ANTENTOP-
02- 2003, # 003
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Old computer's PSU
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The efficiency vs.
frequency
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On ranges of 160 -80 meters
it is possible to use the autotransformer only for a reception
mode with the transformer loaded to 450 or 600 Ohms and its primary
winding is connected to a 75-Ohm coaxial cable. On ranges of 160
-40 meters it is possible to use the autotransformer only for
a reception mode with the transformer loaded to 300 Ohms and its
primary winding is connected to a 50-Ohm coaxial cable.
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Note: Do not use the transformer without a load! It causes
a high VSWR and damage to the transformer. If the transformer
is used outside it should be protected against atmospheric influences.
It is possible to use an egg from a sweet surprise
"Chupa - Chups" for such a protection.
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One
more application - An RF ammeter
I found one more useful application for AT-33T transformer.
This one was turned to a current transform for an RF ammeter. You need
to add only a current loop to AT-33T transformer and this one
will be a current transformer for an RF ammeter. The current loop
(or a current winding) contains only one turn of a wire placed
on a cheek of transformer's core (see Fig.
6). There was used a copper wire of 0.8 mm in diameter/#
20 AWG.
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Current
loop on the transformer side
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I found that the 24 volt winding (Fig. 7A)
as well as the inverter's winding (Fig. 7B) works as well as the meter's winding.
A germanium diode was used in an RF detector at the meter's winding.
A d.c. meter had a 1mA full scale deflection and 140-Ohm resistance.
To verify the work of the RF ammeter made on the base of AT-33T
transformer I connected it in serial with a control ammeter. Fig. 8 shows
the circuit. Note:
A control ammeter was a home brew RF ammeter designed by the reference
[1].
The RF ammeter was calibrated with the help of a
standard measuring equipment.
Tab. 4 contains testing data for the RF ammeter shown in Fig. 8. Using
data from Tab.
4 I made diagrams "meter reading vs. frequency"
to the 24 volt winding and to the inverter's winding (see Fig. 9 ). The curve shows that the
inverter's winding (A- B) is the optimal winding for application in the
RF ammeter made on the base of AT-33T transformer.
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Current
loop on the transformer side

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