# Automatic antenna switching circuit using RF switch

##### New Member
Hi all,
I am very new to the field of RF so excuse me if my post is not the most detailed.

I am tasked with creating a circuit which automatically switches between two antennas. In this case Antenna 1 has precedence, if it is plugged in it should be the priority, Antenna 2 is a back up and should only be switched to when Antenna 2 is not connected. Ideally the circuit should be fully analog.
Antenna 1 is connected through SMA while Antenna is connected through U.FL.
I was provided with this switch https://www.mouser.co.uk/ProductDetail/Qorvo/QPC7512TR13?qs=GedFDFLaBXGSmuRUCJmdeQ==
But I can ask for another one if it is not the most suitable.

Honestly, I have no idea where to start so any help is appreciated.
Thanks

#### JimB

##### Super Moderator
Too many unknowns and not enough information.

What equipment is connected to the switch?
Transmitters?
What frequency?
What RF power?
Why is antenna 1 removed?

JimB

##### Well-Known Member
The easiest way to do this electrically is to find a suitable mechanical switching connector. These are designed so that there are two pins (usually pcb mount) which form a pass-through RF circuit. When an external connector is mated, the connection between the two pcb pins is broken and one pin is instead connected to the external connector. The other pin is left open circuit. This latter pin would normally be routed to an internal antenna which is the default antenna when no external connector is attached.

SMA may not be the best choice for this because the switching SMAs tend to be expensive (like $15 and more) , but here are some examples: Manufacturer : Example part number or link Radiall : R124 422 001 Amphenol RF : 901-10416 (Digikey pn 115-901-10416TR-ND) Aliner : http://www.aliner.com.tw/RF_Switch.aspx Yin Sheng Technology: https://www.yinsheng-tech.com/en/product/SSA-0018-1B20Z25B0A0.html I found these above with the search keywords SMA SWITCHING CONNECTOR. I'm sure there are other manufacturers. I have not used any of these types. I have used switching connectors in pcb mount series such as those from Murata (link:https://www.murata.com/en-us/products/connector/switchconnector) but these types are meant for manufacturing test probing and not routine use. Also see Amphenol pn 902-9049 for an example of this type. Several of the larger manufacturers make switching coax connectors in various series including MCX, BNC and others. Types like MCX and SMB may be suitable for your application, however they are not SMA so they do not meet your stated requirement. Other well known manufacturers that are worth investigating (depending on where you are in the world): Hirose JAE Electronics ITT Cannon Molex Rosenberger TE connectivity/AMP Wurth Last edited: #### nadirEatsKoukies ##### New Member The easiest way to do this electrically is it find a suitable mechanical switching connector. These are designed so that there are two pins (usually pcb mount) which form a pass-through RF circuit. When an external connector is mated, the connection between the two pcb pins is broken and one pin is instead connected to the external connector. The other pin is left open circuit. This latter pin would normally be routed to an internal antenna which is the default antenna when no external connector is attached. SMA may not be the best choice for this because the switching SMAs tend to be expensive (like$15 and more) , but here are some examples:
Manufacturer : Example part number or link
Amphenol RF : 901-10416 (Digikey pn 115-901-10416TR-ND)
Aliner : http://www.aliner.com.tw/RF_Switch.aspx
Yin Sheng Technology: https://www.yinsheng-tech.com/en/product/SSA-0018-1B20Z25B0A0.html

I found these above with the search keywords SMA SWITCHING CONNECTOR. I'm sure there are other manufacturers.

I have not used any of these types. I have used switching connectors in pcb mount series such as those from Murata (link:https://www.murata.com/en-us/products/connector/switchconnector) but these types are meant for manufacturing test probing and not routine use. Also see Amphenol pn 902-9049 for an example of this type.

Several of the larger manufacturers make switching coax connectors in various series including MCX, BNC and others. Types like MCX and SMB may be suitable for your application, however they are not SMA so they do not meet your stated requirement.

Other well known manufacturers that are worth investigating (depending on where you are in the world):
Hirose
JAE Electronics
ITT Cannon
Molex
Rosenberger
TE connectivity/AMP
Wurth
That's quite helpful thanks! Shame none of those are ip-67 rated/ blkhd. Will continue to investigate.

#### Dick Cappels

##### Active Member
Go to minicircuits and look up T/R switches!