I finally finished the construction of the filter. Now it was time to tune the filter for 145.550Mhz. Many of my fellow radio amateurs know that RF Power can be "unpredictable" in many ways. I learned that by constructing several 2 Meter amplifiers in the past and tuning them needed patience and a steady hand. I connected the filter to the 145.550 Mhz link radio fitted with a SWR meter. The first push of the PTT button reflected a high SWR. I tuned the filter in and out without any movement of the SWR needle. I was looking for a dip but the needle was stuck on one spot. Something was terribly wrong. I once again made sure about my measurements etc. Removing the lid of the filter resulted in a drop in the SWR. However I cannot leave the lid off while transmitting. I definitely do not want to have RF floating in the Shack. With the lid off the SWR was 1.3:1. The lid was the problem. I used a stainless steel strap on the inside of the lid to lock the lid in place. This is were the problem was. I used my metal cutter and cut 3/4 of the strap only to leave two very small clips in place. Lid on and guess what, a flat 1:1 SWR with full 25 watt of output power. I then checked for leaking RF in the Shack. I could not be happier with the results. Now to check the signal for "cleanliness". I used my little RTL SDR Receiver which is really not ideal but at least I will get a good indication if there are some unwanted spikes (harmonics) that should not be prevalent with the filter in line. Thankfully no "Murphy's" were seen on the spectrum display in normal mode and with demod off. Ideal would have been a real Spectrum Analyzer and a Signal Injector to test the filter. The final test will be to look for some commercial breakthrough to further test the band-pass filter. I will provide a short update when I run into commercial interference as to the effectiveness of the filter.
