Switch Mode or Linear Power Supply?

[VK3ERW]

Having passed my foundation exam and studying for next week's standard exam I am doing some planning for my station - one of the basic components I need is a gutsy power supply that can deliver 25A or 30A (for when I get my full call).

Back in the days when I was a young lad and played with radio's, a transformer based (regulated) power supply was all one would ever consider for a transceiver but technology has come a long way and transformer based power supplies have been replaced with smaller and more efficient switch mode technology in may applications.

I would appreciate some advice/opinion as to the current thinking amongst experienced AR operators on the suitability of a switch mode power supplies for use with a HF transceiver.
Should I stay away from switch mode and stick with transformer based power supplies? Or should I seriously consider a (good brand?) switch mode power supply?
How do you power your rig and what's been you experience with switch mode?

I apologies if this subject is already covered somewhere else on this forum - I did search but couldn't find any threads relating to switch mode power supplies.

Many thanks for your input on this subject.

Erwin

[VK2GOM]

I have always used linear (transformer) supplies for radios, but use the odd SMPSU here and there for ancillary equipment.

The main thing to look out for, especially operating on HF, is noise from a SMPSU. Some are better than others, and it basically comes down to how well they have been designed, what financial shortcuts have been taken in their design/specification, and the quality of components and the actual build within.

I recall the ARRL did a review of a few SMPSU's a while back in QST magazine, and plotted noise spectra for each PSU as part of the review. Some were, as you'd expect, worse than others, but they did manage to identify a clear winner that was reasonably quiet.

If you can find a good (quiet) SMPSU, they can certainly save room on your bench and help prevent deep leg dents from your bench forming in your carpet. They are certainly more prolific these days too, than good old linear supplies.

73 - Rob VK2GOM / GW0MOH

PS. I have also Private Message'd you a useful link.

[VK5TM]

This forum entry has various posts about power supplies. including switch mode ones that are quiet.
Bit of a read as there are a few pages to look through.

viewtopic.php?f=22&t=11681&hilit=power+supply

[VK3ERW]

Terry / Rob,
many thanks for your replies.
The other thread is quite interesting reading.

I'd still like to hear if anyone has had any RF interference issues with SWPSU's.

Thanks

Erwin

[VK2OMD]

Terry / Rob,
many thanks for your replies.
The other thread is quite interesting reading.

I'd still like to hear if anyone has had any RF interference issues with SWPSU's.

Thanks

Erwin

You seem in some sort of doubt that SMPSs can or do make significant RF noise.

The method by which the power supplyies work creates voltage and current waveforms with very fast rise and fall times. That necessarily means there is a lot of energy available at radio frequencies.

Good power supplies effectively filter the input and output to prevent escape of significant RF energy from the internals.

Some people's strategy is to never use SMPS... but I doubt that it practical as somewhere in your home there will be some SMPS (everything from mobile phone chargers to inverter airconditioners). At a guess, there are probably 60 or more running here right now.

Make the Australian Consumer Law work for you if you purchase from an Australian business. Advise the seller what you intend to use the power supply for, and their selling it to you for that purpose gives you a warranty of fitness for purpose and you can return it if it turns out to be unsuited for that stated purpose.

Of course, if you buy one of the $30 LED lighting jobbies on eBay from China, you are pretty much on your own.

BTW, in some states power supplies (new or used) of the type you mention must be approved to certain standards before they can be sold (by anyone).

You have been given a link to a relevant recent discussion. You might have found that before posting, but you don't really expect all the same stuff to be repeated do you?

Owen

[VK3APW]

Hi Erwin,
I have tested noise on switchmode power supplies, in applications other than running a transceiver, but the point of the exercise was the same, Noise.
I tested a number of supplies, with a high power resistive load, volt meter, amp meter, scope and spec an attached. I went through most the brands that I could buy easily, off the shelf, that would supply over 20A at 13.8V. What I found, was that there are large variations in the noise output, between different models, and also between examples of the same power supply. ( One of the 'cheapies' had well over a 2 volts peak to peak switching noise, that I could see ).

I think most would agree, for HF, a linear regulated supply, will give you less noise related problems than a SMPSU. VHF transceivers are a little more forgiving. However, this is a generalization, and not to say that a quality SMPSU, will not be suitable for the HF application.
If you do decide on a SMPSU, I would make sure before you buy it, that you can return it, for a cash refund.
There are ways to improve the 'noise' performance. A suitable ferrite on the supply cables, close to the radio, will help, and Drew Diamond has an excellent write up, in one on his books, on how to tame a SMPSU. It does work.
Good luck on your quest, and license upgrade

Regards

Peter vk3apw

[VK2AAH]

Owen,

I like your assessment of the issue...

