Instructables

Icom Handheld Dual-Band Radio Mod

This Instructable demonstrates how to modify a standard Icom IC-T7H hand-held dual-band radio transceiver to both receive and transmit on a wider range of frequencies.

Original:

2 Meter: 144.0-148.0 MHz
70 Centimeter: 420.0-450.0 MHz.

Modified:

2 Meter: 118.0 - 174.0 MHz
70 Centimeter: 400.0 - 470.0 MHz.

Hopefully this will be the first of many ham radio related Instructables I will post.

Side note:

This modification should only be made in preparation for emergency situations where communications out of regular ham bands are necessary, at no other time should an amateur radio operator transmit on frequencies outside of ham bands.
 
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Step 1: Step 1, Disassembly

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ic-t7h_disassembly-a.gif
There are 10 screws that need to be removed to gain access to the internal control circuitry.

Four above the battery compartment

Two at the top of the battery compartment

And two at the bottom of the battery compartment

Remove these screws and set them aside carefully so they don't get lost or knocked around and then proceed to step two.

Step 2: Opening the Tranciever and Identifying D15

After removing the ten screws the radio should separate fairly easily into 3 parts,

The top "controller unit"

The back-plane "logic unit"

And the battery compartment cover which is just a piece of metal.

Next take a second to locate D15, a 3 pin diode in the lower right of the back-plane logic unit.

After locating the diode and checking out the rest of the awesome circuitry head to step three.
camogreen1 year ago
This is legal in an emergency. Doesn't mean you may not need a lawyer but what jury will convict if you helped save life? Handsome boy BTW.

Mike
welder guy4 years ago
if i do this i would be able to rx and tx on 160 to 161 MHz right. evn though it ould be illegal unless in an emergency i would still be able to right? another thing the pin you have to desolder is the one on the left side of the diode right? please reply' 73's KC2VDM
This Mod opens up every freq that you can listen to on the receive section.
With the proper length antennas you can transmit from 118-174MHz 2 meters
and 400-470MHz 70cm. The whole 9 yards but better to stay in ham bands to stay legal.
camintmier5 years ago
You could also put in a small spst switch in series with the diode. That would enable you to turn on/off the mod at will.
Blastwavelabs (author)  camintmier5 years ago
Good idea definitely, that would prevent any accidental transmissions off band and keep the mod handy, instead of having to breakdown the radio to make the mod in some kind of emergency situation. Cool idea.
There are memories to put the Freq's in that you use. To go into the VFO is ah deliberate act and very unlikely to have an accidental transmission that way. Short of some un-authorised person, accidental transmissions off band are not likely.
Yeah but the insides are so tight there be no place to put the switch short of just letting it hang. Mod is done. Radio not broke. No need to add stuff.
Joe Hahn5 years ago
will this work on other icom radios also? like the IC A24?
No.
sr1sws5 years ago
Any info on the theory of why this works or how you discovered the info?
Hoopajoo sr1sws5 years ago
Probably they used the same boards for commercial bands, civil bands and ham bands. They just limit the bandwidth to suit their need and don't have to design and produce multiple boards. Emergency or not, FCC law states that at NO TIME is a ham to transmit outside the allowed bandwidth for any reason. It is a felony to do otherwise. My elmer (the one who helped me get my license) worked at a major radio equipment manufacturer with a gentleman who did that. That gentleman got 4 years in jail when he was caught. Where I live, we had a tornado knock the police, fire and rescue communications off the air for 72 hours. I am a ham with a local group that serve at the leisure of the regional emergency services. We were called to step in and provide communications. We used our radios, our repeaters and frequencies to fill their need. We rode with police fire and rescue in shifts for the entire 72 hours.
>FCC law states that at NO TIME is a ham to transmit outside the allowed bandwidth for any reason. It is a felony to do otherwise



Not true.



If there is legitimate emergency that threatens life, a Ham can use any means available to summon help. If that means calling for help on the fire/rescue repeater input frequency, that's just fine w/ Uncle Charles.



This may not stop the local po-po from confiscating your HT, mind you, but what's more important than saving a life?



There use to be a question on this very topic for the Novice Amateur Radio exam. 
Blastwavelabs (author)  Hoopajoo5 years ago
Exactly, I'm sure the logic chip they use is designed for use by many types of radios and that diode simply keeps it in ham band. As for the legality Hoopajoo is absolutely right, this mod should never be used except in a real emergency where for some reason you need to go off band. I'm talking to save lives or prevent injury or something not just because.
static sr1sws2 years ago

To find the mod info for your radios visit
http://www.mods.dk
abadfart4 years ago
very nice do you know how i can get a walky-talky to transmit CB
Blastwavelabs (author)  abadfart4 years ago
Sell the walky-talky and use the money to buy a CB probably
i have a CB in my car and so dose my buddy but not my girlfriend so we wanted one for her when we go camping
ok i got the frequencys now i need help getting a 49 MHz unit to transmit at 27-MHz
static abadfart2 years ago
There is not an easy mod like this one is, to do what you want to do. The 49 MHz unit probably didn't cost much anyway, give to someone who can use it, and buy your girl friend a new CB handheld, they don't cost much.
Ha Ha Ha LMFAO
rich_moe5 years ago
The reason for the modification is, that should you own one of these radios, AND you are a bonifide MEMBER of the Civil Air Patrol (CAP) or Military Affiliated Radio Service (MARS), you can use your own radio to communicate on those frequencies (which lie just outside the Amateur Bands) IN THE PERFORMANCE OF OFFICIAL DUTIES DIRECTLY RELATED TO CAP/MARS. This modification is only for those individuals who require the TRANSMISSION of signal on the frequencies outside the amateur band. If I remember correctly, the IC-T7 series radios can receive outside of band quite well. Pardon for the caps i the last paragraph, I just needed to make the point very clear.
Emsaid rich_moe4 years ago
im a member in Civil air patrol!
Dr.Bill5 years ago
I did this with my IC-T7H and it works really good. I put FRS freqs into the radio and now I can communicate with those radios that are out there though only on 1/2w power setting. To go higher is not only against the FCC Rules, it is also useless to go to 6 watts when the guy on the other side has a half watt. he hears you but you don't hear him. As for transmitting out of band well if you are a licensed Ham you know your band limits. KB1LZL
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