Your ham radio shack power supply is the lifeblood of your shack. We put a lot of emphasis on our antenna systems (for very good reasons), but we sometimes forget where it all starts: Our power supply.
When our power supply is not powerful enough to supply a full 13.8 volts when under load and our voltage drops, our transceivers will not transmit at full power. If our power supply can not provide the amps that our transceiver needs (especially when using full duty cycle digital modes), the voltage will drop, or the power supply will stop providing power, and your radio will power off.
I recently upgraded my QTH radio to an Icom IC-7610. This radio on idle receive draws over two amps, which is more than an amp more than my Icom IC-7300 pulled. On full duty cycle transmit, the IC-7610 draws over 20 amps at full power. This resulted in my previous power supply failing to provide enough power and my rig powering off.
When looking for a new power supply, I discovered there is not a lot of inconsistency in how various manufacturers rate their power supplies regarding their amp rating. Here is what I discovered.
You will see a few specifications when looking at power supplies.
Advertised/Max Amp Rating
This is usually a part of the model number. A power supply might be called RS-50M, SEC-1235M, or DM-30T. Each model number implies a rating: 50 amps, 35 amps, and 30 amps, respectively. This is a great start when looking for a power supply that will fit your use case. If you know your radio will pull a max of 25 amps, you know you should start looking for a power supply greater than 25 amps.
Astron calls this rating ICS (Intermittent Communication Service: 50% duty cycle – 5 minutes on/5 minutes off)
Continuous Amp Rating
This rating is how many amps the power supply can output continuously – full duty cycle. If you plan on running digital modes at full power, you want to ensure that your power supply provides a continuous amp rating that matches your radios max amp rating. Personally, I am going to look for power supplies that have a continuous rating that matches my shacks max amping rating just to be sure that I am going to be able to deliver reliable power.
Current Limit Rating
Samlex advertises their “Current Limit” rating, the rating at which the power supply will stop providing power.
Each manufacturer and spec sheet may use these terms a little differently, so read them carefully to determine which rating aligns with full duty cycle and max output (when not in full duty cycle).
My Previous Power Supply
My original QTH power supply was an Alinco DM-30T. This is a great power supply and met all of my needs with a smaller radio. It was very cost-effective, and to be honest, I abused this power supply at times, and it continued to perform well. I will continue to use this in my shack.
As you can see, it is advertised as having a continuous output rating of 20A. It performed exactly as it should have. When I pushed this power supply over 20A for extended periods of dull duty cycle, the voltage dropped, and my rig powered off.
Power Supplies I Considered
I considered power supplies from Astron and Samlex as new additions to my shack to power my more power-hungry IC-7610.
Astron
My first stop was to look at the Astron line of linear power supplies. Although noise from my switching power supply has never been an issue in my shack, I have always wanted a high-quality linear style power supply in my shack.
The Astron RS-35M has a continuous amp rating of 25A. Although it has a 50% duty cycle (ICS) rating of 35A, I wanted to make sure that I chose a model that would also meet my needs at full duty cycle.
Samlex
I did take a peek at the Samlex models as well. Samlex only manufactures switching power supplies, and all of their models support a much higher continuous amp rating when compared to their advertised/max rating. In the case of the Samlex, their power supply is advertised as “Continuous”, and their model number is listed as the “Current Limit” max.
In all cases, make sure to not just look at the specs on the power supplies web page but take the time to download the full spec sheet, as some of these details are only in the full spec sheet.
Which power supply did I choose?
As I mentioned, I wanted to upgrade to a linear style power supply. So I choose the Astron line of linear desktop power supplies. I chose the RS-50M-AP for the following reasons:
- I went with the 50A model, which gives me a continuous rating of 37A at full duty cycle. I chose this model as I also want to power some other shack accessories off this power supply.
- I picked the M series from Astron as these come with the analog volt/amp meters on the front panel.
- I chose the AP version as these models provide two Anderson Powerpole connectors on the front panel should I need to attach some other device to them quickly.
A high-quality power supply will last a decade or more in your shack. I chose to look at this as more of a long-term shack investment and purchased one with a bit of extra headroom so that I do not have to push it as hard when running full duty cycle.
I am thrilled with my Astron RS-50M-AP and look forward to it powering my shack for many years.
