Dipole Length

{
  "asOf": "2026-10-12T00:54:03.704Z",
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "eachLegFeet": 16.451,
  "eachLegMeters": 5.0141,
  "freeSpaceQuarterWaveMeters": 5.278,
  "frequencyMHz": 14.2,
  "fullWaveLoopMeters": 21.629,
  "halfWaveDipoleFeet": 32.901,
  "halfWaveDipoleMeters": 10.0283,
  "notChecked": [
    "height above ground, nearby objects and wire diameter, which shift resonance",
    "tuning with an antenna analyser (always trim in the field)",
    "…1 more"
  ],
  "quarterWaveVerticalFeet": 16.451,
  "quarterWaveVerticalMeters": 5.0141,
  "reasons": [
    "The classic 468 / f(MHz) feet rule corresponds to a velocity factor of about 0.95.",
    "Cut slightly long and trim to the lowest SWR."
  ],
  "rule468FeetOverall": 32.958,
  "source": "computed locally (standard antenna rules of thumb)",
  "summary": "At 14.2 MHz: wavelength 21.112 m; half-wave dipole about 10.028 m (32.9 ft) overall, each leg 5.014 m.",
  "velocityFactor": 0.95,
  "verdict": "COMPUTED",
  "wavelengthMeters": 21.1121
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://radio-calc.x402tookit.com/dipole-length?frequencyMHz=14.2'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://radio-calc.x402tookit.com/dipole-length?frequencyMHz=14.2' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fradio-calc.x402tookit.com%2Fdipole-length
const res = await pay("https://radio-calc.x402tookit.com/dipole-length?frequencyMHz=14.2");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://radio-calc.x402tookit.com/dipole-length?frequencyMHz=14.2")
    print(res.status_code, res.text)