def construct_base_config(outdir, outfile_name, output_format):
    """Create a minimal working configuration file."""
    base_config = """
filing:
    outdir: %s
    outfile_name: %s
    output_format: %s
    clobber: True
    kwargs: {}
freq:
    n_freq: 50
    channel_width: 122070.3125
    start_freq: 100234567.333
time:
    n_times: 10
    integration_time: 8.59
    start_time: 2457458.174
telescope:
    array_layout: !antpos
        array_type: hex
        hex_num: 3
        sep: 14.6
        split_core: False
        outriggers: 0
    omega_p: !Beam
        datafile: HERA_H2C_BEAM_MODEL.npz
        interp_kwargs:
            interpolator: interp1d
            fill_value: extrapolate
    
""" % (outdir, outfile_name, output_format)
    return base_config[1:]