2020 SDR Guide EP8 : Overcoming FM Broadcast Interference with a Nooelec flamingo band stop filter

[@eonrucm]

Hello, after watching this video I ordered two Nooelec flameingo band stop filters. These are not the first FM broadcast filters I have tried but they are by far the best. I am now hearing traffic on my SDR's I have never heard before. Really enjoy your content, thanks for posting your videos!

[@FrugalRadio]

Great to hear they have worked so well for you Mark. They are definitely frugal filters that do exactly what that are supposed to! Thanks for commenting to let others know, and I hope you enjoy discovering more signals 😃

[@acestudioscouk-Ace-G0ACE]

That's a pretty stunning difference! I guess we will see a generation of SDRs where such filters are included within the main unit rather than an add on. Another clearly presented video. Thank-you!

[@FrugalRadio]

Such SDRs are already available. I'll be demonstrating 2 of them in the next video!

[@acestudioscouk-Ace-G0ACE]

@@FrugalRadio Thanks, I look forward to it.

[@MalcombMedia1]

Great Video! Do you think this one is better than the Channel Master FM filter CM3202?

[@mickhurley7305]

Looks like these are needed by default. Very intersting, are there any other filters one needs for a Nooelec SMart V5 SDR ?

[@FrugalRadio]

It really depends on the area in which you live. Some folks add cell filters if they are located close to several towers. I have also now installed a filter for 139.95 MHz which is a strong pager system only 2km (little over a mile) from home. If you live out of town, you may find you don't need a filter at all.

[@RedLine_Renesis]

I use this in combination with the RSPdx notch filter. The software notch doesn't fully block strong FM broadcasts. Great little filter.

[@FrugalRadio]

Thanks for your report Johnny!

[@Aerotower]

Hi, I've a question, I'm not living in a urban area but I have the interference from some FM station that my discone antenna pick up. Do you think that adding a FM filter like Flamingo or flamingo+ or RTL-SDR can help? I will put also an LNA near the antenna but this will increase also the FM signals, wright? What is the db losses at 118Mhz with filter?

[@FrugalRadio]

Yes, an FM Broadcast Band filter like the ones you mention will work. It is always best to place the filter right after your antenna, before your LNA. By doing so, the LNA isn't being hit by all the FM Broadcast stuff as strongly and overloading. You will lose some reception in the 118 MHz range. If you purchase a more expensive filter such as the Mini Circuits ZBFS-95+ which has sharper edges and will result in less loss in the lower airband frequencies.

[@Aerotower]

@@FrugalRadio Ok, thank you for the explanation and suggestion. I'll check the availability to put inside the same aluminum box the filter and LNA. That Mini Circuit is expensive 😅. Thank you for your videos.

[@heavenbird2258]

Hi ..thank you for your nice presentations & useful..I ask : can I build an antenna that receive hf vhf uhv by connecting dipole & yaggi antenna...also I ask about earthing ,is it so vital to do and if so how it is done..thank you

[@FrugalRadio]

Got these questions I would recommend you ask at forums.radioreference.com/forums/antennas-and-associated-hardware.203/

[@krishnakanth3004]

I have purchased RTL-SDR dongle and i am using basic dipole antenna provided along with the dongle and i have used 60cm length (each side of dipole antenna) and placed it horizontally very high at the roof I can hear approach and radar frequencies but with a lot of noise Should i buy 88-108Mhz band stop filter from RTL-SDR ? Also can you please provide tutorial on how to make antenna and feeder line( transmission line) especially for 118-137mhz ? (The place from where i listen is 10-12kms away from ATC ) Should i also use an amplifier to boost faint voices from ATC ?

[@FrugalRadio]

Band stop filters can help, for sure. Their effectiveness depends on your local RF environment. It certainly helped my reception. For an amplifier, it may help, but you would want it closer to your antenna, and after your filter. Sorry for the short answer. I'm traveling in the Arctic right now.

[@jekkodejekkis7372]

I have the rtl-sdr 88-108 bandstop filter. Does the flamingo have a better performance? Thank you

[@FrugalRadio]

Performance should be about the same on both these filters.

[@ralphthebrick]

Great example....Thanks for demonstrating

[@FrugalRadio]

You bet! So many people run into issues with FM Broadcast stations overpowering their SDRs. I know I like to see items in action before I purchase them, so figured others would too. Thanks for watching.

[@paulnortham]

I'd seen the flamingo on Amazon but had no idea what it was. You don't make the assumption that everyone is at your level, so this explanation was really helpful. Fortunately I've not run into trouble with FM interference. Is it just the power of the FM signals that does this or is there less of a gap between FM and Airband in Canada? Thanks again.

