calling all Car and Tractor specialist

[anotherjim]

Eric, if you pulse the source at some hz, do you need to band pass the receiver, or should it be sufficient to AC couple and get the envelope. The Ultrasonic system is that way by default - it wont send without running at the right hz. Receivers don't need to filter, because they already are tuned to that frequency. However they assume there's nothing else transmitting nearby at similar hz that could confuse it.

[Kipper4]

Another thing to note is that a black snoot worked better than a white one in my ghetto test.

[EBK]

Eric, if you pulse the source at some hz, do you need to band pass the receiver, or should it be sufficient to AC couple and get the envelope. The Ultrasonic system is that way by default - it wont send without running at the right hz. Receivers don't need to filter, because they already are tuned to that frequency. However they assume there's nothing else transmitting nearby at similar hz that could confuse it.

In this case, the filtering is the tuning.
Yes, I'd use a bandpass filter here.

AC coupling and taking the envelope is essentially the idea, but it probably wouldn't hurt to AC couple with a high pass cutoff above the audible frequencies.  If we don't want to make too many assumptions about the spectral composition of the background IR, we can use a bandpass filter to simply get rid of as much potential noise as possible.  Plus, it's usually (always?) a good idea to cut off the frequencies above what we're interested in.