PXI-2558 2.5 GHz Quad SPDT 75 Ω PXI RF Relay Module
The PXI-2558 is a general-purpose PXI RF relay module designed for automated video testing, 75 Ω RF signal routing and high-channel-count switch systems. It provides four independent single-pole double-throw relays in a single-slot PXI module.
Each relay bank contains a common connection, a normally closed connection and a normally open connection. This quad SPDT architecture allows four independent 75 Ω signal paths to be switched between two destinations or sources under software control.
With a DC to 2.5 GHz operating range, low insertion loss, strong isolation and direct mini-75 Ω SMB connectivity, the PXI-2558 is suitable for cable television, set-top box, video distribution and broadband RF test applications.
Key Features of the PXI-2558
- Four independent SPDT RF relays
- Four common, four normally open and four normally closed connections
- DC to 2.5 GHz frequency range
- 75 Ω nominal characteristic impedance
- Electromechanical latching relays
- Less than 0.6 dB insertion loss through 1 GHz
- Less than 1.1 dB insertion loss through 2.5 GHz
- Greater than 60 dB typical isolation through 1 GHz
- Greater than 36 dB typical isolation through 2.5 GHz
- 30 V maximum switching voltage
- 0.5 A maximum switching and carry current per channel
- 10 W maximum RF switching power
- Less than 20 ps typical channel-to-channel skew
- 700 ps typical propagation delay
- 12 gold-plated mini-75 Ω SMB connectors
- Onboard relay-count tracking
- PXI hardware trigger support
- NI-SWITCH and NI Switch Executive compatibility
PXI-2558 Technical Specifications
| Product Model | PXI-2558 |
|---|---|
| Part Number | 778572-58 |
| Product Type | PXI RF relay switch module |
| Topology | Four-bank SPDT |
| Number of Independent Banks | 4 |
| Relay Configuration | SPDT, single-pole double-throw |
| Connections per Bank | COM, normally open and normally closed |
| Frequency Range | DC to 2.5 GHz |
| Characteristic Impedance | 75 Ω nominal |
| Maximum Switching Voltage | 30 V |
| Maximum Switching Current | 0.5 A per channel |
| Maximum Carry Current | 0.5 A per channel |
| Maximum RF Switching Power | 10 W |
| Initial DC Path Resistance | Less than 0.35 Ω typical |
| End-of-Life DC Path Resistance | 1.0 Ω or greater |
| Maximum Insertion Loss through 1 GHz | Less than 0.6 dB; less than 0.3 dB typical |
| Maximum Insertion Loss through 2 GHz | Less than 1.05 dB; less than 0.7 dB typical |
| Maximum Insertion Loss through 2.5 GHz | Less than 1.1 dB; less than 0.7 dB typical |
| Maximum VSWR through 1 GHz | Less than 1.25; less than 1.1 typical |
| Maximum VSWR through 2 GHz | Less than 1.6; less than 1.45 typical |
| Maximum VSWR through 2.5 GHz | Less than 1.6; less than 1.45 typical |
| Typical Isolation through 1 GHz | Greater than 60 dB |
| Typical Isolation through 2 GHz | Greater than 43 dB |
| Typical Isolation through 2.5 GHz | Greater than 36 dB |
| Typical Crosstalk through 1 GHz | Less than -62 dB |
| Typical Crosstalk through 2 GHz | Less than -56 dB |
| Typical Crosstalk through 2.5 GHz | Less than -48 dB |
| Typical Channel-to-Channel Skew | Less than 20 ps |
| Typical Propagation Delay | 700 ps |
| Typical Rise Time | 55 ps |
| Maximum Relay Operate Time | 10.4 ms |
| Relay Type | Electromechanical latching |
| Expected Mechanical Relay Life | 1,000,000 cycles |
| Expected Electrical Relay Life | 300,000 cycles at 30 V, 10 mA DC resistive |
| Input Trigger Sources | PXI trigger lines 0 through 7 |
| Minimum Input Trigger Pulse Width | 150 ns |
| Output Trigger Destinations | PXI trigger lines 0 through 7 |
| Typical Output Trigger Pulse Width | 2 µs |
| Front-Panel Connectors | 12 gold-plated mini-75 Ω SMB jacks |
