Update: Mini Circuits ZBFS-95+

[kd8mkg]

In reference to my previous post: Looking for input on antenna placement options... I promised to provide an update when my Mini Circuits ZBSF-95+ FM Notch Filter arrived.

First of all, this thing is beautifully made and built like a tank. The enclosure is machined aluminum. Very nice looking piece of kit. Also, I ordered it on Friday afternoon and it arrived today. Nice. I didn't expect it until at least mid-this week.



But more importantly, how does it perform? Well, everything is coming in better across the civilian air band. The lower range, where most of the local frequencies of note are located (118-120MHz), is noticeably better compared to the RTL-SDR FM Filter I was using. This isn't surprising, as the RTL-SDR is down -14dB at 118MHz... that's so bad. In contrast, the ZCSF-95+ is only down -2.9dB @ 118MHz; an enormous improvement.



This has drastically improved the reception of KDAY's Approach/Departure and Tower frequencies. Ground, as one might expect, is still pretty scratchy.,, it is 17 miles away after all. Unfortunately, though, the Brookville RCAG site for Indy Center still isn't where I'd like it to be. I can hear it, I can copy it, but just barely. The next step is the DPD Miltenna in the attic, but I really doubt if that will be a huge improvement over my Arrow 144/440 J-pole. I hope so, but if not, outside it is!

 

[Ubbe]

J-pole antennas are narrow banded so any other antenna type will be an improvement.

/Ubbe

 

[rabrol]

$87USD least expensive shipping option to me in Canada. On a $114USD item. Crazy.
Guess I'll have to wait until me next visit to the US and have it shipped there.

 

[prcguy]

Great review, thanks! Imagine locating the MiniCircuits notch filter along with a VHF air band pass filter in front of a low noise high level preamp at the base of the antenna. This would lower the overall system noise figure and more than make up for feedline loss. The components would look something like these, although you may not need the notch filter with this band pass filter.

In reference to my previous post: Looking for input on antenna placement options... I promised to provide an update when my Mini Circuits ZBSF-95+ FM Notch Filter arrived.

First of all, this thing is beautifully made and built like a tank. The enclosure is machined aluminum. Very nice looking piece of kit. Also, I ordered it on Friday afternoon and it arrived today. Nice. I didn't expect it until at least mid-this week.

View attachment 130290

But more importantly, how does it perform? Well, everything is coming in better across the civilian air band. The lower range, where most of the local frequencies of note are located (118-120MHz), is noticeably better compared to the RTL-SDR FM Filter I was using. This isn't surprising, as the RTL-SDR is down -14dB at 118MHz... that's so bad. In contrast, the ZCSF-95+ is only down -2.9dB @ 118MHz; an enormous improvement.

View attachment 130291

This has drastically improved the reception of KDAY's Approach/Departure and Tower frequencies. Ground, as one might expect, is still pretty scratchy.,, it is 17 miles away after all. Unfortunately, though, the Brookville RCAG site for Indy Center still isn't where I'd like it to be. I can hear it, I can copy it, but just barely. The next step is the DPD Miltenna in the attic, but I really doubt if that will be a huge improvement over my Arrow 144/440 J-pole. I hope so, but if not, outside it is!

 

[737mech]

What scanners are you using?

 

[Ubbe]

$87USD least expensive shipping option to me in Canada. On a $114USD item. Crazy.
Guess I'll have to wait until me next visit to the US and have it shipped there.

Maybe you do not need all that attenuation depending of how close the broadcast transmitters are. If you only need som 1000 times attenuation you could probably use a HPN-30118 filter. If you have no strong transmitters at the edges at 88MHz and 108MHz you can use a $20 filter. FM Notch Filter 88-108 MHz band Excellent Rejection -97dBm RTL SDR FM trap | eBay

FM bandstop filter comparison

I rolled some numbers on the RTL-SDR FM bandstop filter and the HPN-30118 AM/FM filter using a VNA. The results are interesting compared to the ZBSF-95+, especially when you hit VHF Air voice at 118 - 137 MHz. The ZBSF-95+ numbers come from their spec PDF as I do not own that yet. There are...

forums.radioreference.com

/Ubbe

 

[kd8mkg]

What scanners are you using?

BCT-15x

Maybe you do not need all that attenuation depending of how close the broadcast transmitters are.[/URL]

/Ubbe

I certainly do, but others may not. I'm about 2.8 miles from a 30kW firehose at 107.7MHz.

 

[kd8mkg]

Great review, thanks! Imagine locating the MiniCircuits notch filter along with a VHF air band pass filter in front of a low noise high level preamp at the base of the antenna. This would lower the overall system noise figure and more than make up for feedline loss. The components would look something like these, although you may not need the notch filter with this band pass filter.

Since I'm also interested in milair, and located within shouting distance of Wright-Patt, as well as being in an area with fairly regular air national guard activity, the bandpass doesn't work for my use case. I am planning to insert a Stridsbergeng PRE-20 at the antenna. The better notch definitely improved reception, but KFFO tower, as well as KDAY tower/ground are still pretty weak.

 

[skywarrior]

Hi, KD8,
Where did you locate the source for the mini circuits ZCSF-95+?
TIA

 

[kd8mkg]

Hi, KD8,
Where did you locate the source for the mini circuits ZCSF-95+?
TIA

I purchased directly from Mini Circuits, specifically, the N-type connectorized version, here: Connectorized Band Stop Filter, 88-105 MHz | ZBSF-95-N+ | Mini-Circuits

Shipped out same day, received 2 business days later.

