Broadcast AM Block High Pass Filter

This filter was designed to eliminate broadcast band AM (BCAM) stations by attenuating (blocking) all signals below 1.7 MHz. In reality due to the roll-off the filter is usable from approximately 2.5 - 2 .6 MHz and above.
The AM broadcast band exists at approximately 525 kHz to 1,705 MHz. These signals are generally local and if you live near a transmitter they can sometimes be extremely strong. AM broadcast signals that are too strong can overload the SDR or radio, causing poor reception even in other HF bands. The filter also helps attenuate any other strong VLF/LF/MW interference. Note that this filter is a high pass and not a bandstop, so it also blocks VLF signals. Below are the specifications:

Filter Type: LC High Pass Filter
3 dB Cutoff: 2.5 - 2.6 MHz
Attenuation: ~60dB
IL Bandwidth: Typically well below 2 dB
Power Levels: RX power only, can't pass DC.

We have also uploaded a video below demonstrating reception when using an RT3-VDR3 dongle in Direct sampling mode together with the BCAM HPF. In the video we first compare reception with an upconverter (the Spyverter). It's worth nothing that the upconverter can receive signals even without the filter in place. Using the filter still helps the upconverter receive a little better, but the effect does not show up in the video. Then we simply scroll through the spectrum and listen to some signals.

This filter is designed to eliminate broadcast band AM (BCAM) stations by attenuating (blocking) any signals below 1.7 MHz. In reality due to roll-off the filter is usable from about 2.5 – 2.6 MHz and above.

The broadcast AM band exists at around 525 kHz to 1.705 MHz. These signals are usually local, and if you live close to a transmitter they can sometimes be extremely strong. Broadcast AM signals that are too strong can overload your SDR or radio, causing poor reception in other HF bands too. The filter also helps attenuate any other strong VLF/LF/MW interference. Note that this filter is a high pass and not a bandstop, so it will also block VLF signals. Specifications are shown below:

(see photo up)

We've also uploaded a video below that shows a demonstration of reception when using an RTL-SDR.com V3 dongle in direct sampling mode together with the BCAM HPF. In the video we first appear reception against an upconverter (the Spyverter). It's worth nothing that the upconverter can receive signals well even without the filter in place. Using the filter does still help the upconverter receive a little bit better but the effect is not shown in the video. Then we simply scroll through the spectrum and listen to a few signals.

Filter Type: LC High Pass Filter
3 dB Cutoff: 2.5 – 2.6 MHz
Attenuation: ~60dB
Pass band IL: Typically well below 2 dB
Power Levels: RX power only, cannot pass DC