Hello everyone, my question: Is there any advice, tips, or tricks that you could share to lower the SWR reading of my VHF Com Antenna for Citabria?
I am working with my mechanic to install a new radio in my 1974 Citabria 7GCAA. When I purchased this airplane I later came to realize that the radio had a very weak transmitter and receiver. We removed the old radio and ran an SWR test and found the SWR to be 1:4 - 1:7 and above across the 118-136MHz bands. I believe this high SWR was probably the cause of burning up the King radio. To remedy this bad radio I purchased a new Garmin GTR 225 radio, RAMI AV-10 Antenna, RG400 coax cable, 50 Ohm Amphenol BNC connectors.
The antenna was installed yesterday and I am still getting high SWR readings with a brand new antenna and new coax. They are lower than the previous antenna but I wouldn't be confident to transmit with my new radio until I get them lower. Before installing the antenna I tested the SWR by holding it up against a metal workbench. I was getting SWR readings below 2 across the 118-136 MHz bands. After installing it I am still getting high SWR readings of 4 and above from about 118 to 127MHz.
I've called my friend who owns an avionics shop and he shared to ensure that the plate the antenna is attached to is grounded to the aircraft. We inspected it and found two wires attaching the plate to the airframe. I'm at a loss and thought I would ask the community if you have ever had this issue and how you fixed it. Thanks in advance.