 

[prcguy]

If you want mil air you can do the same thing in UHF like this:



Or you can combine VHF air and UHF air onto one coax using a band pass filter for each band into a preamp for each band feeding a combiner like this (signals would go right to left in all pictures).



Or you can use one antenna like a Discone, diplex out to the separate VHF and UHF air bands into band specific filters and preamps then combine onto one coax like this:



Or you could diplex from one antenna into just the two filters for VHF and UHF air then diplex back to one coax and use one high level preamp like this one:



In all cases the filters and preamps would be at the antenna giving the lowest system noise figure.

Since I'm also interested in milair, and located within shouting distance of Wright-Patt, as well as being in an area with fairly regular air national guard activity, the bandpass doesn't work for my use case. I am planning to insert a Stridsbergeng PRE-20 at the antenna. The better notch definitely improved reception, but KFFO tower, as well as KDAY tower/ground are still pretty weak.

 

[kd8mkg]

All good information! There will definitely be some experimentation, but my next strategy will be as follows:

DPD MilTenna -> Nooelec Wideband LNA (I already have this for SDR stuff) -> Mini Circuits ZVSF-95-N+ -> 50' LMR-400 -> Stridsberg MCA204M/N Multicoupler -> BCT-15x & SDRs

I realize that putting the LNA before the filter will result in greater sensitivity, but although I'm going to try that first, given how close I am to FM transmit towers, I expect to ultimately have to put the filter before the LNA.

There is also the complication that I have many transmit antennas in close proximity, including 144/440MHz, so I will have to put an RF limiting device (probably a Stridsberg LIM-01WB, although I'm open to other suggestions) immediately after the antenna.

 

[prcguy]

The Nooelec LNA is something you might have found in a Kracker Jack box as the 2c prize, the input overload spec on at least one of their models ranges from -10dBm to 5dBm depending on frequency. Those are probably the worst specs I've ever seen on a commercially made LNA for radio reception.

Even with an FM trap in front of the LNA it WILL overload and cause problems if its connected to a wideband antenna. Placing the FM trap after the amp would be even worse. Your trying to get 300mph top fuel dragster performance but you stuck a lawn mower engine under the hood.

 

[kd8mkg]

The Nooelec LNA is something you might have found in a Kracker Jack box as the 2c prize, the input overload spec on at least one of their models ranges from -10dBm to 5dBm depending on frequency. Those are probably the worst specs I've ever seen on a commercially made LNA for radio reception.

Even with an FM trap in front of the LNA it WILL overload and cause problems if its connected to a wideband antenna. Placing the FM trap after the amp would be even worse. Your trying to get 300mph top fuel dragster performance but you stuck a lawn mower engine under the hood.

Like I said, just something I have on hand, not what I plan to stick with permanently. Just waiting for a single adapter to arrive in order to try it out. I suspect you are correct, but it won't hurt anything for me to experiment with it.

Ultimately, I'll probably go with a Mini Circuits or Stridsberg LNA.

 

[rabrol]

Maybe you do not need all that attenuation depending of how close the broadcast transmitters are. If you only need som 1000 times attenuation you could probably use a HPN-30118 filter. If you have no strong transmitters at the edges at 88MHz and 108MHz you can use a $20 filter. FM Notch Filter 88-108 MHz band Excellent Rejection -97dBm RTL SDR FM trap | eBay

/Ubbe

FM Broadcast is a major issue in my part of the city unfortunately. As soon as I added an RTL-SDR FM notch filter I was able to monitor airband again. However I've got 2 local towers, one on 118.3, the other on 118.8 and I want to monitor them both with the best possible RX. The Electroline drop amp adds too much noise (and too much boost), so I'm thinking of getting this Mini Circuits one and hooking up to my GPIO Labs LNA, then running RG6 to a passive splitter in the shack. So it would be antenna -> Pager notch filter -> Mini Circuits FM Filter -> GPIO Labs PG103 LNA -> 8 port splitter -> Stidsberg MCA208.

I'd probably run a UHF / 700 / 800 MHz feed to the electroline TV AMP as it would overload less away from the FM Broadcast band, although I could also use my then spare RTL-SDR FM filter for that line.

This was the essence of my earlier thread which never received any replies.

 

[vagrant]

@prcguy - Always with the superb filter and preamp porn that is impossible to find! Bastid!

 

[kd8mkg]

So it would be antenna -> Pager notch filter -> Mini Circuits FM Filter -> GPIO Labs PG103 LNA -> 8 port splitter -> Stidsberg MCA208

I can't speak to any of the other products, but the Mini Circuits ZBSF-95+ is an outstanding FM broadcast band filter. Very deep filter, steep roll-off at both ends. Tons of gain reduction within the stop band. Roll-off into the upper passband is almost complete at 118MHz, it's still attenuating a tiny bit, but much less so at that frequency than lesser alternatives.

 

[kd8mkg]

@prcguy - Always with the superb filter and preamp porn that is impossible to find! Bastid!

Yeah, I did hop on the Angle Linear website to take a look. Nothing there that specifically fits my needs. Definitely didn't see a milair or air band bandpass. Me suspects those are either older products, or custom orders.

 

[prcguy]

This forum could use a fold out picture page that you can hold up with one hand.

@prcguy - Always with the superb filter and preamp porn that is impossible to find! Bastid!

 

[prcguy]

All the stuff in my pictures came from eBay and it was fairly cheap. I did run one of the amps over to Chip at Angle Linear to modify the frequency range but Chip has since sold off his preamp business and retired.

Yeah, I did hop on the Angle Linear website to take a look. Nothing there that specifically fits my needs. Definitely didn't see a milair or air band bandpass. Me suspects those are either older products, or custom orders.