fix(beacon): close the four gaps in the FM beacon frequency pool

[FullGas1]

Summary

• Closes The FM beacon pool is missing a third of its band (36-39.9, 46-49.9, 56-59.9, 66-69.9 MHz) — deliberate? #127. _buildFreqPools's FM loop capped its tens digit at s=0..5 instead of 0..9, leaving four gaps (36.0–39.9, 46.0–49.9, 56.0–59.9, 66.0–69.9 MHz) unreachable, including ordinary frequencies like 38.00 MHz.
• Confirmed inherited from legacy (migration/source/CTLD.lua, identical shape) and confirmed as an artefact rather than a deliberate exclusion — the legacy source carries a dead loop and a comment describing a never-implemented finer scheme right above the generator, unlike VHF's principled _ndbSkip list.
• Widens s to 0..9 for f=3..6 only; f=7 keeps s=0..5 — widening it too would silently push the pool's top past the declared 75.9 MHz ceiling to 79.9 MHz, caught during implementation by the existing test cross-checking _bands' declared min/max against the actual pool. 300 → 460 total steps, continuous 30.0–75.9 MHz.
• Updates the two tests that hard-coded the gap as expected behavior (fmMHz=38 refused) to a value still genuinely off-grid (38.05); adds a pool-size regression test and a "gap now closed" behavior test; updates the two doc rows (EN+FR) that documented the sub-ranges as real.
• Grilled with the user 2026-08-26 (.backlog/FIX-BEACON-FM-POOL-GAP/PRD.md).

Test plan

• TDD: new tests written red first (pool-size=460, gap-frequency-now-granted), confirmed failing against the old pool, then green after the fix.
• Full suite: busted --pattern=_spec --helper=tests/ci/helpers/init.lua tests/ci → 1355 passed / 0 failed / 1 pending (pre-existing, DCS-live gated).
• luac -p CTLD.lua — Lua 5.1 syntax OK (rebuilt via merge_CTLD.ps1).
• luacheck not installed locally (per CLAUDE.md, relies on CI).

Summary by Sourcery

Restore the complete FM beacon frequency pool while preserving its declared 30.0–75.9 MHz bounds.

Bug Fixes:

• Restore the missing FM beacon frequencies so the pool continuously covers 30.0–75.9 MHz at 0.1 MHz intervals, including previously unreachable frequencies such as 38.00 MHz.

Enhancements:

• Update beacon behavior tests to cover the expanded pool and retain valid off-grid refusal cases.
• Document the corrected FM frequency range and stepping in English and French API and subsystem references.

Documentation:

• Correct the documented FM beacon frequency range in the English and French developer documentation.

Tests:

• Add regression coverage for the exact 460-entry FM pool and successful allocation from a previously missing frequency.

Chores:

• Record the FM beacon pool correction in the unreleased changelog and backlog documentation.

[sourcery-ai]

Reviewer's Guide

The PR fixes the FM beacon pool’s decade-loop boundary so it now provides all 460 100 kHz steps from 30.0 through 75.9 MHz, while preserving the declared maximum. Tests cover exact pool size, successful allocation from a formerly missing range, and continued rejection of off-grid values; English/French API docs, changelog, and backlog records are updated accordingly.

Flow diagram for FM beacon frequency pool generation

flowchart TD
    A[_buildFreqPools] --> B{f = 3..7}
    B --> C{f = 7?}
    C -- Yes --> D[s = 0..5]
    C -- No --> E[s = 0..9]
    D --> F[t = 0..9]
    E --> F
    F --> G[FM pool: 460 steps from 30.0 to 75.9 MHz]

Loading

File-Level Changes

Change	Details	Files
Expand the FM beacon frequency pool to cover the full declared range without changing its endpoints or 0.1 MHz granularity.	Use s=0..9 for leading digits 3–6 and retain s=0..5 for 7 to preserve the 75.9 MHz maximum. Update the generator comment to document the intentional boundary behavior.	src/CTLD_beacon.lua
Add regression coverage for pool density and successful allocation from a previously unreachable FM gap.	Assert the pool contains exactly 460 entries. Verify 38.00 MHz is granted and assigned correctly. Replace gap-dependent refusal cases with off-grid 38.05 MHz cases.	tests/ci/unit/beacon_spec.lua tests/ci/unit/beacon_scripted_api_spec.lua
Align user-facing and project documentation with the continuous FM frequency range.	Document FM as 0.1 MHz steps across 30–75.9 MHz in English and French. Record the behavior fix and restored 300-to-460-step coverage in the changelog. Add the completed fix rationale and implementation acceptance details to backlog documentation.	docs/developer/api-reference.md docs/developer/api-reference.fr.md CHANGELOG.md .backlog/FIX-BEACON-FM-POOL-GAP/PRD.md .backlog/FIX-BEACON-FM-POOL-GAP/tickets/01-widen-fm-pool.md .backlog/README.md

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#127	Expand the FM beacon frequency pool to include every 100 kHz step from 30.0 to 75.9 MHz, eliminating the gaps at 36–39.9, 46–49.9, 56–59.9, and 66–69.9 MHz while preserving the declared upper limit.	✅
#127	Ensure previously unreachable frequencies such as 38.00 MHz can be requested successfully, while retaining rejection of frequencies that are genuinely off the 100 kHz FM grid.	✅
#127	Update documentation and regression tests to reflect the continuous FM range and prevent the gaps from being reintroduced.	✅

Possibly linked issues

• The FM beacon pool is missing a third of its band (36-39.9, 46-49.9, 56-59.9, 66-69.9 MHz) — deliberate? #127: The PR directly fixes issue The FM beacon pool is missing a third of its band (36-39.9, 46-49.9, 56-59.9, 66-69.9 MHz) — deliberate? #127 by widening FM generation, adding regression tests, and documenting continuous coverage.

