Force 12 Sigma-280 Magnum, Руководство по сборке

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DW-Manual-Sigma-280 Magnum-001 FORCE 12 SIGMA-280Magnum Assembly Instructions Page 9 of 32
_____11)
Attach a balun and coax feed line to the feed point end of the relay box on the reflector.
_____12)
Leave the feed point of the driver element open – if this is not done, all tuning will be
fruitless. The driver will be coupling to the reflector and the reflector will not be set on the proper
frequencies.
_____13)
A VSWR meter of some type that is accurate is needed for tuning purposes. If using an MFJ,
read only the left-hand (VSWR) meter and ignore the readings on the right-hand meter.
_____14)
Energize the CW/Phone relay (relay #2, the one with larger coils). If the antenna was
ordered with an optional third relay to open the elements, energize it as well; otherwise, the element
is not in the circuit. With 3 relays, the CW/Phone relay is #3.
_____15)
With the antenna at a reasonable height, read the frequency of lowest VSWR on the
reflector. This is the LOW PHONE position.
_____16)
The target frequency is 25-30 kHz below the intended operating frequency, so if the DX
window at 3790-3795 is wanted, the reflector should be set for 3760-3765. This is the reflector
frequency for maximum F/B ratio on the desired driver frequency (i.e. 3.790-3.795). If wider
bandwidth is desired, such as working down to 3.750 for the JA window, the reflector should be
tuned lower to about 3.750. The F/B in the window will be a bit less, but the operating bandwidth
will be much wider. The VSWR curve for the antenna (both elements active) will rise sharper on
the low side and slowly on the high side.
_____17)
If the frequency is low, spread the coils on both sides of the center, trying to keep them
equal (not absolutely critical for them to be exact). If the U-bolts and saddles securing the far end of
the coils need to be moved, go ahead and move them.
_____18)
If the frequency is high, compress the coils, moving the U-bolts and saddles if needed.
_____19)
After setting this frequency, open the CW/Phone relay and read the frequency.
_____20)
The frequency should be set for 25-30 kHz lower than the target frequency of, say 3.505.
Adjust the coils on both sides of the relay (not the large coils already set) for the desired frequency
(i.e. 3.505 – 25 = 3.480). The coils will always be expanded to reach this frequency.
_____21)
Remove the balun and feed line from the reflector relay box and short out the feed point
using the supplied copper jumper (about 2-3” long).
_____a) Secure the cover on the relay box.
_____22)
Secure the coils in position, if not done so already.
_____a)
Be sure the U-bolt is tight and the coil is in position for proper tuning.
_____b) Use a ¼” drill and drill through the tip end of the coil (flattened end) and
through the element.
_____c) Use a ¼ - 20 bolt and ny-loc to secure the coil.
_____23)
Secure the covers.