C-POLE PORTABLE ANTENNA FOR 20M
A vertical that's small, light and portable, needs no counterpoise and performs as well as a home antenna
![](http://www.qsl.net/hb9mtn/c-pole-total.jpg)
C-Pole Antenna for 20m
on a non conductive glass fibre fishing rod (beware of conductive carbon fibre material!)
![](http://www.qsl.net/hb9mtn/c-pole.gif)
Dimensions of C-Pole Antenna for 20m
[Design frequency 14.240 MHz]
Overall wire length roughly 1/2 wavelength, feedpoint 25% from end,
electrically an off center fed dipole.
The two stubs -- 10cm and 5cm -- at the insulator on the left of the drawing
are to be trimmed for fine tuning, the lower for best SWR, the upper for resonance.
![](http://www.qsl.net/hb9mtn/insulator.jpg)
Detail of insulator and the two stubs
The dimensions for other frequencies can be computed by multiplying the above values
with the design frequency, divided by the target frequency:
![](http://www.qsl.net/hb9mtn/frequencyformula.jpg)
Formula for 17m [18.120 MHz]
![](http://www.qsl.net/hb9mtn/c-pole-base.jpg)
Detail of Balun and Feedpoint (experimental hookup)
![](http://www.qsl.net/hb9mtn/toroidbalun-rg174.jpg)
1:1 Current-Balun, 2 x 7 turns RG-174 Teflon on Amidon FT-240/61
(loss about 0.3 dB on all bands [Brian, KF2YN])
![](http://www.qsl.net/hb9mtn/c-pole-balun-open.jpg)
Current-Balun in waterproof box
![](http://www.qsl.net/hb9mtn/c-pole-via.jpg)
Excellent SWR, easily adjustable to desired frequency!
![](http://www.qsl.net/hb9mtn/20_1040vs240vs40cm.jpg)
EZNEC simulation of take-off angle versus hight of bottom wire/ground.
The resonant frequency increases with height/ground,
add some extra wire length if you rise the C-Pole!
![](http://www.qsl.net/hb9mtn/coax-balun.jpg)
Alternative Coax-Balun, 60 turns RG-58 on 48 mm plastc tube
(loss about 0.6 dB on 20 m, about 0.8 dB on 10 m [Brian, KF2YN])
![](http://www.qsl.net/hb9mtn/smithtoroid.jpg)
![](http://www.qsl.net/hb9mtn/smithcoax.jpg)
SWR between 3 MHz and 30 MHz, Toroid-Balun vs. Coax-Balun,
both terminated with 50 Ohm Dummy-Load
Performance
My results with C-Pole are surprising:
OH0/ES1AX, D4B, 9Y4ZC, SV9/F6JXR, SV8/DF1UX/mm, 7X3VRK, 4X0T, 9H3YM, EI6JK from HB9 within the first few hours with FT-817 and 4W-50W! Recently I picked HS0/IK4MRH out of a huge pile up!
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