eHam

eHam Forums => Station Building => Topic started by: VE7REN on November 13, 2022, 10:18:52 AM

Title: curious! switcher vs linear power supply? what you use and why?
Post by: VE7REN on November 13, 2022, 10:18:52 AM
pondering what most people use in the shack? size,weight power consumption  with a linear. i own both,but prefer a switcher,although the linear is easy to repair. 50 amp astron linear ,and a ss-30m ap switcher are used here,along with a couple samlex switchers in the shop. what are you using and why? for me ,i like the compactness and less power consumption of the switcher.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: AK5B on November 13, 2022, 10:35:18 AM
Most switchers generate RFI, my old Astron was terrible in that regard.  Once I went back to a linear supply all was and is well now.

73,

Jeff, AK5B
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: K6SDW on November 13, 2022, 10:56:16 AM
I prefer switching supplies, small and light weight compared to a linear supply....I've done lotsa testing on my MFJ-4230 (which fits in my hand) and MFJ-4225 switchers and no birdies detected. Fan noise is another topic of discussion.

I don't have any issues with linear supplies, if I find a good deal on one and have the room, I'll buy it.

GL/73
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: AA4PB on November 13, 2022, 11:26:09 AM
If it's for a fixed station where size and weight are of little concern then I'd use a linear supply. If it's to be used portable, where size and weight are a concern, then I'd use a switching supply.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: VE7REN on November 13, 2022, 03:09:01 PM
interesting replies. thanks guys.

i dont notice ANY noise from my switchers. my older ss-50 astron developed noise on 75/80 meter,but no where else. the samlex are rock solid and clean,and so are my NEWER version astron ss-30m-ap. the fans on the astron have come a long ways too,as they are whisper quiet. the samlex only comes on after some usage in higher demand,and are noticable,but there is a fan mod available online for this. i think the linears are just to bib,and very expensive. if a person takes care of his gear and has adequate cooling and no animal hair,it will be interesting to see the longevity of the switcher vs the linear.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: N5CM on November 13, 2022, 04:39:25 PM
In the shack, I use linear supplies.  As you mentioned, the are reasonably easy to repair if they break, and they're RF quiet.

I got tired of lugging a 30-amp linear supply out for Field Day and other "portable" operations, so after reading lots of reviews and threads on the subject over a spread of a couple of years, I bit the bullet and bought a Samlex SEC-1235M.  After three marathon field day efforts, some POTA activations, and a few other trips, I can say that the 1235M is RF quiet and has plenty of headroom for my 100-watt portable station and accessories.  I am pleased with the performance of the Samlex.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: AI5BC on November 13, 2022, 04:46:36 PM
Most switchers generate RFI,
Not if you know what to buy. The switchers are less expensive and can actually deliver their rated current.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: SWMAN on November 13, 2022, 06:39:50 PM
 I use an Astron SS-30m. It is 21 years old, light and very reliable. I get no RFI anywhere that I have ever heard on any bands. I bought it because my local Texas Towers recommended it at the time. If it ever died I would buy another one for sure.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: K4WH on November 13, 2022, 07:18:34 PM

Own a Alinco 330 MVT SS supply, got it as part of a used rig I purchased.  Worked fine seems to have no RFI. 

That being said I use daily a 70 amp Astron with the meters and front controls, and a 35 amp Astro packed away for now.

Just like the old pig iron supplies. 
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: G8FXC on November 14, 2022, 12:02:38 AM
Following a long, and very painful, thread on another forum, I've just replaced a pair of linear supplies with a single high output Astron switcher...

A lady ham had an FTdx101D - just a few weeks old - which had been completely destroyed by a power surge. Yaesu were refusing to repair under warranty because the damage was done by an external fault and the repair estimate was effectively the price of a new radio. This got me thinking about the risk to my own radio and an inspection of the circuit diagrams for my linear PSUs showed that they offered no protection against such an event. Most PSUs claim to have protection circuits in them, but look in detail and you'll see that in many cases the thing that's being protected is the PSU, not the load!

I bought an Astron 50A SMPSU to replace my two linears. It has crowbar surge protection, so the radios should be pretty safe. I've scanned the HF bands with my SDR with the PSU both on and off and there is no obvious RFI. I'm very happy with it.

Not many PSUs on the market have proper surge protection for the load - check yours. Without it, you could be faced with a very large repair bill... Linear PSUs are the worst culprits - the basic design has not changed in forty years. A transformer and rectifiers produce unregulated power at around 25v and three or four big power transistors bring that down to a nice smooth 13.8V - but the most common failure mode for those big power transistors is short-circuit - feeding that unregulated 25V straight into your radio. The PSU needs a crowbar and most don't have it.

Martin (G8FXC)
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: G4AON on November 14, 2022, 02:09:44 AM
I use both, a 35A linear (Racal ex military with crowbar) and SEC-1235G in the shack. With both, I also use a "BOB" protection board with each of my shack radios, I just don't trust any power supply. The BOB project was in our RadCom magazine and is described by the author here:
https://gm4wzg.co.uk/wp/home/projects/bob/ (https://gm4wzg.co.uk/wp/home/projects/bob/)

When operating portable with a generator, I use a switching supply, a linear one just adds weight to my kit bag.

