IC-746 FAQ
The simple thing to do is to switch modes to either AM or RTTY briefly. After making your
measurement, switch back to SSB.
3.2.12 How do I tune up in CW without a key?
Usually you don't. You probably don't even want to be in CW mode without a key.
Odds are, you're trying to tune up for a different mode, for example, PSK on SSB. The
simplest thing to do is switch briefly to AM or RTTY and tune there.
If you insist upon tuning up in CW without a key, then you really only have one option;
simulate a key. You could turn on the mic-keyer, which uses the scan buttons (UP/DN)
operate the keyer. Or you could wire up a dummy key jack and key the rig by plugging the
dummy jack in and out. There's even one ham who uses his headphones as a dummy key,
but very few of us are willing to take that risk!
3.2.13 What about using an external, automatic, ATU?
There are many automatic ATUs you could use. Your choice boils down to two basic
questions:
Do you want to tune at the antenna or in the shack?
Do you want an Icom tuner or a third party tuner?
Tuning at the antenna is far more efficient than tuning in the shack (feedline SWR, etc...),
however tuning in the shack is more convenient (no power or control cables).
Icom tuners will be "plug-n-play" with the IC-746, while third party tuners may require
cabeling or a change in procedure.
Remember, the transceiver's internal ATU must always be disengaged when driving an
external tuner. Cascading tuners can reflect high reactance values back into the internal ATU
and/or LPF. As a result, dangerously high RF voltages can appear across capacitors in these
networks, leading to component failure.
Icom's cabling to their own antenna tuners takes care of the above automatically.
There are too many possible automatic ATUs to cover in this document, but here are a few
that merit special comment.
AT-500
The AT-500 in intended for use in the shack with near-resonant antennas. It is documented
as handling mismatches of up to 3:1 SWR, but in practice can do better than that, particularly
at lower power levels. It’s rated for 500w, 160-10m.
The hard part to using this tuner is finding an OPC-118 interface cable (they’re not made
anymore). W2ENY has a clone available at:
http://members.fortunecity.com/w2eny/icom_opc118a/
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2003-02-08
