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Simon_V · 25th Apr 2018, 2:48 pm

Just to tie up a few loose ends.

To make the mod work refer to fig 4 below. Lift out the control board (very carefully) Add C56 which will not be fitted in an E version radio (470pF disc ceramic). Remove R55 and add wire link W2 and a tall 6 pin header in the unused holes next to the 4 pin header that supported the 1750 Hz tone board.

The original mod is supposed to activate the tone board by placing a logic 1 (5v) on pin TH when the repeater offset is on. I must admit that while I was experimenting I just wire linked pin TH to pin 5C to activate it. However, there is a slightly more user friendly way to do it. As we want the tone active regardless of if the repeater shift is 1.6 MHz or 7.6 MHz as it is here in the UK we can use the output of the mode driver chip (IC23). Refer to Fig 3 below and make up a wire link with a 1N4148 diode in series, insulate with a bit of heat shrink tubing as indicated in red and attach one end to pin 6 of IC23 and the other end to the cathode of D15. This provides a logic 1 (5v) to pin TH in FM mode only. If you have the boards deviation set correctly no one will ever notice on simplex that you are putting out a CTCSS tone.

25th Apr 2018, 2:48 pm	#12
Simon_V Retired Dormant Member Join Date: Feb 2014 Location: Pembrokeshire, UK. Posts: 52	Re: Trio TS711 & 811 Just to tie up a few loose ends. To make the mod work refer to fig 4 below. Lift out the control board (very carefully) Add C56 which will not be fitted in an E version radio (470pF disc ceramic). Remove R55 and add wire link W2 and a tall 6 pin header in the unused holes next to the 4 pin header that supported the 1750 Hz tone board. The original mod is supposed to activate the tone board by placing a logic 1 (5v) on pin TH when the repeater offset is on. I must admit that while I was experimenting I just wire linked pin TH to pin 5C to activate it. However, there is a slightly more user friendly way to do it. As we want the tone active regardless of if the repeater shift is 1.6 MHz or 7.6 MHz as it is here in the UK we can use the output of the mode driver chip (IC23). Refer to Fig 3 below and make up a wire link with a 1N4148 diode in series, insulate with a bit of heat shrink tubing as indicated in red and attach one end to pin 6 of IC23 and the other end to the cathode of D15. This provides a logic 1 (5v) to pin TH in FM mode only. If you have the boards deviation set correctly no one will ever notice on simplex that you are putting out a CTCSS tone. Attached Thumbnails Last edited by Simon_V; 25th Apr 2018 at 2:53 pm.