Which filter for airband?

[btlacer]

I'm looking for a filter for airband but not sure which one I need? I get alot of just static dead channels while my bct15x is scanning. I have turned on the attenuation and turned the squelching up but then I miss transmissions. Any insight will be appreciated.

 

[pro92b]

This might help if out of band interference is affecting the scanner.

BPF-AIR Air Band Band Pass Filter | Scanner Master

BPF-AIR Air Band Band Pass Filter

www.scannermaster.com

 

[kc2asb]

I'm looking for a filter for airband but not sure which one I need? I get alot of just static dead channels while my bct15x is scanning. I have turned on the attenuation and turned the squelching up but then I miss transmissions. Any insight will be appreciated.

I get noise and static on dead channels at my location also. The AM mode used on the aircraft band is more prone to noise and interference than FM used on other frequencies. I live in a high noise area and I ended up locking those channels out of scan and/or search. Not the best answer, of course. Hopefully the bandpass filter above will help solve your issue.

 

[Ubbe]

I'm looking for a filter for airband but not sure which one I need? I get alot of just static dead channels while my bct15x is scanning. I have turned on the attenuation and turned the squelching up but then I miss transmissions. Any insight will be appreciated.

It would probably not help using any kind of filter. In my car my FM broadcast radio receiver are generating several dead carriers in the VHF airband. Try and find the source of the dead carriers. It has to be some kind of electronic device. If you have portable scanner then tune to those frequencies and then walk around and try and find where the signal are the strongest.

If the portable scanner doesn't receive anything on the same frequencies as the BCT15 then make it do a search of the VHF airband using 5KHz steps.

/Ubbe

 

[vagrant]

That Air bandpass filter suggested above will attenuate/reduce signals not within that 112-140 MHz it notes on the label. Thus, if you mainly/only plan to monitor 112-140 MHz, it might be an option.

I use an FM broadcast band filter. Many people have FM broadcast stations nearby pushing out tens of thousands of watts that can cause interference. I monitor other signals as well, so I avoid that 112-140 MHz filter. Even if I did use it, I would still put an FM broadcast notch filter in front of it. Basically, try an FM filter first. Take a look at the URL in my signature and read through the posts.

 

[Hdc30474]

RFI is quite common on VHF airband. The BCT15X is not prone to internally generated RFI. It is probably something near the scanner. On any airband receiver I have, I will pick up something inside the house that is a strong carrier without modulation on a few frequencies. As soon as I remove the antenna or hook them up to an outside antenna it goes away. Relocating the scanner in the house may help, but usually not. Leaking CATV cable on the utility poles causes this to happen as well. So, even with an outside antenna you may still pick up something. And, the power companies transmit RF signals on the power grid for collecting all sorts of information. These days it is a harsh RFI envinronment with so many electronics inside and outside the home generating noise. I once had to throw out a USB power cube for cell phones that started sending out lots of RFI. Also the LED troffer lights in my home office did this when we moved into our new house. I had to replace them with something else.

I do not think a passband filter will help, as the scanner is probably picking up a signal being generated nearby from some other electronics within the 108 to 137 MHz band, or a harmonic of a lower frequency.

Try unplugging electronics in the house and turning off lights to maybe find the source. Could be a nearby TV, desktop computer, laptop or plug in power supply. Unplug the device. When computers and TVs are off their power supplies are usually still on. Modern switching power supplies put out a lot of RF noise. I would suggest trying an outside antenna which doesnt need to be anything fancy or expensive. Take the BCT15X outside using a 12 volt battery power source of some type to see if maybe it is coming from inside the house. But, electronics in modern cars emit a lot of RFI, so hooking it up in the car may still get you some interference.

 

[StoliRaz]

I'm looking for a filter for airband but not sure which one I need? I get alot of just static dead channels while my bct15x is scanning. I have turned on the attenuation and turned the squelching up but then I miss transmissions. Any insight will be appreciated.

