Mercury Systems MVS +5/-5V 2S3020-95 SC00126-01 RF Pin Diode SPDT Switch

October 29, 2025 Admin

The item described as “MVS +5/-5V 2S3020-95 SC00126-01 RF Pin Diode SPDT Switch” appears to be a PIN-diode based single-pole double-throw (SPDT) RF switch (i.e., using a PIN diode switch architecture) rather than a simple relay. Here’s a breakdown of what the designation likely means, what it probably is, and things to watch if you have one in hand (as you may from surplus/hobby use).

What it is

The core of the designation is the part series Reflective SPDT Pin Diode Switch (in general) and specifically the “2S3020” series is referenced in a Mercury Systems RF-microwave product catalogue:“2S3020 Series SPDT 2.0–18.0 GHz … Isolation Loss 60 dB to 55 dB … switching speed ~50 ns”
So this suggests the “2S3020-95” is a variant of an RF switch module capable of rapid switching (tens of nanoseconds) across the 2-18 GHz band, using PIN diodes for the switching.
“SPDT” (Single Pole, Double Throw) means one input (common) and two selectable outputs. A PIN-diode switch uses forward-bias and reverse-bias of diodes to steer the RF path — typically one leg “ON” (low insertion loss) and the other “OFF” (high isolation).
The “MVS +5/-5V” likely refers to the bias/control voltages required for the switch driver: a +5 V and a −5 V supply (or control rails) to properly bias the PIN diodes and maybe internal driver circuitry (“MVS” perhaps “Manual/Voltage Switch” or vendor code). So to operate the switch you’d typically apply +5 V to one control node and −5 V to the other, to toggle the state.
“SC00126-01” is likely a specific internal/manufacturer part number or variant revision — e.g., version “-01” of SC00126.

Thus, in summary: You have a high-speed RF PIN-diode SPDT switch module (2.0-18 GHz) designed to operate with ±5 V control rails.

Why this is useful / what it’s good for

As you’re into radio astronomy and SDR/instrumentation, such a switch module is potentially of use:

Very fast switching times (tens of ns) compared to mechanical relays, making it good for fast signal routing, beam-steering, duplexing, calibration switching.
Broadband frequency coverage (2-18 GHz) means it handles a wide chunk of microwave/RF band, so you could use it for e.g., L-band (1420 MHz) or other bands in your interferometry setup.
PIN-diode switches generally have high reliability, no mechanical wear, suitable for high duty cycle use, and good isolation when off.
If you have one in surplus, it offers a professional RF building block for antenna switching, feed routing, or calibration injection.

What you should check & things to watch

Since you might be using or repurposing this module, here are key considerations:

Control voltage / biasing: Confirm the +5 V and −5 V rails are present and correct. Ensure you understand which control line drives which throw of the SPDT. Incorrect biasing can cause poor isolation or damage PIN diodes.
RF port connectors / interface: Identify the common (C) and the two throws (T1, T2) — check the mechanical connector type (SMA, N, etc), and any impedance matching (likely 50 Ω).
Switching characteristics: Insertion loss (ON state), isolation (OFF state), VSWR, and frequency range. If this is indeed a 2.0-18 GHz device, make sure your application is within that range (for your 1420 MHz you’re ok).
Power handling: Although PIN diode switches can handle moderate RF power, many are intended for small-signal or moderate power. Ensure you’re not exceeding average or peak power ratings.
Package / footprint & pin-out: If this is a module, check how it is mounted, heatsink requirements, and pin-outs for bias/control. Some units will require careful layout (grounding, decoupling, RF path isolation).
Vendor/manufacturer reference: Try to locate an exact datasheet for “2S3020-95” and “SC00126-01” variant. The Mercury systems overview mentions “2S3020 Series SPDT” but does not list full detail in that PDF.
Condition: If sourced used (e.g., from eBay listing shown) confirm that it is functional, no damage to diodes or connectors, verify switching works, measure insertion/ isolation.
Biasing current: Often these types of switches require a DC bias current for the “ON” leg (to forward bias the diode) and zero or reverse bias for OFF. Also there may be dissipation from the bias network.

Practical take-away for your use (Radio Astronomy context)

Given your interests (you’re operating at 1420.405 MHz with SDRplay RSPduo and doing interferometry, correlating signals, etc), this is how you might use such a switch:

Use the switch to select between two antenna feeds (e.g., feed A or feed B) before going into the SDR. The SPDT allows one common input to the SDR and two inputs from different antennas or feed chains.
Use it to insert a calibration/test signal path vs antenna path (common to either calibration or observation).
Since the band at 1420 MHz is well within the 2-18 GHz range, you’ll likely get good performance (low insertion loss, good isolation).
Ensure your control circuitry provides the ±5 V rails and reliably toggles the control input. You might integrate this into your Raspberry Pi/SDR system: one control line from GPIO drives a small DC-DC converter or bipolar supply to generate +5 and -5 and switch the PIN-diode state.
Because the switching is very fast (ns range), you could even implement fast switching between two antennas or feed states (useful for calibration/beam-switching) though your equipment may not need such high speed.

Caveats

The exact datasheet for your “SC00126-01” variant is not easily found from public sources, so you may need to rely on functional testing or vendor spec.
The “2S3020” part number search turned up a BJT transistor listing (likely a different device) so ensure you’re not confusing with non-RF device. The RF switch series reference is broad and may be proprietary/obscure.
Even though nominal 2-18 GHz, performance (insertion loss, isolation) may degrade significantly at the lower end (around 1-2 GHz) so measure or check.
Bias currents and DC isolation of the RF path: Make sure DC biasing does not interfere with your SDR front end or antenna feed (especially if the antenna feed is grounded or has other biasing).
Thermal / power dissipation: RF switching can cause diode dissipation. If you run continuous power or carry high RF power, you’ll want heat-sinking or ensure module cooling.

astronomy.me.uk The Website of Lichfield Radio Astronomy Observatory (LRO)