DX Engineering DXE-TW-8080-P Tuning the

TECH TIP

Tuning the DXE-TW4040 or 8080 center sections

Applicable to:

DXE-TW4040 - DX Engineering TW Antennas 40 Meter Monoband Box and Center Post
DXE-TW8080 - DX Engineering TW Antennas 80 Meter Monoband Box and Center Post

Setup the TW antenna on its stand or fixed mount in a clear open area. Ensure cables are run as specified
in the TW antenna manual. One of the most important points to heed, the feedline must come away from
the center piece (coil boxes) at 30 to 45 degrees down toward the ground, and heading over to the analyzer
or transmitter. This is a vertical dipole antenna and allowing the feed line to droop straight down along the
bottom half of the dipole has detrimental effects.

Remove the TW4040 cover exposing the internal coils.
Run a few sweeps on the antenna analyzer without adjusting the other coils to see where the “dip”

(lowest SWR) is located on the sweep. If this frequency is too low, adjust only one set of coils at a time,
one from the top grouping and one from the bottom.

Make the spreading adjustments identical top and bottom and closely the same amount. This should
require very small amount of adjustment by spreading the coil loops apart (little by little).

Run as many sweeps as needed while adjusting the loop spacing on just these first two pairs. If not
enough adjustment is possible then move to another top and bottom pair and do the same. If the
frequency becomes too high reverse the process or to erase the adjustment and start over by
compressing all coil loops together and start over.

Adjust the shunt coil: First verify a sweep reveals the frequency dip at or very near the targeted
operating frequency. Note the SWR at that targeted frequency and adjust the shunt coil (smaller coil in
middle of PCB). Compress the coil in or out to get the SWR as low as possible.

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For the DXE-TW8080 that has two boxes: You can make adjustment in both boxes
starting with the box that has the SO-239 input connector. You may not need to get
into the second box. Remove the TW8080 cover exposing the internal coils

Adjust the first coil above the center shunt coil and at the same time adjust exactly
the same the coil just below the shunt coil.

Coils above the shunt are for the top part of the element and coils below the shunt
are for the lower part of the vertical dipole. They should be adjusted roughly the
same spacing on top and bottom coils.

If that does not move the frequency enough, adjust the next ones up and the next one
down again trying to match the spacing while stretching them out. If it is too high
already then you will need to push the coils together and start over.

Adjusting the shunt coil (in middle of PCB): Verify a sweep reveals the frequency dip at
or very near the targeted operating frequency. Note the SWR at that targeted

frequency and adjust the shunt coil. Compress it in or stretch out to get the SWR as low as possible.

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Specifications subject to change without notice.
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TW4040-8080Tuning – 8 Dec 22 email: [e-mail]