Switching Antennas from a RSP2.

[Mike HModerator]

Here are the details of another little RSP2 project if people are interested…

When our house was built, the builders installed one coaxial line from the attic to the room where I use my RSP2. I wanted two stealth antennas in the attic: an array of dipoles up to 10m length and a random wire/counterpoise, and to connect these I wanted to share the coax cable. I devised this small switching box to install in the attic that selects either the dipole array or the random wire/counterpoise depending on the RSP2 bias-T button in SDR Uno. This makes antenna switching very simple and quick.

There’s nothing too critical about the project except the relay. For this I chose a RF IC production tester relay, a Teledyne 712D5 in a TO-5 can. These are very reliable and work well into the giga-Hertz region. They are DPDT so both the signal and screen connecting to the RSP2 can be switched. The ‘D’ classification for the relay indicates that it has a reverse polarity diode across the coil’s power supply to clamp any back-EMF. I used an external 1N4148 diode in addition because I am a bit paranoid about such things. These Teledyne relays are often available on eBAY and that’s where I got mine.

I can report that the configuration as described seems to work well, so it is at least a ‘proven recipe’ that has been working well for people out there with a similar need.

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[eliotmansfieldParticipant]

interesting – don’t suppose you took a photo of internals of the die-cast box?

[johnk5moParticipant]

That’s a really clever idea and a nice implementation. What kind of current does the “bias T” supply furnish?

Thanks for the idea!
John

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