| PXI Power Requirement | 3.7 W at 5 V; 0.3 W at 3.3 V |
| Operating Temperature | 0°C to 55°C |
| Storage Temperature | -20°C to 70°C |
| Relative Humidity | 5% to 85%, noncondensing |
| Maximum Operating Altitude | 2,000 m |
| Dimensions | 21.6 × 2.0 × 13.0 cm |
| Weight | 227 g |
| Module Format | 3U, single-slot PXI/cPCI module |
| Software Support | NI-SWITCH and NI Switch Executive |
PXI-2558 Part Number and Connectivity
| Item | Part Number | Description |
|---|---|---|
| PXI-2558 | 778572-58 | 2.5 GHz, 75 Ω, quad SPDT PXI RF relay module |
| Mini-75 Ω SMB Cable | Verify availability | Mini-75 Ω SMB to mini-75 Ω SMB coaxial connection |
| Mini-75 Ω SMB to BNC Cable | Verify availability | 75 Ω coaxial connection for compatible BNC equipment |
| Mini-75 Ω SMB to Type-F Cable | Verify compatibility | Connection option for cable television and video equipment |
NI lists the original mini-75 Ω SMB cable options for this product family as no longer available. Before ordering third-party or replacement cables, verify the connector dimensions, gender, 75 Ω impedance and required frequency range.
Quad SPDT Relay Architecture
The PXI-2558 contains four independent SPDT relay banks. Each bank has a common terminal, a normally closed terminal and a normally open terminal.
When a bank is in its default position, the common connection is routed to the normally closed connection. Changing the relay state routes the common to the normally open connection.
This architecture can select between two RF sources, direct one signal toward two possible destinations or create larger custom multiplexer networks using multiple relay banks.
Four Independent RF Switching Banks
Each of the four SPDT banks operates independently. One bank can select a video source while another switches an analyzer input or connects a separate device under test.
Independent control makes the PXI-2558 more flexible than a single common multiplexer when the application requires several unrelated changeover paths.
When designing a larger switch network, consider the cumulative insertion loss, VSWR and isolation of every switch stage in the final route.
75 Ω Video and RF Signal Routing
The PXI-2558 is designed for 75 Ω signal environments commonly used in cable television, broadband video, video distribution and broadcast test equipment.
Maintaining the correct impedance helps reduce reflections and amplitude errors. Cables, adapters, terminations, sources and instrument inputs should all use 75 Ω impedance whenever possible.
A physical connector adapter does not convert electrical impedance. If a 50 Ω instrument must be connected to the module, use an appropriate impedance-matching solution and account for its loss.
DC to 2.5 GHz Frequency Range
The electromechanical relay paths support signals from DC through 2.5 GHz. This allows the same module to route baseband, video, intermediate-frequency and RF signals.
Actual system bandwidth depends on the complete signal path, including cables, adapters, fixture wiring and connected instruments. Every external component should be rated for the highest required frequency.
Low Insertion Loss
The PXI-2558 provides less than 0.6 dB insertion loss through 1 GHz and less than 1.1 dB through 2.5 GHz. Typical insertion loss is approximately 0.3 dB through 1 GHz and 0.7 dB through 2.5 GHz.
Low path loss helps preserve RF and video signal amplitude. For precise measurements, characterize each route with the installed cables and apply path-loss compensation when required.
VSWR Performance
Maximum VSWR is less than 1.25 through 1 GHz and less than 1.6 through 2.5 GHz. Controlled VSWR reduces reflections when the module is connected to properly matched 75 Ω equipment.