---

Tips and commands

Interacting with Sourcery

• Trigger a new review: Comment @sourcery-ai review on the pull request.
• Continue discussions: Reply directly to Sourcery's review comments.
• Generate a GitHub issue from a review comment: Ask Sourcery to create an
  issue from a review comment by replying to it. You can also reply to a
  review comment with @sourcery-ai issue to create an issue from it.
• Generate a pull request title: Write @sourcery-ai anywhere in the pull
  request title to generate a title at any time. You can also comment
  @sourcery-ai title on the pull request to (re-)generate the title at any time.
• Generate a pull request summary: Write @sourcery-ai summary anywhere in
  the pull request body to generate a PR summary at any time exactly where you
  want it. You can also comment @sourcery-ai summary on the pull request to
  (re-)generate the summary at any time.
• Generate reviewer's guide: Comment @sourcery-ai guide on the pull
  request to (re-)generate the reviewer's guide at any time.
• Resolve all Sourcery comments: Comment @sourcery-ai resolve on the
  pull request to resolve all Sourcery comments. Useful if you've already
  addressed all the comments and don't want to see them anymore.
• Dismiss all Sourcery reviews: Comment @sourcery-ai dismiss on the pull
  request to dismiss all existing Sourcery reviews. Especially useful if you
  want to start fresh with a new review - don't forget to comment
  @sourcery-ai review to trigger a new review!

Customizing Your Experience

Access your dashboard to:

• Enable or disable review features such as the Sourcery-generated pull request
  summary, the reviewer's guide, and others.
• Change the review language.
• Add, remove or edit custom review instructions.
• Adjust other review settings.

Getting Help

• Contact our support team for questions or feedback.
• Visit our documentation for detailed guides and information.
• Keep in touch with the Sourcery team by following us on X/Twitter, LinkedIn or GitHub.

[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path=".backlog/README.md" line_range="17" />
<code_context>
+| [`FIX-BEACON-FM-POOL-GAP`](FIX-BEACON-FM-POOL-GAP/PRD.md) | ⬜ ready | Reported by **Zip** ([GitHub issue #127](https://github.com/VEAF/CTLD/issues/127)): the FM beacon pool (`_buildFreqPools`) caps its tens digit at `s=0..5` instead of `0..9`, missing 160 of 460 possible 100 kHz steps (four gaps: 36.0–39.9, 46.0–49.9, 56.0–59.9, 66.0–69.9 MHz), including ordinary frequencies like 38.00 MHz. Confirmed inherited from legacy (`migration/source/CTLD.lua:6171`, same `s=0..5` shape) — fixing it is a legacy-parity deviation, which the issue explicitly requests. Confirmed as an artefact, not a deliberate exclusion: the legacy source carries a comment describing a never-implemented 4-digit/0.05 MHz scheme, and a dead loop right above the FM generator that reads as an uncleaned UHF-generator copy-paste. Minimal fix: widen `s` to `0..9`, closing the gaps at the existing 0.1 MHz granularity — the finer 0.05 MHz grid the dead comment gestures at is explicitly out of scope. | `fix/beacon-fm-pool-gap` |
</code_context>
<issue_to_address>
**nitpick:** The backlog index labels `FIX-BEACON-FM-POOL-GAP` as `⬜ ready` even though its added PRD and ticket both declare the work `✅ done`, so the repository's backlog dashboard reports the wrong status.

**Suggested fix:** Change the README row status to match the completed PRD/ticket state, or leave the index at `ready` only while the ticket is actually pending.

```suggestion
| [`FIX-BEACON-FM-POOL-GAP`](FIX-BEACON-FM-POOL-GAP/PRD.md) | ✅ done | Reported by **Zip** ([GitHub issue #127](https://github.com/VEAF/CTLD/issues/127)): the FM beacon pool (`_buildFreqPools`) caps its tens digit at `s=0..5` instead of `0..9`, missing 160 of 460 possible 100 kHz steps (four gaps: 36.0–39.9, 46.0–49.9, 56.0–59.9, 66.0–69.9 MHz), including ordinary frequencies like 38.00 MHz. Confirmed inherited from legacy (`migration/source/CTLD.lua:6171`, same `s=0..5` shape) — fixing it is a legacy-parity deviation, which the issue explicitly requests. Confirmed as an artefact, not a deliberate exclusion: the legacy source carries a comment describing a never-implemented 4-digit/0.05 MHz scheme, and a dead loop right above the FM generator that reads as an uncleaned UHF-generator copy-paste. Minimal fix: widen `s` to `0..9`, closing the gaps at the existing 0.1 MHz granularity — the finer 0.05 MHz grid the dead comment gestures at is explicitly out of scope. | `fix/beacon-fm-pool-gap` |
```
</issue_to_address>

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}