15
Side Length in
Feet
Diagonal
Physical Length
in Feet
Factored 0.95
Electrical Length
in Feet
DLY3 Physical Length
in Feet (0.82 VF)
135 (160m)
190.9
181.4
148.8
98 (160m & 80m)
138.6
131.7
108.3
70 (80m)
99.0
94.0
77.1
Table 3 - Examples of DLY3 Required Length
After calculating the required electrical length, you must include the VF of the coaxial cable being
used when determining the correct physical length of DLY3. Multiply the factored electrical length
by the VF. The result is the correct physical length for DLY3. See
Figure 4
and the sidebar for an
example.
Note:
These calculations are in feet, not feet and inches.
To find the physical length of DLY3, calculate the
diagonal length of the array by either directly
measuring the diagonal or by multiplying the array side
length by 1.4142. DLY3 will be significantly shorter
than the actual physical length. The diagonal length is
first multiplied by 0.95. This gives the factored
electrical length for DLY3. Next, multiply the DLY3
electrical length by the VF of the delay line coaxial
cable. The result is the correct physical length for
DLY3.
Figure 4 - Array Diagonal Dimension
For Example
: An array with 90 foot side spacing, the diagonal length is 127.3 feet. The 0.95
factored physical length for DLY3 electrical length is 120.9 ft. Multiply 120.9 ft.
by 0.82 (the VF of DX Engineering 75 Ω quad shield coaxial cable).
The correct physical length for DLY3 is 99.14 feet, or 99 feet 1-5/8 inches.
Delay lines DLY1 and DLY2 must be half the length of DLY3
. Make DLY1 and DLY2 as close
to half the physical length of DLY3 as possible. To avoid performance degradation due to
inconsistent coaxial cable construction, all the delay line coaxial cable should be cut from the same
spool.
Delay line cables can be neatly coiled in a 1-1/2 foot diameter coil. Support the weight of the cables
by taping or securing them to the support pole or mast rather than allowing them to hang from the
connectors.
It is important to use 75 Ω feedline to the operating position from the
DXE-RFS-3
. Do not use
amplifiers, combiners, filters or splitters that are not optimized for 75 Ω systems.
