Larsen NMO-K Mount Kit
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| Frequency | frequency-agnostic mount; the antenna on top decides |
| Bands | mount hardware - any NMO antenna, HF through UHF per antenna choice |
| Power | limited by the coax and antenna, not the mount; RG-58 class |
| Modes | SSB, CW, AM, FM, digital |
| Connector | NMO socket up top (1-1/8 in x 18 thread), 17 ft of RG-58A/U down, ending in a PL-259 you solder yourself |
| top | NMO (Motorola-style) socket |
| radio end | PL-259, supplied loose for post-routing soldering |
Estimated (unverified): none of note for a passive mount; thick-surface and high-frequency variants exist with their own part numbers
This is the install the radio shop would do: a drilled, clamped, permanently weatherproof NMO at the roof's center, where the ground plane is symmetric and the pattern is honest. The unterminated-coax design is the right engineering (RG-58 snakes through pillars where a connector never could), and twenty dollars buys hardware that outlasts the vehicle.
You must drill a hole in your roof - the sentence that ends most consultations - and the supplied solder-it-yourself PL-259 assumes a skill the YouTube era has made optional. RG-58's loss says keep runs short and expectations VHF/UHF; the thick-roof and low-loss variants cost extra.
For a vehicle you intend to keep, the drilled NMO mount is the correct answer and the NMO-K is its commodity form: cheap, standard, permanent. Everyone else buys magnets and accepts the compromise.
The NMO-K is the unglamorous correct answer in mobile antenna mounting: a permanent through-hole NMO mount that asks you to drill a 3/4-inch hole in your vehicle's roof and rewards you with the installation every other scheme - magnets, lip clamps, glass couplers - exists to avoid imitating badly. Center-roof mounting puts a symmetric ground plane under the antenna, the clamped-through connection survives car washes and decades, and the NMO interface on top ('New Motorola' - the 1-1/8-inch-by-18 thread Motorola standardized for 1960s fleet radios) accepts essentially every mobile VHF/UHF antenna made in North America.
The kit's design choices are installer's logic. Seventeen feet of RG-58A/U comes pre-attached to the mount but unterminated at the far end, because a bare cable end threads through headliners, pillars, and grommets where a moulded connector never could; the PL-259 is supplied loose, and soldering it after the route is the one skill the kit assumes. RG-58's loss budget at this length is honest pocket change - about 1 dB at 2 m, under 2 dB at 70 cm - and sibling part numbers in the family cover thick panel surfaces and low-loss-coax needs when they're not.
Larsen has built mobile antennas in Vancouver, Washington since 1965 (riding under the PulseLarsen banner today after Radiall and Pulse Electronics ownerships), and its own engineering catalog is the classic citation for why center-roof beats every other mounting spot, and the NMO-K pairs naturally with the brand's own whips like the NMO 2/70 dual-bander - or anyone else's: the entire point of NMO is that the usual suspects all ship NMO versions. Drill once, and the antenna question becomes a thread-on decision for the life of the vehicle.