Modifications for the Icom IC-T81

Picture(s) of Icom - IC-T81

03-07-1999 IC-T81 AM/FM/Wfm function English language
05-09-1999 IC-T81 Frequency Expansion English language
30-07-2000 ICOM IC-T81A Cellular Mod English language

03-07-1999
IC-T81 AM/FM/Wfm function

Just got an Icom T81A quad bander. There is a simple mod to expand the RX capability.
To perform the mod hold the "Multi" key and the SQL keys while turning on the power. The display will light all segments.
RX is now enabled for the following frequencies:

50.000 - 75.995 Mhz
76.000 - 107.995 Mhz
108.000 - 135.995 Mhz
136.000 - 174.000 Mhz
174.000 - 229.995 Mhz
300.000 - 229.995 Mhz
400.000 - 470.000 Mhz
470.000 - 599.995 Mhz
600.000 - 800.000 Mhz
800.000 - 824.000 Mhz
849.000 - 869.000 Mhz
894.000 - 999.000 Mhz
1240.000 - 1300.000 Mhz

Note: from chogue@canac.com - Chet
Hello....on the mod to expand the receiving capabilities, (powering up while holding the multi and squelch keys), If the xcvr was previously programmed via Icom software and cable via PC, and the mod was enabled, you cannot re-program the radio via PC. The software reports an error that the version doesn't match.....the only way to access the xcvr via PC again is to do a CPU reset (power up while holding the squelch, vfo, and, mr).....

Solution.
You can reprogram the radio if it was previously programmed. You just have to rerun the CS-T81 setup option that's in the start menu with the radio turned on. It will retrieve the programming info from the radio. I've done it myself several times. I use my opened T81 with my software and program my buddy's newer t81s that the receive trick does not work on just fine with this little tip.

Steve AI6Q

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05-09-1999
IC-T81 Frequency Expansion

Remove the Diode D53 and D61.

Frequencyrange after modification:
50.000-53.995MHzRX/TX
118.000-173.995MHzRX
136.000-173.995MHzTX
400.000-469.995MHzRX/TX
1240.00-1300.00MHzRX/TX
FM Broadcast (WFM):
76.000-109.995MHzRX

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30-07-2000
ICOM IC-T81A Cellular Mod

The IC-T81A may be blocked from direct entry of cellular frequencies, but you can still receive analog cellular frequencies on it quite nicely. All you need is a little arithmetic...

If you've performed the mods listed on this site to open up the receive range to 999.95MHz, cellular is no problem. All you have to do is dial in the image frequency for cellular. That is, dial in a freq that is the cellular freq minus 2 times the IF frequency for the T81A, which is 69.4 MHz.

The cellular band (for analog phones only) from handheld to cell site is 824-849 MHz. Transmit back from cell site to handheld is 869-894 MHz. (There are a few control and data channels interspersed in those ranges too.) That corresponds to 685.1 to 755.1 MHz display on the T81A.

So, for example, to receive transmissions from a cellular phone at 826 MHz, just set the T81A to 826 - 138.9 = 687.1 MHz.

Towers Output (display on T81A 730.1 to 755.1 MHz) to RX 869-894 MHz
Cellular Input (display on T81A 685.1 to 710.1 MHz)to RX 824-849 MHz

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Have you any tips, trick or modifications you can't find here, please E-mail them to me, or use the mail form.
Can't you find a mods, please don't e-mail to me. All mods i have is listed on this site.!
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