IC-746 FAQ
Load Capacity
The size, weight, and cost of a power supply all tend to increase with its load capacity.
Those factors encourage us to get the smallest supply we can. There are also factors that
encourage larger supplies; such as noise, heat, accessories, etc...
The IC-746 specifications list a current drain at maximum transmit power of 20A at 13.8Vdc.
Thus, the recommendation that your supply should handle 20 amps (or more) continuously.
It is possible to run the IC-746 with a smaller supply, but extreme caution and discipline are
required. Very few, if any, of us recommend it for normal operation.
For example, the 20 amp maximum in the IC-746 specifications is full key-down at full
power. You could just lower your RF power to help match your load to the supply. You
could even run the IC-746 QRP, drawing as little as 3-4 amps on transmit.
Another factor is operating mode. Some of us have measured full-key loads as high as 21-22
amps. Normal SSB transmit at full power draws 6-15 amps. But FM, digital, and CW will
generally pull 18-20 amps at full power.
Consider the following measurements on 20m into a dummy load.
Continuous vs. Intermittent Load
There are issues concerning a supply's "intermittent", "peak", or "surge" capacity. A supply
might be rated for 16 amps continuous and 20 amps peak. Normally, the IC-746 runs at
about 2-3 amps for receive and only hits the 20 amp maximum during transmission.
Thinking of transmitting as "peak" or "intermittent" activity can lead one to think that such a
supply is acceptable. It might even be. However, a problem develops when we try to define
what peak or intermittent activity is.
Page 25 of 113
2003-02-08
Содержание IC-746
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