the FT-736 is one of the best (maybe the best) VHF/UHF Transceiver manufactured until today.
It was build in the late 80's until 90's where fast digital modes were not commonly used. It does not have a Paket-Radio socket and no direct connection to the demodulator or varactor diode. Therefore it is only useable for digital modes like Packet Radio up to 1200 Bd.
In the 90's the company Symec produced a PCB with a separate FM demodulator which gave the FT-736 the ability to handle 9k6 and 19k2 signals properly. This board is not manufactured any mode.
Fortunately we don't need such speeds for D-Star, 4800 Bd are good enough. And 4800 Bd can be done with the standard filters built in the FT-736. We just need to add the direct connections the the demodulator and varactor, and that's really easy to do.
These (and maybe more) applications can use the FT-736:
| DV-Adapter from Satoshi Yasuda |
| Node Adapter von Satoshi Yasuda and it's clones |
| Software Repeater from G4KLX und DG1HT |
| Reception of D-Star signales: Connection to
the FM-demodulator:
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the RX board is mounted vertically on the left. Remove the top cover of the FT-736, there is no need to remove the bottom. |
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The received D-Star signal is available at resistor R91, at
the side which is closer to the electolytic capacitor. Connect the inner
wire of a shielded cable to this point. Connect the shield to the ground
as shown in the picture.
Connect this cable with the input of you D-Star device. |
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Transmission of D-Star signals: feeding the signal to the varactor diode
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the TX board the the upper left board mounted horizontaly.
There are some descriptions in the internet showing a direct connection between a resistor and a capacitor. This is not ideal since the performance depend on the setting of an internal trimmer. |
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A better coice is to solder a 10k resistor in series with a
10uF capacitor and connect this directly to the varactor diode. Refer to
the picture to locate this point.
The negative lead of the capacitor should point to the FT-736, the positive to your external D-Star device. Additionally put a ferrite bead over one lead of the 10k resistor and put two 1nF blocking capacitors from this ferrite bead to ground. This is required to block external RF received by the cable from going to the varactor diode. |
Depending on your external D-Star device it may be neccessary to invert the polarity of the transmitted D-Star signal.
PTT:
The FT-736 has a PTT input on the rear side (the chinch plug).
According to the manual this PTT input works with 8 volt peak. Before connecting your D-Star device make sure that it can handle 8 volts. If the PTT output uses an open collector then it should be fine.
Do this modification on your own risk and only if you have the skills and knowlegde to do it !