TXAdvance : Radio Frequency Scanning on your Phone

TXAdvance, available on the Google Play store for Android, is an RF scanning and planning app that makes use of a USB SDR RF tuner. You can scan specific frequency bands that you plan to operate in and see any spurious RF and retune your kit to make best use of the available spectrum. With 5kHz resolution you can really zoom in on the interesting points of the spectrum and see how different radios affect the spectrum.


I'm using the app on my OnePlus 6T, and a Nooelec NESDR SMArt v5, going in through a standard USB-C to USB-A OTG cable. The tuner accepts antenna cables on SMA connector which is great as I can just screw on a standard whip antenna from one of my radio mic kits to make it super portable for location recces or adapt a cable to run it through the actual antennas I use for location work when I'm actually on site.


TAKING A VIEW

When planning your RF for radio mic channels your default tuning will be fine about 80% of the time. When it's not ok, and you have to retune your kit around other sound crew, that's the time you need this app. Being able to see exactly where that interference is coming from and being able to change your kit to work, can save you precious minutes in a pressurised environment that can be the tv production world.


TIME FOR A CLOSE UP

One of my favourite things to use this for (because I'm fascinated by RF and intermodulation) is to examine the RF output of your radios, as the various flavours interact differently to one-another. One interesting recent development in the radio mic world is the emergence and widespread adoption of digital RF. Digital RF is supposedly intermodulation free. Each transmitter has a steep roll off either side of the tuned frequency and deposits no harmonics into the spectrum. The reality is that there hare small harmonics generated but they are orders of magnitude smaller than anything created by traditional analogue RF systems. They also react quite differently to proximity to the antennas. Here are a few examples of the RF field generated by a variety of radio mic transmitters that I happened to have on hand. You can examine them and see for yourself how they affect the RF field.


Audio Ltd A10 TX - Low power - and 4 adjacent channels of them

An ultra modern, high-end digital transmitter.


Sennheiser 5212-II - Low power - and 2 adjacent channels

A last generation, but Sennheiser's flagship broadcast analogue transmitter.



Sony UWP-D TX - Low power - and 2 adjacent channels

A modern, midrange hybrid transmitter.



Sennheiser G3 IEM TX - Standard power on external omni paddle

A modern, standard level analogue rack transmitter which outputs a stereo audio modulation for IEM feeds.

Looking at this I'm not sure if my transmitter has a problem, as it seems to be generating a heavy harmonic adjacent to the primary frequency... possibly a tuning problem in the transmitter...



Sennheiser G2 Bodypack TX

An older, basic, but very popular in it's time bodypack transmitter still often used for feeding IEMs in bag work.


I'll add a note here that the transmitters were measured from different ranges on different days. for points of comparability the A10's and Sennheiser 5212's were at the same range, with a wall between them and my antenna and measured using my Lectrosonics Dipoles through my Audio Wireless DADM226 antenna distributor.

The UWP-D's and Sennheiser G3 IEM and G2 transmitters were measured from within the confines of my living room.


Here's a scan of all of my main talent transmitters all on at the same time and all cluttered together within a 2 metre space with a wall between them and my receive antenna:

You can see that the interaction of the two 5212's starts to build some small extra intermodulation peaks all the way up to nearly 610MHz. With more channels in play on a production I would probably opt to have more A10's or A20's to get that more predictable intermod, and be able to use the ultra simple frequency plan set out by Audio Ltd/Sound Devices.



As you can see it's got some serious uses, and seems to be extremely accurate. With a range of preset scan settings you can scan all of the useful radio mic frequency ranges globally, including the two ranges in the 800MHz part of the spectrum and the DME clearance bands that Wisycom kit is starting to cover.


I see this being a very helpful tool on bigger complex productions that make use of radio kit for more than just radio mics. Radio lighting controllers and camera control modules, because frequency co-ordination isn't just a sound problem any more.

48 views0 comments

Recent Posts

See All