Filter in a die-cast box

Sunday comes bright and early and I decide to put the FM broadcast band notch filter into a die-cast aluminum box.

First, I found in the garage the G112T box I had purchased a long time ago. Measuring somewhat carefully, but not enough, I estimate the spots on the two ends of the box that I’ll have to put 1/2″ holes to install these little TNC-f to coax pigtails.

The TNC-f chassis mount bodies are just about as big as the sidewalls of the box, so aiming carefully is important. However, I miscalculate low on the first hole, and have to oval it just a hair to fit the body of the connector. The second hole I overcompensate, and it’s a little high. But, within 30 minutes I have the case drilled and ready for the filter/coax assembly.

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The little TNC coax pigtails came from a buddy of mine – he had a billion of them from some former project.

Before I take the filter off the roof, I measure it one more time while it’s foil-wrapped. Didn’t have a photo of the install from last night, so here it is today.

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Kinda ugly, no?

Using the Icom setup, it appears a little worse than yesterday night. Could be so for a number of reasons, including propagation, xmtr power output changes between night and day, or the foil moved a bit during the night. Not sure.

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Taking the filter down off the roof, I cut off the SMA-f board mount connectors, clean off the excess solder, and prepare the TNC jumpers to solder directly to the board in place of the former connectors.

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The reason I prepared the coax open end as shown in the above picture is apparent in the next photo when I solder the TNC jumpers to the filter board.

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Now to install the filter and coax assembly into the enclosure and prepare the sealing gasket.

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The box is almost ready to close up. Don’t want to lose the little screws that are intended to hold down a board inside the case so I install them now.

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Next, put on the lid and tighten down the screws. Use a compression clamp to squeeze the case closed instead of making the screws do the work. Aluminum strips out very easily.

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All done. Now, since the rooftop cable from the antenna is an N-m connector, and the feed down to the shack is currently a UHF-f adapter, I add those to the case.

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Voila! All done. Now, to the roof!

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Here’s a shot of the discone up on the roof. The thing attached to the chimney is a 2.4 GHz Ubiquti 2.4 GHz Bullet M2 set up as an access point, so I can get Wi-Fi pretty much anywhere around the neighborhood.

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It does appear that the box is certainly no worse than the foil and at least for a few stations it’s actually improved on the rejection. That pesky 107.9 MHz station is down 10 dB with the box.

Since that wasn’t as hard as I thought it’d be, I need to orderĀ a few more of those nice little G112T boxes, or something similar!

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