Butternut HF9V, Instructions Manual

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CHECKOUT AND ADJUSTMENT
For adjustment purposes a simple VSWR indicator may be used. More accurate
measurements may be made at the antenna (i.e., at the junction of the coax 75
ohm matching (R) and the main transmission line) than at the input end of the line,
but the tuning conditions that exist at the transmitter will usually be of greater
interest in that one's principal concern will be to couple power from the
transmitter into the transmission line.
1. Determine the frequency at which VSWR is lowest on 80/75 meters. The coil
setting given earlier should produce resonance and lowest VSWR at
approximately 3700 kHz. To raise the frequency of resonance of the lowest
VSWR, simply loosen the wing nut on the lower coil clamp of the coil
assembly 80/40 meter (C) coil on tube (B) and stretch the coil a bit more. To
lower the frequency, compress the coil. A 1 in (2.5 cm) change in the setting
of this coil will produce a frequency shift of approximately 125 kHz.
NOTE: Remember that the antenna tunes very sharply in this
range and that high values of VSWR may be encountered only a
few kHz either side of the lowest VSWR readings, so it would be
well to take VSWR readings every 25 kHz or so to avoid running
past the frequency of resonance and lowest VSWR.
NOTE: To minimize interference to other stations and to avoid
erroneous reading use only enough power to produce full-scale
deflection of the meter in the forward or r.f. out position.
2. Once the proper coil setting has been found for the desired band segment, coil
(Q) base matching at the base of the antenna may be adjusted for even lower
VSWR. If earth losses are moderate to high a good match may be possible if
coil (Q) base matching is left fully compressed; if earth losses are low (as with
an extensive radial system) coil (Q) base matching may have to be stretched
to twice its compressed length or more for a good match. In any case, a
single setting for coil (Q) base matching should suffice for operation over most
of 80/75 meters provided the 80 meter coil is readjusted for each different
band segment.
3. Determine the frequency of minimum VSWR on 40 meters. The coil setting
given earlier should produce resonance and lowest VSWR at approximately
7150 kHz. The 40 meter VSWR and resonance curve may be shifted in the
same manner as on 80/75 meters by changing the setting of the upper coil
clamp of coil assembly 80/40 meter. On this band the setting is much less
critical, and a 1 in (2.5 cm) change in the clamp setting will shift the VSWR
curve approximately 80 kHz. Be sure to loosen the clamp around tube (E) that
supports the 30 meter assembly and to reposition it as needed to avoid
distorting the 40 meter coil.