Published on 10/13/2026
A cable inside a warm enclosure has to carry a 2.4 GHz signal and remain stable while the equipment heats up. A feeder outside the enclosure has to carry the same band over several meters. Choosing PTFE everywhere can add cost without solving the long-run loss problem; choosing PE everywhere can miss the temperature requirement.
PTFE and PE are dielectric materials between the center conductor and shield. PTFE often suits higher-temperature cable designs. PE, especially foam PE, is widely used in economical low-loss feeders. Complete cable construction determines attenuation, phase behavior, bend performance and operating limits.
Do not rank dielectric materials with one universal claim such as "PTFE always has lower cable loss". A thin PTFE cable can lose more signal per meter than a larger foam-PE feeder. The material name is only one part of the design.
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PTFE means polytetrafluoroethylene; PE means polyethylene. Solid, foamed and low-density structures have different effective dielectric properties. Adding air can lower effective permittivity and increase velocity factor, but the resulting mechanical behavior also depends on manufacturing and geometry.
| Decision | PTFE-based cable | PE-based cable |
|---|---|---|
| Temperature | Often used in high-temperature constructions | Often used in moderate-temperature feeders |
| Low loss | Depends on density, geometry, conductors and frequency | Foam PE can provide low feeder attenuation |
| Velocity factor | Use the exact cable value; solid and low-density differ | Solid and foam PE values differ substantially |
| Phase over temperature | PTFE transition effects can matter | Cable-specific thermal behavior still matters |
| Cost | Often a higher material/process cost | Often economical for volume feeders |
| Jacket | May use FEP or other specified material | May use PE, PVC or another specified jacket |
A PTFE dielectric does not make every assembly a 200 °C product. The jacket, plating, shield, adhesives, heat-shrink and connectors can impose lower limits. A representative RG316 cable with PTFE dielectric and FEP jacket is rated from -65 °C to 200 °C for operation, while its installation-temperature range is narrower. Those numbers belong to that product.
A representative solid-PE RG58/U cable has a much lower operating range. Use the selected cable datasheet rather than treating polymer melting temperature as its continuous service rating. Enclosure hot spots, current heating and nearby equipment can raise cable temperature above the measured room ambient.
Distinguish installation temperature from service temperature. A cable that operates cold may not safely tolerate tight bending while cold. Also distinguish dielectric from jacket: FEP in a cable name may describe the outer jacket rather than the material controlling the coax geometry.
Get the interface right before ordering
Send the equipment-port details, cable length and operating band to SigmaRF.
Specify a Custom AssemblyAttenuation measures signal reduction along the cable. Velocity factor describes propagation speed relative to vacuum. Phase stability describes how electrical length changes under conditions such as temperature or bending. A cable can have low attenuation but insufficient phase stability for an interferometer or coherent RF measurement.
PTFE can show a phase-versus-temperature transition near room temperature, often called the PTFE knee. For phase-critical assemblies, ask for measured phase change over the required temperature profile rather than assuming PTFE is automatically phase-stable. Manufacturing methods and alternative dielectric constructions can change this behavior.
Foam PE is not restricted to low-frequency use by its material name. Low-loss PE-based feeders have attenuation data at microwave frequencies. Check the complete cable cutoff and operating recommendation, connector transitions and loss budget. Avoid an unsupported rule that PTFE is mandatory above 1 GHz or 3 GHz.
Key idea: Select separate limits for insertion loss, operating temperature and phase change. Passing one limit does not establish the others.
The useful cost comparison includes assembly yield, termination tools, test requirements and installation. A more expensive cable can be justified if it avoids a temperature failure or reduces phase drift. A larger economical feeder can be justified if it saves loss on a fixed outdoor route.
For short pigtails, connector compatibility and bend space may dominate. For long feeder runs, attenuation and jacket suitability often dominate. For repeated motion, qualify dynamic flex behavior rather than assuming either polymer guarantees fatigue life.
Read SigmaRF's RG316 guide for a PTFE-based compact-cable example and its RG58 vs LMR-240 guide for a solid-PE versus foam-PE feeder comparison. Those guides address actual cable families; this one addresses how to avoid attributing every performance difference to the dielectric.
Compare the propagation delay of two hypothetical 1 m cables with velocity factors 0.66 and 0.83. These are illustrative values, not a guarantee for every PE or PTFE cable.
The calculation describes nominal delay, not phase stability. Two cables with the same nominal velocity factor can have different phase change with temperature. A material substitution can also change impedance unless the geometry is redesigned.
Is PTFE coax better than PE coax?
It depends on the application. PTFE often suits higher-temperature designs, while foam PE is common in economical low-loss feeders. Compare the complete cable's loss, temperature, mechanics and phase data.
Does PTFE always have lower insertion loss?
No. Cable diameter, conductor, shielding and dielectric density also matter. A larger foam-PE feeder can have lower attenuation per meter than a thin PTFE pigtail.
Is PE coax suitable for microwave frequencies?
Yes, selected PE-based cables are used at microwave frequencies. Use their actual attenuation data, recommended band and connector qualification. Material name alone does not establish a frequency ceiling.
What is the PTFE knee in coax cable?
It is a phase-versus-temperature change associated with PTFE material transition near room temperature. It can matter in coherent or phase-sensitive systems. Ask for the selected cable's phase-temperature data.
Does an FEP jacket mean the dielectric is FEP?
No. The jacket and dielectric are separate layers. A common construction uses PTFE dielectric with an FEP outer jacket. Read the construction table.
Can I replace PTFE with PE without changing cable geometry?
Do not assume so. Dielectric properties affect impedance and propagation speed. A material change may require redesigned dimensions and new electrical qualification.
Buy the required assembly performance, not a polymer label. Match thermal requirements with the whole assembly rating, and match loss and phase requirements with measured cable data.
State the operating band, length, hot-spot temperature, motion and phase limits in the RFQ. That allows a useful cost trade-off between compact PTFE-based assemblies and economical PE-based feeders.
SigmaRF VNA-sweeps every assembly for VSWR and insertion loss before shipment. Its testing capability spans 100 MHz to 40 GHz; each assembly is specified for its own operating band. Builds are supported by the Vadodara volume facility and Cleveland-area precision facility. Lead times can be as short as 2 days, depending on the build and component availability.
Get the interface right before ordering
Send the equipment-port details, cable length and operating band to SigmaRF.
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