Karl trys to help other Club with some of their projects. For example KBARA's 147.28 repeater broken it's antenna the other month, so its off the air.
Here's a typical repeater site tower, but with one problem. It had some damage done to it; the center of the tower broke off, so the KBARA antenna fell to the ground, apparently un-harmed. Pictures.....
and.........here's a type letter of coordinating and group efforts...
That was several years ago. Since then Charlene and Walt sold the repeater to Ken Crosswhite, KA7DDQ, who needed some help with the station. Here, Karl checked out his duplexer. It's a band-reject type only, which might not be enough for the site the station is operating at.
To get set up you need to connect the antenna (T port) which is the common to the transmit and receiver side of the duplexer to either a spectrum analyzer or tracking generator. The latter makes it easier to check the operation of the duplexer.
You need to terminate any unused ports as well.........
Here's what the response curve looks like when frequency sweeped on a tracking generator. The left is the "low pass" frequency of 147.28. with a nice notch at 147.88. The right the opposite; "high pass" frequency of 147.88, with a nice notch at 147.28. Both notches protect the receiver, which the lower pass does this and other nearby stations, as well.
As you can see this "DB products" duplex has several years on it, however if properly transported (vertically) and no lighting can provide limited service for many years. On the right is another nice little device, called a "band pass cavity". For a little additional protection this "window" band pass cavity array can be added to either the station transmitter or receiver, or one of each on both. Possibly another arrangement might be on the antenna port, since the window is 4 MHz wide, from 144-148 MHz.
The left picture is looking at a wide frequency band, while the right is a "close up" looking at just the 144-148 2 meter Amateur band
For more information on that club you can go to their web site from here which will open a new browser window.
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