROM CONTENTS FOR 11.1125 CRYSTAL0000 .. .. .. .. .. .. .. ..0008 .. .. .. .. .. .. .. 010010 02 03 .. 04 05 06 07 ..001880 81 82 83 .. 89 85

27LOC.EPROM CONTENTS FOR 11.3258 CRYSTAL0000 .. .. .. .. .. .. .. ..0008 .. .. .. .. .. .. .. 190010 1A 1B .. 1C 1D 1E 1F ..001898 99 9A 9B .. 9C 9D 9

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29Another Eprom BoardThe previous design was specifically for certain rigs but this Eprom board for the Cobramay be used with most versions. Six pull-

30ExampleThe TC9109 and MB8733 PLL ICs are both similar in that they use eight of theconnections between the channel switch and the LED channel number

31TC9109 input codes. LC7137 input codes. 17 16 15 14 13 12 11 10 - 9109 pins 6 5 4 3 2 1-7137 pinsCH 2f 2a 2c 1d 1e 1g 1a 1f - LED Segmentloc

32µPD858 – ExampleThere is a range of AM/SSB rigs which includes the Cobra 138/139 XLR, RealisticTTRC457/458/449 and "President Adams" that

33Adams uPD858 "Novice" conversionpins-22 - - - - - - - - 13 "N" +Eprom code *locationch. + + + + + + +40 1 0 0 1 0

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IVWritten By: Martin T. Pickering - “The Specialist”© Copyright Martin T. Pickering 1987. All rights reserved.Third Edition 1997.The information in th

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36µPD2824 – ExampleThe uPD2824 is a popular PLL in America but is internally programmed for only fortychannels. The internal "N" codes are 9

37Cobra 146 GTL uPD2824 "Novice" using MC145106P FCC channels Novice Channels (location)dec. H

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40PLL02A ExampleThe PLL02A chip is used extensively for export models and in 40 channel rigs in the USA.It is a versatile PLL with nine programming pi

41Ham International "Novice" conversion "N" codePLL02A pin numbersEprom contents locationch dec. 7 8 9 10 11 12 13 14 15 HEX H

42A General Purpose Eprom BoardWe have designed a simple printed circuit board which you could use for experimentation,or even build and sell to your

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44APPENDIX 1ErasingEproms, by definition, are erasable under Ultra Violet light. Since many second handEproms are available, cheaply, it is worth cons

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45Non-E-promsThere are also some plastic encapsulated "Eproms" which can't be erased. These areknown as One Time Programmable (OTP) Epr

46ProgrammingMany designs for Eprom programming units have been published. Some are very good,some mediocre. All work well, within their limitations.

47Gang BangersIf you are going into Eprom copying in a big way there are commercial units (known as"gang bangers" in the trade) which will p

48In the VERY crude circuit shown here you must first set the binary location code onswitches A0 to A10. Then set the binary data on switches D0 to D7

49EpromsThe 2716 and 2516 have 24 pins and are generally interchangeable, although slightdifferences in programming parameters exist between the vario

50Decimal to BinaryThe following simple computer program in BASIC will convert any decimal number lessthan 4096 into Binary.10 DIM W(12)200 Z=Z MOD 16

51APPENDIX 2Pin Out Sketches

52...more pinouts...

53APPENDIX 3 (not included in the original publication)Convert to 10 metres the Chip WayYou may wonder why an ordinary mortal who is not a licensed Am

54Now, the original idea was to use a simple transistor mixer to combine the V.C.O. outputwith the output from IC2. The difference frequency would the

1INTRODUCTIONMy interest in CB conversions began some years after Lou Franklin first published his"Screwdriver Expert's Guide" and &quo

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56By this method we blank out one V.C.O. pulse after the input square wave goes low, resetthe square wave at the end of the blanked V.C.O. pulse, then

57Normally IC2 would be linked directly to IC4 but, if IC3 is added, there is an option tolower the frequency band by the use of an extra divider stag

582) "How to Convert 'Unconvertible' CB rigs to Work on the Ten-Metre Band". HughAllison. "The Short Wave Magazine" Ma

1Glossary of Terms• “A” channelA frequency between legally allocated CBchannels which may not be used for CBtransmissions.• ActinicRadiating light wh

2• OTP “One Time Programmable”A type of (E)prom which can not beerased.• P.C. “Personal Computer”• PD “Phase Detector”This PLL pin provides

2Simple as A B C D E FMail BoxesThe Eprom is a basic, mechanical device which can be considered simply as a block of"mail boxes", each holdi

3Messages in CodeThe actual message in each box consists of just eight numbers, each of which can be "1" or"0".So a typical messag

4All we have to do is to find out what code number comes from the switch for EACHchannel and put into each box SELECTED BY THIS NUMBER the NEW code wh