DX Engineering DXE-MBVE-5A - Coaxial Cable and 160 Meter Notes

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to structures, other antennas, number of radials, or personal preference for the mounting location. It
may be necessary to adjust the top element section slightly longer or shorter, or to vary the length of
the coaxial cable, if tuning to best SWR is not achieved with your tuner on all bands.
The performance of this versatile, rugged antenna is highly dependent on the ability of your tuner to
deliver a low SWR when tuned. Refer to your tuner user's manual for correct tuner operation.
Coaxial Cable and 160 Meter Notes
A 43 foot vertical antenna is a short antenna for 160, but it will get you on the air. In this instance,
coaxial cable type is a very important item to consider. DX Engineering recommends a length of
150 feet of DXE-213U an RG-213/U to give most tuners the ability to match the antenna on the
lower frequency bands where most tuning problems are encountered. One needs to examine the
complex impedance (R ± j) to see the problem.
On 160 meters, the use of 150 feet of polyethylene dielectric cable (such as DXE-213U which has a
Velocity Factor of approximately 0.66) will transform the 2 – j183 impedance at the output of the
UNUN to a more tunable 38 + j180 at the tuner.
If you use 150 feet of coaxial cable that has a Velocity Factor of 0.85 (like foam dielectric LMR-
400), the impedance on 160 meters would be transformed to only 3.5 + j45 – still too low an R
value for many tuners. In order to achieve the recommended results, the LMR-400 length would
need to be approximately 190 feet.
In general - the higher the R value, the easier it will be for the tuner to match the antenna system to
your transceiver.
Figure 19
Completed Antenna
Base Pictures