Distill:AM Barebones - Broadcast AM Bandstop (Notch) Filter for Software Defined Radio (SDR) Applications

I recently purchased a KiwiSDR. Though I do not live in a large city, there are 3 different 5000 watt AM broadcast towers within 4 miles of my location, and a 1000 watt tower less than 1 mile east. This was causing constant ADC overloading in the Kiwi, with spurious signals across the whole range of the receiver. The filter definitely works well. All of the local stations are attenuated by at least 18 to 20 DB, and the spurious signals in the waterfall are gone. It appears to have no attenuation on a local LF NDB on 245 KHz, nor on CHU at 3.330 MHz, so the bandstop limits appear to be as advertised. It has definitely improved the performance of the Kiwi on HF. Another reviewer remarked that the antenna should be connected to the SMA jack marked “output” and the receiver connected to “input”. I tried it both ways, and it seemed to work exactly the same in either configuration. My only concern is the way it was packaged for shipment. The filter is in a small plastic bag, which placed in a non-padded envelope. It arrived with no damage, but packaging it that way could easily result in the unit getting crushed in transit. I would recommend that the item be shipped in a small box.

The filter works as expected as far as I can tell. I've added a few photos of the filters performance as measured on a nanoVNA. The nano VNA was calibrated for to 50kHz to 3MHz range prior to taking the measurements. As others have stated, 60dB of attenuation is a exaggeration. But it does attenuate signals from the AM broadcast band enough to be usable. I used the filter with an upconverter and also with a SDR receiver with direct conversion. Once the filter was put online all the aliasing from local AM broadcasts was removed. As I only looked as signals above the AM band I can't report on its effectiveness on the LF and MF bands. I am happy with the performance of the filter and would reccomend it.

Found out that the filter passes DC and can be connected from either end. Not sure if that’s ok with the DC pass? The filter is very broad 480-2000khz and does help listening in the lower hf band if near a big AM station. Not helpful below 400. Well built and recommended but you’ll need two or three in line to get full results.

Would be a little better if it came with some kind of case or enclosure but other than that works wellWould be a little better if it came with some kind of case or enclosure but other than that works well

The product works to attenuate AM broadcast interference, but by my measurements the seller is telling a lie (known or unknown) about the typical attenuation and needs to correct this. The measured attenuation on the AM broadcast band is ~25dB max and no where near ">40dB typical" as advertised. Product seems well built and would still sell, without lying about its capabilities. Seller - change your product description.

Fixed SDR overload problems from a 100mW Part 15 AM transmitter operating 24/7, located 25' from loop and monopole receive antennas. Transmitter is a Chez Radio Procaster, SDR receivers are SDRplay RSP-1 and Airspy HF+ Discovery. Minimal impact on HF DX reception and strong AM BCB signals remain receivable. Great solution! Also, unit has optimal thickness and sheerness for this use case, especially if you like tiny blue PCB boards.

Average attenuation is ONLY 25db and NOT 40db as claimed. I measured the response curve of 2 of these with Siglent SSA-3032X, HP-8591E and an HP-8712 VNA with identical results. But for $9.95 you can't expect it to work like a $50 filter. I am using this filter on my Flex 5000a to receive WSPR on the 630 meter band with

I installed a 100 ft plus Sloper for use with my RTL-SDR V3 dongle. But strong AM stations nearby overloaded the front end, making the use of direct sampling (HF) mode impossible. I purchased this filter and installed it in seconds. WOW. Now I can hear SW broadcasts, Hams, as well as MW DX (WSM, etc). It does seem to favor stations on the higher MW band. but that could be the non-resonant sloper as well. Bottom line is it worked for me by attenuating strong local AM stations that were splattering the bands and making the SDR practically deaf in HF direct sampling mode. I am interested in LF Beacons as well and will be installing a "Ham it Up" upconverter shortly and will report on the effect of the filter on the LF in the future. *** I am still receiving NDB in the LF with this filter installed, s it does not completely cut LF, but I wanted to do some in/out testing with this filter, but when I take it out, the local AM BCB'ers overwhelm my SDR and there is no LF reception period. It works!

I recently purchased 3 of these filters to use with wideband loop antennas. They work as specified; I have measured performance on a VNA. However, one of the units arrived without a shield cap on the filter module. I would appreciate a replacement or at least a shield cap I can attach myself. Thanks.

Does exactly as it says - blocks all weak medium wave broadcast signals and substantially reduces the stronger ones. This solved my issue of station imaging on the higher hf bands leaving just actual signals from those bands.

Buen producto, todo perfecto.

Tenía interferencia de una estación de AM de 640kHz en 7020kHz. Al poner el filtro la interferencia desapareció y mejoró la recepción de 40 metros.