Broadcast AM Reject High Pass Filter (2.6 MHz HPF) by RTL-SDR Blog

I have a 5K AM station station close by that swamps my SDR. This little device took care of that. Knocked the signal way down and cutoff most of the other AM stations. Small, Compact, easy to install and seems to be well built. I'm happy with the results on my SDR.

For any ham or shortwave listener experimenting with Software Definable Radios (SDR), this little item is a must. Strong broadcast band signals can make a sensitive SDR essentially useless. This little filter significantly attenuates these broadcasts and enables the SDR to achieve its full dynamic range over the rest of the bands. As pointed out by the seller, this unit will attenuate the 160 meter ham band, but its -3dB cutoff of 2.6 MHz allows for good performance on 80 meters and up. Hard to beat the price! Added a network analyzer evaluation of the unit (see figure). Insertion loss ~ 0.15 dB, -3dB @ 2.7 MHz and -40dB @ 1.98 MHz. Ultimate out of band loss is on the order of 45 to 55 dB.

After having used this for a couple years now, this does work. It does let some through at times, but I believe it is due to close proximity. However, if I don't use this as well as the FM bandstop, it makes SWL almost impossible at times. I'll put these on, and the interference I get stops.

This item works very well, so far as I can see in my short tests. I have a massive AM station a couple of miles to my north, at 50KW during the day, and it splattered all over the bands, with harmonics everywhere. As long as I connect this filter *directly* to my SDR (an SDRPlay2) with the included adapter, the station is just gone, and I can hear other signals (except in the filter's blocked range) quite nicely. If I connect it via a balun or feedline, the interference is back: I'll try various shielding strategies, but as long as the shield is there after the filter, all is well. Shipped promptly, arrived in good order (had one tiny screw on the case loose, easily fixed)

RTL-SDR makes good products. This little filter keeps the pesky MW bands out of my Airspy HF+ receiver front end at lower HF frequencies. Without this filter on the lower HF bands, I needed to add 20 dB attenuation to prevent the receiver from overloading thus limiting sensitivity. With the filter I can run full gain. The added bonus is the very low through-line loss all the way to 500 MHz. As you can see on the attached plot the filter meets specs. MW is down by -40 dB, -3 dB is as specified at 2.6 MHz, -1 dB is at 4.36 MHz. Midband loss is less than 0.5 dB from 5 MHz all the way up to 500 MHz.

Seems to do its job fine, but it is not a panacea for suddenly getting clean 80m ham band signals for me like others have reported. I cannot tell a difference on that band with it in place or removed on any ham band, using a Airspy HF+ Discovery SDR and a magnetic loop antenna. So this is not a silver bullet, and may not solve your interference issues. But it does attenuate the AM band as it claims to do. May be most beneficial to proper third harmonics of AM frequencies. Also with it in place it does attenuate the 160m band as it says in the title (2.6MHz HPF, 160m band is 1.8-2.0MHz). Would be better if it had a sharper rolloff closer to the edge of the AM band like 1.4MHz so that 160m could still be used. But, it does what it says it does, and is high quality and inexpensive, so 5 stars.

I have 3-4 local 1KW+ AM stations nearby in a major metro area and this filter eliminated all of it entirely. There are some international stations but the local stations were killing my SDR front-end and I couldn't hear ZILCH. This thing is perfect for my Magloop receiver +SDR. I included two photos. The one without all the red on the far left side of the screen, is where the filter is attached. In the one with all the red to the left side, you can see how far all that noise bled into all the other bands.

I have this BCB high pass filter in series with an FM broadcast band pass filter to prevent my RTL-SDR from overloading. The FM BPF unit is a definite plus for my cheap SDR dongle, but I haven't confirmed that the AM unit helps. My discone antenna is not a great antenna for MF BCB signals either, so I'm not really presenting a challenge to the filter. It seems to have low insertion loss at VHF and UHF.

I purchased a genuine RTL-SDR dongle which worked very well right through the HF radio frequencies through VHF and up to UHF. Decent enough sensitivity but it was plagued with interference from very powerful AM broadcast transmitters which saw spurious signals appear in various parts of the radio spectrum. It was still usable but annoying. Except for the 11 metre CB bands and the 10 metre Ham band. These were completely swamped with broadcast breakthrough. So I purchased this high pass filter which blocks signals below 2 Mhz and passes signals above. This completely cured the problem and made the RTL-SDR dongle even better. Well worth adding to your SDR setup.