Most used transceivers don't plug into the wall. They run on 13.8 volts DC, and the supply that feeds them is a separate box you'll need to buy if the listing doesn't include one. Others have an AC supply inside, and tube sets often need their own matching supply. This guide covers what each kind needs, with the figures from the makers' spec sheets.
13.8 volts, and the amps matter more
A 100-watt solid-state rig runs on 13.8 volts DC. Yaesu's FT-450D manual says you can wire it straight to a car battery or to a DC supply. Voltage is the easy part. The current on transmit is what decides your supply, and it's much higher than on receive. Here's what the spec sheets list as maximum current on transmit.
- The Icom IC-7300 draws 21 amps, against 1.25 amps on receive.
- The Icom IC-7610 draws 23 amps.
- The Icom IC-718 draws 20 amps.
- The Icom IC-7000 draws 22 amps.
- The Yaesu FT-450D draws 22 amps.
- The Yaesu FT-991A and FTDX-10 draw 23 amps.
- The Yaesu FT-857D draws 22 amps.
- The Kenwood TS-590SG, TS-2000 and TS-480SAT draw 20.5 amps.
- The Kenwood TS-130S draws 18 amps.
- The Drake TR-7 draws 25 amps.
- The Icom IC-9700 draws 18 amps, at 100 watts on 2 meters.
Pick a supply rated a bit above the rig's peak. Yaesu's FT-450D manual asks for a supply that can deliver at least 22 amps at 13.8 volts. Kenwood's TS-480 manual says each supply must handle 20.5 amps peak or more, and the 200-watt TS-480HX needs two of them, or one 41-amp supply.
Stay inside the voltage window
Spec sheets give a tolerance. Most of these rigs accept 13.8 volts plus or minus 15 percent, and the FT-450D allows plus or minus 10 percent. Icom's IC-718 manual says never to apply AC to the DC jack, and never more than 16 volts, such as a 24-volt battery. Use the DC cable that came with the rig. Kenwood warns not to swap in a cable with thinner wire, and Yaesu says the FT-450D needs a 25-amp fast-blow fuse, so check the right one is fitted. If a listing has no DC cable, add one to your list, since the plugs differ. The FT-857D uses a 6-pin Molex, for example, and the FTDX-10 a 4-pin plug.
What to ask about a supply in the listing
If a supply comes with the rig, ask for a photo of its label so you can read the voltage and current rating. Ask too whether the seller ran the rig at full power from it, since the rig only meets its spec inside its voltage window. A rated supply with the right plug saves you a separate purchase.
The makers' own supplies
Each maker sold a matching supply, and a listing that includes one is worth more. Icom lists the PS-126, 13.8 volts at 25 amps, as an option for the IC-7300, and the PS-85, 13.8 volts at 20 amps, for the IC-718. Kenwood lists the PS-60 at 22.5 amps for the TS-590SG and the PS-53 at 22.5 amps for the TS-480SAT and TS-2000. The older PS-30 for the TS-130S is rated at 20 amps with a 50 percent duty cycle. Yaesu lists the FP-1030A AC supply for the FT-857D. A supply from another maker works too, as long as it holds 13.8 volts and covers the rig's peak current.
Linear or switching
There are two kinds of regulated supply. A linear supply uses a transformer running at 50 or 60 hertz, so it's heavy, and it burns off extra power as heat. A switching supply switches at hundreds of kilohertz to several megahertz, so its transformer is much smaller and it runs cooler. Wikipedia's article on switched-mode supplies names the trade-off. Switching currents can cause electrical noise if they're not well suppressed, and cheap units can push that noise back onto the mains. For a receiver that hears weak signals on HF, that noise matters. Either kind works if it's well made. If a used switching supply comes with the rig, listen across the bands with it running before you judge the radio's receiver.
Rigs with the AC supply inside
Some rigs plug straight into the wall. The Yaesu FTDX-5000 takes 90 to 264 volts AC and makes 200 watts. The Kenwood TS-940S and TS-830S both run on 120, 220 or 240 volts AC. Those are heavy radios. The FTDX-5000 weighs about 46 pounds, the TS-940S about 41.
Check before you assume. The IC-7610 and TS-590SG are big base rigs, but their spec sheets both list 13.8 volts DC, so they need a separate supply. The FT-991A doesn't have a supply inside either.
Portables
The low-power portables are easy. The Icom IC-705 makes 5 watts on its BP-272 or BP-307 battery pack and 10 watts on 13.8 volts external, drawing 3 amps at most. The Yaesu FT-817ND makes 5 watts on 13.8 volts and 2.5 watts on its 9.6-volt internal pack, and it can also run from eight AA cells. A small supply or battery covers either one.
Tube sets and their matching supplies
Many tube rigs need a separate supply that makes several voltages at once. Heath's HP-23, for the HW-101 and other Heathkits, delivers about 700 volts at 250 milliamps for the finals, two lower B+ voltages, bias, and filament power, from 120 volts AC at up to 350 watts. Drake's AC-4 does the same job for the TR-4 series and the T-4XC, which needs 650 volts, 250 volts, a negative bias and 12.6 volts. The HW-101 can also run mobile from Heath's HP-13 on 12 volts DC.
These supplies are as old as the radios, and their capacitors age too. A Drake specialist describes AC-4s whose filter capacitors dry out, short or open, and whose failing bias capacitors let the finals run away. Heath's HP-23 manual warns that the output can be lethal and that the large capacitors hold a dangerous charge after switch-off. Ask whether the supply has been rebuilt, and leave the inside to someone who knows high voltage.
Amplifiers on 120 or 240 volts
Linear amplifiers draw far more than a transceiver. Heath's SB-220 runs on either 120 volts AC at up to 20 amps or 240 volts at up to 10 amps, and Heath recommended 240. It has a circuit breaker on each side of the line cord and can be switched between the two. Drake's L-4B used a separate L4PS supply producing over 2,500 volts at almost an amp, and WB4HFN notes that many L-4Bs now turn up without it. FCC rules cap any amateur station at 1.5 kilowatts PEP, so check what you'll run before you plan the wiring. Ask an electrician before you add a 240-volt outlet to your shack.
