RTL-SDR.com Broadcast AM Block High Pass Filter Now for Sale

Back in October we released a broadcast FM bandstop filter for removing strong signals in the 88 – 108 MHz region. Today we’re releasing a new broadcast AM high pass filter (BCAM HPF) with a 2.6 MHz cutoff. The cost is the same as the BCFM bandstop filter at $14.95 USD including free international air shipping. Faster shipping options may also be chosen if desired. We’ll eventually have this product on Amazon USA in a few months too, but for now it is only available from our Chinese warehouse.

The filter comes in a 2.8 cm x 2.8 cm x 1.3 cm aluminum enclosure and uses female SMA connectors on each end. Included in the package is also a SMA male to SMA male straight barrel adapter.

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The Broadcast AM High Pass Filter
The Broadcast AM High Pass Filter

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:

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

Insertion Losses

Insertion Losses

Insertion Losses

Insertion Losses

Return Loss

Return Loss

V3 Direct Sampling no Filter

V3 Direct Sampling no Filter

V3 Direct Sampling with BCAM HPF

V3 Direct Sampling with BCAM HPF

BCAM_Filter_PCB3

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 compare 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.

21 comments

  1. Enrique Martin Scheuer

    I am working already for 4 months with FM RTL-SDR NO STOP Filter ALSO on TX up to 20 W with no heating or efficiency losses;
    I have now purchased the AM Pass Band Filter to make the same tests; I have 18 FM and AM High Power towers in 2 miles radius. I will later report 73 Enrique PU2PSP

  2. Dennis

    GM!
    Injected noise and measured average output of filter, terminated to 50Ohm resistive load.

    -7MHz abt 5dB loss compared to terminated output of generator,
    -14MHz abt 6dB loss,
    -21MHz abt 9dB loss and
    -28MHz abt 10dB loss.

    Source used was a Rigol AWG and measurement device a PicoScope digital oscilloscope.
    Any comments?

    73 de SV1CDN, Dennis!

  3. Brian

    I have an SDRPlay RSP2 which is very badly affected by a 5,000 watt AM broadcast station, only 2 miles from me, which kills shortwave reception with images and spurs. I highly recommend this video which demonstrates the amazing effectiveness of the FM filter, and the second half of the same video, which demonstrates the excellent effectiveness of the AM filter.

    Well done — I just ordered one!!

    • admin

      Thanks! The RSP2 has problems with overloading due to the silicon switches used on the front end. If the signal is extremely powerful those switches overload, making the internal bandstop AM and FM filters work poorly. So an external filter like this can definitely help in that case.

      • Brian

        Received the filter in about 10 days from China. Looks great. Very high quality. Absolutely killed the spurs/intermod from AM broadcast and both of the 5 kilowatt AM stations about 2 miles from me. The SDRplay RSP2 is like a new radio with the filter. No effect on FM broadcast, or SW broadcast bands, which is good, and no effect on the AIR, WX band, or 453 mHz police band. HIGHLY recommended!

        Brian

  4. AnonDX

    I have an active RX antenna with a power feeder unit. How do you install this filter? Is it installed between antenna and power feeder? Or is it installed between power feeder and receiver?

    • admin

      This HPF does not pass DC, so you’d need to install it between the antenna and powered LNA, or if that’s not possible because the amp is built into the antenna, then between the bias tee and radio.

  5. Anonymous

    What’s the insertion loss at higher frequencies? (10’s of MHz through GHz) Can you leave it in place without taking a major performance hit at higher frequencies?

    • admin

      A BCAM HPF probably won’t function well at higher frequencies as the SRF of the large inductors required doesn’t go much higher than the HF bands.

      Update: Tested on the VNA, biggest loss is between 500 – 700 MHz, here it goes over 3dB loss, with the max at about 7dB @ 600 Mhz. Pretty much everywhere else on VHF/UHF is below 2.2 dB loss, so not too bad.

  6. Dan

    Do you plan to make the full FM (62-74MHz OIRT, 76-100-108MHz CCIR) bandstop reject filter? In some countries are broadcast in both standards not only one, hope you make it someday!

  7. gnar :3

    have you guys ever thought of making like a switchable filterbank consisting of several LP&HP filters (for HF/SWL, could also be used for IF), or something like a combined bandstop filter for BCFM&Airband ATIS (130MHz HPF) and TETRA (for VHF/UHF)?

  8. Nicolas

    Thnak you for this new product.
    I ordered one to blcok a strong AM broadcast near my home.
    I already own the FM filter that gives good result too.
    Like RF boy, now I’m waiting for the DAB 174–240 MHz band filter.

    • admin

      If we do make one we’ll need a few beta testers in Europe for it, so email us at rtlsdrblog_AT_gmail_DOT_com, and we’ll put you down on a beta tester list.

  9. toronto

    Thank you for all your work in this hobby. Your site, information and products are fantastic. I have been looking for an AM filter and here it is. Amazing price also. Thank you.

    • admin

      If we do make one we’ll need a few beta testers in Europe for it, so email us at rtlsdrblog_AT_gmail_DOT_com, and we’ll put you down on a beta tester list.

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