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Bandpass Filter for noisy site

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W8XG
Bandpass Filter for noisy site

The Sarasota Digital Group recently deployed a node (Rocket/Omni) at 175' on top of a large building's roof. We surveyed it first with a Nanostation, with good results to the existing network, but by chance were standing in the ideal spot for the test. The actual install turned out different. There is a lot of cellular equipment (big boxes) and antennas on that roof. 

Our actual install node was swamped with simple signal overload. We could hear it some 7 miles away, but it was deaf as a post. All we'd see was the ip address, and never the node name as that round trip information never made it. 

Searching online, we found these little band pass filters, and decided to give them a try.  https://www.ebay.com/itm/2-4-GHz-Bandpass-filter-WiFi-Bluetooth-ISM-2450-MHz-RP-SMA-Female-Connectors/283443045866?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

We happened to have a spare set of coax cables. You come out of the rocket, with the standard cable into this unit, then out with an identical set of cables to the antenna. Your antenna box will have one set of those cables, but you need a second set.  https://www.ebay.com/itm/USA-NEW-8-RP-SMA-Male-to-RP-SMA-Male-Jumper-Cable-Pigtail-Wi-Fi-2-4ghz-RG-316/272280837461?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Bottom line, the filter knocked out the offending strong signals, and it's working great. Best we can tell there is maybe 1 db of signal loss. I can live with it. So, after getting the filter installed between the node and the antenna, some of that sticky vinyl waterproof tape, to waterproof the filter works well (not that messy coax seal). It's now been working very well for several months. We've also got a 5g nanostation at that site. It's mounted on the side of the elevator shaft, shielded a bit from the powerful cell antennas. It's doing ok, without filters.  We found some 5g filters but they are considerably more expensive than th 2g filters. Also, don't know how to mount inside a nano either. 

Now a comment about the extra set of cables you need to buy. The cable type is SMA-Male_RP to SMA-Male_RP. I ordered a set of SMA Male to Male cables and tried to install and found they don't fit. Seems the SMA-Male-RP (reverse polarity) doesn't have a center "stinger". It has a "receiver". Seems the RP means,  while the shell is Male or Female, the RP, means the stinger is backwards. 

I can tell you that sparked an interesting conversation around the club house. 

There are some other type band pass filters out there,  they have the correct female on one end, but have a male "normal" on the other requiring a custom cable with a female normal, to male rp to make the final connection. This unit, with female on both ends, means you can use the cable that comes with a sector, omni or other antenna that is separate from the node. 

I don't know if there is a way to get inside a Nanostation and insert these filers or not. 

73  Brent W8XG

K6AH
K6AH's picture
Thanks for your post

Thanks for your post, Brent.  I've been looking on and off over the past couple years for a reasonably priced filter.  I have a couple sites that need this on Ubiquiti 2GHz Rocket/Sectors.

Andre, K6AH
 

K9CQB
K9CQB's picture
I gotta try these filters.

I'll pop 2 of these on a BaseBox 2 and see how well they do in a place where we have tons of noise (and we have a couple of those places).

-Damon K9CQB
 

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