Published on 10/13/2026
A dual-band GPS antenna feed must support both L1 at 1575.42 MHz and L5 at 1176.45 MHz, including the antenna and receiver's required bandwidths. Check cable loss, active-antenna gain and DC bias at both bands; a cable advertised only as GPS compatible does not prove a complete L1/L5 system.
An existing L1 antenna installation can look reusable when a receiver is upgraded to dual band. The coax may be usable, but the antenna, filters, bias arrangement and receiver gain limits also need checking. Replacing only the receiver is not a dual-band qualification.
This guide addresses cabling rather than promising positioning accuracy. Dual-frequency capability helps a compatible navigation system, but cable selection alone does not establish accuracy, availability or safety-of-life suitability.
On This Page
| GPS signal reference | Center frequency | Feed requirement |
|---|---|---|
| L1 | 1575.42 MHz | Loss and matching across required L1 bandwidth |
| L5 | 1176.45 MHz | Loss and matching across required L5 bandwidth |
| Dual-band feed | Both signal bands | Antenna, filters and receiver must all support both |
The center frequencies are not a substitute for the receiver's required bandwidth or the antenna specification. Ask for insertion-loss and VSWR acceptance over the defined bands. Other GNSS constellations may add different signal requirements; do not equate a GPS L1/L5 feed with every GNSS band automatically.
An active antenna includes an LNA. Its gain ahead of the feeder can reduce the relative noise contribution of the cable and receiver, but it does not make any cable length harmless. The receiver still has an allowed input gain and level range, and excessive gain can overload it.
| Item | Check at L1 and L5 | Reason |
|---|---|---|
| Passive antenna response | Required bands and mounting conditions | LNA gain cannot fix a poor radiator |
| LNA gain and NF | Band-specific antenna specifications | One combined gain number hides two effects |
| Feeder loss | Complete assembly versus frequency | Different losses can change net gain by band |
| Receiver input limits | Allowed active-antenna gain and conditions | Avoid insufficient or excessive gain |
Do not copy a generic active-antenna gain range from another receiver. Use the exact antenna and receiver documents, including any built-in filters and amplifier settings.
Many active antennas receive DC through the coax center conductor with the shield as return. Verify voltage, current, receiver bias capability and any external bias tee. Intervening adapters, surge protectors, filters or splitters may pass or block DC; identify them explicitly.
Step 01
Calculate the DC loop
Use the sum of center-conductor and shield resistance over the route, plus relevant contact resistance. Voltage drop equals antenna current multiplied by that loop resistance.
Step 02
Check the antenna supply range
A radio-side voltage does not establish the voltage at the antenna. Include cable and protection-device drop and startup current where specified.
Step 03
Keep RF and DC acceptance separate
Low RF insertion loss does not establish a suitable bias path. A continuity pass does not prove acceptable GHz matching.
Specify the loss you can afford, not only the cable name
Send SigmaRF your frequency band, connector interfaces, installed length and insertion-loss target. Every assembly is VNA-swept for VSWR and insertion loss before shipment.
Specify a Custom AssemblyPropagation delay equals length divided by propagation speed. For timing systems, account for antenna and cable delay using the receiver's supported configuration and calibration method. Do not trim a cable by physical length alone and call the timing path calibrated.
A single common antenna feed has a delay shared by the path, but band-dependent delay, filters and receiver processing are not captured by one generic VF value. Precision dual-band applications may need characterized group delay over the bands rather than a ruler-based estimate.
Read SigmaRF's Does Coax Cable Length Affect GPS Accuracy for system context, Antenna Cable Loss vs Amplifier Gain for LNA placement and Cable Length in Wavelengths for delay arithmetic. This guide focuses on dual-band feed qualification.
Illustrative active-antenna gain budget: LNA gain 20 dB in each band, assumed complete feeder loss 2.0 dB at L1 and 1.6 dB at L5. Receiver limits must come from the actual receiver, not this example.
These are assumed design inputs, not SigmaRF measurements or antenna ratings. Check that 18.0/18.4 dB falls within the receiver's specified gain budget and that 3.22 V meets the antenna's supply requirement after any other drops. Neither result proves positioning accuracy.
Can the same coax carry GPS L1 and L5?
Yes if the complete assembly supports both required bands with suitable loss and matching. The antenna, filters and receiver must also support both.
Does L5 use a different cable impedance from L1?
The usual GNSS antenna feed is a 50 ohm system for both. Follow the actual hardware specification; dual band does not itself require a different impedance.
Is an L1 GPS antenna usable for L5?
Not by assumption. Its radiating element, filters and amplifier must be specified for L5 as well as L1.
Does more active-antenna gain allow unlimited cable length?
No. Cable loss, DC drop, receiver input gain limits and noise behavior still constrain the feed. Use the exact antenna and receiver specifications.
Should I include cable delay in a GPS timing setup?
When the timing application requires compensation, use the receiver's supported delay-calibration method and include the relevant antenna and feed path. Physical length alone is not a complete calibration.
What should a dual-band GNSS cable RFQ include?
List all required signal bands, loss and VSWR limits, connector interfaces, length reference, active-antenna bias needs and any timing or group-delay requirement.
Qualify the full L1/L5 chain, not only the coax label. Check band coverage, net gain, DC supply and any timing requirement independently, then confirm the completed assembly in the installed design.
SigmaRF VNA-sweeps every assembly for VSWR and insertion loss before shipment. Requirements span 100 MHz to 40 GHz through Vadodara volume and Cleveland-area precision facilities, with lead times as short as 2 days for suitable builds. Specify additional delay characterization separately when the application needs it.
Specify the loss you can afford, not only the cable name
Send SigmaRF your frequency band, connector interfaces, installed length and insertion-loss target. Every assembly is VNA-swept for VSWR and insertion loss before shipment.
Standard AssembliesCustom AssembliesTalk to an Engineer