That gives me an idea, Greg.? I wonder if I can add the blocking cap and resister to my radio internally between the TRS and the mini-DIN and just use the mini-DIN plug with my rigblaster plug-n-play?
73, Mike - W1MI
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On Tue, Nov 16, 2021 at 07:25 PM, Greg D wrote:
I've not used the RigExpert, but have interfaced a Raspberry Pi to the 847.? The diagram looks good, at least on the 847 side.
The TRS jack is used for the HF (SSB) modes.? As shown in your diagram, the PTT line from the TNC goes through the 2k resistor to the TRS Tip, along with the transmit audio which is passed through the 10uf DC blocking capacitor.? Receive audio from the radio (TRS ring) is a direct connection to the TNC.? Ground / Shield is common to both.
The trick is what is shown in the diagram to parallel the TRS and mini-DIN connectors, giving access to the VHF FM modes as well.? The 847 splits these out, and uses a different interface scheme for the DIN connector, keeping PTT separate from the audio circuit.?
Do note that you cannot use the CAT interface for keying the radio.? The 847, for some bizarre reason, assumes the microphone jack as the source when CAT is keying the rig, instead of either of the rear jacks (TRS or DIN).? If you use CAT, you will find you are able to key the rig, but have no audio transmitted.? I had to use a separate USB-Serial dongle on my Raspberry Pi for PTT, attaching one of its modem control lines (DTR / RTS) through a buffer circuit.? I expect the RigExpert has this built-in, so when configuring your software you need to make use of the RigExpert's PTT feature and not the direct CAT interface.
Hope this helps,
Greg? KO6TH
