This article defines Crosstalk and provides design criteria to mitigate it when using Tigo's TS4-F (fire safety) products.
Contents:
- Introduction
- Which Tigo products are affected by Crosstalk?
- How to mitigate Crosstalk
- Installation case studies
Introduction
What is Crosstalk?
Crosstalk is a phenomenon that involves the unwanted transfer (or bleed-over) of signals between cables or wires that are close to each other. Crosstalk is not specific to Tigo technology, and it can cause issues in any PV system that uses Power Line Communication (PLC), i.e home automation networks, home entertainment systems, Smart buildings, etc.
What causes Crosstalk?
Electrical signals that pass through wires, junctions, or hardware have varying electromagnetic fields. These fields are susceptible to Electro Magnetic Interference (EMI) from other signal-emitting sources. This type of interference can cause an attenuation in signal strength, line noise, or phasing issues.
Which Tigo Products Are Affected By Crosstalk?
The Tigo Flex MLPE solution has two families of products that use different communication methods: 
Crosstalk is not necessarily an issue with TS4 Monitoring Solution as it uses wireless communication. However, the Tigo Fire Safety (TS4-F) family of products uses PLC communications, which may be affected by EMI if there is more than one transmission source on site.
PLC products rely on a 'keep alive' signal source to initiate the Rapid Shutdown response. If the RSS signal is compromised by Crosstalk, then Rapid Shutdown initiation may be affected.
How to Mitigate Crosstalk
Any system designer will want to mitigate (or reduce) the potential for crosstalk, especially when designing larger commercial/utility-scale systems that require multiple inverters and signal transmission sources.
The process starts by identifying how many Tigo RSS Transmitters (RSSx) are on site and ensuring that their individual DC signal paths (PV lines) are separated to prevent interference. The physical separation of conductor paths will ensure a quality signal.
Note: The minimum distance suggested for PV conductor separation is 8 inches between the individual conductor paths (both on the roof and in the cable tray).
Below is an informative chart to illustrate the various methods of crosstalk reduction. This is also provided in the Installation Manual TS4-F, TS4-A-F, TS4-A-2F, and RSS Transmitter.
| Path | Recommended | Avoid |
| Conduit |
DO: Keep the + and - conductors from each transmitter together in the same conduit. DO: Twist the + and - of each string or homerun lead.
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DO: Separate conduits associated with different transmitters, as far apart as possible, with a minimum of 8 inches of separation.
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 DO NOT: Run the conduits associated with different transmitters close together. Conduit alone does not significantly mitigate Crosstalk. |
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| Cable Trays |
DO: Run conductors from the same transmitters in their own separate cable trays.
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DO NOT: Intermix or run conductors for different transmitters in the same cable tray. |
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DO: Keep positive and negative conductors close together in the cable tray and twist them. |
DO NOT: Keep the positive and negative conductors of a string apart inside a cable tray.
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Installation Case Studies
Note: The white side of the RSS Transmitter Core should always be oriented toward the inverter.
Single Core RSS Transmitter:
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1x Inverter 1x RSS Transmitter - Single Core
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Probability of Crosstalk: 0% - Most small residential systems will not experience Crosstalk Note: Do not exceed standard design limitations - Refer to Installation Manual |
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Dual Core RSS Transmitter:
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1x Inverter 1x RSS Transmitter - Dual Core
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1x Inverter 1x RSS Transmitter - Dual Core
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A Dual Core RSS Transmitter can be used to increase the signal strength if the cable run exceeds a distance of 1000 ft (300 m), but no more than 1640 ft (500 m). Both transducer cores can be deployed on the same source circuit. Make sure to face the cores in the same direction (to avoid reverse-polarity issues): Correct Incorrect |
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Multiple RSS Transmitters:
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Bottom Line: Run strings associated with different transmitters in their own conduit. |
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Mitigating Crosstalk will result in a reliable signal with a solid Rapid Shutdown response. Tigo has added the RSS Transmitter with Pure Signal Technology to its product portfolio. This Tigo innovation essentially syncs the RSS Transmitter outputs to eliminate the potential for signal interference.
Tigo highly encourages our partners and customers to take the Tigo Academy TS4 Installation Certification Course. 100% of the installers and designers who take and follow the course criteria are successful 100% of the time with their Tigo installations. The installs go faster, smoother, and are more robust in the long run.
If you have system design questions or would like your design reviewed, email our sales engineers at se@tigoenergy.com. If you need technical support help, Contact Support.