Damaged connectors, incorrect cable impedance and unterminated external paths can degrade system VSWR. Inspect each connection and use suitable termination where required by the source or instrument.
Isolation and Crosstalk
Typical relay isolation is greater than 60 dB through 1 GHz and greater than 36 dB through 2.5 GHz. Typical crosstalk is below -62 dB through 1 GHz and below -48 dB through 2.5 GHz.
System-level isolation can be affected by cable routing, shielding, grounding and external fixture design. Keep high-level video and RF sources separated from sensitive measurement paths.
10 W RF Switching Capability
The PXI-2558 supports up to 10 W of RF switching power. The connected signal must also remain within the module’s 30 V maximum switching-voltage and 0.5 A maximum current ratings.
Evaluate voltage, current and power limits together. Meeting the RF power rating alone does not guarantee that every other electrical limit is satisfied.
Cold Switching Recommendations
NI does not recommend changing relay states while significant RF energy is present. During relay operation, a signal source may briefly experience an unterminated condition that can create damaging reflections.
Remove or reduce the RF signal before switching whenever the test sequence permits. Cold switching also reduces contact stress and helps extend electrical relay life.
Electromechanical Latching Relays
The PXI-2558 uses electromechanical latching relays. Electromechanical contacts provide broadband operation extending to DC and typically offer lower insertion loss than comparable solid-state signal paths.
Latching relays maintain their selected state without continuous coil power. Their electrical life depends on the switched voltage, current, RF power, load characteristics and switching conditions.
Relay-Count Tracking
Onboard relay-count tracking records switching operations and helps users monitor relay utilization. Maintenance teams can identify heavily used paths before contact wear affects test-system reliability.
Where fixture wiring permits, frequently used routes can be distributed across different banks to balance relay usage and extend the system’s service interval.
Low Skew and Propagation Delay
Typical channel-to-channel skew is less than 20 ps, and typical propagation delay is approximately 700 ps. Typical signal rise time is 55 ps.
External cables often introduce more delay and skew than the relay module. Use matched 75 Ω cables when timing consistency between channels is important.
PXI Hardware Triggering
The PXI-2558 supports input and output triggers through PXI trigger lines 0 through 7. Hardware triggering allows relay operations to be coordinated with other instruments in the PXI chassis.
Trigger-controlled scan lists can provide more repeatable timing than individual software commands. Allow sufficient relay and instrument settling time before making the associated measurement.
Typical PXI-2558 Applications
- Cable television equipment testing
- Set-top box production testing
- Video switch network development
- 75 Ω RF signal routing
- Video source and destination selection
- RF analyzer input switching
- Broadband tuner testing
- Broadcast equipment validation
- High-channel-count multiplexer construction
- Automated production test systems
- Laboratory RF automation
- Device-under-test signal selection
Video Switch Networks
The four independent SPDT banks can add programmable changeover paths to a video switch network. Each relay can select between two video sources or route a common signal toward one of two destinations.
Multiple PXI-2558 modules can be combined when the system requires more switching points. Route planning should account for every relay stage and preserve consistent 75 Ω impedance throughout the network.
High-Channel-Count Multiplexers
SPDT relays can be arranged in a tree structure to build multiplexers with additional inputs. This gives system designers flexibility when a standard single-bank multiplexer does not match the required topology.
Cascading relays increases total insertion loss and can reduce isolation. Characterize the longest signal path and ensure that it still satisfies the required RF performance.
Set-Top Box and Tuner Testing
The PXI-2558 can switch signals in automated tests for set-top boxes, cable tuners and video receivers. Test software can select RF sources, DUT outputs and analyzer paths without manually moving cables.
Its 75 Ω impedance is compatible with common cable and video equipment. Confirm that any Type-F, BNC or other adapters maintain 75 Ω impedance through the required frequency range.
