5
Tuning Considerations
Tuning the 80m-30m option is different from the 40m-10m option. While the band positions are factory preset,
they may not be correct for your particular environment. The vacuum tuning capacitor is very high Q. One could
easily miss the sharp dip in VSWR, especially on a wide band such as 80m. A good starting point is:
Band
Recommended Step
Your Final Step Value
80m
6360
60m
16635
40m
23742
30m
27939
Figure 7 suggested starting step values
By carefully and patiently scanning for the lowest SWR for each band, using an antenna analyzer, and then using
the band pre-set feature, your bands can be set to your specific environment. This provides repeatable band
settings. Once set, you can auto tune as in 40m-10m bands. We recommend you use an antenna analyzer or a
VNA, such as a
Rig Expert AA-55 Zoom
or equivalent, to set your user band preferences.
Two-turns versus one turn radiator
You might wonder why two turns rather than a single turn radiator loop? The 80m-30m option was tested as a
single turn radiator. A single turn radiator is somewhat unwieldly. Also, to achieve resonance on the lower
portion of 80m requires a considerably longer loop than simply stretching out the two-turn radiator. That is
because the inductive reactance of a one-turn radiator is considerably lower than that of two-turn radiators.
Ham radio operators are at their core very resourceful. For those who enjoy home-brewing, here is a possible
idea. It is conceivable to construct a more rigid loop from copper tubing of the longer length (in the order of
250”).
The actual length needs to be calculated and tested with a VNA. This loop could be connected to the
existing HG3 QRO tuner via a suitable SO239 connector adaptor. The 43K step vacuum capacitor would certainly
work well. The controller is very flexible and could be made to work well with this arrangement. The mast
would need changing to support the heavier loop. We encourage hams to take full advantage of the HG3 QRO
system with such experiments.
Our performance tests (below) bear out that the two-turn design and implementation is an excellent
compromise in mechanical and performance attributes which provided an easy upgrade path to the HG3 QRO
MLA system for an 80m-30m operator.
