|
|
|
|
|
|
|
← FS-5000 ← Toolkit
Transmitter and DSU test device
The X-Unit was a small test device that was supplied as part of the
Toolkit
of the FS-5000 Field Station.
It measures only 9 x 5.5 x 2 cm and has connectors at three sides.
One side has a DB25 female socket which is marked DSU. At the
opposite side
is a simular (male) connector marked TRANSMITTER.
At the short side are three banana-type sockets:
black, red and yellow.
|
The test device is shown in the image on the right, with the DSU connector
at the rear. At the top right is a green LED
that is used as a
power indicator. The test device contains two fully independent circuits
and offers three functions:
(1) Test the output power of the transmitter. This can be useful if you
suspect the transmitter might be broken.
(2) Allow the transmitter to be connected directly to the antenna. This can
be used as an emergency measure when the ATU is broken.
(3) Test the interface of the DSU. This requires stand-alone
(battery) use of the DSU.
|
|
|
|
Please note that the X-Unit can not be used to connect the DSU directly
to the transmitter. The box contains two fully independent circuits and there
is absolutely no connection between them. The functions of the X-Unit are
further described below.
|
|
It was foreseen by the designers that situations might arise in which the user
is uncertain about correct operation of the transmitter.
As the combination of Transmitter
and Automatic Antenna Tuner (ATU) is a rather
complex one, there are various places where things can go wrong.
|
In such situations, the ATU should be removed
from the transmitter by loosening
4 recessed screws on top of the ATU.
Once the ATU is removed, a
socket on top of the transmitter
becomes visible.
This connector carries control and return signals, but also
the direct output of the transmitter, which can be 30W or more.
The X-Unit can now be used as an indicator of the output power,
by placing it
on top of the transmitter's socket.
This is shown in the image on the right.
When a transmission is now started, the green LED
on top of the X-Unit should
be lit.
|
|
|
|
If the LED lights up, the output stage of the transmitter (PA) is working fine
and the transmitter produces sufficient power for a transmission. In this case it is
possible that the ATU is broken. As an emergency measure the transmitter can
now be connected directly to the antenna.
|
As the transmitter produces an output power of 30W or even higher,
the energy reflected by a badly matched antenna could easily damage the
transmitter's output stage (power amplifier).
This problem is overcome by connecting the X-Unit in between the transmitter
and the antenna. The X-Unit is fitted to the transmitter's socket as described
before. The antenna and a suitable counterpoise (ground) is now connected
to the red (antenna) and black (ground) banana-type sockets on the side
of the X-Unit. This situation is shown in the image on the right.
|
|
|
|
The X-Unit contains a so-called dummy load of 59 Ohm
which is used here as an attenuator. The maximum output power with a load
of 50 Ohm is now 10W, which can no longer damage the PA amplifier of the
transmitter when being fully reflected.
The function of the yellow TEST-socket is currently unknown.
|
|
The Digital Storage Unit (DSU) is normally used as part of the
complete FS-5000 field station.
It is connected to the DB25 socket on the side
of the receiver. When powered down, the messages and settings in the
internal memory of the DSU are retained by the internal 7V backup batteries.
|
If the FS-5000 does not work as expected, the DB25 interface of
the DSU can be tested. For this test the DSU is used in stand-alone mode
and is powered by the internal backup batteries.
The image on the right shows how the X-Unit is connected to the DB25
socket at the bottom of the DSU. Once connected, the DSU is powered-up
by pressing the two blue buttons together.
After the normal Power-On-Self-Test (POST) sequence (RAM Test, Crypto Test, etc.),
the text Interface Test appears on the screen.
|
|
|
The DSU will now test each line of the DB25 interface and will show the
progress on the LCD screen. Each test should produce an 'OK', e.g.
Frequency Signals OK, Receiver OK, etc. When all tests are performed as
expected, the message 'Interface OK' appears.
The test is now complete.
Please note that this test can only be performed if the DSU contains
healthy backup batteries. Although the original batteries will probably
show 3.5V each when measured with a volt-meter, this voltage drops when the
DSU is turned on. More information on the DSU-page.
|
The test unit is housed in a die-cast aluminium case with a removable lid at the
top. The image on the rights shows the interior of the X-Unit after the lid has
been removed. It is shown here with the DSU connector towards the front.
A vertical PCB is mounted directly to the DSU connector. It contains circuits
for testing the interface of the DSU.
The bottom PCB contains the dummy-load/attenuator, a small filter circuit
and the power indicator. The connector for the transmitter is at the rear.
Most of the pins are unused; only the antenna signal is used.
|
|
|
- Feldstation FS-5000M, Technisches Handbuch, Teil 1, Beschreibung
Field Station FS-5000, Technical Manual, Part 1, Description (German).
March 1994.
|
|
|
|
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 - 21:26 CET.
|
 |
|
|
|
