Radio & RF Calc
Wavelength and half-wave dipole, quarter-wave vertical and full-wave loop lengths for a frequency, with velocity factor.
OtherLiveeip155:8453Exactvia cdp
AntennaDipoleWavelengthHam-radio
Calls · 30d
1
This endpoint's own trailing-30-day call count, as published by the upstream catalog and snapshotted daily. 4 snapshots so far.
$24.31
Verified settled volume
1,175 settlements proven x402 by their on-chain EIP-3009 marker.
$0.020
Listed price
As published in the catalog. Always read the live 402 before paying.
1
Calls · 30d
Upstream's own call count for this endpoint, not ours.
1
Unique payers · 30d
Last called 2026-10-20 20:44Z
—
Upstream on-chain volume
Reported by the source catalog.
Paid to
0xb531320805C5BED1D46AEaDcF4F008FDF172DBDaThe wallet the 402 directs payment to. Its whole payment record — every payer, every chain — is on the merchant page.
Asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913
Provider
The payTo wallet does not resolve to a registered ERC-8004 agent. That is not a verdict on the service — most of the catalog is unregistered.
Live 402 challenge
Captured by the enrichment pass, not read just now. Prices can change — always read the 402 the endpoint answers with.
{
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"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"scheme": "exact",
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"description": "Wavelength and half-wave dipole, quarter-wave vertical and full-wave loop lengths for a frequency, with velocity factor.",
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"asOf": "2026-10-12T00:54:03.704Z",
"source": "computed locally (standard antenna rules of thumb)",
"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."
],
"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.",
"verdict": "COMPUTED",
"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.",
"notChecked": [
"height above ground, nearby objects and wire diameter, which shift resonance",
"tuning with an antenna analyser (always trim in the field)",
"…1 more"
],
"eachLegFeet": 16.451,
"frequencyMHz": 14.2,
"eachLegMeters": 5.0141,
"velocityFactor": 0.95,
"wavelengthMeters": 21.1121,
"fullWaveLoopMeters": 21.629,
"halfWaveDipoleFeet": 32.901,
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"halfWaveDipoleMeters": 10.0283,
"quarterWaveVerticalFeet": 16.451,
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"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."
],
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"verdict": "COMPUTED",
"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.",
"notChecked": [
"height above ground, nearby objects and wire diameter, which shift resonance",
"tuning with an antenna analyser (always trim in the field)",
"…1 more"
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"halfWaveDipoleMeters": 10.0283,
"quarterWaveVerticalFeet": 16.451,
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"freeSpaceQuarterWaveMeters": 5.278
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"outputSchema": {
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"type": "http",
"method": "GET",
"queryParams": {
"frequencyMHz": 14.2
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},
"output": {
"asOf": "2026-10-12T00:54:03.704Z",
"source": "computed locally (standard antenna rules of thumb)",
"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."
],
"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.",
"verdict": "COMPUTED",
"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.",
"notChecked": [
"height above ground, nearby objects and wire diameter, which shift resonance",
"tuning with an antenna analyser (always trim in the field)",
"…1 more"
],
"eachLegFeet": 16.451,
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"fullWaveLoopMeters": 21.629,
"halfWaveDipoleFeet": 32.901,
"rule468FeetOverall": 32.958,
"halfWaveDipoleMeters": 10.0283,
"quarterWaveVerticalFeet": 16.451,
"quarterWaveVerticalMeters": 5.0141,
"freeSpaceQuarterWaveMeters": 5.278
}
},
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}
],
"x402Version": 1,
"alsoAvailable": {
"llms": "https://radio-calc.x402tookit.com/llms.txt",
"catalog": "https://radio-calc.x402tookit.com/catalog",
"message": "Radio & RF Calc has 9 pay-per-call endpoints (Maidenhead grid squares, path loss, link budgets, Fresnel zones, antenna length, SWR, dBm conversion, Morse and phonetic spelling.), from $0.02 a call. See the full menu and send your agents our way.",
"openapi": "https://radio-calc.x402tookit.com/openapi.json",
"related": [
{
"url": "https://radio-calc.x402tookit.com/maidenhead",
"path": "/maidenhead",
"what": "Convert latitude/longitude to a Maidenhead grid locator (4, 6 or 8 characters) or a locat…",
"price": "$0.02"
},
{
"url": "https://radio-calc.x402tookit.com/morse",
"path": "/morse",
"what": "Encode text to International Morse or decode dots and dashes, with duration at your words…",
"price": "$0.02"
},
{
"url": "https://radio-calc.x402tookit.com/swr",
"path": "/swr",
"what": "SWR, reflection coefficient, return loss, mismatch loss and reflected power from SWR, a r…",
"price": "$0.02"
}
]
}
}Accepts
The payment requirements as published to the catalog. Read the live 402 before paying — a price here is a claim, not a quote.
0.02USDC≈ $0.02 USD
on Base · exact scheme
Pay 0.02 USDC on Base to 0xb531…2DBDa. The signed payment is good for 5 minutes.
- Paid to
- 0xb531…2DBDa
- USD Coin contract
- 0x8335…02913
- Payment window
- 5 minutes
- As published
- 20000 smallest units
20000units
on solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp · exact scheme
That figure is in the token’s smallest units. Roundhouse does not hold this contract’s decimals, so it is shown as published rather than converted.
- Paid to
- DUPiup…eEm8s
- Token contract
- EPjFWd…TDt1v
- Payment window
- 5 minutes
20000units
on Polygon · exact scheme
That figure is in the token’s smallest units. Roundhouse does not hold this contract’s decimals, so it is shown as published rather than converted.
