FM notch filter worthwhile?

[crucialcolin]

Got my FM Notch filter today just installed it. It doesn't really seem to make a difference in reception so far. Thought I had an issue with VHF at first monitoring the Butte County/Paradise, CA Fire but had scanner on the wrong frequency lol

 

[JamesO]

Suggest you read this thread about what I found that worked. I went though a LOT of different hardware configurations before I found this was the best option to date.

https://forums.radioreference.com/s...mp-10-off-december-other-useful-rx-items.html

I needed a 85 dB FM Trap. FM Traps are needed in many cases where people live in Urban areas and are using outside antennas, even without an LNA. If you use an LNA you NEED a FM Trap in many cases and it NEEDS to be installed in FRONT of the LNA.

Not only will you reduce the FM and adjacent frequency problems, FM Broadcast in strong levels will Intermod the LNA and/or radio.

FM Trap is almost a must unless you live in the sticks away from most FM stations. Use the FMFool site to figure out how close you are to any local FM stations as a guide as well.

 

[iMONITOR]

Looks like the RTL-SDR FM Notch filters are back in stock on Amazon. I just ordered one so it should be here on the 13th. Will be interesting to see if it makes a difference on 150/450/800 mhz bands.

I don't think it will. An FM Notch filter istypcially for 88-108MHz.

 

[iMONITOR]

It's not clear to me exactly what you're trying to accomplish. You mentioned Butte County, CA. It would appear you would have been better to purchased filters blocking possible interference from strong paging systems rather than FM broadcasts. Also you mention you do most of your listening on the 800MHz band, yet I don't see any 800MHz systems in Butte County.

 

[crucialcolin]

Oh no definently no 800 MHz band up there. It's kind of unique circumstances with that one monitoring the VHF fire command due wildfire up there. Not within my normal habits. Maybe it would have been better to state my normal monitoring habits are 85% 800 MHz band and 15% VHF high band. I have the ability to pick up 450 MHz too but I don't believe it's in use much around here.

As far as the FM notch filter installed prior to my LNA I haven't noticed much of a real world difference that you can hear on VHF or 800 MHz. Maybe in spectrum analysis. I'm thinking for me it wasn't exactly necessary but still good to have. The strongest local FM signals range from -23dBm to -50dBm according to Fmfool at my location.

 

[crucialcolin]

I had a thought before I got home gee I better check to make sure my new RTL-SDR FM Notch Filter is working with my SDR stick. Wouldn't that be something if wasn't and made me think it wasn't all that necessary for my case.

All but one station which happens to be closest to me at 4.6 miles with a 25kW transmitter at -23.3dBm is filtered out.