Last weekend I was able to attend a Technician class and cram session. I helped by proctoring the overflow room. Many thanks to SWIARC for letting me help. While observing the class I was reminded of reflection and how it can affect the amount of power being transmitted. I have a RigExpert AA-230 Zoom, picked up used last summer, wondered if it could help me figure out the reflection.
Well as luck would have it I had a little time to kill on Sunday. Got the meter out, checked the batteries, and connected it to the Coax run to the antenna. Thought I read the instructions, put the meter on and read -9.04 db. I freaked, thought it was only 10 percent efficient and started looking for possible solutions. Mainly purchasing new Coax.
I jumped to conclusions, finding facts not in evidence. I should have retested, reread the instructions, calmed down, and did my due diligence by searching the internet gathering more information, on reflection and how it is measured. But NNOOO, I figured it must be the coax. So I went to GigaParts and ordered a 19 foot and 50 foot piece of Messi & Paoloni Airborne 5 5mm cable, the really good stuff. It is on its way, so I’ll test it V.S. what I have but I am not sure of a real Difference in the current setup.
Monday night I gathered my wits. (Sometimes tough to gather, they are so small.) Did a search on ham radio reflection. Holy Cow! There is so much data on reflection. the math behind why it happens, what happens, how to measure it with oscilloscopes, and finally after wading through that I reread the manual for the RigExpert. Discovering where I messed up, I tried a different command.
On page 8, the manual describes how to use the Return Loss Chart (RL) to determine the loss if any. Using this chart https://www.markimicrowave.com/blog/wp-content/uploads/2016/11/return-loss-to-vswr.pdf and my new found confidence, I retested following the correct instructions. My reading was 15db. With the chart we can see that 15db equates to 3.16% reflected power, or at 80 watts out , approximately 3 watts reflected back, with 77 wats going to the antenna. I don’t really need the cable but you never know…..
Well that’s my story, and I’m sticking to it. 73 KF7SFU
David Campbell KF7SFU 