Power supply amperage

[emercer]

I have a Jetstream power supply. Spec sheet says 30amp surge, 25amp continuous. Label on units says 22amp total.
When I transmit with a radio that draws 15 amps according to spec, the meter on the power supply is showing only 8.0 amps being drawn.
I've tried other radios with similar results. Is everything ok and efficient or is the power supply not putting out enough current?

 

[popnokick]

What mode(s) are you transmitting with (SSB, AM, FM, CW, RTTY, Digital, etc.)?

 

[emercer]

Icom ID-4100A operating on FM and D-star.

Spec 5.0A (5W), 7.5A (15W) 13A (50W)
Actual 2.5A (5W) 4.5A (15W) 8.0A (50W)

 

[mmckenna]

Radio manufacturers often over spec the current draw on the radios. 8 amps sounds pretty close to what I'd expect.
Also, don't put a whole lot of faith in that analog meter on the power supply. If you really want to know how much current the radio is drawing, use a DMM.

 

[emercer]

Ok. That's what I was hoping.
Those numbers were from my DMM and were close to the built in analog meter.
Thanks for replying.

 

[davidgcet]

also check the voltage while you transmit, if it is staying around 13.8 then the PS is not loading down. when a power supply cannot provide enough power the voltage drops and so does the current. since you are getting rated transmit power then I would say it is properly handling the load. and also are the spec currents for the FUSED supply or for the actual draw, fuses should always be bigger and in general in the radio world you fuse at roughly 2x the expected continuous draw of the highest load, not exactly 2x but "close enough for government work" as we used to say.

 

[emercer]

also check the voltage while you transmit, if it is staying around 13.8 then the PS is not loading down. when a power supply cannot provide enough power the voltage drops and so does the current. since you are getting rated transmit power then I would say it is properly handling the load. and also are the spec currents for the FUSED supply or for the actual draw, fuses should always be bigger and in general in the radio world you fuse at roughly 2x the expected continuous draw of the highest load, not exactly 2x but "close enough for government work" as we used to say.

Just tested voltage and it only drops 0.11 volts from 13.83 to 13.72 on high power, 50 watts.

 

[AK9R]

Just tested voltage and it only drops 0.11 volts from 13.83 to 13.72 on high power, 50 watts.

Measured at the radio or at the power supply? Measuring the voltage at the radio while the radio is transmitting will give you an indication of how much voltage drop there is in your power cable due to resistance in the cable itself and any fuse holders or connectors.

 

[WB9YBM]

When I transmit with a radio that draws 15 amps according to spec, the meter on the power supply is showing only 8.0 amps being drawn.
I've tried other radios with similar results.

What the spec's show is worst-case scenario--what the radio will draw with everything (including the kitchen sink) being lit up and running at max. It's to make sure the users hook it up to a supply that won't get overtaxed, plus a few percent. I've had the same thing happen here.