NI-SWITCH Software Support
The PXI-2558 is controlled through the NI-SWITCH instrument driver. NI-SWITCH provides functions for opening and closing relay paths, configuring scan lists, managing triggers and reading relay-count information.
The driver supports LabVIEW, LabWindows/CVI and compatible text-based programming environments. Relay operations can be integrated directly into automated test sequences.
NI Switch Executive Integration
NI Switch Executive allows users to define named routes instead of controlling every relay by its physical channel name. This simplifies development and maintenance in systems containing several RF switch modules.
Meaningful route names can represent sources, instruments, test points and DUT connections. Fixture changes can often be managed within the route configuration without rewriting the complete application.
PXI Chassis Integration
The PXI-2558 occupies one slot in a compatible 3U PXI chassis. It can be installed alongside RF analyzers, digitizers, signal generators, controllers and other modular instruments.
Before installation, verify chassis compatibility, available cooling, controller communication and NI-SWITCH support. Provide enough front-panel clearance for all required mini-SMB cables.
PXI-2558 Troubleshooting
The PXI-2558 Is Not Detected in NI MAX
Confirm that the module is fully seated in a compatible PXI slot. Check chassis power, controller communication and NI-SWITCH installation, then restart NI Measurement & Automation Explorer.
The Common Port Is Connected to the Wrong Path
Verify the selected relay bank and whether the application expects the normally open or normally closed connection. Compare the software channel names with the front-panel labels.
No Signal Appears at the Common Connection
Check the RF source, selected route, cable continuity and receiving-instrument settings. Inspect the mini-SMB connectors and confirm that the cable is fully engaged.
Insertion Loss Is Higher Than Expected
Verify that every cable and adapter is rated for 75 Ω operation and the required frequency. Inspect connectors for damage and measure the total loss of the complete signal path.
Signal Reflections Are Excessive
Check for 50 Ω components accidentally installed in the 75 Ω path. Confirm that sources and loads are properly terminated and minimize unnecessary adapters.
Signals Leak Between Relay Banks
Inspect external cable routing, shielding and grounding. Separate strong RF sources from sensitive measurement paths and check the fixture for unintended coupling.
A Relay Does Not Change State
Verify the commanded relay name and review its operation count. Disconnect external signals and test the bank using a known low-level source. A worn or overstressed relay may require service.
Relay Life Is Shorter Than Expected
Check whether relays are being operated with active RF power. Use cold switching where possible and confirm that voltage, current and RF power remain within the specified limits.
The Fault Timing Is Not Repeatable
Use PXI hardware triggers and a scan list instead of relying only on host-software timing. Include sufficient relay settling time before initiating the measurement.
PXI-2558 Comparison with Similar 75 Ω RF Switches
| Model | Primary Configuration | Best Suited For |
|---|---|---|
| PXI-2554 | 2.5 GHz, unterminated 4×1 multiplexer | Selecting one of four RF sources or test paths |
| PXI-2555 | 2.5 GHz, terminated 4×1 multiplexer | Four-channel routing requiring internal termination |
| PXI-2556 | 2.5 GHz, dual 4×1 multiplexer | Two independent four-channel multiplexers |
| PXI-2557 | 2.5 GHz, 8×1 multiplexer | Routing eight signals to one common instrument |
| PXI-2558 | 2.5 GHz, quad SPDT relays | Four independent changeover paths |
| PXI-2559 | 2.5 GHz, dual terminated SPDT relays | Independent changeover paths requiring termination |
PXI-2558 vs PXI-2557
The PXI-2557 provides a single 8×1 multiplexer that connects one of eight inputs to one common port. The PXI-2558 provides four independent SPDT changeover relays.
Choose the PXI-2557 when eight signals must share one instrument. Choose the PXI-2558 when the test system requires four independent two-way switching paths.
PXI-2558 vs PXI-2559
The PXI-2558 provides four independent unterminated SPDT relays. The PXI-2559 provides two terminated SPDT relay banks.
