Also known as: expand the channels, more channels, 10 meter conversion, wideband modification.
On the non-UK models the display shows "Mhz" instead of ".25" and "AM/FM" instead of "UK/EU". When you do these frequency mods on a UK EM-27 the radio will be on frequency, but will still show ".25" in the display. There is no known easy way to remove the ".25" from the display window (other than to buy a knackered Stabo and change the display panel).
UK Stealth Mod (Devised by Norm of normsweb.com)
This mod will allow you to mod your Maycom EM-27 to 400 channels mode "secretly". When turned on, it looks and works exactly the same as a non-modified 80ch UK EM-27. However, if M4 is held whilst turning on, the radio will be in 400ch mode (25.165 MHz - 29.655 MHz).
How to do it:
Near the main processor, on the Front Board, you will see 8 solder-links (as pic) labeled 2,1,4,3,8,7,6,5. Link 2,1, & 3 then clear all other links. (except 5 & 6 if you've done those mods). Make sure the back-up battery is installed (if it isn't then the radio may lock up). Momentarily short the battery to reset the CPU.
Depending on which country your radio was from originally, there will be tiny SMD capacitors on some of the links. (EG. on link 3 for a UK radio) If the capacitor is on a link which you want to use in the modification you can just leave it there and do not need to solder that link, however if a capacitor is on a link which you do not want to use for modification then it MUST be removed or your mod won't work correctly.
When you have done all your solder-links for your modification, the backup battery MUST be shorted momentarily to reset the CPU. With the radio turned off and unplugged from the power supply, use a short wire to link the 2 points shown in the photo for about a second.
Your battery may be different to this one, or it may even be a small capacitor. To my knowledge there are at least 4 different types of battery / capacitor used in this radio, but you still need to short these same 2 points whatever battery / capacitor your radio has.
Non Stealth Mod:
This mod will allow you to convert your radio to 200, 400 or 600 channels mode.For 200ch link 8, for 400ch link 7, for 600ch link 7 & 8. Clear all other links (except 5 & 6 if you've done those mods). Make sure the back-up battery is installed (if it isn't then the radio may lock up). Momentarily short the battery to clear the memory.
200 channels is 26.065 to 28.305 MHz (A,B,C,D,E)
400 channels is 25.165 to 29.655 MHz (-D,-E,A,B,C,D,E,+A,+B,+C) Also known as 10 meter mode
600 channels is 23.815 to 30.555 MHz (-A,-B,-C,-D,-E,A,B,C,D,E,+A,+B,+C,+D,+E)
It's not possible to get the radio transmitting from 23.815 Mhz to 30.555 Mhz without major VCO mods.