While it might not seem much for the price, but when you need one and you do not have one – you feel that you want to scratch your face off. We are talking about different type of SMA antenna connectors and adapters.
First off, let me specify that there are 2 different SMA standards out there:
Standard SMA can be male of female, see the below pictures:
The RP-SMA stands for “Reversed Polarity” SMA connector, this you can mostly find on bulk Chinese RF products. Anyway the bad news is that SMA and RP-SMA do not mate with each other. See the pictures of the RP-SMA connectors below to understand why:
Now who came up with that idea? The RP-SMA male now has a hole and the RP-SMA female has a pin. Do you see now why this is all reversed? The RP-SMA male can never mate with the SMA female, and vice versa, the RP-SMA female can never mate with the SMA male. To overcome this connector standard madness – or just to create one more product which can be sold – they came up with an adapter, so the RP and the SMA can now be used together safely by using this RP-SMA to SMA adapter:
This will allow you to use products equipped with RP-SMA connectors with other products which have SMA connectors.
Now, very often you need to extend an existing antenna cable to add more length to it. Soldering additional cable is not always available – and most of the time is not an elegant solution. However we have now SMA male to SMA male adapters and SMA female to SMA female adapters with will allow extension of the antenna cables which have the same gender.
These days nobody seem to care about the following thing: please note adding any adapters or any additional length to your antenna cable increases the signal loss. This is very important, especially when you are working on the receiving side, because adding losses to your “feed line” means that good portion of the incoming signal will be potentially lost by the time it gets to your receiver. This will be more accentuated on higher frequencies, for example on 5.8Ghz the same cable will have much more loss than on 900Mhz.
You should always check it the type of the antenna cable/adapter you are using is rated or not for the frequency you will be using it for. Many cheap SMA connectors and adapters are only rated 900-2400Mhz, this means using these on 5.8Ghz will potentially loose you more than half of your signal strength! If you have signal problems and your transmitter/receiver seem to be fine always remove every single feed line and connect the antennas directly to the transmitting/receiving devices to do the first hand troubleshooting.