Maldol AH-7 / AH-21 / AH-28 / AH-C 14 QRP Whip Antennas

maldohl

A quick look at the Maldol series of  base coil type assembly whip antenna. These antennas have been popular for the Ft-817 and Mizuho QRP radio users. These are rare in North America but have been popular for years in japan. I understand they have been discontinued for many years.
The antennas are AH-7 for 7 MHz , AH-21 for 21 MHz , AH-28 for 28 MHz  have been released. In addition to this, AH – C7 for 7 MHz, AH – C 14 for 14 MHz, AH – C 21 for 21 MHz, AH – C 28 for 28 MHz .

 Length :  110.2 cm
 Contraction :  18.3 cm
 Diameter :   7 mm
 Screw diameter :   4 mm
 Screw hole depth :  15 mm
 Weight :  40 g

 

Base Coil

 AH-C 7 :  Length 22.6 cm  Weight 68g
 AH-C14 :  Length 14.7 cm  Weight 50 g
 AH-C21 :  Length 14.7 cm  Weight 50 g
 AH-C28 :  Length 14.7 cm  Weight 50 g

SWR Plots

coil Impedance
50 Ω Frequency
SWR minimum value
/ SWR lowest frequency
  Band
AH-C 7 6.64 MHz 1.10 / 6.69 MHz   6.39 to 7.19 MHz (SWR ≦ 1.5)
AH-C14 15.33 MHz 1.10 / 14.87 MHz   14.39 to 15.34 MHz (SWR ≦ 1.5)
AH-C21 21.88 MHz 1.05 / 21.85 MHz   21.53 to 22.16 MHz (SWR ≦ 1.5)
AH-C28 29.73 MHz 1.20 / 29.99 MHz   28.97 to 31.36 MHz (SWR ≦ 1.5)

Measured by the M-BNC conversion plug directly connected to an antenna analyzer (Rig Expert AA-1000)

band coil SWR minimum value
/ SWR lowest frequency
Rod length Whip
expansion and contraction standard
Band Frequency
variation
30 m AH-C 7 1.05 / 7.07 MHz 79.5 cm 4 stage shortened ± 35 kHz (SWR ≦ 1.5) 30 kHz / cm
17 m AH-C14 1.05 / 18.10 MHz 38.5 cm 1 stage 2/3 extension ± 100 kHz (SWR ≦ 1.5) 100 kHz / cm
12 m AH-C21 1.00 / 24.90 MHz 48.0 cm 2 stage half extension ± 200 kHz (SWR ≦ 1.5) 150 kHz / cm

 

agv-free

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