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- FEBUARY NEWS LETTERIsotron 160/80, one feedline. THE BEST WAY TO OPERATE HF EASY INSTALLATION EXCELLENT PERFORMANCE DURABLE CONSTRUCTION CC&R FRIENDLY (XYL ALSO) PLEASE FORWARD THIS ARTICLE TO THOSE YOU FEEL WOULD BE INTERESTED. If you have questions about the product or articles feel free to contact me. The Vector Network analyzer - VNA The Vector Network Analyzer has become quite popular. It is not only an excellent tool, but the cost is very reasonable. It is small and comes with a battery that will last a couple of hours and is rechargeable. I use the Nano-VNA by Sysjoint. It comes in two sizes and frequency ranges. I chose the 50 kHz to 3 gHz and the larger screen. It is very stable and the display is clear. When it is turned on, normally 3 graphs will appear. Yellow, green and blue. A violet graph could be added. You can use it at the antenna and this will not need to be calibrated to get a reading. However, most use it at the radio end of the coax. Therefore, the instrument should be calibrated for the length of feed line. This will require connecting the radio end of the coax to the S11 Port or Port 1 (Tx). These are SMA connectors therefore an adapter will be needed for a UHF connector. Set your frequency range for the band you are analyzing, let's say 40M or 7.0 - 7.5 mHz.The antenna end of the coax will be terminated in an open, short and 50 ohm load as you go through the calibration mode. When completed "Save" the values. Now connect the terminated end of the coax to the antenna (40M). The yellow graph will display the SWR curve by default. The green will display the Smith Chart by default. The blue makes a line at the bottom making the position of the marker more visible. Move the marker to the minimum SWR. It will give the frequency it occurs at. Next at this point look at the green resistance number. This will tell you the resistance of the antenna. You are hoping for 50 ohms. You can change the green graph to "Resistance" by going to "Format", then "More". It will give the same resistance value, but no reactance value. If you want to check other bands using the same feed line, it can be done by changing the frequency range, let's do 20M (14.0 to 14.5), The display may look like the analyzer lost its mind. This is because the "saved" value was done at 40M. No need to calibrate again, you are still using the same feed line. Go to "Cal", then select "Reset" or "Apply" and remove the check mark. Go back to the main screen. Now it should look like it got its brains back. Go to minimum SWR with the marker and read the Resistance. Adjustments to the antenna can be made while you keep track of your progress on the screen. 73, Ralph WD0EJA BILAL COMPANY 137 MANCHESTER DR. FLORISSANT, CO. 80816 U.S.A PH/FX: 719/687-0650 |
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