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Big Ed
03-11-2022, 02:46 PM
Hello All. So how many amps is required to drive a 500 watt linear?? I'm not sure what power supply to purchase. Thx.

Alabama Buckeye
03-11-2022, 03:33 PM
You make no mention of what it is, homebrew or commercial brand. Is that a confirmed 500W PEP or just bragging rights.
Take for example a Palomar 450HD. It is presumed to be a 450W amplifier. You take 78% of that you get its true PEP. I drove it with a 35A/40A surge Pyramid PK-46KX, $185 (discontinued) with no smoke or blown fuses. PEP is less important than RMS.

500 / V = Amps
500 / 13.8 = 36A; I use float voltage.
500 / 24.0 = 20.8
My M200 max draw 46A, in the specs. It is supposedly capable of 580W. But, sadly neither are realized; it draws but 15A which is at its RMS wattage output (too embarrassed to note PEP). You do the math. Clue: [1x2290 x 2x2879 (2sc2879 100W RMS, each)].

I wouldn't know how you'd feel about a Power Max Converter Charger / Power Supply; they are switchable to selectable single voltage output. It has its intended purpose then it has its power supply redirected purpose. They range from 55A to 120A at prices worth considering as an alternative to dedicated PS. I'm told (idiot sales person parroting "clean") they are pure sine wave output; you should confirm if in consideration. TMI

Big Ed
03-11-2022, 04:14 PM
Its an RM Italy KL703.

Alabama Buckeye
03-11-2022, 05:05 PM
Looks nice. Importantly it requires 30W input from your radio. A Cobra 29 isn't likely to do it with 25W PEP. Neither would me Ranger RCI 2950, also 25W SSB. Not the point...but clearly this is a high drive amp or straight 4 pill though there doesn't look to be "pills" in the common sense.

Specs read Max I/P current 50A. Don't speak Italian couldn't say what I/P stands for; other than "I" is amperage and "P" is watts in electrical equation. Which makes no sense to me, Amps/Watts is nowhere in the equation. For all I know, in Italian the noun precedes the adjective; where watts/amps is volts.

I'm gonna go out on a weak limb here and say a 50A power supply will more than suffice for your amp and radio.

On a second look I see I/P RF Drive 1-35W which suggests anywhere including and between. Can you drive a 4 Pill with 1W; good luck.

Big Ed
03-11-2022, 05:52 PM
Thank you for the information.

Alabama Buckeye
03-11-2022, 09:30 PM
If youll allow me, if you see a 10+ year hobby ahead of you? Don't skimp on the Power Supply. You're eyes will get as big as your heart, in short order.
I see the RM Italy KL703 is not small change. Surely a good buy compared to the $50 more expensive competition box, a DaveMade (DM) 400, which will produce 400W without raising the heart beat and probably >twice that PEP, provided your radio is putting out 10W. With that said I reflect back on the stated 30W input into the KL703; then there was that I/P RF range of 1-35W.
Your KL703 is far more ergonomically designed than the DM400. It would look far more appealing racked below your radio while on the move. In that case, upgrade your alternator. My '70 CST Truck has an upgraded 145A alternator just for this reason and it runs on water, from hydrogen generator requiring loads of amps.

Archy
03-13-2022, 08:59 AM
You can't just use ohms law/power formula (P=VI). You have to take in the the efficiency of the amplifier. For instance, class AB is less efficient. Let's say the amplifier is 80% efficient, that is, 20% of the input power is absorbed by the amp, the rest is your output. To put it more simply, you need to overate your supply current for this, then up it again for headroom.
This method is only when you know what the realistic power output of the amplifier is.