RTCM to Kenwood TKR-750

App_rpt-users
1

I am looking for any guidance on interfacing an RTCM to a TKR-750. In particular:

  1. should I use TA or TD for feeding in the transmit audio (I am using TD)

  2. how should I configure the channel (‘duplex’?)

  3. what about other settings like PTT priority (currently local mic, external ptt, repeat ptt)

I initially used channel mode ‘repeat’ which is not right because then you get local repeat mixed with the transmit audio coming from the RTCM (slightly delayed). I switched to duplex mode and now I am PTT but transmit audio.

Form my contribution, I can offer a solution to the level problem interfacing the CTCSS decode (TOR) to the CTCSS line on the RTCM.

I used an NPN transistor and a voltage divider (15k, 5k) to ground fed by the TOR (active high) from the Kenwood. This works nicely.

-Doug-

KD7DK

2

I am looking for any guidance on interfacing an RTCM to a
TKR-750. In particular:
1) should I use TA or TD for feeding in the transmit audio (I
am using TD)

You should be using the TA input.

TD is the low-speed data input. It is a wideband input with response down
to near-DC. It has no preemphasis. Even with the softpot cranked all the
way up you still need several volts of audio to deviate to 5 kHz. Also, if
you enable PL on the transmitter, it will disable the TD input (i.e. you
can't both encode PL AND use the TD input concurrently), so if you have the
TKR configured to encode PL, you're not going to hear anything coming in the
TD input.

2) how should I configure the channel ('duplex'?)

Yes, duplex.

3) what about other settings like PTT priority (currently
local mic, external ptt, repeat ptt)

Shouldn't matter since you won't have more than one PTT source active
anyway, you can leave it at default. Also be sure to disable TOT on the
external PTT, disable CWID, etc..

        --- Jeff WN3A

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3

Jeff, thank you. Your advice was perfect. We are looking good now.

-Doug-

···

On Mon, Feb 19, 2018 at 6:42 AM, Jeff DePolo jd0@broadsci.com wrote:

I am looking for any guidance on interfacing an RTCM to a

TKR-750. In particular:

  1. should I use TA or TD for feeding in the transmit audio (I

am using TD)

You should be using the TA input.

TD is the low-speed data input. It is a wideband input with response down

to near-DC. It has no preemphasis. Even with the softpot cranked all the

way up you still need several volts of audio to deviate to 5 kHz. Also, if

you enable PL on the transmitter, it will disable the TD input (i.e. you

can’t both encode PL AND use the TD input concurrently), so if you have the

TKR configured to encode PL, you’re not going to hear anything coming in the

TD input.

  1. how should I configure the channel (‘duplex’?)

Yes, duplex.

  1. what about other settings like PTT priority (currently

local mic, external ptt, repeat ptt)

Shouldn’t matter since you won’t have more than one PTT source active

anyway, you can leave it at default. Also be sure to disable TOT on the

external PTT, disable CWID, etc…

                            --- Jeff WN3A

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4

I myself, find myself wiring a RTCM to a Kenwood TKR. I too have noticed the CTCSS circuit not performing as expected. I believe this should fix the problem.