Now that I have my WiNRADiO G31 SDR up and running, my next concern is getting a decent antenna connected to it. I currently have a random length of wire connected to it, which is about 25 feet long. It’s not that high up either.
The roof of my house is higher, so it’s not ideal. It’s winter here right now, though, and I don’t have the inkling of going out in the snow to make it any better at the moment. I know, I know, the performance of any antenna is directly proportional to the severity of the weather while putting it up, but I can wait a few months.
Meanwhile, I have ordered a long-wire impedance matching transformer from Winradio. This is the WiNRADiO WR-LWA-0130 Long Wire Adapter as shown here.
Often referred to as Long Wire Balun (or an Unun), this device is used to match the impedance of a long wire HF antenna to a 50-ohm input impedance of a receiver. Such impedance matching usually results in a significant signal strength increase (up to 17 dB in some cases, and approximately 5 dB on average), compared to the long wire antenna connected directly to the antenna input of the receiver. At least that’s according to their site.
| Technical Specifications | |
| Type | Dual-transformer passive impedance adapter |
| Frequency range | 100 kHz to 30 MHz |
| Impedance ratio | 1:9 |
| Connectors | BNC (receiver side) M4 screw with winged nut (antenna side) |
| Enclosure | Diecast aluminum |
| Size | 60 x 35 x 30 mm (2.3 x 1.4 x 1.2 in) (excluding connectors) |
| Weight | 105 grams (3.8 oz) |
There are lots of different makers of these baluns and many varying prices out there – you can even build your own if you’re so inclined. Me, I liked the compactness of this one so just ordered it. I have never bothered with matching a listening antenna before now.
There are many smart people out there that say you don’t need to, and I know from my own experience that if you attach a big piece of wire to a shortwave receiver, it’ll start picking up lots of signals. Others go out of their way to match the antenna and even put up resonant antennas for listening. I have a different reason for using one.
Sometimes when the wind blows or there’s a snowstorm or even a thunderstorm many miles away, my antenna will bring some pretty high voltages into the shack. I have seen my coax spark across the connector with the electricity of many thousands of volts. Think of what that can do to the tiny circuits that are specifically made to be sensitive!
This type of balun shorts all of that, or most of it, to the ground. There is a DC connection of the antenna directly to the ground through the balun. Granted some of this energy will transfer through the transformer, but the frequencies in this type of build-up are generally very very high and will not transfer efficiently. That’s the real reason I’m using one of these baluns.
