915 MHz ISM Antenna Calculator

915 MHz is a common sub-GHz ISM band for LoRa, sub-GHz RF links, and proprietary radios in the Americas. This page is a topology-comparison page, not a single application — it walks through PCB Monopole (λ/4), Meander Line, and Helical/Coil in detail. They are not the only options: 915 MHz appears in the `suitableFrequencies` list of 9 of the tool's styles — Inverted-F (IFA), Meander Line, Helical/Coil, Chip Antenna, PCB Monopole (λ/4), PCB Dipole (λ/2), Small Loop, Microstrip Patch, Meandered Inverted-F (MIFA) — and the calculator will synthesize any of them at this frequency. The three below are the ones this page compares.

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What it does

Three engine-backed topologies at 915 MHz, each with its own reported gain range: PCB Monopole (λ/4) (0 to 2 dBi), Meander Line (-3 to 1 dBi), and Helical/Coil (0 to 5 dBi) — the widest and generally highest range of the three, at the cost of a larger wound-wire footprint.

How the model works

There is no `?application=` boundary for a bare frequency or style choice in this tool today — App.tsx's URL prefill accepts only an application id (BLE/Wi-Fi/Zigbee/Thread/LoRa), never a topology or frequency directly — so the CTA below opens the plain calculator rather than a fabricated deep link this app cannot actually honor. Set the frequency to 915 MHz and pick a topology once inside.

Limitations

All three topologies are counterpoise-class styles, so finite-ground feed behavior is disclosed the same way for each: Finite-ground detuning of the feed impedance: not calculated by this analytical model (feed model assumes a counterpoise ≥ λ0/4). The helical option additionally does not calculate electrical length the way the other two do: Electrical length: not calculated by this analytical model (a normal-mode helix resonates by turns/diameter/pitch self-inductance and self-capacitance, not by wound-wire length — requires measurement or EM simulation).

Frequently asked questions

Which antenna topologies work at 915 MHz in this tool?

All 9 styles whose suitable-frequency list includes 915 MHz: Inverted-F (IFA), Meander Line, Helical/Coil, Chip Antenna, PCB Monopole (λ/4), PCB Dipole (λ/2), Small Loop, Microstrip Patch, Meandered Inverted-F (MIFA). This page compares three of them in detail — PCB Monopole (λ/4), Meander Line, and Helical/Coil.

Which topology has the highest gain at 915 MHz?

Helical/Coil, with a reported 0 to 5 dBi range — the widest of the three, though it needs the largest footprint.

Does opening the tool from this page prefill 915 MHz automatically?

No — there is no URL boundary for a bare frequency or topology in this app today, only for the five application ids. Set the frequency and pick a topology once inside the calculator.

Is the feed impedance for these topologies measured?

No. Finite-ground detuning of the feed impedance: not calculated by this analytical model (feed model assumes a counterpoise ≥ λ0/4).

Other antenna calculators

Landed on the wrong application or antenna type? These use the same synthesis engine.