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Author Topic: switching power supply noise  (Read 2836 times)
K1QQQ
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Posts: 282




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« on: March 24, 2018, 02:34:12 AM »

Can anybody recommend a switching power supply of around 30 amps that does not produce noticeable noise on HF ?
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KAPT4560
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Posts: 552




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« Reply #1 on: March 24, 2018, 03:08:35 AM »

 12 volt?
I have added regulation and filtering to linear car battery chargers for quiet operation where higher current is desired.
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K1QQQ
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Posts: 282




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« Reply #2 on: March 25, 2018, 05:56:40 AM »

Interesting.


I am in need of some 12-13 volt power supplies to just power a 100 watt transceiver, etc. Kinda helps on knowing what to avoid. At lest now I possess numerous Astron boat anchors.
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K5LXP
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« Reply #3 on: March 25, 2018, 07:13:33 AM »

So any of the amateur dealer offerings from various manufacturers aren't adequate?

Should point out too that interference is a 2-way street - EMI generation and EMI susceptibility.  Even a very "quiet"supply will still be picked up by a receiver without adequate antenna isolation.

Mark K5LXP
Albuquerque, NM
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AA4HA
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« Reply #4 on: March 25, 2018, 07:44:43 AM »

So if you think about what a switching power supply is;

It's an oscillator, amplifier and transformer running at a few hundred watts at a frequency between 50-100 KHz. It is very harmonically rich due to the switching mode design of the transistor so it will be generating harmonics up in to the MHz to 10's of MHz; right in the middle of the HF band.

To make it "clean" the entire primary side of the switching supply would need to be shielded. The AC line connection would need very good filtering. So would the DC output following the transformer.

This is more than just a metallic can with slots for air vents.
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If you want to make it not oscillate in the 50-100 KHz range then it would operate at a lower frequency.. closer to the line-side transformer that runs at 60 Hz for a linear supply.

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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
AE5GT
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« Reply #5 on: March 25, 2018, 10:02:21 AM »

The standard offline sub 200 W switcher will operate in the 130 -140 Khz region (inside the old power line comm band) . Buck boost like some of the LT switchers can operate in the Mhz region . I've seen charge pumps as low as 10 Khz and LED offline current ramp switchers at 200 Khz .

Its possible to make a "clean" switcher but to do it you have to use a clean high frequency sine wave instead of a square wave to drive the transformer ...Unfortunately effeciency goes out the window because the transistor switch is no long going into saturation and large amounts of power are dissipated in the "switch".

You can also get frequencies that are not harmonics of the fundamental switch frequency. When the supply transistor currents are large , and the transistor turns off  ...a large magnetic field collapses in transformer which induces a reverse voltage spike on the primary . The size of that spike will be a function of input voltage and the design of the transformer. You can get wideband noise as well .

AA4HA is right you need more than just a can .  You need a linear supply because it uses a sine wave. Thats not to say you cant get harmonics on a linear supply, you can...especially if there is a switch mode supply on the same power drop, switch modes are notorious for causing line harmonics. Switch mode supplys are much more difficult to design than a linear ...few are done well.

The reasons for using switch modes over linear are size,price , weight, and efficiency. If those are not a concern, use a linear. If you have to use a switcher at least look for one that has CE /FCC cert that way you know its at least supposed to meet a conducted / radiated EMC standard and Good Luck.

I don't like to "switch" but when I do I use a Samlex SEC 1223 (Kenwood /Yaseu sell rebranded versions)  . .. Power your radio Responsibly.
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AA4PB
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« Reply #6 on: March 25, 2018, 10:21:07 AM »

Can anybody recommend a switching power supply of around 30 amps that does not produce noticeable noise on HF ?
The problem is that "noticeable noise" depends on the particular station installation. How far away is the antenna, do you have any common mode currents on the coax shield, how well shielded is the radio and other wiring. A switcher that is quiet at one station may be noisy at another. Personally, in a fixed station where power supply size and weight is not a concern I'd rather use a linear supply.
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Bob  AA4PB
Garrisonville, VA
WZ7U
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Posts: 1073




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« Reply #7 on: March 25, 2018, 11:43:44 AM »



I don't like to "switch" but when I do I use a Samlex SEC 1223 (Kenwood /Yaseu sell rebranded versions)  . .. Power your radio Responsibly.


That was funny, I could hear the voice when I read that. Advertising is scary that way.  Thanks for the chuckles!

At one point not too long ago I was really strapped for cash and needed a power supply for my rig. I found a pair of switching supplies originally designed as server supplies. I repurposed them, with the requisite modification to get them to start, and for a whopping  $20 I have a pair of 82 amp @ 12.8 volt supplies that are surprisingly clean, turned up to 13,8 volts. One died on start a few months into it and the other is still working but I started to get paranoid and now with a couple of nickels I bought a used linear supply. I'll probably repurpose the switcher into some sort of battery charging scheme  (which was how I found out about it in the first place) or just keep it as a backup and do some harmonics charting sometime down the line.

If you must have a switcher, there are options. You sometimes need to get creative, that's all. GL
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K6CPO
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Posts: 529




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« Reply #8 on: March 25, 2018, 12:00:27 PM »

In answer to the OP's question (which no one else felt like answering) here's one:

https://www.hamradio.com/detail.cfm?pid=H0-003728

I use an earlier version of this power supply and there is no noise on HF at all.
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K1QQQ
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Posts: 282




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« Reply #9 on: March 29, 2018, 01:31:44 AM »

Thanks all the info.


I always liked Alinco and I think their stuff is still made in Japan.

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WZ7U
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Posts: 1073




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« Reply #10 on: March 29, 2018, 09:26:39 AM »

In answer to the OP's question (which no one else felt like answering) here's one:

https://www.hamradio.com/detail.cfm?pid=H0-003728

I use an earlier version of this power supply and there is no noise on HF at all.
Agreed about the Alinco, but what was this?

"I don't like to "switch" but when I do I use a Samlex SEC 1223 (Kenwood /Yaseu sell rebranded versions)  . .. Power your radio Responsibly."

Looks like a suggestion to me.  Roll Eyes
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KB2WIG
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Posts: 625




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« Reply #11 on: March 29, 2018, 01:14:15 PM »





I'd rather fight than switch.


KLC
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EXTRALight  1/3 less WPM than a Real EXTRA
WZ7U
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Posts: 1073




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« Reply #12 on: March 29, 2018, 07:49:39 PM »

Quote from:  link=topic=119800.msg1063182#msg1063182 date=1522354455




I'd rather fight than switch.


KLC

SMOKER!

It's ok, I retired from smoking after 31 years in the biz. I'm loving retirement!
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K6BRN
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Posts: 1269




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« Reply #13 on: March 30, 2018, 09:40:27 PM »

Quote
Can anybody recommend a switching power supply of around 30 amps that does not produce noticeable noise on HF ?

PowerWerx SS-30DV  $110 at HRO (sometimes on sale for $100).  https://www.hamradio.com/detail.cfm?pid=H0-010662

Dual Powerpole outlets on the front, binding posts on the rear.  About the size of two paperback novels stacked.  Recommended by Elecraft to power their HF rigs.  I have four, including two with digital meters.  They are RF quiet, easily support extended TX at 100 watts out on a Kenwood TS-440S, Yaesu FTDX-1200, FTDX-3000, IC-7300, FT-991 (etc., etc.).  Rated 25 amps continuous, 30 amps surge.  Pretty similar to the Astron RS-35 at 1/8th the size and 1/5th the weight.  Fan-cooled (temp controlled fan speed - usually OFF).

Brian - K6BRN
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