Astron RS-35M-AP Review: The Boring Supply That Outlives Radios

Twenty five amps continuous, no fan, real meters, and no switching noise to chase.

Specifications

Specifications above come from Astron's published specifications for the RS-35M-AP. Treat pricing as approximate, since Amazon pricing moves.

What it does well

• A linear design generates no switching hash, so it adds nothing to your receive noise floor. This is the entire reason to buy one.
• No fan means no fan noise and one fewer moving part to fail.
• Twenty five amps continuous is a genuine continuous rating, not a peak figure with an asterisk.
• Real analogue voltage and current meters, so you can see a problem developing rather than guessing.
• Both screw terminals and Powerpole connectors fitted, which covers a shack wired either way.

Where it falls short

• It is heavy. A linear supply at this current uses a large mains transformer, and that is the price of the quiet.
• Linear supplies are less efficient than switching ones, so more of your electricity becomes heat.
• It costs several times what a competent 30 amp switching supply costs.
• Twenty five amps continuous suits one 100 watt radio comfortably. It is not a station bus for a radio, an amplifier and accessories all at once.

Linear or switching, honestly

The case for linear is noise. A switching supply chops mains at a high frequency, and a poorly filtered one puts that energy into your receiver as a comb of birdies right where you are trying to listen. A linear supply cannot do this because it does not switch. The case against is weight, heat and money, all of which are real.

A well designed modern switching supply is often quiet enough, and if it is not, ferrite and better filtering usually fix it. Read linear versus switching power supplies for the full trade, and if you are chasing an existing noise problem the RFI hunting guide lists the usual sources in the order worth checking. Mains wiring and station grounding are safety matters governed by the National Electrical Code and local rules, so bring in an electrician where the work calls for one.

What owners report

Published owner reports on Astron linear supplies read more like reports on furniture than on electronics. The dominant theme is longevity: owners describe units still working after decades, being repaired rather than replaced, and being passed between stations. The second theme is silence, both acoustic, because there is no fan, and electrical, because there is nothing switching at a few tens of kilohertz to appear as birdies across the bands.

Criticism is almost entirely about weight and price. Owners who move their station, operate portable or have limited desk space consistently say a switching supply was the better answer for them, and that is a fair conclusion. A few note that the meters are indicative rather than precise instruments, which is true of most panel meters.

One recurring practical point: size the supply to the radio's peak draw with headroom, not to its average. A supply that just meets the number sags on voice peaks and produces distorted transmit audio that gets blamed on the radio. Run your own numbers on the power supply sizing calculator before choosing a rating.

Who it suits

• Base stations with a permanent desk, where weight never matters again after installation.
• Operators fighting a high noise floor who have already eliminated the obvious sources.
• Anyone who wants one supply to outlive several radios.
• Stations wired with Powerpole connectors who want the distribution to start at the supply.

Who should skip it

• Portable and go box operators. The weight is disqualifying.
• Anyone on a budget. A good 30 amp switching supply costs a fraction as much.
• Stations that need to run a radio and an amplifier and accessories from one supply. Size up or split the load.
• Anyone who has not yet checked whether their existing supply is actually the noise source.

Alternatives worth considering

Keep reading

• Linear vs switching power supply
• Best power supplies
• Power supply sizing calculator
• How to size a power supply
• Finding and fixing radio noise
• Xiegu GPA100 amplifier review

This review draws on published specifications, manufacturer figures and the consensus of verified owner reviews. We have not tested this product ourselves, and we say so rather than implying otherwise. As an Amazon Associate we earn from qualifying purchases.