VHF (Not UHF) Specific Filter for Aircraft Monitoring

iMONITOR

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Most of us are familiar with the FM-Notch filters for VHF aircraft band monitoring that blocks out interference from strong FM broadcast stations. I found a new filter that does that and more! If you have an antenna/scanner/receiver that is dedicated to VHF aircraft monitoring check this out.

PAR VHFBP Aero Band Pass Filter

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The Par VHFBP is a special bandpass filter designed for the VHF aero band listener. It passes the VHF civil aeronautical band 116 to 134 MHz and blocks other frequencies. Unlike other aerocom bandpass filters, the VHF-BP not only provides protection from VHF pagers, NOAA, 2 meter amateur signals etc., but also offers excellent attenuation of the FM broadcast band - the primary offender of aerocom signals. BNC female input and BNC male output.
 

radio3353

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Most of us are familiar with the FM-Notch filters for VHF aircraft band monitoring that blocks out interference from strong FM broadcast stations. I found a new filter that does that and more! If you have an antenna/scanner/receiver that is dedicated to VHF aircraft monitoring check this out.

PAR VHFBP Aero Band Pass Filter

View attachment 88579

The Par VHFBP is a special bandpass filter designed for the VHF aero band listener. It passes the VHF civil aeronautical band 116 to 134 MHz and blocks other frequencies. Unlike other aerocom bandpass filters, the VHF-BP not only provides protection from VHF pagers, NOAA, 2 meter amateur signals etc., but also offers excellent attenuation of the FM broadcast band - the primary offender of aerocom signals. BNC female input and BNC male output.
What are the three adjustment screws for since they are not marked in any way?
 

MDScanFan

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Depending on the circumstances it may be a good option. However, it has 1.5-2 dB of IL in the airband. And the rejection at the upper end of the FM BCB is only 20 dB, which may not be enough in some cases. If FM is the main culprit, then there are better options that have less pass band loss and more rejection.
 

iMONITOR

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What are the three adjustment screws for since they are not marked in any way?
They are used to adjust the blocked frequencies using specialized equipment during manufacturing. They are adjustable for special custom settings or by the end user if they have the proper know-how and equipment to do so. They aren't marked because to be done properly you need the appropriate test gear to do so.
 

ATCTech

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Looking briefly at the band pass diagram and the references to both 132 and 134 MHz I'd be very wary of that filter attenuating the top end of the band, especially for anyone interested in VDL decoding above 136 MHz. It looks like it might be down 4-6 dB at that point.
 

iMONITOR

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Looking briefly at the band pass diagram and the references to both 132 and 134 MHz I'd be very wary of that filter attenuating the top end of the band, especially for anyone interested in VDL decoding above 136 MHz. It looks like it might be down 4-6 dB at that point.
Contact Dale Parfitt, President at PAR Electronics he will custom tune it to your specs or design you a custom one.

PAR Electronics, Inc.
P.O Box 645
Glenville, NC 28736
Voice: 828-743-1338
Fax: 866-304-8479
 

majoco

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Unless you have a tracking generator and spectrum analyser then I'd leave well alone! :)

especially for anyone interested in VDL decoding above 136 MHz. It looks like it might be down 4-6 dB at that point.
That's why it says on the box "116 - 132 MHz"
 

nr2d

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Those screws are most likely are used for tuning by the manufacturer. Looking at the specs as shown above they could move the lower end cut off frequency up to 118 MHz and the top cut off to 137 MHz. From what I've seen at work 1.5 to 2.0 dB insertion loss isn't really that bad. I had a custom bandpass filter made for the L1, L2 and L5 GPS band and it had 1.5 dB insertions loss and < 1.5 VSWR across the bandpass and it cost $1100 each which was cheap. I had quotes for up to $10k from other filter companies.
 
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prcguy

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If you move the low end up to 118MHz the top end will probably go to 134Mhz with similar specs. Try and stretch it further and you will have to give up more insertion loss, etc.

Those screws are most likely are used for tuning by the manufacturer. Looking at the specs as shown above they could move the lower end cut off frequency up to 118 MHz and the top cut off to 137 MHz. From what I've seen at work 1.5 to 2.0 dB insertion loss isn't really that bad. I had a custom bandpass filter made for the L1, L2 and L5 GPS band and it had 1.5 dB insertions loss and < 1.5 VSWR across the bandpass and it cost $1100 each which was cheap. I had quotes for up to $10k from other filter companies.
 

spanky15805

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Was kinduv disappointed nobody had a link to a video using a 2947 to tune this type of filter or a two stage circulator. ;)
 

iMONITOR

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The PAR VHFBP Aero Band Pass Filter has been installed on my BCT15X for a couple months now. I don't have any formal/technical way to test it buy it definitely appears to be making a difference. Air traffic reception has increased significantly and appears to have less noise associated with it.
 

MDScanFan

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Can you please provide more details on your setup? Antenna type, antenna installation location, length of coax run, where did you place the filter, are you using a preamp, etc. Thanks.

The PAR VHFBP Aero Band Pass Filter has been installed on my BCT15X for a couple months now. I don't have any formal/technical way to test it buy it definitely appears to be making a difference. Air traffic reception has increased significantly and appears to have less noise associated with it.
 

iMONITOR

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Can you please provide more details on your setup? Antenna type, antenna installation location, length of coax run, where did you place the filter, are you using a preamp, etc. Thanks.
I've been trying different setups. I've been unable to install any outdoor antennas this year so for now everything has been indoors. Originally I had a mag-mount on a 4 drawer steel file cabinet inside my home office. I mounted the filter on top of the mag-mount and various antennas on top of the filter. Most recently has been a GRE dual-band 144 MHz/70 cm antenna. No preamp. For the last few days I've been trying a DPD Productions VHF Blade Antenna mounted on an outside wall of my office. With this antenna the filter is mounted directly on the back of my scanner with an 18' RG8 coax to the antenna. This antenna along with the filter is performing better than anything I've tried over the last few years. I monitor Selfridge Air National Guard Base as well as in-the-air aircraft, primarily on VHF, no UHF at this time. I also receive an extensive list of commercial & private aircraft in addition the the VHF traffic from military aircraft.
 
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