Kessler AT-AUTO Operating Manual page 125

Why does the AT-AUTO
match at low power?
After I QSY if the SWR is bad, the AT-AUTO
radio to tune against. The tuning process seems to work fine, but occasionally when I
subsequently transmit, the AT-AUTO
match at low power?
Answer: The output of the RF bridge rolls off non-linearly at very low power levels. This
is the reason that the AT-AUTO
a good match was previously found at QRP levels. The tuning algorithm is intentionally
extremely conservative (attempting to match to 1.05:1 or better). At 10 W input to a
load matched to 1.2:1 or better SWR, the reflected power levels are indeed very low and
approach the hardware's limit to detect these power levels. However, when QRO is applied,
the reflective power may be sufficiently increased (even at extremely good SWR) and detected
by the AT-AUTO
(tm)
an radio that is configured to utilize the radios external tuner interface and rely upon the
radio to produce a steady 10W carrier. From experience, it turns out that this power level
may vary from radio to radio with some radios producing a stronger carrier (fine) (≈ 15 W)
while others less (≈ 6-7W) (problematic).
The tuner sometimes retunes after autotuning using the radio's
TUNER button. Why?
My AT-AUTO seems to work fine if I tune in high power and then operate. However,
(tm)
if I tune using the Tuner button on the Icom radio, the AT-AUTO
to re-tune once I switch to high power operation. It does this about 30% of the time when
using the coax-fed loop, but rarely does this when using a similar loop which is fed directly
with ladder line. Why does it do that? Is there something wrong with my AT-AUTO
Answer: Tuning at low power has a couple of advantages It reduces QRM and it
places less stress on the transmitter while a match is being sought. It is also convenient
when using an Icom or Kenwood radio you merely press the rigs' TUNER button and
it all happens automatically... However, if there are losses in the antenna system greater
than the resolution of the Forward/Reflected power sampling, then tuning might need to be
re-accomplished when subsequently operating at higher power output levels.
Why is tuning different depending upon whether using coax-fed or
balanced-fed antennas?
OK But Why? And why does it seem to be different depending upon whether it is a coax-fed
or balanced-fed antenna?
retune at high power when it found a
(tm)
(tm)
sometimes retunes upon application of QRO although
(tm)
. This is most often manifested when the AT-AUTO
www.KesslerEngineeringLLC.com
gets a low-power carrier from my Icom
(tm)
starts re-tuning. Why does it do this if it found a
117
is coupled to
(tm)
quite often wants
(tm)
?
(tm)