Quick Answer
A 1.2GHz analogue video transmitter can put unwanted energy near a 2.4GHz control link through harmonics. A correctly rated low-pass filter helps, but it does not solve the bigger UK issue: Ofcom says an Amateur Radio Licence is not compatible with drone telecommand or FPV video transmission.
Why 1.2GHz and 2.4GHz Can Clash
The problem is not that a 1.2GHz video signal and 2.4GHz ELRS use the same frequency. It is the transmitter’s second harmonic. At 1200MHz, twice the fundamental frequency is 2400MHz, right where a 2.4GHz receiver is listening. A noisy VTX mounted centimetres from the control receiver can therefore reduce receiver sensitivity even while the video picture looks clean.
That arithmetic changes with the selected video channel: twice 1280MHz is 2560MHz, for example. We would not treat “1.2GHz interferes with 2.4GHz” as a universal diagnosis. Channel choice, transmitter filtering, antenna separation, cable quality and the actual receiver all matter. Test the complete RF stack at low power before increasing range.
The Holybro Atlatl HV V2 1.2GHz VTX makes the trade-off unusually clear. Holybro specifies nine channels, pit, 25mW, 200mW and 1000mW settings, a 2-8S input, 30.5mm mounting and a 9.3g board. Those options are useful in an authorised system, but more output power also raises the cost of poor RF layout.
The Filter Is Small; Its Job Is Not
Our 12LPF 1.2GHz low-pass filter is rated for under 0.7dB insertion loss at 1300MHz, more than 35dB attenuation at 2.4GHz and up to 8W. Install it between the VTX output and antenna, not at the receiver. The filter suppresses energy above the wanted video band before it reaches the transmitting antenna.
We would still separate the VTX antenna from the ELRS receiver and its antenna, keep coax runs sound, start in pit mode and perform a restrained range check. Our antenna placement guide covers the mechanical side. The filter is protection against a known RF mechanism, not permission to ignore layout.
The UK Legal Trap Most Product Pages Miss
The Readytosky 1.2G/1.3G receiver covers 1080-1360MHz and outputs PAL or NTSC composite video. Matching hardware is easy. Authorising an airborne transmitter is not.
RSGB lists 1240-1325MHz as the UK 23cm amateur allocation, with the amateur service secondary. Ofcom’s current guidance is more direct: using an Amateur Radio Licence for drone control or FPV video is not compatible with that licence. Ofcom also says airborne amateur use is allowed only in primary amateur bands, so the secondary 23cm allocation does not provide a shortcut for airborne FPV. It points longer-range operators towards the UAS Radio Operator Licence instead.
Our position is simple: do not power a 1.2GHz airborne VTX in the UK because the hardware is available or because a channel appears in an amateur band plan. Confirm the correct authorisation for the intended operation first. For authorised bench or specialist systems, browse our FPV video transmitters and receivers and use our VTX power guide to choose the lowest output that completes the link.
FAQ
Q: Will a low-pass filter stop every 1.2GHz and 2.4GHz interference problem?
A: No. It reduces out-of-band transmitter energy, but poor antenna separation, damaged coax, receiver overload and an unsuitable channel can still cause trouble.
Q: Can I fly a 1.2GHz FPV transmitter under a UK amateur licence?
A: Ofcom’s guidance says drone telecommand and FPV data transmission are not compatible with the Amateur Radio Licence. Seek the appropriate Ofcom authorisation for your operation.
Q: Can the Readytosky receiver connect to analogue goggles?
A: It provides standard PAL/NTSC composite video. It can feed goggles or a monitor that has a compatible AV input and cable pinout.