This note is for a radio module on your own product, with an antenna you can see and service. It is not a guide to conceal an antenna or to raise power past the grant. The buying question is whether the antenna you want is the one the module was approved with.
Start from the module’s antenna conditions
Read the module datasheet list of approved antennas, or the maximum gain in each band. If your mechanical design needs a remote antenna, the cable and the connector are part of that gain. An RP-SMA and an SMA look alike and mate badly. Write the connector, the gender, and who supplies the pigtail.
Band has to cover the channels you will use. A Wi-Fi antenna is not automatically a cellular antenna. State the bands. State the mounting: PCB trace, adhesive, or outdoor bulkhead, and the IP rating only if the antenna itself is outdoors. The enclosure rating does not transfer to a hole you cut unless the gasket is specified.
- Bands and the maximum gain the module approval allows.
- Connector type and impedance, almost always 50 ohm.
- Cable type and length, because loss is part of the link.
- Mounting and whether the antenna is inside a plastic housing.
- The module certificate reference your compliance person will file.
| Choice | RFQ line | Risk |
|---|---|---|
| Approved antenna | Maker and part number from the grant | Lowest surprise |
| Equivalent | Gain at or below the listed max, same type | You own the comparison |
| Higher gain | Do not substitute to stretch range | The approval may not cover it |
Incoming check
Confirm connector, band marking, and gain printed or stated on the datasheet you filed. A longer cable than the approved pigtail is a design change, not a warehouse convenience. Do not tune matching networks on the module unless the module maker documents that step. Keep the antenna inside the conditions of the approval you intend to ship under.
What to lock on the order
Attach the module maker’s antenna conditions to the RFQ so the purchasing agent is not choosing a gain from a catalog photo. Name the product so it is obvious the antenna is an overt part of a device you sell, mounted where a technician can see it. If the mechanical design needs the antenna off the board, specify the cable loss you can spend and the connector gender at both ends. Ask the compliance owner which antenna identities are already on the file, and buy one of those unless they have accepted a comparison. A warehouse substitute with a higher gain is not a favor. On the sample, check the connector with the mating part you will ship, and check that the cable length matches the approved pigtail. File that antenna datasheet next to the module datasheet under the same product revision.
Questions buyers actually ask
Can I pick any 2.4 GHz antenna?
Only if it stays inside the gain and type the module grant or declaration allows. A higher gain antenna is a different radiated result.
Does cable length matter?
Yes. Loss in a thin cable can erase the link you calculated, and the certification may name a maximum gain including the cable.
What should the RFQ forbid?
Do not ask for a design that hides the antenna or raises power to punch through a shield. Specify an overt antenna on a product you are building.