I have 2 different signals coming in I wanted to be able to switch between them (choose what to transmit) using a simple DPDT switch. I have the following configuration, but I feel like I'm missing something in my schematic.

  • \$\begingroup\$ The schematic shows two antennas, but your description suggests only one. Can you update the description to be clear on (1) where the signals are coming from (2) where they are going (3) how many each of source and sink you have (4) if any signals are differential \$\endgroup\$ – Ben Voigt Apr 29 '15 at 18:40
  • \$\begingroup\$ With the circuit shown you basically have two separate (but linked) on-off controls (sig 1 -> ant 1 and sig -> ant 2) \$\endgroup\$ – JIm Dearden Apr 29 '15 at 18:46
  • \$\begingroup\$ the signals are coming from an RF splitter. They're going to 2 different antennas. \$\endgroup\$ – JACK Apr 29 '15 at 18:53
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    \$\begingroup\$ I'm not sure exactly what you're getting at here. What do you want to switch between? Are you trying to switch between s1 to a1/s2 to a2 vs. both disconnected (as drawn) or s1 to a1/s2 to a2 vs. s1 to a2/s2 to a1 or something else? \$\endgroup\$ – alex.forencich Apr 29 '15 at 19:01
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    \$\begingroup\$ Hint: move Antenna 1 from B1 to B3. \$\endgroup\$ – DoxyLover Apr 29 '15 at 19:39

From your text I understand that you have two signals which you want to switch between for broadcasting. As in: Two inputs(signals)/One output(antenna). The DPDT switch you're using has two outputs. You might be looking for a SPDT switch.

Please give us more background information, like the type of signals and frequency of these signals.

As for the simple DPDT switch. You might be able to pull this off if it's a simple hobby project and the frequencies stay in the MF band or lower. For everything else, please don't do this. It probably adds a lot of parasitic capacitance and inductance to the signal path which won't help if you want a nice power transfer. RF is a delicate and very precise field where every parasitic property matters.

But there are options, there are dedicated RF switches out there and you might also find DIY schematics on the internet.

  • \$\begingroup\$ Sorry. I have two inputs and two outputs (two antennas) and I'm trying to use the switch to toggle between them. \$\endgroup\$ – JACK Apr 29 '15 at 18:51
  • \$\begingroup\$ Also if you know a good RF switch, please let me know. \$\endgroup\$ – JACK Apr 29 '15 at 18:52
  • \$\begingroup\$ And lastly, it's not MF, it's UHF. \$\endgroup\$ – JACK Apr 29 '15 at 18:56
  • \$\begingroup\$ This is still unclear, you want to choose/toggle between signals? Do you mean like: IN1->OU1, IN2->OU2 //(SWITCH)// IN1->OU2, IN2->OU1? I can't give you any information about a good RF switch, since I don't know anything about the signals you're broadcasting, the transmitter and the antenna. Even if I would know, this is still a too broad question to answer. \$\endgroup\$ – Rick van Loo Apr 29 '15 at 18:58
  • \$\begingroup\$ what i want to do is to keep one on while the other is off and vice versa. \$\endgroup\$ – JACK Apr 29 '15 at 20:23

You might want to use a transfer switch.

A transfer switch has 4 ports, which I'll call P1, P2, P3, and P4. In one state, P1 connects to P2 and P3 connects to P4. In the other state, P1 connects to P3 and P2 connects to P4.

In your situation, you'd connect source 1 to P1, source 2 to P4, antenna 1 to P2, and antenna 2 to P3. Then your two states would be

  1. S1 -> A1 and S2 -> A2

  2. S1 -> A2 and S2 -> A1

An example of a transfer switch, which might be overkill for your application, is Minicircuits MTS-18-12B+. For lower frequencies, it's also possible to construct a transfer switch from two SPDT switches.

  • \$\begingroup\$ what i want to do is to keep one on while the other is off and vice versa. \$\endgroup\$ – JACK Apr 29 '15 at 20:23
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    \$\begingroup\$ @JACK, you should edit your question to make it clear. \$\endgroup\$ – The Photon Apr 29 '15 at 20:37

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