Icom IC-746, Часто задаваемые вопросы

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IC-746 FAQ
6.5 Why isn't my output power up at 100 watts?
There are quite a few possibilities. Here are a few that have been discovered over the years.
Low DC supply voltage.
As shipped, the IC-746 really wants a full 13.8 V dc to yield full output power. While the rig
can operate at voltages as low as 11 V dc, power starts dropping off as soon as you drop
below 13.5 V dc. Check the actual voltage your rig is receiving. You may need to adjust the
voltage setting on your power supply.
If your rig isn't getting the voltage you think it should, then check for voltage drops along the
power cord as well as across joints, fuses, and connectors. It's possible to lose as much as a
half-volt per connection. Solder joints and use high quality connectors where possible.
12 AWG wiring is the minimum, but 10 AWG is better.
Some in-line fuses have had their solder end caps oxidize, thus interfering with current flow
and dropping the voltage.
If you absolutely can't get your voltage up (for example, total battery power), then you might
consider adjusting the power settings for the RF PAs (there are 4 of them). However, trying
to run a full 100w output at the reduced voltage will most likely degrade the quality of your
transmitted signal (clipping, IMD, etc...). Most hams decide that 1-2db gains don't justify the
crumby signal.
There is one more possible remedy for the low voltage problem. You could get a DC-DC
voltage converter. These are also called voltage boosters. Such a device accepts 12Vdc in
and yields 13.8Vdc output. There's a price. First, they tend to only be 80-90% efficient, so a
20A draw by the IC-746 can translate to a 25-29 amp draw by the converter. Secondly,
commercial units like the Newmar 12-12-35I DC-DC Converter can retail for more than
$900.
There is a more affordable, ham designed and built, voltage booster system from W4RRY
that should do the job. Check out:
http://www.fastq.com/~w4rry/
You have an IC-746s instead of an IC-746
The ‘s’ variation on the IC-746 is limited to only 10 watts output power to match up with the
restrictions of one of the Japanese amateur radio license classes.
Blown Internal Fuse
Check the 5A fuse within the RF power amplifier of the IC746 - reference page 81 of the
instruction manual. If this fuse is blown - there will be little to no output (< 10w).
There has even been a case of an intermittent fuse. Outside the rig with a multi-meter, the
fuse would test OK. However, replacing the fuse still fixed the problem.
Page 67 of 113
2003-02-08