Draft — reply to Steve Koster, Washington Laboratories¶
Status: draft, not sent. Written 2026-08-12.
Send as a reply on the existing thread — emails/WL Labs Exchange.md, his 2026-08-11 reply to quote request #1.
Placeholders: none. Everything here is already established in the vault.
Why this one is allowed to be long¶
fanstel-exposure-category.md argues that a short email is what actually gets sent. This is the opposite case and the difference is worth being explicit about. Steve offered a call. He is a paid vendor who wants the work, he is a lab engineer rather than a supplier doing you a favour, and most of what is open is TCB judgement rather than rule text — which is exactly what a call is for and an email is not.
So this is an agenda, not a question list. It exists so the call is 20 productive minutes instead of 40 minutes of you explaining the product. Two items are lookups he can do in seconds beforehand, and they are placed where he will see them.
The order is by how much each answer changes, not by how easy it is to answer. Item 1 decides the architecture; item 2 has the largest dollar figure; items 4a/4b could make items 1–3 unnecessary.
One thing deliberately not done: no arguing. He corrected a real mistake and was right. Leading with what you got wrong buys more from an expert than leading with what you have since worked out.
Subject¶
Body¶
Hi Steve,
Thank you - that reply saved me from a serious mistake. I had been treating
the WM02C's certification as settled and spending my effort on the exposure
arithmetic. I had not read the grant conditions, and the 20 cm clause is not
something any arithmetic was going to fix.
Yes please to the SAR quote, and I would like to take you up on the call.
Most of what is still open looks like TCB judgement rather than rule text, so
here is what I would want to cover, roughly in order of how much each answer
changes for me.
1. Exposure category versus duty cycle. My device is a wrist-worn watch with
a BLE radio and a WiFi radio. The BLE radio has to transmit while the watch
is worn - that is the product. The WiFi radio does not: it is only needed
when the watch has been taken off, and I can enforce that in firmware from
an IR worn-sensor, so the WiFi module would never transmit while the device
is against a body. Does that change the exposure category for that radio,
or is a wrist-worn device a "portable configuration" regardless of when its
radio actually transmits? Both WiFi modules I am considering reserve
portable configurations for separate approval, so this one question decides
my architecture.
2. KDB 178919. For the WM02C, is mobile to portable genuinely a Class II
permissive change, or would a TCB treat it as a new certification? I have
seen guidance suggesting a permissive change cannot amend an application
that was represented as mobile-only with no SAR. This is the largest
unpriced number in my project.
3. Is Washington Laboratories a TCB, or a test lab? I want to know whether you
can carry a change of ID and a permissive change end to end, or whether I
need a second organisation for the filing itself.
4. Two grant lookups, if you have a moment before we speak. These could make
items 1 to 3 unnecessary, so they are worth thirty seconds each:
a. X8WBC15 - Fanstel BC15, nRF54L15. Its RF exposure exhibit says
"According to 2.1093 this is a Portable device" and shows SAR exclusion
at 5 mm separation, ratio 2.82 against 3.0. Does the grant itself carry
the portable category, and does it have a co-location condition?
b. XPYNORAB2 - u-blox NORA-B2. Their integration manual states the modules
are approved for mobile and/or portable host platforms.
If either is genuinely portable-granted, a BLE-only build - or a BLE build
with the gated WiFi in item 1 - might need no permissive change at all.
5. The complete WM02C grant. The page you sent lists rule part 15C,
2412-2462 MHz only, but grant note CC says the module is certified under
two different Part 15 sections. Is 15E / 5 GHz actually in the grant? I
declared UNII-1 and UNII-3 modes in my original quote request and I would
rather correct that now than have three labs quote the wrong scope.
6. Two things your reply raised in passing that I would like said explicitly.
Does the wrist count as an extremity, giving a 10 g threshold of 7.5 rather
than 3.0? And does BLE/WiFi coexistence arbitration count as preventing
simultaneous transmission, or do the two ratios sum?
7. Composite investigation. With two certified modules in one host, what does
testing the host with both installed add to the scope and the price?
On the quote itself, could you price two configurations rather than one?
(a) The dual-radio watch as described, including whatever permissive change
route you would recommend.
(b) A BLE-only variant, which on my arithmetic needs no SAR test at all.
I am asking for (b) because it prices my contingency, not because I am
planning to build it.
Thanks again for catching this early.
David Macpherson
What to do with the answers¶
| Answer | Consequence |
|---|---|
| 1 = yes, gating changes the category | The best available outcome. Module Alternatives.md §8.4 becomes a real architecture and FCC Respin.md §4.1 becomes a firmware requirement. Record the declared maximum in firmware_spec_v3_nrf.md §1.1 |
| 1 = no, a wrist device is portable regardless | §8.4 is dead. Every WiFi watch needs a permissive change with a SAR test, and the only doubt-free build is BLE-only (Module Alternatives.md §5.1). Re-open the 2026-08-11 "v1 ships with WiFi" decision on that basis |
| 2 = new certification, not Class II | The BM20C route's cost moves by roughly an order of magnitude. Route 3 — certifying the composite device — stops being a fallback and becomes competitive. Module Grant Conditions.md §5 |
| 3 = test lab only | You need a TCB as well. Element/PCTEST was already researched as lab candidate #2 and is both |
| 4a = portable, no co-location bar | BLK-15 is survivable without Fanstel's cooperation at all. This is the single highest-value lookup on the list |
| 5 = 5 GHz not in the grant | FCC Lab Quote Responses.md §2 is wrong and labs 2 and 3 must not go out until it is fixed. Already on ⛔ hold |
Tracked in¶
Todos.md → The WM02C's grant doesn't cover the watch · Module Grant Conditions.md §5 · Module Alternatives.md §8 · AUG-12 AUG-13 BLK-15