[Sticky] BAV RCA

If you are using the BAV RCA for a digital output, it is a ~ 110 ohm cable designed for analog. The 4694P is a true 75-ohm RF serial digital cable and is better matched to the expected load that is a 75-ohm resistor. The cable to load has lower RL reflections than the BAV. Technically yes, the 4694P is a better cable for DIGITAL where the BAV is the better cable for ANALOG. We don’t try to mix the two applications but optimize to the expected load.

The proper resistive load for RF is matchiung to the cable impedance =SQT(L/C). There is no phase angle at RF as it cancels out. Thus the cable is a pure resistive vector at RF. We can use a high tolerance resistor matching the cable impedance. Analog isn’t like this…read on.

On shorter digital runs, where the RL reflections can be high, the best resistive load match is important. Longer improper cable impedance (too low 50-ohm or too high 110 ohm) cable lengths attenuate the RL reflections more for moderate distance runs but as you get longer, those RL reflections are a form of attenuation and will limit the maximum reach (less signal voltage) to a lesser distance. On a shorter run with improper cable (110-ohm analog), RL reflections are pretty severe and can swamp the error correction.

Analog cable does not need the extreme geometry as digital and we can use AIR TUBE design (the BAV) to lower capacitance as analog IC cable is a voltage transfer function into a high impedance 47-kohm load (not a 75-ohm resistor like RF, big difference) with analog wavelengths that are far, far in excess of the cable length so the RL reflections aren’t a thing for analog cable.

Using the proper 75-ohm cable will allow optimum use from the shortest to the longest runs because the RL reflection losses are removed and the signal strength is maintained over longer runs. Shorter 75-ohm runs also see far less RL signal bounce and the error correction can be less impacted.

Galen