You could call this part of the board by various names, most of which are printable. Here, we’re just calling it “damping”. It’s rudimentary and is there to be adjusted across assembly variants and system needs, with some basic runtime operability. It can tune the output and cable/XD interface a bit. Mostly, from early work, it was just an attenuator, and a way to control some pulse characteristics, in addition to the control parameters for pulse shaping in time and the (“Tx Gain”) pulse voltage selection. Here are tables of assembly variant components values and information about how the components are engaged with different settings.
RefDes | Value: Customer BOM from 2015/17 HT Variant [Ω] | Value: Original / Design Opt (a) (Comps) [Ω] | Value: Original / Design Opt (b) (Early HT)[Ω] | Note |
R60 | 100 | 1k | 1k | |
R61 | 51 | 2k | 2k | |
R62 | 0 | DNP | 0 | R jumper connecting R14, R17, R18 into the circuit. |
R14 | 100 | 600 (N/A) | 600 | |
R17 | 200 | 200 (N/A) | 200 | GXN uses only this component at 41 (as of 2021 repair and rework for the GXN500V with XDs at the time) |
R18 | 200 | 100 (N/A) | 100 |
For the descriptions here, the board orientation is with the SMAs facing or pointing left or West. Headers or jumpers or shunts on the board typically use an adjacent silkscreen dot for position or pin 1.
R Combination (R14,17,18 apply ONLY if R62 pop) | JP Position | Damping SW/FW Setting | Customer BOM from 2015/17 HT Variant [Ω] | Earlier BOM (a) (no R62) (Comp XD) [Ω] | Earlier BOM (b) (Early HT XD)[Ω] |
R18 | DNP | N/A | 200 | >10k | 100 |
R60 || R18 | East/RHS (Pins 2-3) | N/A | 67 | 1k | 91 |
R61 || R18 | West/LHS (Pins 1-2) | 0 | 41 (Like GXN & Assembly Integrator Default) | 2k (Damp N/A) | 95 |
R61 || R17 || R18 | West/LHS (Pins 1-2) | 1 | 33 | 2k (Damp N/A) | 65 |
R61 || R14 || R17 || R18 | West/LHS (Pins 1-2) | 3 | 25 | 2k (Damp N/A) | 58 |