Good morning,
The Preliminary Announcement of Bencher Skyhawk 3x10
has aroused some interest among readers.
So how does it compare with standard models?
We are fortunate to have an exhaustive analysis of
the full-Size 2-Element Yagi published by L.B. Cebik, W4RNL:
http://funnelweb.utcc.utk.edu/~cebik/beam2.html
A sample model is given at a centre frequency of 29 MHz:
wl = 0.12 (4.1 ft boom length at 29 MHz)
Gain = 6.25 dBi in free space
Gain = 11.61 dBi at 1 wl above ground.
F/B = 11.19 dB
Feed Z = 32.47R + j0.24
Comparing with the Skyhawk 3x10 on 10 meters-
> effective boom length = 16' 9"
> VSWR is better than 1.5 from 28.000 to 29.000
> Front to Back is better than 14 dB across band
> F/B peaks at 28.500 MHz at 15 dB
> Gain is better than 7.7 dBi across band
> Gain is 7.7 at 28.0 dBi and 9.3 dBi at 29.0
* Can we assume that the gain for the Skyhawk
is calculated for free space? If so,
the net gain over the 2 element yagi model
is around 2.25 dB.
< (7.7+9.3)/2 - 6.25 = 2.25 >
* Can we accept 2.25 dB improvement for an increase in
boomlength of 12.65 feet? < 16.75 - 4.1 >
This seem to be reasonable. The ARRL Antenna Handbook
indicates around 2 db improvement for a change from
.5 wl to 1 wl.
So the real question is...*how does it compare with
existing commercial antennas?*
Regards,
Martin ZL1ANJ
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