Re: Homemade ADS-B in/out?
RZ, correct no TSO is required but it has to be documented that it is compliant. That’s so your Tx emissions are in band, at the correct power levels, calibrated and the data transmitted is within specs. I have included what the FAA says.
I operate an amateur built experimental aircraft. What should I install?
The ADS-B Out equipment installed in an aircraft must meet the performance requirements of the ADS-B TSOs. A TSO authorization, issued in accordance with 14 CFR 21 subpart O, is not required. However, ADS-B Out systems and equipment installed or used in type-certificated aircraft must have a design approval issued under 14 CFR 21(or must be installed by field approval, if appropriate).
The performance requirements include those requirements referenced in section 3 of the applicable TSO (UAT or 1090ES), including considerations for design assurance and environmental qualification. Deviations to the requirements can be approved for equipment which does obtain a TSO authorization, as identified in 14 CFR91.227.
For experimental category aircraft there is no FAA approval required for the ADS-B Out system installation. Owners of these aircraft may elect to install equipment authorized under a TSO, in accordance with the installation instructions provided by the manufacturer. Alternatively, owners of these aircraft may elect to purchase uncertified equipment. For uncertified equipment, the owner should obtain a statement of compliance from the supplier, along with installation instructions, that identifies that the ADS-B equipment complies with section 3 requirements of the applicable TSO and that, when installed in accordance with the installation instructions, complies with the aircraft requirements of 14 CFR 91.227. The FAA expects manufacturers to perform appropriate engineering efforts to ensure the equipment complies with all requirements of Section 3 of the TSO before issuing their statement of compliance, and expects installers to consider the guidance in the current version of AC 20-165B when performing the installation.
Owners of experimental aircraft should retain the statement of compliance from the equipment supplier in the aircraft records to assist in resolving in-service issues, should they arise. The FAA monitors compliance to the ADS-B Out requirements, and if the equipment, or an installation, is determined to be noncompliant the operator may not be able to enter the airspace designated in 14 CFR 91.225 until the equipment or installation is brought into compliance.