Current draw, Full Quantro

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kb4mdz
Posts: 281
Joined: Tue Oct 02, 2001 4:00 pm
What radios do you own?: Too many for the time I have.

Current draw, Full Quantro

Post by kb4mdz »

Need a good faith (or spec. sheet) value for current draw of a Quantro station; VHF, for what it's worth.

Why? I hear you ask?

Yes, I'll tell you; can I cheat by making a temporary adapter from 15A outlet to the 20A plug, enough to power it up, read it, program it with lower power?

Or do I have to wait for the electrician to install a full 20A outlet for my testing? I know the Power supplies are vastly inefficient and draw far in excess of what the repeater itself needs.

DEFINITELY NOT for long term; don't worry about that.

Thanks,
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Astro Spectra
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Re: Current draw, Full Quantro

Post by Astro Spectra »

Do you need to transmit?
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kb4mdz
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Re: Current draw, Full Quantro

Post by kb4mdz »

Yes; I'll just set the TX power down to a 'reasonable level'; say, just over 100 Watts.
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Astro Spectra
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Re: Current draw, Full Quantro

Post by Astro Spectra »

So you can set the power down before you transmit and this will keep the AC draw down.
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kb4mdz
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Re: Current draw, Full Quantro

Post by kb4mdz »

Right. But those MSF5000 power supplies are notoriously inefficient. They hog a lot more current, all out of proportion to the RF output power. So, even at 100W RF, how close to 15A AC current am I likely to come?
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Astro Spectra
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Re: Current draw, Full Quantro

Post by Astro Spectra »

It's OK to draw more than 15A for a few moments on a 15A circuit. Buy yourself one of those Kill-a-Watt wall plug power meters http://en.m.wikipedia.org/wiki/Kill_A_Watt and see what the draw is. This will give you peace of mind and allow you to set the power within the outlet rating. Please post what you find.


When your done with the Quantro you can check out the rest of your appliances and maybe save yourself sometning off your utility bill!
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kb4mdz
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Re: Current draw, Full Quantro

Post by kb4mdz »

All done, questions answered:

Put a Fluke Clamp-on ampmeter on one of the conductors in the electrical junciton box; (1 mV on DMM equals 1A.);

Idle, no activity: 2A (unplugged the very noisy fans that have to be replaced; 1.89 Amp)

175 Watts RF = 6.8 Amps AC
200 Watt = 7.2 Amps.
250 Watts, = 7.9 Amps.
300 Watts, = 8.6 Amps
350 Watts, = 9.2 Amps.

So, well within the capability of a 15 Amp circuit & plug, for temporary, but no way I'd put it in service like that! Hmmm, dedicated outlet, 20A rating.

Do NOT want this baby to shoot fire out of anything!! YIKES!!
Will
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Re: Current draw, Full Quantro

Post by Will »

kb4mdz wrote: Do NOT want this baby to shoot fire out of anything!! YIKES!!
That is what the proper size fuses are for....
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Astro Spectra
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Re: Current draw, Full Quantro

Post by Astro Spectra »

Thanks for reporting the reuslts back. An output of 175W sounds pretty good to me given that mobiles are typically only up to 100W. A draw of 7 amps will be fine on the circuit if you use decent plugs as the thransmitter will be only only intermitently.
khw
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What radios do you own?: Quantars, Quantros, APX, XTS..

Re: Current draw, Full Quantro

Post by khw »

Is this a 350W VHF Quantro with two amps?

The Motorola manual lists the requirements of: "an AC source capable of supplying a maximum of 1550 Watts. For a nominal 110V ac input, the ac source must supply 16 amperes and should be protected by a circuit breaker rated at 20 amperes."
As I recall, 170W is the lowest output you can set.
Kevin
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kb4mdz
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Re: Current draw, Full Quantro

Post by kb4mdz »

Yup, two amplifiers of the MSF5000 flavor;

I agree with the manual, what SHOULD be the source, but in a pinch in the shop, and before the electrician can put in a proper NEMA 20A outlet, I can get away with a 15A outlet & plug. Light duty, short transmissions. When it goes into actuall service, even down at 175 Watts, it's gonna get the correct outlet.
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