Sunday, October 18, 2015

Beware The Dreaded RP SMA Connector

If you're getting started with software-defined radio (SDR) be prepared to find yourself needing yet another connector adapter or pigtail as you try different pieces of hardware in different combinations.

SDR dongles, SDR receivers/transmitters, antennas, cables, up/down converters, filters, preselectors can all use different connector types. Connector types include SMA, Type N, MCX, MMCX, PL-259, SO-238, BNC and on and on. Pigtails are short cables with different connector types on either end.

And they all come in male and female.

If you pay attention you'll usually be able to find the adapters or pigtails you need for a particular project without too much worry.

But beware RF SMA vs. RP SMA! Yikes, what a pain in the hindquarters. I've been playing with RF for a few years but SMA is pretty new to me so I've been burned a couple of times lately by the RF/RP incompatibility and wanted to save someone the time, money and frustration if I could.

The long and the short of it is - RF=YAY, RP=NAY. RP stands for reverse polarity and will not work with RF SMA.

Unless your hardware specifies otherwise, if the hardware uses SMA connectors you more than likely need the RF variety of SMA connector. And don't rely on the description. Look at a picture and see if there's a pin where there should be.

I'm not including more detailed explanations or photos since there are hundreds of both all over the internet. You can start with this Wikipedia article and go from there.

You have been warned.

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