Can the Motorola GTX 800MHz mobile or handheld be modified to operate on the 33cm 902MHz US ham band?

I know the GTX 900 MHz version can and requires a filter change if you want to receive towards the bottom of the band.

If so, what is required for the modification? I assume a change of front end filter, and hex editing of the software, is there anything else?

If not, are there any parts in this radio that are useful in this band or should I not bother with these radios? I have a few that I got off eBay dirt cheap for 900MHz before I realized I needed the 900MHz version.


1 Answer 1


It is virtually impossible to modify a 800 MHz GTX to transmit on the ham bands. To start with, the 800 MHz radios transmit a 5 MHz signal, while the 900 MHz devices transmit a 2.5 MHz signal. This is not something that can be configured, it's hard wired.

Similarly, the filters for both receive and transmit for the 800 MHz GTX are all wrong, and even if you modified the Motorola code plug with a hex editor, the radio would still be deaf and dumb on 900.

I've found the 800 MHz variants of these radios are good for spare parts - knobs, antenna jacks, buttons, speakers - but not much else.

  • $\begingroup$ Thanks for the answer. Even though it is deaf at the lower portion of the band, and probably impossible to transmit at the upper portion, is there a place I can find where I can modify the hex code? 860 is 40 megs away from 900 where 930 is 30 megs away from 900. Since it is possible to get the 900 meg GTX to receive at the bottom by tuning it down 30 megs, why can't the GTX800 go up 40 megs? I guess we still have the 2.5KHz vs 5KHz issue. $\endgroup$
    – Skyler 440
    Jan 2, 2016 at 4:55
  • $\begingroup$ I'm not sure if this will be useful, but the places to hexedit the 900 MHz code plugs are here: repeater-builder.com/motorola/gtx/gtx-info-common.html $\endgroup$ Jan 4, 2016 at 16:52

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