To me it is not a question of whether SMPS generate noise (they do) but:

(a) If weight and efficiency are important to you choose SMPS. If they aren't and you don't mind the odd hernia choose a large linear supply.

(b) If the SMPS has been properly designed to filter and shield the noise what is the issue?

(c) If people still live in the past full of the horrors of massive voltages being created when an SMPS fails then don't ever go to a hospital... chances are your life may depend on something powered by a SMPS! Ssssshhh... don't tell the media.

My employer has just eradicated southern NSW of our old linear power supplies (the Imarks) and every radio tech that works on our gear is popping champagne corks. Heavy, prone to fail far more than the SMPS we are now using- hams need to join the 21st century and realise that technology moves on. What was true about SMPS in the 1980s and even the 1990s is not true in 2013.

Cheers

Richard
VK2AAH

[VK2OMD]

Owen,

I like your assessment of the issue...

To me it is not a question of whether SMPS generate noise (they do) but:

(a) If weight and efficiency are important to you choose SMPS. If they aren't and you don't mind the odd hernia choose a large linear supply.

(b) If the SMPS has been properly designed to filter and shield the noise what is the issue?

(c) If people still live in the past full of the horrors of massive voltages being created when an SMPS fails then don't ever go to a hospital... chances are your life may depend on something powered by a SMPS! Ssssshhh... don't tell the media.

My employer has just eradicated southern NSW of our old linear power supplies (the Imarks) and every radio tech that works on our gear is popping champagne corks. Heavy, prone to fail far more than the SMPS we are now using- hams need to join the 21st century and realise that technology moves on. What was true about SMPS in the 1980s and even the 1990s is not true in 2013.

Cheers

Richard
VK2AAH

A good SMPS had certain advantages over a good linear supply, but then a good linear supply had certain advantages over a good SMPS. Lets leave bads ones of each out for the moment.

Fans in either type are a maintenance issue and a noise issue. Some are worse than others, and thermostatically controlled fans are usually better. Whilst ball bearing fans tend to last longer than bronze bushed fans, they are noisier. Fans with ceramic bearings seem good, a bit more expensive but quieter than ball bearings and I have not had to replace one yet (over 15 yrs of service in some cases).

All power supplies need an ample supply of cool air.

I use linear power supplies exclusively for 'lab' power supplies where the risk of blowing them up is higher. Linear power supplies are less hazardous to the repair technician, and usually easier to repair with less knowledge and experience, but no one should take the cover off a power supply unless they are competent. I use a mix of linear and SMPS for high power 13.8V supplies, one needed modification to reduce noise adequately.

My count of 60+ SMPS technology things in the house in my earlier post includes things like plug pack chargers and power supplies (if they are light, they are probably SMPS), electronic flouro ballasts (modern T8, all T5 flouros), CFL, LED lighting power supplies, most high power LEDs for lighting, some QI downlight power supplies, TV, inverter air conditioners, ... the list goes on. So, like it or not, most homes probably have some SMPS technology deployed... and it is likely to grow.

For a beginner, a linear supply for 20A or so can be had for around $300 (DIamond or Yaseu rebadge), or one of the Manson SMPS starting at $125 are probably a good way to start.

http://www.strictlyham.com.au/diamond-gsv-3000

http://radioparts.com.au/product/337716 ... oaSvif656E

BTW, being able to adjust the voltage on the front panel is somewhat of a disadvantage!

Owen

[VK3ERW]

You have been given a link to a relevant recent discussion. You might have found that before posting, but you don't really expect all the same stuff to be repeated do you?

Owen, thanks very much for your input.
The other thread is titled "Cheap Power Supplies" and has very useful information (which I don't expect to be repeated here) but nevertheless focuses on $$$ as the main criteria and hence polarises the discussion around SWPS. The thread focuses around VK3FACE getting 20A for as little $$ as possible.
My question is not at all price related (hence not biased towards SWPS), my interest is in getting the technology that works best for my intended purpose (HF), and particularly how one technology compares to the other.
Apologies if I failed to make this clear my initial post (it was my first post on this forum).

Cheers

Erwin