Digital Wireless (2.4GHz) Radio Mic Antenna HOWTO
Digital radio microphones are great, but you can still get interference from other transmitters in the area. External high-gain antennas are available from the manufacturer’s but they’re very expensive for what they are. Since digital radio microphones use the same frequency band as standard WiFi, the vast range of different WiFi antennas can be used to improve reception.
I have tested this antenna with the Line 6 XD-V55 system but it should work with any digital radio mic with removable antennas that work in this frequency range. Sadly, the more affordable offerings from Shure and AKG ‘feature’ fixed antennas so I’d recommend looking at the Line 6 gear unless you’re spending thousands on a high end professional system.
Total cost: about £50 for 2 antennas, cables and mounts plus bits left over, and you get to keep the crimp tool (shiny!)
What you need
- one or more 2.4GHz WiFi antenna (I used a Liehou flat panel antenna from eBay) but you can choose whatever matches your needs
- 2-5m of RG58 coaxial cable per antenna
- BNC connectors, 50 ohm, 2 male and 1 female per antenna
- a dual mic holder bar per pair of antennas (I found a pair quite cheap on eBay) if you want to mount them on a mic stand
- tools: side cutters, knife, spanners, BNC crimp tool (again I found a cheap one on eBay)
If you’re not used to making antenna cables, it’s important to know the right impedance. This is not the same as the loss down the cable, it’s the characteristic impedance that the receiver expects to see. For 2.4GHz, all the cables and connectors must be 50 ohm, RG58 or you will get signal degradation. This is especially important with the BNC connectors as it’s not always clear when you order them. I won’t go into how to wire BNC connectors here as there’s many tutorials online, but keep cable lengths as short as possible, and you will need a crimp tool, a pair of pliers won’t do the job.
- crop off the SMA connector on the antenna and replace with a male BNC connector
- make up a BNC extension cable for each antenna using a male and female BNC; keep the lengths as short as possible but obviously make sure you can site the antenna in a convenient place above head height in your venue; I put some heat shrink over each end to make them easy to identify
- take the mic screws off the mic stand bar and replace with the universal joins that came with the antennas – I used some extra washers from my junk box and added a bit of ‘no nails’ glue to hopefully lock the threads a bit
- mount the bar on a suitable mic stand and get it up above head height and angled down a bit towards the stage or wherever the mics will be used
The universal joints supplied aren’t great – you have to tighten them with an allen key, but if you make them too tight then they tend to just loosen the other bolts into the antenna or the mic stand when you move them about. I guess a DIY solution will never be perfect.
The antennas do come with surface mounting brackets so you could fix them to the wall if you have a permanent venue. Watch out! I found the edges of the mounting dish razor sharp.
I’ve been using these one per receiver with the factory-supplied omni feeding the other input, which is handy if someone decides to wander around with the radio mic. I’m not sure of the benefit of using a pair of these feeding one receiver but I’m open to opinions.
Female BNC connectors are a bit harder to get hold of, and a bit more fiddly to wire up. You could use male plus a female-female coupler but make sure it’s 50 ohms. You do lose a bit of signal doing it that way.