OK, OK, don't start to teach me to use a CAD software because I 'm too old for that and I am not an engineer but attorney!
I made a nice interface for using my HTC Desire S for HF Digimodes as it's piece of junk as a phone...
The schematics come in two versions, one is of extreme simplicity but the second has to be fine tuned to work with the phone.
As you may know, the Android phone is made to be also a music player so it has a stereo output. This is the key for making the PTT circuit. One channel is for modulation and the second one is for detecting and for PTT circuit. I used a double detector to have a sufficient voltage to trigger the 2n2222 PTT transistor, in Open Collector circuit. If you transceiver use a negative voltage for PTT, the schematic is simple to transform.
The second version use the same circuit for audio In/Out but have a small preamplifier for the audio before the detection is made. This is suitable for low volume Android devices and uses the approximative 3 V from the microphone. The input of the Android device is not using a condenser microphone, therefore we can use that DC.
The preamplifier is made with a 2N2222 transistor and it may be necessary to tweak the positive polarisation for a better result.
As a response to a comment from Catalin, YO3FVR (TNX!) , I must admit that, indeed, there is a error in the HTC connector!
From ring to tip, the sections are:
-Microphone / Control / AUDIO IN
-AUDIO OUT Right
-AUDIO OUT Left
So, I think this answer to your question!
Many thanks for notice me about this!
Kenwood Programing Software FIRMWARE: KDS-100 504XXXXX 4A46 PTT ID Display feature 176.86 KB CURRENT 401XXXXX F7FC Corrects lock up wh...
Icom programming Software GM-110SC rev.1.2. ex1725. IC-3FX 245MHZ THAILAND CB HANDY RADIO, EX2020 REV 1.0. IC-3FGX 80 CHANNELS 245MHZ THA...
Yaesu Vertex Programming Software Yaesu, Standard, Vertex, Stabo, etc,,. YAESU-VERTEX-STANDARD-MARANTZ: Yaesu Handheld Radios: ADMS-1C Ad...
Looks to me like Kenwood decided to comite suicide! In a market divided between Yaesu and Icom as ham equipment producers, each one with ...
LATER EDIT: Here you can find a solution for a "military-like" backpack radio based on FT857D. TIP for mobile useres: Two male RJ...
I added some detailed pictures of the setup: Spacers detail: Antenna solution: Battery solution: I am not intend to make a...