FM notch filter worthwhile?

[devicelab]

ha $300! I did not think to check eBay. I should sell mine along with my super duper Scantenna!

Yeah there's another one for $599. Yes I'm thinking about selling mine too. I just compared my RTL-SDR unit to my GPIO filter

On 97.3 FM:

Without filter is +5 to +10 dBFS
With RTL-SDR filter is -5 to -10 dBFS
With GPIO filter is -35 to -40 dBFS

 

[vagrant]

Your GPIO filter is a GPIO Labs filter? If so, I have not used any of their stuff yet.

 

[devicelab]

Your GPIO filter is a GPIO Labs filter? If so, I have not used any of their stuff yet.

Yes it is.

 

[crucialcolin]

According to what I got out of RTL is that they are having a new batch manufactured with a two week processing delay behind it due to the Holiday season in China. Once that's completed they then have to have them shipped out to the stores(possibly adding another delay) before availability.

I've looked at GPIO Labs Filters as well, which actually seem a little better in noise reduction, but with the lack of any kind of enclosure or environmental protection to it. Their stuff is just basically exposed circuit boards.

 

[devicelab]

I've looked at GPIO Labs Filters as well, which actually seem a little better in noise reduction, but with the lack of any kind of enclosure or environmental protection to it. Their stuff is just basically exposed circuit boards.

It's a passive device so it doesn't matter. I just used a piece of heat-shrink tubing around mine. You can buy an enclosure or just go cheap and wrap it in electrical tape if you wish.

 

[crucialcolin]

I suppose so.

My plan is to directly attach to my antenna via a PL-239 to SMA adapter with a filter first then my RTL LNA second and finally a SMA to F adapter output. Can see a circuit board being to flimsy for that sort of a setup.

 

[iMONITOR]

Ebay: $16.95/ea

https://www.ebay.com/itm/Broadcast-...h=item41b855853e:g:7BEAAOSwNRdX~vJ2:rk:6:pf:0

 

[Ubbe]

GPIO Labs always have good products like this 85dB $25 FM trapfilter with SMA male-females.

https://www.ebay.com/itm/FM-Notch-F...n-Bandstop-9th-order-SMA-M-SMA-F/282948298069

/Ubbe

 

[trp2525]

I use a Radio Shack #1500024 FM Trap inserted into my RG6 rooftop scanner antenna coax line just ahead of a 2-way splitter with decent results. The trap uses F connectors in and out so it hooks up easily if you are using RG6 coax with F connectors to feed your scanner(s). It's very economical and may just solve any issues you may be having with local FM broadcast stations before resorting to more expensive solutions.

If anyone is interested I have one brand-new Radio Shack #1500024 FM Trap for sale in the RR classifieds: https://www.radioreference.com/apps/classifieds/showproduct.php?product=9050&cat=18&date=1256124957

 

[SDRPlayer]

+1 for the old Radio Shack #1500024 FM Trap. Got a used one from ebay some years back and it does the job nicely.

 

[crucialcolin]

I miss radio shack (at least some of their stuff haha). Anyways I think I decided to wait it out on the RTL stock. Either that or I may wind up trying a GPIO Labs.

Also Noelec sells them now but I'm not sure about the reviews:
https://www.amazon.com/Distill-Barebones-Broadcast-Bandstop-Applications/dp/B076D354LW/
https://www.amazon.com/Flamingo-FM-Broadcast-Bandstop-Applications/dp/B079CNCR8V/

 

[SDRPlayer]

yep, some of their stuff is still worth using, having said that - most of my gear is from rtl-sdr.com as listed above. Modern, good quality and price. Surface mounted componants have made huge difference to our hobby.

 

[crucialcolin]

yep, some of their stuff is still worth using, having said that - most of my gear is from rtl-sdr.com as listed above. Modern, good quality and price. Surface mounted componants have made huge difference to our hobby.

RTL stuff definitely seems good. I'm curious if your using their LNA do you leave it powered all the time? Debating if I should concern myself unplugging my power source when my scanning equipment isn't in use.

 

[SDRPlayer]

Their lna is powered via bias-t so it is only on when i'm using the dongle.

 

[crucialcolin]

Their lna is powered via bias-t so it is only on when i'm using the dongle.

Ah yeah forgot most probably use the dongle. I have mine powered off an electroline power injector with a DC power adapter that feeds it over coax (bias-t method) so it's on 24/7. Not exactly sure how that will effect longitivity.

 

[jimvm]

FM notch filter

FLT201A FM Notch Filter, Stridsberg Engineering.

 

[Ubbe]

The picture shows that the reference level are set at -15dBm and attenuation are set to 10dB but the level outside of the filters range are -20dBm istead of -25dBm, so something isn't right with that instruments calibration.

I got that Stridsberg filter and it's way to wide. Even down at 75MHz it still attenuates 10dB and at 118Mhz it's a 20dB loss in signal.

/Ubbe

 

[devicelab]

I got that Stridsberg filter and it's way to wide. Even down at 75MHz it still attenuates 10dB and at 118Mhz it's a 20dB loss in signal.

Yeah that's pretty bad.

 

[Ubbe]

I also have the Scanner Master filter HPN-30118 which comes with different labels from different companies but they all use the same modelnumber.

/Ubbe

 

[crucialcolin]

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.