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Friday, July 31, 2009

Hustler 5BTV Performance Results

Here are the performance results from the Hustler 5BTV (4BTV with 80M add-on). Click on the image for a larger view. This is the data before I built the final transceiver end 1:1 balun, its the temporary balun (black coax). Also, 80M was not tuned and 40M was not quite finished being tuned but close. 10M is also almost a 1.1:1 SWR across 28-29MHz band From left to right is MHz, SWR, resistive impedance, reactive impedance, and overall impedance.

A word to the wise, DO NOT BE FOOLED BY SWR! A perfect 1:1 SWR does not mean that the antenna performs well or radiates efficiently. a 50 ohm resistor at the end of the coax with give a 1:1 SWR but I can guarantee that you will not contact anyone unless the sunspot cycle is incredibly active, there are stories of people making contacts on dummy loads... but you get my point!

The most important column is the reactive impedance (Xs) information. The Hustler 5BTV antenna is resonant when the reactive impedance is 0 ohms. The closer to 0 ohms the more efficient the antenna is at radiating the RF. Even if this value shows an SWR of >2:1. Yes, there will be loss in the coax due to the SWR mismatch but more of the RF getting to the antenna will be radiated.

A great explanation of this is on the ARRL TIS (Technical Information Service) article titled "Why an Antenna Radiates" written by By Kenneth Macleish, W7TX
in QST November 1992.

"Both kinds of resistance dissipate energy at a rate equal to the resistance times the square of the current. Of course, energy dissipated this way doesn't actually disappear. An alternating current, flowing against radiation resistance, turns electrical energy into radiant energy, which wings its way off into space. Current flowing against ohmic resistance transforms electrical energy into heat, which is mechanical vibration of the atoms of the conductor -- the atoms vibrate when they're hit by the moving free electrons"

I hope this post helps and provided a lot of information on the Hustler 5BTV antenna as well as a better understanding of antennas in general. While I haven't perfectly tuned the antenna yet its in "the ballpark"! Please let me know any comments or suggestions or if you have any questions!


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