AOR The New Classic AR3030 Operating Manual page 50

Dipoles
For the very best results you should consider a dedicated aerial such as a
single or multi-band dipole or similar aerial. The problem with a wide coverage
receiver like the AR3030 is that for the ultimate results many dedicated aerials
are required to cover the whole spectrum. This may involve complex aerial
switching and reduces the ability to quickly monitor many bands.
As a compromise it may be worth making up a dipole aerial for a band of
particular interest and have a second random wire for general listening.
It is quite easy to make a dipole for shortwave, for that matter one can be easily
made up for VHF should you have the optional VHF converter fitted.
It is worth noting that dipoles are also quite effective on two and three times
their design frequency so you can cover a few bands at once. Reception using
a half wave dipole is best at 90 degrees to the direction the aerial is laying,
however if used at two or three times it's fundamental design frequency,
reception is best closer to the direction the aerial is lying.
A dipole has two legs running in opposite directions and can be mounted
vertically or horizontally (most VHF activity is vertical). One leg is connected to
the centre conductor the coaxial feeder cable while the other leg is connected to
the outer screen of the coaxial feeder cable. If mounted vertically the centre of
the coaxial feeder should be connected to the leg facing upward.
A simple formulae can be used to calculate the required length of each leg for a
half wave dipole:
————————
Frequency in MHz
————
Coaxial cables
When constructing dipole aerials or connecting VHF aerials 50 OHM coaxial
cable should be used. For shortwave or short runs of VHF URM43, URM76 or
RG58U is ideal, for longer runs of VHF feeder it may be worth considering a
heavier URM67 or RG213.
ATU
Aerial tuning units (ATU) may improve the shortwave section of a wide range
receiver by rejecting unwanted signals and only allowing a specific band of
frequencies through. These ATUs are normally constructed in small boxes
AR3030 operating manual
75
= Length of each leg in metres
i.e. For 14.2 MHz
75
= 5.28 metres (i.e. the total length of
14.2 the aerial is twice 5.28m.)
49