Broadcast FM Block Filter (88-108 MHz Block) by RTL-SDR Blog

I live 2 miles away from (and in actual line of sight of) a 50 kW FM station, and no fewer than 2 other smaller transmitters. The 50kW station was coming in at -8 dBFS. Trying to receive P25 public safety radio with my two RTL-SDRs mostly worked, but it was clear that the front end of the SDRs was being overloaded by the FM station(s). Installing these units significantly improved the noise floor, and has helped P25 reception.

I was skeptical, but the reviews were good and the price was reasonable, so I ordered one. Am I glad I did. This tiny filter easily installed right at the Uniden Home Patrol SMA input connector and because they give you an adaptor, it easily will go right in line with your existing SMA cable. I primarily listen to the Air Band (aircraft and airports). The FM Broadcast band is very close and those stations are very powerful, which can desensitize your receiver. I am located near several FM broadcast towers (within 2 miles), and my airband reception on the scanner was always substandard. Add to that my location is in a "shadow" of a small mountain between me and SD Airport.So, I put it in line and immediately I picked up the San Diego Airport ATIS frequency which I could not hear at all before. They old rule is if you can't hear the ATIS, you can't hear the tower since they broadcast from the same spot. Needless to say, the tower now came in too along with ground control. This was an amazing improvement without having to add any amplifier to my antenna. All airborne aircraft now came in loud and clear, when before there was some hiss static. Great product, small size, very reasonable price. I will probably order another for use in my car. Reception across the board was improved in all frequencies for the scanner.

I have begun to play around with SDR, looking at various bands to see what I can get. One problem is FM broadcast. I am about a mile away from a 5kW FM station. Depending on what I am trying to pick up, that station can cause issues. No fault of the station, it is just the way radio works. This filter helps cut down the interference to a level where it ceases to be of consequence.

I have compared the RTL-SDR FM bandstop to the NESDR FM bandstop with 3 different SDRs, which are the NESDR Smartee v2, NESDR Smartee XTR, and recently the Airspy R2. I have several strong FM signals in my area and the NESDR FM bandstop could not filtered this FM signals out. The RTL-SDR FM bandstop could filter out the strong FM signals except for one signal the showed a response using SDRSharp, but you have to try both SMA connections rotated 180 degrees to find out which side is better. One side of the SMA connector for me was the same as the NESDR FM bandstop filtering capabilities with the strong FM signals. The other side flipped reduced the strong FM signals. I have read there was no difference in which end to connect to the SDR, but it does matter in my case with the RTL-SDR FM bandstop. The NESDR FM bandstop was the same with each SMA connection into my SDRs allowing in the strong FM signals above 100 MHz. Both FM bandstops worked the same below 100 MHz and are good bandstops, but someone should try both first and buy the one that works best for their area.

I have a Boafeng UV-5R series radio I was beginning to regret buying. Not that it's expensive but being new to this, I jumped in and bought a bunch of Baofeng accessories that I don't want to return. Come to find out the Boafeng's get easily overloaded on the front end and with any upgraded antenna it's been useless - cuts out or receives nothing. Based on reading and a guess, I ordered this and with a Nagoya 771 antenna it's working right out of the box! In fact, it works better with the stock antenna too. It's apparently reducing the overall SWR enough to allow the Boafeng to function. If you're having similar issues with any of the more inexpensive HAM or GMRS HT's, I recommend this filter.

Worth every penny. Great for aircraft band. Lowers noise helps sensitivity. A must if your using a broadband amp. Place between the antenna and amp.

Used this with my RTL-SDR V4 and my Baofeng UV-5RM. made absolutely no difference. This has a good amount of positive reviews, might work for you but didn’t work for me.

This worked great for blocking high power FM radio broadcasts with an RTL-SDR.