868/900/915 MHz Notch_Tiny filter

868 / 900 / 915 MHz Notch_Tiny Filter

The Notch_Tiny is a compact RF notch filter designed for 1.2 GHz video systems used together with 868 MHz, 900 MHz or 915 MHz radio links.

If you are running a strong sub-GHz transmitter close to a 1.2 GHz video receiver, the problem is not necessarily that the transmitter is operating on the same frequency as your video. A strong nearby signal can overload the receiver's RF front end and cause video noise, interference, reduced sensitivity or even loss of video.

This is exactly what the Notch_Tiny is designed to deal with.

The filter strongly attenuates the selected 868, 900 or 915 MHz frequency while leaving the 1.2 GHz video signal almost untouched.

Strong rejection without unnecessary loss

The Notch_Tiny provides at least 38 dB of rejection at the selected notch frequency. Depending on the individual unit and tuning, rejection can reach around 40 dB or more.

At the same time, insertion loss at 1280 MHz is only around 0.2–0.3 dB.

That balance is the main point of this filter: deep rejection where it is needed, and very low loss where it matters.

So, what does 38 dB actually mean?

RF specifications are usually given in decibels, and this can be slightly misleading if you are not used to logarithmic scales.

The important thing to remember is that 10 dB is not "twice as much" as 5 dB. Every additional 10 dB represents another tenfold reduction in power.

For example:

So with 38 dB of rejection, only about 1 part in 6,300 of the unwanted RF power remains.

With 40 dB, only 1 part in 10,000 remains.

To put that into a more practical example, imagine a 1 W transmitter operating exactly at the filter's notch frequency.

After 38 dB of attenuation, the equivalent unwanted power reaching the other side of the filter is only about 0.16 mW.

At 40 dB, it is about 0.1 mW.

Of course, the actual effect in an FPV system depends on the transmitter power, antenna coupling, distance, receiver design and the exact frequencies involved. But the numbers give you an idea of just how deep a 38–40 dB notch really is.

And this is why a notch filter can make such a noticeable difference to a receiver that is being overloaded by a strong nearby transmitter.

Individually tuned and VNA tested

Every Notch_Tiny is tuned to the frequency specified when ordering.

We do not simply assemble the same filter and assume that the result will be identical every time. Each unit is measured with a Vector Network Analyzer (VNA) after tuning.

The guaranteed minimum rejection is 38 dB.

This also means that the filter can be tuned specifically for your system — whether you are using 868 MHz, 900 MHz or 915 MHz.

Very low loss at 1.2 GHz

Filtering out an unwanted signal is only half of the job. The filter should also have as little effect as possible on the signal you actually want to receive.

At 1280 MHz, insertion loss is only around 0.2–0.3 dB.

For comparison, 0.3 dB means that roughly 93% of the original signal power remains.

So the filter can provide tens of decibels of rejection at the unwanted frequency while costing only a fraction of a decibel at the desired video frequency.

That is exactly what we want from a notch filter.

Where it can help

The Notch_Tiny is particularly useful with:

• 1.2 GHz / 1280 MHz FPV video

• 868 MHz long-range RC systems

• 900 MHz radio systems

• 915 MHz RC and telemetry systems

• TBS Crossfire

• FrSky R9

• other high-power sub-GHz transmitters

The filter is installed between the video receiver and the antenna. Its job is to stop the unwanted RF energy before it reaches the receiver input.

It is especially useful when the video system works well on the bench but starts showing interference once the 868/900/915 MHz transmitter is powered up or operated at higher output power.

Small and light

The Notch_Tiny weighs only 7 g, so it can be installed in applications where weight and space are important.

It is suitable for FPV aircraft, UAVs, ground stations and compact video receivers where a full-size RF filter would simply be inconvenient.

Specifications

In short

If you have a 1.2 GHz video receiver operating next to a strong 868, 900 or 915 MHz transmitter, the Notch_Tiny gives the receiver some much-needed breathing room.

It is a very small filter, but 38 dB of guaranteed rejection is not a small number.

And because the insertion loss at 1280 MHz is only around 0.2–0.3 dB, you are not paying for that rejection with a significant loss of your desired video signal.

Small, individually tuned, VNA tested and built specifically to deal with sub-GHz interference in 1.2 GHz video systems.