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The stock 'double jointed' antenna
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The R20 comes supplied with a
telescopic antenna with a BNC connector. What is immediately noticeable
about this antenna is that it has not just one swivel knuckle, but two.
The reason for this is that the antenna can be folded down the side or
back of the radio either for storage or to use where space is restricted.
Folding the antenna down rather than removing it also saves wear on the socket
and antenna and prevents dust and dirt ingress when being carried. |
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Internal
bar Antenna
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The R20 has an internal bar antenna for long wave
and medium wave listening. |
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Headphone
Antenna
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When using an earpiece or headphones, the R20 can use
the cable as an antenna and you don't need to plug an antenna into the BNC
socket. This only works for FM Band II reception and performance may not
be fantastic but it is convenient. |
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 The
attenuator function has no effect if either the
the internal bar antenna or headphone lead are in use. |
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Replacement
portable antennas
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There are a number of
aftermarket scanner aerials available which can give better performance
than the stock antenna. For the R20, you will need one which covers the bands you are
interested in and which has a BNC connector. I use a
Comet SH95 tri-band
144/430/1200MHz colinear which is very
good, especially on or around two metres. |
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I don't like to use it when I'm out and about though.
It's very flexible and almost unbreakable, but none the less, it's size
(378mm) makes it ungainly and I feel it can put too much
strain on the BNC socket during active perambulation. It's great for use
in a vehicle or around a house or office. |
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Antennas for HF
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If you want to hook up a long
wire (random wire) antenna to the R20 for short wave, you might be interested in this
little widget. It's not aimed at the scanner market at all but it is
designed to be used with test equipment and can be seen in most
electronics labs. It has a 50Ω male BNC plug on one end and a pair of 4mm
sockets or binding posts at the other. The centre of the BNC connects
through to the live terminal and the outer goes directly to the ground.
Alternatively, you can use one of these as a feed point to a halfwave
dipole with a length of wire a quarter of a wavelength on each binding
post. |
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This is a typical BNC to 4mm adaptor |
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Here's
the offset type |
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the fully insulated type of adaptor, this one having touch proof 4mm sockets rather
than binding posts.
Adding an earth connection is optional but can dramatically increase
signal and reduce noise. Do not connect an earth to mains wiring, a radio
needs its own separate earth. You can buy an earth rod for less than a
tenner from an electrical wholesaler. |
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Miracle Antenna
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 The
Miracle Ducker IL |
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I've not
tried one of these but they come highly recommended by R20 users and
members of the portable HF fraternity. What it is essentially is an
in-line antenna matcher based on an auto transformer.
A typical small antenna on a portable is usually working
at a ludicrously high SWR, and by adding a matcher, the transfer of signal
into the receiver can be much improved.
The Miracle Whip is a similar device but
has a built in whip antenna. |
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See more on aerials in A
Beginners Guide To Scanning |
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