The “PoRG” is a very simple but useful device in your ham shack. “PoRG” is an abbreviation for “Power over RG-cable” and allows you to put DC on your antenna cable. Some people call it a phantom power supply.
With the PoRG you can:
- turn on/off a RX preamp just beneath your antenna;
- switch between two antennas to share a single coax cable;
- provide power to an active antenna (e.g. the “mini whip” which is quite popular at the moment);
- power a top light in your main antenna tower;
- etc… (use your own imagination to find more applications)
I originally built my PoRG to switch between two beverage antennas (these are receive-only antennas, used to receive weak signals on the lower HF bands). Depending on the frequency and power requirements, you want to select the right components. The PoRG shown in this article can only be used for receiving HF.
Directly attaching a DC power supply to your antenna cable is not a good idea; DC on the antenna connector of your radio might damage it. So a capacitor is put between the two connectors of the PoRG to block DC, while RF can still pass (highpass filter).
You also don’t want to insert RF into your power supply, so a lowpass filter is put between the antenna cable and the power supply.
I added two LEDs: the red LED shows that DC power is available, and the green one lights up when power is applied to the coax cable (triggered by the switch). Not because it’s very useful, but because you want to have homebrew devices with many LED’s and buttons…
The input voltage for this circuit is rated at 12-14 volts, for lower voltages you probably want to lower the value of the LED series resistors, e.g. 330 ohm for 5 volts.
Be sure to attach your radio to the correct connector! Some radios get damaged when putting DC at the antenna connector. Label the RF connectors of your PoRG so you can check you have the right connector attached to your radio, or use different connector types.