None of my switching supplies generate noise that I can detect.

I have experienced two linear supply failures, one was a cheap bench supply used in the shack to power a 10 Watt radio, fortunately I had retro fitted a crowbar and it saved the radio. The other was an audio amplifier that blew when it's linear supply failed, it was replaced under warranty and the new amp used a switching supply.

73 Dave
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: KT4WO on November 14, 2022, 02:13:37 AM
I have 3 SMPS- Samlex, Astron and Kenwood.

ALL have RFI issues at or below 80M. Some are worse that others.
160M and 630M are unusable due to RFI.

My RS-70 hums along, for 25 years now, NO RFI.

YMMV
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: W1SPS on November 14, 2022, 02:30:06 AM
I have a Agilent (HP) 6032A power supply. I got it for free when a place I used to work was liquidating unused equipment. It's always worked well and has bee RF quiet for me.

73
Rich
W1SPS
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: NA4IT on November 14, 2022, 05:12:39 AM
Shack is powered with a 12V / 150AH UPS Battery, and a IOTA 30 amp supply / charger from Cascade Audio.
The IOTA supply is an Recreational Vehicle type supply / charger and have good RF shielding.
The DC voltage stays near 13.5V at all times, and when AC fails, there is NO loss of DC.

(https://www.qsl.net/na4it/052010power.jpg)
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: W9FIB on November 14, 2022, 05:44:56 AM
I also learned the value of a switcher with good crowbar protection the hard way. The linear supply had a pass transistor short delivering almost 36 volts to my Icom. Needless to say it was fried.

I now use battery in the shack and a switcher when portable. Similar set up as NA4IT.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: G8FXC on November 14, 2022, 07:52:22 AM
I also learned the value of a switcher with good crowbar protection the hard way. The linear supply had a pass transistor short delivering almost 36 volts to my Icom. Needless to say it was fried.

I now use battery in the shack and a switcher when portable. Similar set up as NA4IT.

You have my sympathy! I would not say that it is a common problem but, when linear supplies go bad, they usually do push a lot of volts into the load. Switchers are more likely to "fail safe" anyway, and the better ones come with crowbar fitted...

Martin (G8FXC)
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: K9AO on November 14, 2022, 08:34:12 AM
A crowbar circuit is just going to fire on overvoltage and blow the fuse. FOr that to work it has to be after the protection fuse, so any fuse in the power cord to the radio externally from the power supply is not going to fulfil the requirement. There needs to be a fuse internal to the PS. Generally this is the case.

However this won't protect against the case where the radio fails. What you want is full foldback current limiting. Ordinary current limiting will simply limit the current to a set max value by decreasing the PS output voltage to not exceed that value. Meanwhile the radio fries away and whatever failed keeps drawing current. With full foldback current limiting the overcurrent event causes the PS to go into extreme current limiting, practically zero in fact. This shuts down the power to the radio after the event and does not let the failed device keep drawing excess current.

Of course if this is a 50 amp PS and your radio only needs 20 amps then the PS protection circuit isn't going to fault at values reasonable over the 20 amps draw of the radio. So in that case a PS better matched to the needs of the radio is safer.
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: G8FXC on November 14, 2022, 10:43:23 AM
There are many possible failure modes - we have to protect against the most probable and most expensive! The Astron SMPSUs are amongst the best specified - according to the sales brochure, they have


which should cover most bases...

What I was trying to do as best as I could was to insure against expensive failures that will not be covered by warranty... In the case I described, a £3,000 radio that was just a few weeks old was destroyed by a PSU failure and Yaesu washed their hands of it. If an internal fault in the radio makes it draw 50A and melt itself, the warranty will cover that!

Martin (G8FXC)
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: AK4YA on November 17, 2022, 10:14:59 PM
can most any switching power supply noise not be solved with enough toroids and ferrites?
Title: Re: curious! switcher vs linear power supply? what you use and why?
Post by: KD6VXI on November 18, 2022, 03:28:46 AM
can most any switching power supply noise not be solved with enough toroids and ferrites?

I use both.

Currently I'm using a 30A Jetstream switcher.  I haven't really noticed any noise on it.  That is connected to the shack radios.

On my test bench I have a pair of 60A Tripp-Lite power supplies married together (1 control board controlling all pass transistors) for 120A.  I also have a homebrew 600A benchtop supply (iron based, weighs in the hundreds of pounds).

Whatever I have on hand.  I don't buy junk, so it doesn't matter which kind of power supply I use.

I do notice in 30 years of using switchers in PCs, ham shacks, helping CBers with their stations, etc. that switchers have a lot (I mean a LOT) more breakdowns.  And when they break, it's better to usually trash them.

I also use an external crowbar via back to back zeners so when they fail, if they fail with 120 on the output, they blow a fuse instead of blowing up my unobtanium 2879 finals.


--Shane
WP2ASS / ex KD6VXI