remote control through coaxial cable

[neazoi]

Hello I have a small active loop outdoors antenna and I power it up fro the same coaxial signal cable (phantom power supply).
I need to find a way to also switch a relay at the antenna side using the same coaxial cable.
At the beginning I was thinking of these "memory-pulse" latch relays.
Any ideas?

 

[FvM]

You can think of switching the supply voltage level, as used for polarization switching in TV satellite LNBs.

 

[neazoi]

You can think of switching the supply voltage level, as used for polarization switching in TV satellite LNBs.

Variable voltage level will be used for tuning the loop, so this cannot be used, unless a high coil voltage relay is used, that will be activated on higher voltages only, leaving it inactive at lower voltages. Of course voltage regulation will be provided for the rest of the circuits.
What about a polarity change trick ?

 

[jiripolivka]

Then another existing solution is available for satellite receiver frequency switching: adding 22 kHz signal to the cable at the bottom end, and a detector for this signal at the antenna end. By filtering it is easy to separate the "slow" variable DC voltage for tuning and the "fast" 22 kHzfor switching.
You can also add another coaxial cable (or an optical fiber ) for more additional functions in the future.

 

[neazoi]

Then another existing solution is available for satellite receiver frequency switching: adding 22 kHz signal to the cable at the bottom end, and a detector for this signal at the antenna end. By filtering it is easy to separate the "slow" variable DC voltage for tuning and the "fast" 22 kHzfor switching.
You can also add another coaxial cable (or an optical fiber ) for more additional functions in the future.

How about some kind of digital encoder/decoder to switch the relevant relays BEFORE applying power to the preamplifier?
Can this be done? Any ideas?

 

[betwixt]

I would go with the tone method, 22KHz or any other tone. It's easy to detect on the co-ax and also easy to filter out so it doesn't disturb the tuning voltage. You could even use it to control a remote microcontroller so you can do other things at the antenna end. For ideas, do a search on "Diseqc" or look at:

Eutelsat are the designers of the Diseqc system but it has been used widely for other purposes.

I use it here for controlling a remote RF switch and also turning a steerable satellite dish along a single coaxial cable. The cable also carries the satellite downlink signals.

Brian.