|
|
|
|
|
|
|
← FS-5000 ← Transmitter
Automatic Antenna Tuner
As the FS-5000 radio station had to be operated by non-technical
operators, a fully automatic antenna tuner was designed as part of the set.
It allows a wire of approx. 15 meters long to be used as antenna. The
antenna can be a long-wire, a dipole or an inverted-V. The antenna tuner is
mounted on top of the transmitter and is located at the
rear left of the radio station.
|
The image on the right shows the antenna tuner.
It is a fairly simple device with
two banana-type sockets for the antenna
at the rear left and a connector at the bottom
that mates with a similar socket on top of the transmitter.
Signal and power are obtained from this plug, and some extra signals
are present in the connector for communication between the two units.
The antenna tuner contains a series of filters that are selected and adjusted
under control of a built-in microprocessor, making the tuner
autonomous and transparent to the user.
|
|
|
|
Apart from the HF output from the transmitter, the main connector also
carries a number of test signals that allows a badly matched antenna,
and hence a bad Standing Wave Radio (SWR or VSWR),
to reduce the power output from the transmitter.
This creates a fail-safe situation. During the tuning stage (i.e. when
trying to match the antenna) the RF-output power is less than 5mW.
|
|
The antenna tuner is a fully autonomous device with its own logic.
It can be accessed from the top, by removing the top panel, and contains
a single PCB that fills the entire interior. The PCB is roughly divided
in two parts: the matching coils at the left and the digital
control at the right.
|
The left half is the actual antenna matcher that consists of a series
of coils and capacitors that are selected by no less than 22 relays.
The relays are controlled by a series of SG2003 (ULN2003) transistor
arrays on the right half. Feedback signals are provided to the transmitter,
to allow output power reduction in case of a mis-match.
The right half of the PCB contains the control logic. At the heart is
a National Semiconductor NCS-800 microprocessor.
This mil-spec Z-80 compatible CPU [1] is also used in the
DSU.
The firmware is contained in an EPROM on its left.
|
|
|
As a lot of control lines are needed, two NSC-810
I/O expanders are used. These peripherals each have three 8-bit I/O ports,
some timers and 1024 bits of static RAM [2].
The smaller chip next to the EPROM is an MM82PC12
8-bit I/O port [3].
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Friday 20 August 2010. Last changed: Monday, 25 February 2019 - 21:13 CET.
|
 |
|
|
|
