If you are a radio nut like me, your junk box is probably full of useful coax cable adapters. Boy, these sure come in handy.
Our world revolves around connectivity with coax cables and connectors. These are used to connect radio receivers to antennas. Our most popular cables have a nominal impedance of 50Ω or 75Ω. Each type of cable requires a connector.
You will notice that the most popular connectors are UHF (SO-239), BNC, F, and SMA. Generally, these are used on progressively smaller diameter cables and progressively higher frequencies. UHF connectors became standard during World War II and work well up to 300 MHz. BNC increases that range to 4 GHz. F-connectors are standard for cable television using 75Ω cable. And, the newer SMA reach up to 18 GHz.
So, why do we need coax cable adapters? Simple. There is no standard “one size fits all” connector. Most ham gear uses the UHF connector, so that is almost standard. But, none of my SDR receivers use these. They are either BNC, or in the case of the wideband gear, the tiny SMA.
On top of that, a lot of us use cable TV patch cords for switching or routing antennas to different radios. These use the F-connector. So, how do we make all this connectivity work?
Enter Cheap Coax Cable Adapters
Shown above is a collection of coax cable adapters. These are readily available on E-bay, Amazon or local electronics stores.
If you know much about impedance matching, you can probably guess that inserting adapters may introduce loss. That’s true. Every connector you attach to a cable may create 0.2 dB insertion loss. Typically, a coax cable adapter creates 0.5 dB insertion loss. As does a short run of 75Ω cable connected to a 50Ω input on your radio.
But for those of us focused on HF and below, these insertion losses and reduction in power transfer are trivial and don’t really make a difference. Not so at UHF and microwaves, though.
When you can live with minor losses, coax cable adapters offer huge convenience at very low cost. And besides, who really wants to solder tiny coax onto an SMA connector?