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Midland 75-820/Cobra HH-45 160 channel mod 10 meters+Achannels FIRST ON INTERNET

Discussion in 'CB Radio Modifications' started by towerdog, Oct 19, 2011.

  1. towerdog

    towerdog one-niner-seven

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    I discovered this somewhat by accident.

    [​IMG]

    You can get an extra band of 40 channels, 27.865-28.335 on the Midland 75-820, 75-822, and Cobra HH45-WX........this will likely work also on Cherokee AH-27, and other similar radios but tested on 75-820 and HH45.

    I also discovered how to get the 5 alternate, "A" channels.
    3A, 26.985
    7A, 27.045 (wreak havoc on kids cheap RC cars)
    11A, 27.095
    15A, 27.145
    19A, 27.195

    It is really simple, but first you must modify the radio for 120 channel (export mode)

    For the Cobra HH-45,
    http://www.worldwidedx.com/radio-radio-related-modifications/101454-cobra-hh-45wx-channel-mods.html
    For the Midland 75-820 or 75-822,
    Bill's CB & 2-Way Radio - Midland 75-820 Modification information

    Now that you soldered the jumpers and RESET the CPU for uppers and lowers.....continue, the rest is just pushing buttons :D

    Go to channel 40L



    Now the hard part,
    You must hold the channel down button for about 5 seconds or until it starts rapidly going through the channels, basically hold it until it starts beeping more rapidly.........and keep holding it.

    As you are holding channel down button, you should see the channels are now 80H, 70H, 60H, 50H, 40H.....and so on..........

    YOU MUST STOP ON CHANNEL 80H, its a trick, you might want to get your video game addicted son to do it for you, what I do is let go the button when it says 10H, because by the time I release it its gone to 80H.

    Once you got it on 80H, press channel up button until you get to channel 88H...DO NOT GO PAST 88H OR YOU MUST REDO

    You got it on 88H, GOOD!!!! now save it to a memory button.

    For Cobra HH-45, Press "FUNC" once and then hold the memory button of your choice, I used M4 on my Cobra.

    THATS IT FOR 27.865-28.355, which are now channels 41H-88H.
    You can see the frequency by holding the "FUNC" button for several seconds.




    Now to get the 5 "A" channels.

    Go to channel 40

    Now the hard part, just like deja-vu all over again.

    You must hold the channel down button for about 5 seconds or until it starts rapidly going through the channels, basically hold it until it starts beeping more rapidly.........and keep holding it.

    As you are holding channel down button, you should see the channels are now 80L, 70L, 60L, 50L, 40L.....and so on..........

    YOU MUST STOP ON CHANNEL 80L, its a trick, you might want to get your video game addicted son to do it for you, what I do is let go the button when it says 10L, because by the time I release it its gone to 80.
    Actually, channel 70L might work, or even 50L or 60L because its still in that range, but I havent tested it with another channel.

    Now save the channel to memory, just in case you screw up so you dont have to do it over again.

    Now hold the "FUNC" button for several seconds to change to frequency display, and keep scrolling through the channels until you find the following frequencies

    26.985 (ch.43L)
    27.045 (ch.49L)
    27.095 (ch.54L)
    27.145 (ch.59L)
    27.195 (ch.64L)

    Go to each of these frequencies and save it to the memory button of your choice, unfortunately the Cobra does not have enough memory buttons for all of them, but the Midland has more memory buttons, maybe enough.

    You should also be able to get the A channels for the lowers as well.


    THATS IT, YOU NOW GOT THE A CHANNELS AND AN EXTRA BAND OF 40 UP IN 10 METERS. Remember not to transmit above 28.000 unless you are a licensed amateur using morse code, it really pisses them off and the FCC too as everything from 28.000-28.300 is morse, data and beacons.
     
    #1 towerdog, Oct 19, 2011
    Last edited: Oct 19, 2011

  2. Moleculo

    Moleculo Administrator
    Staff Member

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    Wow. Too cool. I'm really curious as to how you discovered this mod?
     
