Clarification requested for resonant feed line verses non-resonant feed line
"Michael" ha scritto nel messaggio
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In the ARRL Antenna Handbook it discusses feeding the Lazy H
antenna. The handbook states; "Matching stubs are recommended in
cases where a non-resonant line is to be used". Is the handbook
referring to coax verses ladder line, is it referring to a resonant
length of ladder line verses a non resonant length of ladder line, it
is referring to ladder line with an antenna tuner at the transmitter
verses ladder line without an antenna tuner? In any case I'm not sure
what they are specifically referring to. Clarification requested
please.
Thank you,
Michael Rawls
KS4HY
A possible explanation is the following one.
If you use an appropriate matching stub at the antenna, the antenna impedance
can be made equal to the ladder line characteristic impedance. In such (matched)
condition, the impedance seen by the transmitter is independent of the ladder
line length. You will most likely need a tuner at the transmitter to adapt that
impedance to the 50-ohm transmitter impedance.
On the contrary, not using any stub, the antenna impedance will most likely be
different from the ladder line characteristic impedance. In such (unmatched)
condition the impedance seen by the transmitter varies with the ladder line
length. Trimming that length, you may obtain an impedance close enough to 50
ohm, so avoiding the need for a tuner (although a balun will stiil be needed).
73
Tony I0JX
Rome, Italy
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