I am not an automotive expert, but I work in the RF world and I’m familiar with what we call transmission line theory. I would expect the video circuit load impedance (in the radio between signal and return) to be matched to the source and line impedance at the operational frequency. 75 ohms seems typical for this application, though theoretically your DC impedance (resistance) value may differ from the impedance at the operational frequency, and the DC resistance of the source and load may be different even if the terminations are healthy. In practice this may be uncommon, I don’t know. But the OL measured on the radio input and the 70 – 80 ohms measured back to the source makes me agree that the radio termination is probably the issue. A bad termination resistor to the data input would cause high reflections along the transmission line and a bad received signal at the radio. I am anxious to hear if the radio replacement fixed the issue, and if you got a chance to measure the new radio termination. I expect it will be 70 – 80 ohms, matched to the source. Love the show.
Hey Jordan! Thanks for the comment, that’s great info. You should email me, I’ve got some questions and it might be cool to have you on the pod to discuss this topic more
I am not an automotive expert, but I work in the RF world and I’m familiar with what we call transmission line theory. I would expect the video circuit load impedance (in the radio between signal and return) to be matched to the source and line impedance at the operational frequency. 75 ohms seems typical for this application, though theoretically your DC impedance (resistance) value may differ from the impedance at the operational frequency, and the DC resistance of the source and load may be different even if the terminations are healthy. In practice this may be uncommon, I don’t know. But the OL measured on the radio input and the 70 – 80 ohms measured back to the source makes me agree that the radio termination is probably the issue. A bad termination resistor to the data input would cause high reflections along the transmission line and a bad received signal at the radio. I am anxious to hear if the radio replacement fixed the issue, and if you got a chance to measure the new radio termination. I expect it will be 70 – 80 ohms, matched to the source. Love the show.
Hey Jordan! Thanks for the comment, that’s great info. You should email me, I’ve got some questions and it might be cool to have you on the pod to discuss this topic more
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