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Draft — Fanstel, the BM20C exposure category

Status: draft, not sent. Written 2026-08-12 on request. Send today, as a reply on the existing 2026-08-04 thread. Their FCC testing is open now; the whole value of this email is that it arrives before the filing closes. Placeholders: [NAME] if their reply was signed. Nothing else — this email deliberately contains no numbers you have to look up.

Why this is separate from fanstel-followup.md

There is already an eight-item draft, written 2026-08-10 and still unsent. This one exists rather than an item nine, for one reason: eight questions is why that email hasn't gone.

This is a single question with a deadline on it. It costs them one sentence to answer, it costs you nothing to send, and the answer decides whether the BLE radio in your watch is legal at all. Send this now; send the omnibus when you have the numeric blanks filled.

The two emails do not conflict. The follow-up asks for grant numbers and conditions once certification completes. This asks about the scope of the filing while it is open. After it grants, question two here is no longer free — it costs a permissive change.

Why it is shaped like this

  • No preamble about the product. One line of context, then the question.
  • It says plainly that the device is wrist-worn. That is the whole point — a vendor cannot scope a filing for a use case you haven't told them about, and being vague here is how you get a mobile-only grant and a $20k surprise.
  • The change-of-ID question is asked unconditionally, not as a consequence of question 1. (Changed 2026-08-12.) The user's read is that the BM20C will almost certainly be mobile-only: no BM-series part is portable-certified, the BC series is the wrist line and it stops at the nRF54L15, and a vendor racing to be first to market on a new Nordic part files the fastest scope available. That is a sound inference. So question 2 is the one you actually need answered, and phrasing it as a fallback to question 1 invites them to answer only the first. Question 1 stays first anyway — it is free, its window closes when the grant issues, and the payoff if the answer is yes is that questions 2 and 3 never matter.
  • Question 3 hedges toward the BC15C, which is a Fanstel part — so it reads as buying more from them rather than shopping elsewhere, and it settles the footprint-compatibility question BLK-15 has carried unanswered since 2026-08-08.
  • It does not ask when certification will finish. They already answered that as precisely as they will ("this month"), and re-asking invites the same non-answer.
  • It does not argue. You are asking a vendor to scope their own filing, not making a compliance case. The reasoning belongs in your head and in Module Grant Conditions.md, not in their inbox.

Subject

Re: BM20C - RF exposure category in your current FCC filing

Body

Hi [NAME],

One quick question while your BM20C FCC testing is still in progress, because
it affects my design and I would rather ask now than after the grant issues.

My product is a wrist-worn device, so the BM20C's antenna will be within a few
millimetres of the body in normal use. That makes it a portable device under
FCC 2.1093 rather than a mobile one.

1. Will the BM20C be certified for portable / body-worn use at less than 20 cm,
   with the RF exposure evaluation included in your filing? I ask because your
   WM02C grant (X8WWM02C) is a mobile grant with a 20 cm separation condition,
   which does not cover a wrist-worn host. I noticed your BC15 filing
   (X8WBC15) does include a 2.1093 portable evaluation, so I am hoping the
   BM20C will be scoped the same way.

2. Separately, and whatever the answer to 1: would Fanstel be willing to grant
   a Change in Identification, for the WM02C now and for the BM20C once it is
   granted? That would let me obtain my own FCC ID for the module and file any
   permissive change myself, rather than asking you to file on my behalf every
   time my host design changes. I would be glad to cover any cost involved,
   and to sign whatever you need.

3. A hedge, in case the answer to 1 is that the BM20C will be mobile only. Is
   the BC15C footprint-compatible with the BM20C, and is it in stock? I would
   rather know now whether a board can take either part than find out after I
   have committed the layout.

Happy to share my host design details if that helps you scope any of it.

Thanks,
David Macpherson

What to do with the answers

Answer What it means Next step
1 = portable, with RF exposure The best outcome available. The BLE radio is authorised for the wrist by exclusion, and BLK-15 reduces to a schedule risk Get the grant number and conditions (fanstel-followup.md items 2–3). Re-run the exclusion at their declared power and gain — including antenna gain, per FCC Certification.md §5's 2026-08-12 correction
1 = mobile only, 2 = yes The expected outcome, and workable Start your FCC Grantee Code application immediately — it has lead time and gates everything (Module Grant Conditions.md §5.1). Get the CoID letter in writing
1 = mobile only, 2 = no The bad case, and not fatal Route 3 — certify the finished watch as its own intentional radiator (Module Grant Conditions.md §5). More expensive, no vendor dependency. Also re-weigh route 4, BLE-only on a portable-granted part
1 = mobile only, 3 = BC15C is compatible and in stock The Module Alternatives.md §8.4 architecture becomes buildable on parts you can order, and BLK-15 stops depending on Fanstel's filing at all Still gated on Steve's answer to the wornness question before any of it is designed
No reply within ~4 days Their filing closes without your question in it Phone. This is the one item where a call beats a follow-up email, and the window is days not weeks

Whatever comes back, do not wait for it to start the grantee code. It is cheap, it has lead time, and it is useful under every branch above except the first.

Tracked in

Todos.md → The WM02C's grant doesn't cover the watch · Module Grant Conditions.md §5, §6 · BLK-15