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Larryf
New member
Username: Larryf
Post Number: 5
Registered: 9-2012
| | Posted on Saturday, December 29, 2012 - 11:43 am: | 
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if the swr of a vertical antenna is 1.5 and the horizontal swr antenna on the same system shows a 1.2 swr, what will be the swr of circularly polarizing these antennas, 2.7 or something between 1.2 and 1.5? Many thanks for reolving this question Larry f |
Tech833
Moderator
Username: Tech833
Post Number: 2232
Registered: 8-2002
| | Posted on Sunday, December 30, 2012 - 10:41 am: |
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Hi Larry.
Without some impedance matching, it will be about 2:1.
Assuming both polarities are about 50 ohms for low SWR individually, summing them will give you an impedance of 25 ohms (this all assumes no reactance).
Besides the impedance matching, you also have to be concerned with phase angles. If you use the exact same type and lengths of cable to each polarity, then the two polarities will be "co-phased", meaning at 0 degrees. If you want to go circular, the phases need to be 90 degrees out of phase. So, you need to add 1/4 wave electrical length of cable to one of the polarities. Remember, the electrical and physical length of coax cable are not the same!
Your radio 'Mythbuster' since 1998
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