  3. Mudfoot

    Mudfoot Sr. Member

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    Darn, sold my Cobra.
     
  4. towerdog

    towerdog one-niner-seven

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    sort of by accident. I had already done the 120 channel mod, and was sitting bored scrolling through the channels of my radio, when you hold the channel button down for 5 or so seconds it jumps 10 channels and beeps faster and I notice it says like, 70H, 80H, etc and I am like, wow ???, and switch to frequency display and its on 10 meters. I began experimenting and discovered the rest from there.

    I also found out today while sitting in truck at work that the Cobra actually has 9 memory channels, the other M buttons are the ch. up and down, lock, and backlight button, accessed by pressing FUNC just like M1, M2, M3 and M4.

    There exist, supposedly a 400 channel mod for the midland, however it requires adding a rare IC chip to the board, that is, if its not horsecrap like the FM mod. Now if I could just find a schematic to compare against its European cousin the Alan 42 maybe I could get FM to work too, at least for the Midland, different boards, but same CPU. Might some day figure out a way to get it to work on the FM portion of the 10 meter band, waaay too cool.

    Anyone with a CPU controlled midland mobile ought to try it too. I have noticed just about all CPU driven midlands have a 120 channel "export" mod for them, maybe they too got the same CPU.
     
  5. topside

    topside Member

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    It's an A3 common anode high speed diode in an SMD chip. It's not rare. The old version Toshiba 1SS181 is impossible to find but there's a new comparable one made by NXP as a 1PS300. It's the same 4nS switch but with a little bit better power handling 300mW vs 150mW and less reverse current at low voltage. I've found them available inidividually at mouser electronics for 4 cents each.

    If you do attempt the mod please report how it goes, I'm interested in finding what 400 channels it opens. I have to use my radio for several trips this winter so can't risk cracking it open for a little while.
     
  6. Blackpaw

    Blackpaw Member

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    Very cool towerdog! Worked for my 75-820!! Thanks for posting! (y)
     
  7. Mudfoot

    Mudfoot Sr. Member

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    That guy really knows the ins and outs of that little handheld.
     
  8. Blackpaw

    Blackpaw Member

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    Ditto in the extra memories on the 75-820 :w00t:
    I know that newer versions of the 75-822 do not have the 120ch export mod, but they might have the hidden memories too, anyone try it out on their 822?
     
  9. towerdog

    towerdog one-niner-seven

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    It will get the 400 channels that dont transmit or receive. My Midland (or was it my cobra?), would not even TX on the lower of the 160 channels. The other of the radios, cobra I think, would TX on all the channels, but with much reduced power on the outer channels. these just dont have the bandwidth, at least for the 75-822 and HH-45.

    Too much trouble do mod the chip, too much risk of screwing up a good radio. It be cheaper to get a UK/EU version, the Alan 42 multi for $200 on ebay, which does TX/RX from 26-29 mhz, AM/FM.
     
  10. The Jerk

    The Jerk Active Member

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    Dredging this up from the dead...

    Are there any mods that can be done for the receive (make it quieter/more sensitive) or output? If so, did it make a difference?

    Thanks
     
  11. Troy B.W.

    Troy B.W. New Member

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    IT WILL NOT WORK!! DO NOT BOTHER!! THIS PERSON IS EITHER IN EUROPE OR ON THE MOON!! IF YOUR 75-820 HAS TROUBLES,LIKE MINE NOW AND WAS ALWAYS A GREAT LITTLE PORTABLE,DON'T LISTEN TO THIS PERSON AS I CANNOT EVEN FIND A SCHEMATIC FOR THE RADIO!! THIS IS FRUSTRATING AND ALL I WANTED WAS A SCHEMATIC FOR THE MIDLAND 75-820 HANDHELD UNIT. TROY
     

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