Samara & Ultrasonic
Samara
Hey, have you seen the latest FCC ruling on frequencies above 40 kHz? We might need to double‑check our gear specs for compliance.
Ultrasonic
Did you get a copy of that FCC memo? I’m still crunching the numbers on the 40 kHz line—any deviation and those high‑frequency transients can bleed into the audible range. Double‑check the transducer specs on the old analog unit; those vintage models usually clip hard beyond 45 kHz, but the newer silicon ones are a lot tighter. Also, make sure the shielded cables you’re using have proper ground paths; a single stray loop can throw your waveform off. Let me know what you find, and we’ll patch it up before we hit the studio.
Samara
I received the memo—file #2025‑FCC‑041. I’ve cross‑checked the transducer tables and the grounding schematic. The vintage units do clip at 48 kHz, the silicon ones stay under 42 kHz. The shielded cables all have a common‑mode choke and a single‑point ground. All good for now. Let me know if you need the exact specs on the new silicon set.
Ultrasonic
Sounds solid so far. If you can drop the exact bandwidth and insertion loss numbers for the new silicon set, I’ll run a quick compliance check against the 42 kHz limit. Also, double‑check that the common‑mode choke is still in the feedline path and not the return—any shift there can sneak in those high‑frequency ghost echoes. Once I have the specs, I’ll run a quick FFT to make sure the roll‑off is clean and the phase response is linear up to the cutoff. Let me know when you have it.
Samara
Bandwidth: 38 kHz to 42 kHz. Insertion loss: 0.35 dB at 40 kHz, rising to 0.48 dB at 42 kHz. The common‑mode choke is located in the forward feedline, not the return path. Let me know if you need the datasheet or additional impedance parameters.
Ultrasonic
Thanks for the numbers. 38 kHz to 42 kHz is comfortably below the 40 kHz threshold, and the insertion loss curve looks clean—0.35 dB at 40 kHz is fine, 0.48 dB at 42 kHz still leaves a good margin. The choke in the forward feedline is perfect, that keeps the common‑mode noise from riding the forward signal. I’d still like the full datasheet and the exact impedance curve from 30 to 50 kHz to run a quick simulation. Let me know if you can forward it.
Samara
Here’s the snapshot of the impedance curve from 30 kHz to 50 kHz: at 30 kHz 50 Ω, 32 kHz 51 Ω, 34 kHz 52 Ω, 36 kHz 53 Ω, 38 kHz 54 Ω, 40 kHz 55 Ω, 42 kHz 56 Ω, 44 kHz 57 Ω, 46 kHz 58 Ω, 48 kHz 59 Ω, 50 kHz 60 Ω. The full datasheet is attached—page count 37, a prime. Let me know if you need any more detail.
Ultrasonic
Got the curve—nice gentle slope. I’ll pull the datasheet and run a quick impedance‑matching check at 42 kHz. Just need the driver’s 50 Ω specification at 40 kHz so I can confirm the load line. Otherwise it looks compliant. Let me know if there’s any extra pin‑out info.
Samara
Driver at 40 kHz: source impedance 50 Ω, insertion loss 0.25 dB, output swing ±12 Vpp. Pin‑out: pin 1 – output, pin 2 – ground, pin 3 – reference, pin 4 – enable, pin 5 – +5 V supply.
Ultrasonic
Looks good to me. With 50 Ω source and 56 Ω load at 42 kHz the mismatch is minimal, and the 0.25 dB loss won’t kill the signal. I’ll run a quick FFT of the output to make sure the phase stays flat up to the cutoff. Just keep the power rail clean; the +5 V supply should be filtered so it doesn’t bleed into the 40 kHz band. Let me know if you spot any quirks.
Samara
Just a couple of quirks to flag: the ±12 Vpp swing at 40 kHz is fine but leaves little headroom if you hit any clipping during transients; double‑check that the output doesn’t exceed the driver’s 14 V supply margin. The +5 V rail will be clean only if the RC filter is low‑pass below ~15 kHz, otherwise a 5 V ripple could sneak into the 40–42 kHz band and show up in your FFT. Also keep an eye on ground bounce – the driver’s ground pin is isolated, so any return‑path inductance can cause a phase slope at the top of the band. All else looks nominal.
Ultrasonic
Got it—headroom is tight, so I’ll keep an eye on the peak amplitude during those short bursts. I’ll run a quick transient test to see if we hit that 14 V ceiling. The 5 V rail filter will get a 10 kΩ/0.1 µF cap combo so it stays below 15 kHz, no 40‑kHz leakage. And I’ll add a small ferrite bead on the ground return to tame any inductive bounce. That should keep the phase clean at 42 kHz. Let’s ping back when the numbers come in.
Samara
Sounds like a solid plan – keep an eye on the 14 V peak, confirm the cap values, and check the ferrite bead’s impedance at 42 kHz. Ping me with the test data, and we’ll verify the phase curve.