[arm-allstar] Baofeng COS without opening the radio

[Doug Crompton]

Steve,

 If this is reliable it looks like a good way to do it. If it is OK with
you I will add the info to the Baofeng  howto mods.  We also could easily
produce a board in quantity to do this if there was a demand. I find any
more that most do not want to turn on (or have) a soldering iron so any
amount of mods are out of the question. We are currently sourcing two
models of FOB's, the ARA1 and the ARA1+. Since the yellow box nodes use
Baofeng radios and are sold in large quantities it might be advantageous to
build a FOB specifically for those radios using this method. If we test it
and it works and we decide it could be a product do you have any objection
to our use of your circuit?


*73 Doug*

*WA3DSP*

*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*


On Sat, Mar 2, 2019 at 8:55 PM "Steve via ARM-allstar" <
arm-allstar at hamvoip.org> wrote:

> I have put together a little circuit that allows connection to a Baofeng
> UV-5R HT providing COS without having to open and modify the radio itself.
> This works great for AllStar, packet, APRS, or most anything that requires
> a soundcard connection to the radio complete with COS. I have even used
> this circuit without the sound card to connect to an RC-210 repeater
> controller.
>
> I built the circuit based on the schematic of the UV-5R but I believe most
> of the Chinese radios will work with it. I have tried it on several
> different Chinese radios including the Anytone AT-D868UV DMR radio and they
> all worked fine. However, even though these radios are mimicking the
> Kenwood two prong speaker/mic connector, this circuit will not work on my
> Kenwood TH-F6. This is due to the fact that the Chinese radios do not block
> the DC of the audio amp from reaching the headset, which is why you hear a
> pop when the squelch opens and closes on these radios, and is what this
> circuit counts on to turn on Q1 and provide COS. The Kenwood doesn’t work
> (or have the pop) because it has a blocking capacitor and an MOS switch in
> the audio line that prevents the DC from coming out the jack. But I’m much
> happier using a $35 radio for this purpose anyway.
>
> I’ve hand etched a couple of boards for it so far and may send it to a
> board house to make some prettier boards, especially if others are
> interested in it (I’ve already quoted them and its just too pricey for
> small quantities, which is why I decided to hand make the few I needed).
> The boards I have made have some extra pads on the end to allow soldering
> directly to the audio jacks of one of the EBay sound FOBs, just makes it a
> bit cleaner than having to cable that side of it, though it still requires
> the two jumpers to the GPIO lines on the sound chip. Also note that there
> is an extra connection at Pin 4 on the sound card side that should allow
> using with an RA-35 or similar that already has the open collector driver
> for PTT. I have not tried this on an RA-35 but feel confident it would
> work, my target was primarily the CM108 open board sound FOB you can get on
> EBay and Amazon.
>
> https://www.ebay.com/itm/CM108-USB-Drive-Free-Sound-Card-Laptop-Computer-External-Sound-Card-Module-New/263928310585?hash=item3d735a6b39:g:SSwAAOSwEVlcDcAU:rk:1:pf:0
>
> Also note there is no activity detection nor time out timer in this
> circuit, so I leave the TOT of the attached radio set to something
> appropriate in case things get hung up in transmit. And as with other
> interfaces, make sure to keep the RF from the attached HT from getting back
> into the RPi.
>
> Schematics, some pictures, and this doc can be found here, hope it helps
> someone.
> https://www.dropbox.com/sh/lrv9uwkgx8tpm6y/AAD2syTNpZDwcjX1gA8zjV9Va?dl=0
>
> Steve – WB4BXO
> http://www.stevemobley.com
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