Have you tried moving your scanner to a different location? Make sure other electronics nearby are off. Computers, monitors, TVs, bluetooth speakers, even lamps, etc. can all cause interference/static

RTL-SDR makes a cheap $16 FM block filter. I've used that with airband and I seem to pull in a lot more activity with it on, if you wanted to experiment.

 

[Hdc30474]

Have you tried moving your scanner to a different location? Make sure other electronics nearby are off. Computers, monitors, TVs, bluetooth speakers, even lamps, etc. can all cause interference/static

RTL-SDR makes a cheap $16 FM block filter. I've used that with airband and I seem to pull in a lot more activity with it on, if you wanted to experiment.

While blocking FM broadcast does help with many receivers on VHF airband, I have never needed one on my BCT15X. The BCT15X is a very solid performer for VHF and UHF aircraft frequecies. As we have suggested, it is likely some other nearby electronics generating the signals.

 

[Hdc30474]

I found a copy of schematics for the BCT15X online. Looking at the Switched front end filter passbands, an FM filter is probably unnecessary. One of the filters is 108-137 Mhz. Screenshot attached.

 

[prcguy]

I found a copy of schematics for the BCT15X online. Looking at the Switched front end filter passbands, an FM filter is probably unnecessary. One of the filters is 108-137 Mhz. Screenshot attached.

If you have strong FM broadcast signals nearly every scanner will benifit from an FM trap filter. The BCT15X internal 108-137 filter probably does little to nothing to keep out FM broadcast and I would be surprised if it was more than 6dB down at 100MHz. If it was really good the filter alone would be larger than the scanner and cost a couple thousand $$.

The top filter below is an example of a really good 118-136MHz VHF air band pass filter. Its got brick wall skirts, its big and its not cheap.

 

[Hdc30474]

If you are searching the 118 to 137 Mhz band, be sure to set the channel step to 25 KHz. This will help avoid interference from frequencies between channels. It also speeds up searching.

North America is only using 25 KHz channel spacing. Europe is using 8.33 KHz in several areas.

 

[Hdc30474]

If you have strong FM broadcast signals nearly every scanner will benifit from an FM trap filter. The BCT15X internal 108-137 filter probably does little to nothing to keep out FM broadcast and I would be surprised if it was more than 6dB down at 100MHz. If it was really good the filter alone would be larger than the scanner and cost a couple thousand $$.

The top filter below is an example of a really good 118-136MHz VHF air band pass filter. Its got brick wall skirts, its big and its not cheap.

I am close to probably a dozen high power FM broadcast stations and have never had any issue with the BCT15X even using an outside antenna with an amplifier at that antenna to compensate for feed line loss. One station in particular at 106.5 MHz is right on top of me. I can receive that station full scale on radios without an attached antenna.

Pretty sure his problem isnt FM broadcast related, but real in band interference from some other device.

 

[Ubbe]

Interference, overload and intermod do not produce dead carriers. External filters will then usually not help to remove dead carriers, but could improve general reception.

The internal filter in a BCT15x are several wide and almost flat bandpass filters in series and in different configurations and as it it is specified to pass down to 108MHz frequencies it doesn't do much for 88-108MHz.

/Ubbe

 

[737mech]

ParElectronics has a nice FM trap filter that I use for better VHF Air. I also have a few scanners downline of that used for only MilAir 225-400 so I installed a Par Electronics 225-400 bandpass filter. Two ways as already posted, one filter out the bad your scanner doesn’t need with a trap or notch filter and two only allow what you want with bandpass.

 

[oceans777]

I also use Dale's ParElectronics filters for FM and VHF, UHF air. (AM Broadcast band, pagers, wx)
Outstanding filters, he supplies defense contractors, NASA etc. He can also do custom filters or tune them for your needs.
Can be chained together if needed, all metal. Mine have been in frequent use over a decade.
Still try to eliminate local interfernce first and understand the issue before grabbing a fliter but yes FM is awful and an effective filter for airband.

 

[Colin9690]

Try them all and pick the one you believe works best? Assuming you’re talking about the filters built into the scanner’s menu.