7
CHECKOUT AND ADJUSTMENT
length of the stranded wire between wire clamp 15M w/wire (L) and wire clamp 15M w/insulator
(K). To raise the resonant frequency, simply shorten the wire by wrapping a longer "tail" back on
itself and sliding the lower clamp upward to maintain tension. To lower the resonant frequency, feed
more of the "tail" back through the hole in the insulator to increase the length of the wire between
clamps L and K. A change of 2", 5 cm will shift the VSWR curve approximately 300 kHz.
5. Check VSWR on 10 meters. To raise the resonant frequency loosen the small hose clamp over the
slotted end of tube (I) and slide tube (J) farther into tube (I). To lower the frequency, slide tube (J)
farther out of tube (I) and re-tighten the hose clamp. A length change of 3" should move the VSWR
curve approximately 200 kHz.
6. Check VSWR on 30 meters. To raise the resonant frequency, loosen the wing nut on the bottom coil
clamp on coil/capacitor assembly 30 meter (P), stretch the coil and re-tighten the wing nut. To lower
the resonant frequency, compress the coil. A change of only 1/4" will shift the VSWR curve
approximately 100 kHz. Large changes in the setting of coil on coil/capacitor assembly 30 meter (P)
may effect 20 and 40 meter tuning, in which case it may be necessary to repeat steps 2 and 3. In
general, the point at which the 30 meter coil taps on to the 40 meter coil will be the major factor in 20
meter tuning.
7. Adjustments for 40, 30, 20, 15 and 10 meters should have little or no effect on the previous
adjustments for 80/75 meters, but final VSWR check for this band should be made as in step 1 above.
8. In above ground installations it will usually be found that resonance and lowest VSWR occur at
slightly higher frequencies on all bands compared to ground level installations. Therefore, on 15 and
10 meters, where length adjustments is the means of setting antenna resonance, it is recommended
that the length of the stranded wire between wire clamp 15M w/wire (L) and wire clamp 15M
w/insulator (K) be increased approximately 3" (7.5cm) and that tube (J) be extended approximately
6" (15cm) beyond the original dimensions given if an above ground installation is contemplated.
These are merely recommended preliminary settings, for it is impossible to indicate precise settings
that will produce resonance or lowest VSWR at a given frequency in all installations.
In the preceding steps it has been assumed that the antenna has been installed in a more or less clear spot
away from other vertical conductors such as TV antenna feedlines, towers and masts, and that a minimal
ground system or a system of resonant radials in the case of above ground installations, has been
installed.
If these fairly basic conditions have not been met it is likely that resonance and low VSWR will be
impossible on some or even all bands without an external matching device. One should bear in mind that
VSWR, even with a resonant antenna, will depend in large measure on local ground conductivity, height
above ground in the case of an elevated antenna, the extent of the radial, counterpoise or other ground
system used, and on other factors over which the operator may have little or no control.
THEORY OF OPERATION
The HF6V-X / HF9V-X operates as a slightly extended quarter-wave radiator on 15 meters, a quarter-
wave stub decoupler providing practically lossless isolation of the upper half of the antenna on that band.
On 20 meters the entire radiator operates as a 3/8 wave vertical with much higher radiation resistance and
VSWR bandwidth than conventional or "trapped" antennas having a physical height of on quarter wave
or less. On 10 meters the HF6V becomes a 3/4 wave radiator with considerably greater radiation
resistance and efficiency than quarter-wave trapped types. On 40 and 80/75 meters the L-C circuits that
provided the inductive reactance for resonance on those bands also provide the capacitive reactance
required for resonance on 20 meters.
On 30 meters, where the height of the antenna is slightly greater than a quarter wavelength, an additional
L-C series circuit effectively "shorts out" a portion of the 40 meter inductor to provide an additional
