ALPHA DELTA DX-A 160-80-40 METER TWIN SLOPER
SPECIAL NOTICE INSTALLATION &TUNING NOTES
Since a quarter wave sloper, such as the ALPHA DELTA Model DX-A, uses the support tower (or pole with down-lead) as the other "half" of the antenna (its ground return path), this type of antenna is more installation-site dependent than some antennas such as a dipole.
The reason being that surrounding objects such as guy wires and other attached antennas may also become part of the other "half" circuit of the antenna and affect the tuning with acquired reactances. If VSWR tuning of the DX-A is a problem, the DX-A can be preset to the following dimensions and an antenna tuner employed. The low angle radiation DX performance is typically not affected, and this method also allows solid state transmitters to fully load!
80 METERS --- REMOVE 3 FT. FROM 80 METER WIRE
40 METERS --- LEAVE AT FACTORY SET DIMENSION
160M. PIGTAIL --- REMOVE 3 FT. FROM 160 METER PIGTAIL
*Please note that the support structure for the DX-A should be of metal construction and offer a low resistance ground pathway. The normal grounded tower found in amateur usage easily fills this simple requirement. If the tower does not offer a good ground return, then we suggest attaching a large diameter (No. 14 or larger) wire to the aluminum DX-A mounting bracket and running this wire to a good RF ground connection at the base of the support. This same method will allow the DX-A to be used in cases where the support structure may be of an insulated type, such as wooden utility poles, chimney mounts, trees etc. Also, if your tower is of the "crank-up" variety, where there may be some doubt as to the integrity of the metal ground path, this same method of running a ground wire should be followed. If this method is needed, the DX-A aluminum, mounting bracket should be drilled for attachment of a machine screw and lug type connector (with found wire attached).
*Refer to FIGURE NO. 1: The DX-A aluminum mounting bracket will have to be drilled for a U-Bolt (user supplied) to fit your particular tower leg or installation method. It should be noted, if your tower is of the "sectional" type (suck as Rohn) then the bracket may be fitted to one of the sectional bolts by simply removing the nut and placing the bracket hole over the bolt and re-installing the nut! In this case, no other hole need be drilled, since the DX-A bracket has already been drilled with a single mounting hole at the factory!
*Plan the layout for your new DX-A "Twin Sloper". The ideal arrangement for the wire elements is such that when installed the two wires are approx. 180 degrees apart (much like the arrangement used for the common inverted vee antenna). We fully realize that this 180-degree span may not be possible in all installation locations. The DX-A will operate very well when the included angle is less that the optimum 180 degrees. Your primary goal should be to fit the DX-A into your property boundaries and antenna system in the best manner possible!
*The DX-A was originally designed as a "free space" antenna (as almost all antennas are). As such, it is possible that the introduction of your DX-A into a tower system employing multiple guy wires or other attached wire antennas may cause a slight detuning of the DX-A antenna. This condition is rarely seen in actual practice, but the chance for it does exist, just as it would for any other antenna of comparable design! The mere presence of other wires or wire antennas can result in direct R.F. coupling which will upset the DX-A antenna system. Refer to Figures No. 5 and No. 6. The point of bracket attachment on the tower should be as far removed as possible from the attachment point for any guy wire system. The angle of slope for the elements of the DX-A should be such that they are not the same angle as made by any guy wires or other wire antennas (see Figure No. 5)! To help lessen interaction between the DX-A and other wires, it is wise to provide as much separation as possible (see Figure No. 6). The DX-A wire elements may be so arranged as to bisect the angles made by guy wires. Guy wires should be electrically broken by the inclusion of insulators. In some few instances, it may be necessary to employ the use of a modest antenna tuner to allow some solid state transmitters to fully load.
*The mounting height for the DX-A is not critical. The DX-A is a super good low angle radiator (highly desired for DX work). We have many users with the DX-A mounted as low as 25 feet, and achieving excellent results on the air! Mounting height for the attachment of the bracket is best left to the decision of the end user and the support structure to be used for the DX-A.
*The DX-A has been designed for use on an unguyed metal tower with a beam on top. The beam provides a capacity hat effect and helps to tune the Twin Sloper. The DX-A will provide excellent DX results on other support structures, such as, poles, masts, trees, etc., but these installations may require the use of a wide range tuner.
TWIN SLOPER HINTS & KINKS
*If at all possible, tape your coaxial feedline to the tower leg (or other support structure). This offers strain relief for the feedline.
*The ALPHA DELTA TWIN SLOPER has the ability to be used on the 10, 18, 24 MHz bands, A small antenna tuner may be needed in some instances with solid state transceivers to allow proper loading! The TWIN SLOPER is also a good choice for SWL while using one of the latest transceivers with general coverage receive.
*For field day or temporary installations: We suggest the use of a counterpoise wire attached to the aluminum mounting bracket and directed to a driven ground rod.
