radioscanner.ru forum. Figure 1
shows design of the antenna.
In the wire parts of the antenna it was used braid
of RK75-9-13 coaxial cable. It is not critical,
it may be used thick wire or braid of the RG58/RG59 coaxial cable.
The antenna should feed through 200/50- Ohm RF transformer. Figure 2 shows one possible design for the transformer.
Transformer may wound on ferrite ring in OD 7- 10- mm with permeability
2000... 200. When used ferrite ring with high permeability- 2000,
the quantity of turns in the transformer may be near 10. When
used ferrite ring with low permeability- 200, the quantity of
turns in the transformer may be near 20
Capacitor at the coaxial cable serves for compensation of the transformer
reactance at the high frequency (15- 30-MHz).
It is very desirable to pick up this capacitor for minimum SWR of the
The antenna was used at the Special Receiving Centre and showed good
workability compare to others receiving antennas.
It is only receiving antenna, it has low
efficiency in transmitting mode. However, I (VA3ZNW)
did some experimenters with such antennas and may say that that
antennas work at good propagation. However, if the antenna will
be tried for transmitting mode it should be used proper RF power
transformer and resistors in the design of this one.
73! de "professor"