- 20 -
6. Check VSWR on 20 meters. Tuning is quite broad on this band because the antenna is
physically much taller than a 1/4-wavelength.
To raise the frequency of the lowest VSWR, reposition the 30 meter assembly so that the coil
support tube 30 meter L bracket (O1) can be replaced on the next lower turn of the 40 meter
coil. Alternatively, to lower the frequency of lowest SWR, reconnect the coil support tube 30
meter L bracket (O1) to the next higher turn of the 40 meter coil.
In some cases moving the tap point a full turn up or down may cause more of a frequency shift
than is desired, in which case the entire 30 meter assembly may be rotated around tube (E) to
permit adjustments of less than one full turn.
7. Check VSWR on 30 meters. To raise frequency, loosen the wing nut on the bottom coil clamp
of coil/capacitor assembly 30 meter (P), stretch the coil and retighten the wing nut.
To lower frequency, compress the coil.
A change of only 1/4 inch will shift the VSWR curve approximately 100 kHz. Large changes in
the setting of coil/capacitor assembly 30 meter (P) may affect 20 and 40 meter tuning, in which
case it may be necessary to repeat steps 5 and 6. 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.
8. Check VSWR on 17 meters. To move the SWR curve to a higher frequency loosen the wing nut
on the upper coil clamp and STRETCH the coil about 1/16” at a time. To move the SWR curve
to a lower frequency range COMPRESS the coil a like amount. 17M is a bit difficult to tune
perfectly. Make small adjustments. A reading of 2.5:1 on 17 is normal.
9. Check VSWR on 12 meters. Stretch the 12 meter coil in increments of 1/16” or so to raise the
resonant frequency, or compress the coil a like amount to lower the resonant frequency. Note:
The 12M coil MUST be compressed as much as possible upon initial tuning. If not, it is highly
probably that 12M will actually be tuned into 10M throwing the ability to tune 10M at all. 12M
is very sensitive when making adjustments changes of 1/4” can cause your tuning to go out of
band (high or low) - make small 1/16” adjustments.
10. Adjustments for 40, 30, 20, 15, 17, 12, 10 and 6 meters should have little or no effect on the
previous adjustments for 80/75 meters, but a final VSWR check for this band should be made.
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 radial system has been installed.
If those fairly basic conditions have not been met it is likely that resonance and low VSWR will be
impossible on some or even all bands. One should bear in mind that VSWR, even with a resonant
antenna, will depend in large measure on local ground conductivity, the extent of the radial system
used, and on other factors over which the operator may have little or no control. Fortunately, the
evils of VSWR greater than unity have been grossly exaggerated in recent decades, and the only
practical difference between a VSWR of unity and one of, say, 3:1 in the average case lies in the
reluctance of modern equipment to deliver full power into lines operating at the higher VSWR
without the help of a transmatch or other outboard matching device.