*We recommend that you install one of our world famous ALPHA DELTA "Transitrap" lighting protection devices in your new "Twin Sloper" coaxial feedline. Check with your ALPHA DELTA dealer for information and pricing on our broad array of "Transitraps"!
*Please note: during the initial tune-up phase, when "folding back" the tip ends of the 160 and 80 meter elements, there is a small amount of capacitance introduced. This will have some effect on tuning and the actual resonant frequency points on these two bands. While folding back the element ends is a wise practice initially, for final installation these ends should be clipped to proper length.
Once again, THANK YOU and good DXing.
INSTALLATION & TUNING INSTRUCTIONS
1. Unroll the DX-A sloper wire elements, removing any kinks that may
have been induced during the packing operation.
2. Install the DX-A aluminum-mounting bracket on your support structure,
as described previously.
3. Using a VOM, check to make certain that there is a good low resistance
pathway between the DX-A bracket and the tower leg (or other ground
return lead)! Also, be sure to route the wire from the end of the DX-A
bracket so that it is separated from the tower leg as much as possible.
PLEASE NOTE: The various elements for each band are supplied longer than needed for resonance within the ham bands. During the initial tuning phase we suggest that you use all of this length and shorten as needed. Please note, also that there is a single "ISO-RES" coil installed in the 160-40m leg of the antenna. Refer to FIGURE NO> @ for nomenclature and general layout.
5. Any 50-ohm coaxial feedline may be employed for use with the DX-A
Twin Sloper Antenna. We suggest the use of RG-213 cable as it is
generally a very good buy and will handle the legal limit of RF power
output. The DX-A bracket has been fitted with an Amphenol SO-239
connector so as to accept the standard PL-259 termination. Attach your
feedline to the bracket coaxial connector. It is wise to cover this coaxial
connection with some form of weather protectant, such as "COAX-
The element ends have been provided with heavy duty polycarbonate
end insulators. Also provided, are two lengths of our special low-stretch
nylon rope to secure these two tie off element ends. Please remember:
the two antenna ends should be so placed that when installed they will
not create a safety hazard since there will be RF voltage present at these
ends during normal use! During the tuning process, a simple knot in the
rope will be adequate to hold the element ends in place before the final
Please note that the 80-meter element is one continuous length of wire.
The 40/160M. combined element has one of our ALPHA DELTA "ISO-
RES" coils installed. During the tuning process you will be trimming the
tip end (insulator end) of the 80-meter element. The 40 meter element
(labeled "B" in Figure No. 2) will be pruned at the top end of the "ISO-
RES" coil. There is a five-turn wrap of wire at each end of the "ISO-
RES". Note the steps in Figure No. 3 for remaking this connection at the
coil. The 160-meter element is adjusted by shortening the wire attached to
the lower end of the "ISO-RES" coil at the bottom end insulator. This
160-element wire need not be cut during the initial tune-up, but rather
simply folded back on itself above the bottom insulator.
8. Turning Note: To raise the resonant frequency for any band, that wire
element must be shortened. The shorter the wire element, the higher the
9. Tune the higher frequency band firs i.e., first tune 40 meters then 80
meters, then 160! You should make two passes through the antenna
when tuning. During the first pass through the various band elements do
not try to achieve a final resonance as there will be some interaction
between the bands and as one element length is adjusted it will cause a
slight shift in resonance on one or more of the other covered bands.
Initially, one should try to achieve resonance at the lower ends of the
bands then gradually shorten the lengths for the exact resonant
frequencies desired. Due to the fact that the DX-A uses a low "Q" "ISO-
RES" coil instead of a tuned trap; there will be some interaction
especially on the 40 and 160 meter elements. However, the use of the
low "Q" "ISO-RES" does not have a trap capacitor to break down under
heavy RF loads!
During the initial tune-up, if you can not seen to find resonance, be sure to check just below the normal band edge. The
longer-than-needed wire elements would tend to make this condition quite normal. As wire is clipped from the bottom of the 40M.
element during the turning process, remake the connection at the "ISO-RES" coil as discussed earlier in this manual. Refer to the
The "ISO-RES" coil has been given two coats of special polyurethane
with UV light blocking agent. All hardware is of 18-8 stainless steel. No
further weatherproofing is needed. If you have some "COAX SEAL", a
small amount may be applied to the copper element wire ends at the
"ISO-RES". The construction of the "ISO-RES" is such that it should
offer a long lifetime of service.
This completes the installation and tuning of your new ALPHA DELTA
DX-A Twin Sloper Antenna. GOOD DXING!
To avoid the possibility of tuning errors and false resonances you will
need to de-couple the coax from the antenna at the feedpoint in the
following manner. Near the feedpoint make 8 turns of coax at 8 inches
in diameter. Tape these turns with electrical tape. Then tape the entire
set of turns to the tower leg or at a convenient place so it doesnt pull at
the PL259 connector.