F210 Stereo mute

[Laz]

Hi,

Does anyone know if it is possible to get some sort of signal out of this radio in tx and rx mode that will allow me to inteface it with my stereo system?

I have a harness that will connect into my stereo nut need a signal to trigger it.

Cheers

[Pauldos!]

Interface it to do what?

[Laz]

Interface it to mute my stereo during conversations and re-route the audio of the RT back through the front speakers of my car stereo unit.

Similar to what they do with Mobile phone car kits. I previously had a Tait 2020 in there till I decide that I would offer it a cup of coffee. I integrated this through my stereo with some modifications.

[Artstar]

After a quick look at the schematics, there are two signals on the mainboard which are mighty handy. TMUT and RMUT which are active low during transmit and receive respectively. In keeping with car kits, which mute the stereo when you make the call as well, I've decided that using the TMUT signal would be a good thing although you can cheat and just slip a wire from RMUT with a diode (cathode towards the RMUT and anode towards the car stereo) leading off to the telephone mute lead of your car stereo (as they all need to receive an active low to mute the stereo). The diode is there for safe measure in case you do have other devices muting the car stereo which may end up feeding their logic 0 back to the transceiver. Although there's already a built-in diode within the unit and theoretically there shouldn't be an issue, adding a 10 cent component wouldn't hurt.

Now then, if you don't want to cheat and you do want to use both signals, again, simply grab two 1N4148 diodes and in the same orientation as mentioned earlier, tie the two anodes together feeding off to the one wire to the car stereo mute. The diodes in this case are DEFINITELY critical to prevent the TMUT signal grounding the RMUT when it shouldn't be and vice versa.

You will find the signals on pins 7 and 13 of IC17, which is located on the bottom side of the main board.

As for feeding the audio into the car speakers ... I don't care much for that but you have the option of taking the line out (for feeding into an amp) from the OPC617 connector (if you want to just get it straight off the mainboard, it's pin 5 of J6 (which leads back to R159). What you could do with this signal is, if you're running amplifiers in your car, you should run a separate little op-amp board with the input to the op-amp adjusted to a very low volume so that you don't run 100WRMS (for example) of transceiver audio through your system!! The idea of the op-amp board is to buffer the signals of both your stereo and transceiver so that you're not loading the input of the amplifier itself, thereby ensuring you don't sacrifice the quality of your music. Of course, depending on how you have your transceiver powered, you would want to ensure that the amp remains on as well otherwise you'll lose the audio from your speakers and would have to rely on the inbuilt speaker in the radio itself.

If that's a bit too much, then you can just make an adapter cable from the speaker out at the rear of the unit and using the RMUT/TMUT lead, have it actuate a 4PDT relay which will cut out your front or rear speakers (unless you want to do all 4 speakers in which you'll then have to use more relays of course) and just feed the audio directly from the in-built amp of the 210.

I intend to do the stereo muting as I definitely need that feature given my musical tastes (and it's not that doof doof rubbish either!) but I've already got my car kit going through both my front and rear amps (using a distribution amp I designed and built which I mentioned earlier) since their audio output is mediocre to begin with.

My question to you is, isn't the speaker at the front of the unit sufficient for volume? I've got an IC-F221 on the way and I haven't seen nor heard one up close to figure it out for myself but I would've thought that with 5W of audio output, it would be sufficient?

[Laz]

Thanks artstar,

Firstly thanks for your reply, I have already done a mod to the radio by picking up the busy line and ptt interupt line on the board which seems to work ok but will definitely try the TMUT and RMUT on the one which I am moddig for a friend shortly.

In answer to your question. I love music loud, well within reason although the people I am talking on the RT don't seem to appreciate it as much, hence automatic mute overcomes me interacting with the stereo all the time and audio in...well thats just a bonus.

[Artstar]

I'm with you there. I enjoy my stuff loud too which is why I intended on using the mute as well. I was just curious about routing the transceiver's audio through the speakers. But if it's only a bonus, I'll relax then with my 221 when it arrives.

I'm relying strictly on the schematics which don't give all that much detail. The BUSY port seemed viable too but it doesn't say in the service manual whether or not it's an active low or high signal and under what conditions it's detecting signal (i.e. if it's purely Rx or Tx as well). If it's both Rx and Tx, then the BUSY signal itself would be plenty to say the least. I'll just have to wait until my beast arrives.

[Laz]

Yeh. I have one of those Autoleads Telemute kits in my vehicle which cuts all the speakers and has an audio input so it was only easy to interface.

As for schematics, I didn't have these so was a matter of opening the radio and testing several ports. The busy line goes low only when recieving a signal and I use the PTT interupt to get a TX signal which also goes low. I have interfaced these with a 8-pin pic microchip which is connected directly to my autoleads kit.

[Artstar]

No offence but that's a waste of a PIC considering all you need is either 2 diodes or in the most extreme case, a simple AND gate.

At any rate, if you want the schematics, the service manual can be found at Hackersrussia.ru

[Laz]

I only used one so that I could get a delay on the TX/RX signal to save the Autoleads kit and my stereo cycling every time I hit the button.
I buy pics in large numbers which keeps the costs right down.