Select the PXI-2558 when the number of independent switching paths is the priority. Select the PXI-2559 when two paths are sufficient and internal termination of unselected connections is required.
PXI-2558 vs PXI-2548
The PXI-2558 and PXI-2548 both provide four independent SPDT relays. The PXI-2558 is designed for 75 Ω systems and uses mini-SMB connectors, while the PXI-2548 is designed for 50 Ω systems and uses SMA connectors.
Choose the PXI-2558 for cable television, video and other 75 Ω applications. Choose the PXI-2548 for conventional 50 Ω RF test equipment.
Recommended Related Products
- PXI-2554 4×1 75 Ω RF Multiplexer
- PXI-2555 Terminated 4×1 75 Ω RF Multiplexer
- PXI-2556 Dual 4×1 75 Ω RF Multiplexer
- PXI-2557 8×1 75 Ω RF Multiplexer
- PXI-2559 Dual Terminated SPDT RF Relay Module
- PXI-2548 Quad SPDT 50 Ω RF Relay Module
- View More NI PXI and PXI Express Modules
Selecting the Right 75 Ω RF Switch
Choose the PXI-2558 when the application requires four independent SPDT routes, DC to 2.5 GHz frequency coverage and 75 Ω mini-SMB connectivity. It is particularly suitable for video networks and custom high-channel-count switch architectures.
Select the PXI-2557 when eight channels must connect to one common port. Choose the PXI-2559 when fewer SPDT banks are required and internal termination is important.
Why Choose the PXI-2558?
- Provides four independently controlled SPDT relays
- Supports signals from DC through 2.5 GHz
- Maintains 75 Ω impedance for RF and video systems
- Offers low insertion loss and good VSWR
- Supports 10 W RF switching power
- Provides direct mini-75 Ω SMB connectivity
- Includes onboard relay-count tracking
- Supports PXI hardware triggering
- Integrates with NI-SWITCH and NI Switch Executive
- Occupies only one PXI chassis slot
Frequently Asked Questions
What Is the PXI-2558?
The PXI-2558 is a 2.5 GHz, 75 Ω PXI RF relay module containing four independent SPDT switching banks.
What Is the PXI-2558 Part Number?
The standard NI part number for the PXI-2558 is 778572-58.
How Many Relays Does It Provide?
The module provides four independent electromechanical SPDT relays.
What Is the Maximum Frequency?
The PXI-2558 supports signals from DC through 2.5 GHz.
Is the PXI-2558 a 50 Ω or 75 Ω Module?
The PXI-2558 is designed for 75 Ω video and RF signal systems.
What Is the Maximum RF Power?
The maximum RF switching power is 10 W, subject to the module’s 30 V and 0.5 A electrical limits.
Are the Relay Paths Internally Terminated?
No. The PXI-2558 uses four standard SPDT relay paths without the terminated architecture provided by the PXI-2559.
What Connectors Does the PXI-2558 Use?
The module provides 12 gold-plated mini-75 Ω SMB jacks.
Does It Use Solid-State Switches?
No. The PXI-2558 uses electromechanical latching relays.
Does the Module Track Relay Usage?
Yes. Onboard relay-count tracking helps users estimate relay wear and plan preventive maintenance.
Which Software Controls the PXI-2558?
The module is controlled through NI-SWITCH and can be integrated into named-route applications using NI Switch Executive.
Is the PXI-2558 Still Available from NI?
NI lists the PXI-2558 as no longer available for direct purchase. Used, refurbished or new-surplus units may remain available from specialized PXI equipment suppliers.
Request a Quote for the PXI-2558
Contact us for current availability, condition, lead time and project pricing for the PXI-2558 2.5 GHz Quad SPDT 75 Ω PXI RF Relay Module. We can also help identify compatible mini-SMB cables, 75 Ω adapters, PXI chassis and alternative RF switch modules for your test system.
