At a recent discussion with Bill VE3LFD, the subject of cavity filters came up. After seeing some commercial units, and getting some much needed guidance from Bill, I decided to try my hand at building one to notch out a severe pager signal at 159.010Mhz that has been plaguing me in the Wallaceburg area. A couple (few?) trips to Canadian Tire and I was in business.
After assembling the unit, it was brought to Bills' for analysis (and tuning), and was determined that a >18db notch was produced at the design frequency. Not bad!
1 - 30"x3.5" aluminum dryer vent
1 - 6 ft pc of 1/2" copper pipe (I cut it to 24")
1 - electrical box strain relief
1 - round electrical box cover
1 - SO239 socket connector
1 - 6" pc of 16g copper wire
1 - 12" pc of aluminum duct tape
cost, approx $14 CAN (2013)
Here is the resulting unit.https://www.dropbox.com/s/lmrq6de2ens5jwo/can_filter_1.jpghttps://www.dropbox.com/s/r6s9sqxbvvtow5b/can_filter_2.jpghttps://www.dropbox.com/s/a8gro8atsqcj2ti/can_filter_3.jpghttps://www.dropbox.com/s/49asfeb8vbiii62/can_filter_4.jpg
Thanks to Bill VE3LFD for the inspiration.