Butternut HF2V, Руководство пользователя

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3. Determine the frequency at which the SWR reading is lowest on 80/75 meters. In order to
minimize interference to other stations adjust the SWR indicator for maximum sensitivity and
use only enough power for full scale deflection in the "forward" position. Resonance on this
band is fairly sharp, so it may be necessary to take readings at every 25 kHz or so across the
band to find the frequency at which the SWR drops to a minimum value. If lowest SWR (not
necessarily less than 2:1 at this point) occurs at a higher frequency than desired, simply loosen
the wing nut on the lower 80 meter coil clamp and readjust its position upward for greater
compression of the coil and increased inductance. If, on the other hand, the initial reading of
lowest SWR occurs at a lower frequency than desired, position the 80 meter coil for less
compression and decreased inductance. Adjustments in either direction should be made in steps
of one inch or less to avoid "overshooting the desired setting." A one-inch change in the
position of the lower coil clamp will produce a 75-100 kHz change in resonance.
Once the 80/75 meter coil adjustment has been made for lowest SWR at a particular frequency it
will be found that the SWR cannot be lowered further without the adjustment of the base
matching coil (Q), especially if an effective ground system is used with the antenna. One
should remember that the radiation resistance of a vertical antenna that is physically shorter than
a quarter-wavelength will be less than 35 ohms and that the total feedpoint impedance at
resonance will be the sum of this radiation resistance, plus conductor and loading losses, plus
earth loss resistance. With a loss-free ground system the resistive part of the feedpoint
impedance of the HF2V on 80/75 meters will be less than 20 ohms and the resulting mismatch
with 50-ohm cable would produce SWR of greater than 2:1. Base matching coil (Q) may be
viewed as a step-up transformer that will match the lower impedance at the feedpoint, to the
characteristic impedance of the feedline, and proper adjustment will produce SWR of close to
unity in those cases where the earth loss resistance is sufficiently low to keep the feedpoint
impedance below the characteristic impedance of the cable used. If earth losses are unusually
great, as in desert areas, and if no efforts are made to reduce these losses, base matching coil
(Q)'s transformational properties will be the opposite of what is needed. In such a case base
matching coil (Q) should be left fully compressed or disconnected entirely, depending on which
condition produces lower SWR.
4. Stretch base matching coil (Q) a slight amount from its fully compressed
condition and observe the effect on SWR. In general, the more efficient the
ground system is in reducing earth losses, the greater the amount of stretch
required for low SWR, and if one is fortunate enough to have a zero-load ground
system base matching coil (Q) may have to be stretched to several times its
compressed length for a proper match, in this case it may be more convenient to
reduce its inductance by sniping off several turns rather than continued
stretching. If you have a good radial system, you will have to remove up to half
of the turns. If base matching coil (Q) has to be stretched a good deal for the
sake of a good match the frequency of minimum SWR may drop slightly, in
which case the adjustment of the 80/75 meter coil setting may be touched up as
in the preceding step.
5. Determine the frequency at which SWR is lowest on 40 meters and adjust the upper or 40 meter
coil in exactly the same manner as the 80/75 meter coil was adjusted. Since the antenna is a full
quarter wavelength tall on this band, tuning will be fairly broad and the radiation resistance will
be close to 35 ohms with negligible conductor loss. Depending on the adjustment that has been
made to base matching coil (Q) in connection with the 80/75 meter tuning, 40 meter SWR
should be no worse than 1.5:1 at resonance, and even lower SWR is likely.