14
If the resistance of the shield increases due to contamination, the active elements may not function
properly. Any splices in the feedline should be high quality and entirely weather tight. Do not use
splices in the delay line cables. The
DXE-RFS-SYS-4P
system has been designed to use only 75 Ω
coaxial cable.
Included with the
DXE-RFS-SYS-4P
package is high quality, flooded 75 Ω CATV F6 type coaxial
cable. The
DXE-F6-1000
flooded coaxial cable automatically seals small accidental cuts or
lacerations in the jacket. Flooded coaxial cable also prevents shield contamination and can be
direct-buried.
Included with the
DXE-RFS-SYS-4P
package is the coaxial cable preparation tool, part number
DXE-CPT-659,
that readies the coaxial cable for connectors in one operation and comes with an
extra cutting cartridge. To ensure weather tight connections, use
DXE-SNS6-25
Snap-N-Seal
compression style connectors are also included.
DXE-SNS6-25
contains 25 Snap-N-Seal
connectors, enough for the entire array plus some spares. The Snap-N-Seal connectors cannot be
installed with normal crimping tools or pliers, so you also receive the installation tool
DXE-SNS-
CT1
, from DX Engineering with the
DXE-RFS-SYS-4P
package for proper connector installation.
Active Antenna Feedlines
Use 75 Ω coaxial cable from each antenna element to the
DXE-RFS-2
. The four feedlines from the
DXE-RFS-2
phasing unit to the active elements can be any length needed to accommodate the size
of the array, but must all be the same length, velocity factor and type. Note the orientation and
numbering of the elements by using
Figure 2
.
Be sure the appropriate antenna element is connected
to the proper ANT connector on the phasing unit. The default (zero control voltage) forward
direction is towards Element 1. Element 3 is the rear or null direction.
Delay Lines
The
DXE-RFS-2
uses a time delay system, not a traditional phasing system. Delay line lengths are
dictated by array dimensions rather than operating frequency. This results in phase being correct for
a rearward null at any frequency. This system is especially effective when used with DX
Engineering
ARAV3
active vertical elements. User-supplied passive elements can also provide
exceptional performance for single or dual band operation where high dynamic range is required.
The
DXE-RFS-2
phasing unit has three sets of delay line connections marked DLY1, DLY2 and
DLY3. Each of these connection pairs will have a specific length of coaxial cable acting as a jumper
between the two connectors. Jumper electrical length is critical. Careful measurements and the use
of 75 Ω coaxial cable (included in this package system) with a known Velocity Factor (VF) is very
important.
If you are not using the included
DXE-F6-1000
coaxial cable, keep in mind that solid Teflon® or
polyethylene 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