- Paid to
- 0xb531…2DBDa
- Token contract
- 0x3c49…c3359
- Payment window
- 5 minutes
20000units
on Arbitrum · exact scheme
That figure is in the token’s smallest units. Roundhouse does not hold this contract’s decimals, so it is shown as published rather than converted.
- Paid to
- 0xb531…2DBDa
- Token contract
- 0xaf88…e5831
- Payment window
- 5 minutes
The catalog’s raw entry
[
{
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"version": "2"
},
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"amount": "20000",
"scheme": "exact",
"network": "eip155:8453",
"maxTimeoutSeconds": 300
},
{
"asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
"extra": {
"feePayer": "D6ZhtNQ5nT9ZnTHUbqXZsTx5MH2rPFiBBggX4hY1WePM"
},
"payTo": "DUPiupXtuox38dcGoXUKer5mAydCzmaHjrbQ66qeEm8s",
"amount": "20000",
"scheme": "exact",
"network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
"maxTimeoutSeconds": 300
},
{
"asset": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
"extra": {
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"version": "2"
},
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"amount": "20000",
"scheme": "exact",
"network": "eip155:137",
"maxTimeoutSeconds": 300
},
{
"asset": "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
"extra": {
"name": "USD Coin",
"version": "2"
},
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"amount": "20000",
"scheme": "exact",
"network": "eip155:42161",
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]Extensions
{
"bazaar": {
"info": {
"input": {
"type": "http",
"method": "GET",
"queryParams": {
"frequencyMHz": 14.2
}
},
"output": {
"type": "json",
"example": {
"asOf": "2026-10-12T00:54:03.704Z",
"source": "computed locally (standard antenna rules of thumb)",
"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."
],
"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.",
"verdict": "COMPUTED",
"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.",
"notChecked": [
"height above ground, nearby objects and wire diameter, which shift resonance",
"tuning with an antenna analyser (always trim in the field)",
"…1 more"
],
"eachLegFeet": 16.451,
"frequencyMHz": 14.2,
"eachLegMeters": 5.0141,
"velocityFactor": 0.95,
"wavelengthMeters": 21.1121,
"fullWaveLoopMeters": 21.629,
"halfWaveDipoleFeet": 32.901,
"rule468FeetOverall": 32.958,
"halfWaveDipoleMeters": 10.0283,
"quarterWaveVerticalFeet": 16.451,
"quarterWaveVerticalMeters": 5.0141,
"freeSpaceQuarterWaveMeters": 5.278
}
}
},
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"type": "object",
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"properties": {
"frequencyMHz": {
"type": "number",
"description": "Operating frequency in MHz (for example 14.2)"
},
"velocityFactor": {
"type": "number",
"description": "Velocity factor of the wire or coax, 0.5 to 1 (default 0.95 for a bare-wire antenna end effect)"
}
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"type": [
"null",
"number"
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},
"eachLegMeters": {
"type": [
"null",
"number"
]
},
"velocityFactor": {
"type": [
"null",
"number"
]
},
"wavelengthMeters": {
"type": [
"null",
"number"
]
},
"fullWaveLoopMeters": {
"type": [
"null",
"number"
]
},
"halfWaveDipoleFeet": {
"type": [
"null",
"number"
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},
"rule468FeetOverall": {
"type": [
"null",
"number"
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},
"halfWaveDipoleMeters": {
"type": [
"null",
"number"
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},
"quarterWaveVerticalFeet": {
"type": [
"null",
"number"
]
},
"quarterWaveVerticalMeters": {
"type": [
"null",
"number"
]
},
"freeSpaceQuarterWaveMeters": {
"type": [
"null",
"number"
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}
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}
}
}Provenance
- Seen in the source catalog
- 2026-10-20 20:44Z
- Last indexed by Roundhouse
- 2026-10-22 12:40Z
- Last enriched (probe, favicon, geo)
- 2026-10-20 23:15Z
- x402 version
- 2
- Max timeout
- 300s
- Liveness probe
- HTTP 402
Hand this page to an agent
Copy the prompt and paste it into Claude, an MCP client or your own agent — it will vet this service and call it over the free read API. No key, no account.
GET api.roundhouseai.io/v0/endpoints
This endpoint's own trailing-30-day call count, as published by the upstream catalog and snapshotted daily. 4 snapshots so far. Verified volume counts only settlements with an on-chain EIP-3009 marker.
Show the promptHide the prompt
Using Roundhouse, look up the x402 service Radio & RF Calc and tell me whether it is worth paying: what a call costs, whether the endpoint answered when last probed, and what its payment record actually shows. curl -s 'https://api.roundhouseai.io/v0/endpoints?q=Radio%20%26%20RF%20Calc' curl -s 'https://api.roundhouseai.io/v0/merchants/<the payTo wallet returned above>' Then call it: read the price from the live 402 at https://radio-calc.x402tookit.com/dipole-length, never from a cached figure, and pay with an x402 client. The /v0 API needs an API key (`authorization: Bearer rh_live_…`) on everything except /v0/unified* and /v0/endpoints. Either pay over x402 (mint a personal key for $0.01 at GET https://api.roundhouseai.io/v0/test/x402), or ask me for an organization key, which I create at https://roundhouseai.io/dashboard/connections. If you have neither, ask before going further. If you do not have Roundhouse tools or skills installed, read https://roundhouseai.io/skill.md first — it is the whole procedure.