[@FrugalRadio]

Yeah, I never needed an FM trap for years. But where I'm located right now there are loads of tall screens towers. Some are pumping out FM radio signals, others TV, and others trunked radio signals. The FM broadcast transmitters throw out quite high power, and software defined radios can struggle to handle that amount of RF energy on the front end, especially closer to the FM broadcast band. With airband being just a few megahertz away, reception can suffer badly. The great thing about SDRs is you can see when this is happening. It's a lot more difficult on a scanner. Broadcast FM is generally 87.5 to 108 MHz in most countries, and airband is officially 108-118 MHz for navigational aids, and 118-137 MHz is for the analog and data. The airband is the same all over the world.

[@drmisfit]

I noticed there is no antenna in and antenna out on the end of the filter so am I correct in assuming it can be fitted either way ?

[@FrugalRadio]

You're correct, mine was the same way. I inserted mine inline and looked at the amount of signal reduction in the blocking band. Then I rotated it and checked again. Wichever end gave the best reduction was the way I inserted it. I actually don't remember which way round that was, or if both were the same.

[@drmisfit]

@@FrugalRadio thanks for getting back to me very much appreciated !

[@anbjr1958]

I would like know if this would help in NOAA weather frequencies, in the 137 band area. It seems I been getting allot of interference or Nooelec Sawbird + NOAA Premium Saw Filter. Thanks

[@FrugalRadio]

The Nooelec Sawbird + saw filter for 137 MHz will be better at keeping out interference. It works a little differently, in that instead of stopping 1 band of frequencies from passing through, it does the reverse. It stops all frequencies passing though, except the desired frequencies. "Pass band" filters like these work very well, because they can eliminate interference from most other frequencies (e.g. high power pager, cellphone or signals on other frequencies). However if you leave a pass band filter inline, and try to monitor frequencies outside the pass band (e.g. aviation, or UHF Public Safety) you won't hear anything. Since you probably have an antenna dedicated to 137 MHz, this would most likely be the better solution, although it will be more expensive than a simple band stop filter as reviewed in this video.

[@canuckchris5733]

Do you know what I love ? Canadian Amazon links in the description 👍👍🇨🇦

[@trentinrodriguez4620]

Thanks

[@FrugalRadio]

You're welcome!

[@heavenbird2258]

I had purchased Flamingo recently, I noticed that it is not that efficient...it made some attenuating of the frequencies 90 - 95 , orhers were not affected..beside that ,it is not clear where is the input or the output ?....

[@FrugalRadio]

Input and output not clear at all. It should attenuate from 88 to 108.

[@zonti]

Thanks for a great set of videos, very informative. I just wanted to let you know there is also a v2 of this Flamingo FM called the Flamingo+ FM... and guys don't make the same mistake as me and think oh v2 must just be a newer version (though it may be..). NooElec recommend the Flamingo+ FM v2 filter for urban environments and other locations with high-wattage FM transmitters nearby, and for other locations, the Flamingo FM v1 is the better option. Be careful as they look identical in the pics at Amazon ;)

[@FrugalRadio]

Thanks for your comments @zonti

[@Aerotower]

My antenna isn’t on a urban area but I’ve fm transmitter near by in 10km without obstacles between. For this case what you recommend, flamingo/rtl-sdr blog or Flamingo +? Thanks

[@fabiodametto4147]

I have a question, I want to receive weak UHF signals with an LNA, do I need to put an FM filter to prevent overloading? Does this problem disappear at all on such higher frequencies?

[@FrugalRadio]

The problem might appear at higher frequencies, it depends on how close you are to a broadcast transmitter, how much amplification you are applying, and a few other factors. I would test it first and see. If you do get interference, listen to it so you can identify it. Interference and overloading can come from other high power transmitters too - pagers for example.

[@fabiodametto4147]

@@FrugalRadio okay, thanks man, I find your video very useful for beginners like me!

[@FrugalRadio]

That's good to know @Fabio Dametto. Hopefully you won't have interference issues, but if you do, you know what kind of solution to look out for. Have a great weekend.

[@candro0713]

Hello sir thanks for these nice videos , but how about sniffing sms and mobile phone traffic with rtl sdr ??? can we do this ?

[@FrugalRadio]

Hi. This isn't something I have tried, but certainly other people have. Check out some of the articles at rtl-sdr.com and you will find more information and some videos. Eg www.rtl-sdr.com/rtl-sdr-tutorial-analyzing-gsm-with-airprobe-and-wireshark/

[@aeron-mw7ofs]

Awesome 👍

[@FrugalRadio]

Thanks!

[@aeron-mw7ofs]

@@FrugalRadio I'm considering getting 2 of these one for am/mw broadcast and one for fm broadcast . Could I run both together or will I have to disconnect them ?

[@FrugalRadio]

You should be able to run them both together, although I haven't tried this.