User’s manual
Making 1/4-
λ
, 1/2-
λ
and other coaxial stubs
2. Cut a piece of cable slightly longer than
this value. Connect it to the analyzer. The
cable must be open-circuited at the far
end for 1/4-
λ
, 3/4-
λ
, etc. stubs, and
short-circuited for 1/2-
λ
,
λ
, 3/2-
λ
, etc.
ones.
A piece of 1.85 m (6.07 ft) was cut.
The margin is 10 cm (0.33 ft). The
cable is open-circuited at the far end.
3. Switch the analyzer to the
All
parameters
measurement mode. Set the
frequency the stub is designed for.
28,200 kHz was set.
4. Cut little pieces (1/10 to 1/5 of the
margin) from the far end of the cable
until the
X
value falls to zero (or changes
its sign). Do not forget to restore the
open-circuit, if needed.
11 cm (0.36 ft) were cut off.
1. Calculate the physical length. Divide
the electromagnetic constant by the
required frequency (in Hz). Multiply the
result by the velocity factor of the cable,
then multiply by the desired ratio (in
respect to
λ
).
299,792,458 / 28,200,000
×
0.66
×
(1/4) = 1.75 meters
- or -
983,571,056 / 28,200,000
×
0.66
×
(1/4) = 5.75 feet
Pieces of cable of certain electrical
length are often used as components of
baluns (balancing units), transmission
line transformers or delay lines. To make
a stub of the predetermined electrical
length,
Example:
1/4-
λ
stub for 28.2 MHz, cable is RG-
58 (velocity factor is 0.66)
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