On 3/17/16 3:09 PM, jimlux wrote:
On 3/17/16 2:54 PM, jimlux wrote:
I just ran a NEC model (using 4NEC2 to compute the matching network)..
the 15 meter long (30m band) dipole with a T network (91nH series, 352pF
shunt, 7.47 uH series) has 1.75 dBi gain (vs 2.14dBi for ideal dipole).
The 2:1 bandwidth is a bit more than 300 kHz; 1.5:1 bandwidth is about
150 kHz.
I leave it as an exercise for the reader to figure out the voltages and
currents on the components (which was the original question)
So, in summary
full size 40m dipole: 2.15 dBi gain
75% size dipole: 1.93 dBi gain
75% size dipole with coil Q 250, cap Q 1000: 1.75 dBi gain (about
80-84 degree 3dB beamwidth)
the 40 m full size antenna has a swr of 1.4:1 at best and a 2: 1 BW of
about 400 kHz (not much wider than the 75% sized antenna with a matching
network). And the match is better with the matching network (50 ohms vs
72 ohms.
The beamwidth of the full size is slightly narrower (76-80 deg)
NEC plots at
http://jim-lux.blogspot.com/
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