Vertical Element Feedlines; Delay Line - DX Engineering DXE-RCA8C-SYS-2P Manual

Vertical Element Feedlines

Use 75Ω coaxial cable from each antenna element to the RCA8C-1. The eight feedlines from the
RCA8C-1 to the elements can be any length needed to accommodate the size of the array, but must
all be the same physical length, velocity factor and type. Note the orientation and numbering of
the elements by using Figure 7. Be sure the appropriate antenna element is connected to the proper
ANT connector on the RCA8C-1. Additional weatherproofing protection can be provided when
using the PTX-22058 Permatex Dielectric grease on all coaxial connections. Dielectric grease is
ideal for keeping moisture from entering your coaxial connectors. It also acts as a lubricant
allowing easy connector removal by stopping corrosion of electrical connectors.
Figure 7 - Vertical Elements
Coaxial Connections
to the RCA8C-1

Delay Line

The DX Engineering DXE-RCA8C-1 uses a time delay system, not a traditional phasing system.
The delay line length is dictated by array dimensions rather than operating frequency, allowing for
the use of a single delay line for optimum directivity over a very wide frequency range. This results
in phase being correct for a rearward null at any frequency.
The DXE-RCA8C-1 unit has two delay line female F connectors marked DELAY. This connection
pair will require one specific length of a coaxial cable assembly with male F connectors acting as a
jumper between the two female F connectors. Delay line electrical length is critical. Careful
measurements and the use of 75Ω coaxial cable with a known Velocity Factor (VF) is very
important.
We strongly recommended the use of DX Engineering DXE-6UF-1000 High Quality, Low Loss,
75Ω F6 type Direct Bury Coax "Flooded" Coax. The DX Engineering DXE-6UF-1000 75Ω
coaxial cable has a nominal VF of 0.83. Keep in mind that solid Teflon® or polyethylene (PE)
dielectric coaxial cable has a VF of approximately 0.66. Foamed coaxial cable cables typically
range anywhere between 0.75 and 0.90 VF, depending on the ratio of air-to-dielectric material in
the cable core. If you do not know the VF of the coaxial cable you are using, you must directly
measure the electrical length of the coaxial cable you have with an analyzer or obtain cable with a
known VF.
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