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[KD6VXI]

Shane,

The filter is symmetrical - it's just not obvious on the picture supplied.  See below for details and alternative view:

https://www.vk-amps.com/products/a-50a-2-stage-dc-line-noise-filter-circuit

73, Peter.

Mucho gusto.  That was a lot better pic to see the negative lead!


--Shane
WP2ASS / ex KD6VXI

[WB2VVV]

Reviewing the schematic this particular filter design would mitigate both common mode and differential mode noise. It works as far as I'm concerned, though I'm unable to state which type of noise was reduced. 

[K1SCQ]

Can anyone suggest any 48 VDC Power Supplies for use with modern Solid State Amplifiers that are:

1. QUIET, from a Mechanical/Acoustical/Airflow perspective.
2. Have low EMI Switching Noise from an Electrical Interference perspective.
3. Can supply low ripple clean 48 VDC for use with modern LDMOS/MOSFET Amplifiers.
4. Are durable and safe.

Thanks in advance for any suggestions of 48 VDC power supplies that satisfy these requirements!

Personally I have been using a MeanWell 48 VDC 1500 Watt switching supply on 240 VAC with a homebrew 1.8 thru 50 MHz MOSFET amplifier and it checks all of the boxes EXCEPT for being Acoustically Quiet. Its fans run all of the time at their highest speed and are very loud from an acoustical perspective, but it works very well from an electrical perspective, and I never hear any sort of electrical interference over the transceiver from the switching basis of the DC power conditioning. The MeanWell SE-1500-48 I am using is rated for 31.3 Amps of current at 48 VDC, though with this amplifier I never ask more than 24 Amps DC from it for ham radio analog modes and duty cycles. I bought it new. When I originally mounted it I hung it from compliant rubber mechanical vibration isolation mounts under my 2 inch thick solid wood work-top, so as to not transmit any mechanical noise into my shack. However, I never thought thru the acoustical noise perspective, and especially that its fans run all of the time at their highest speed. Obviously fans that reduce speed when the duty cycle and temperature warrants it would have been much better for my application.

I have heard recommendations of the Eltek Flatpack2 48 VDC power supply, but with no mention on the acoustical noise of their fan(s) nor whether they are variable speed to reduce noise when there is not the current draw or temperature to warrant running at their highest speed. I have NOT been unable to determine acoustical noise and fan architecture from Eltek's website, plus there are probably a dozen generations of this model over time to make it even more complex, and I would probably not be buying the latest generation anyway. Any experience with these models would certainly be appreciated. Note that these require a push-in PC board connector for access to the electrical connections, and those access board are inexpensively available aftermarket.

If you don't need 3KW, the Eltek Flatpack2 2000W model has a PWM controlled fan and runs nearly silent when lightly loaded, and barely ramps up when running my 600W LDMOS amp at 550w.  It's a similar form factor to the 3KW model and uses the same backplane card to connect.  I've not noticed any EMI or RF noise of any kind so far.  Just another option.

Steve

[N4OGW]

Any of the 48V switching PSU are going to be acoustically noisy if you run them near their max power, even if they have a temperature or load controlled fan. They are designed to be used in places where nobody cares about the noise. If you want something quiet, then either 1) find one without a fan. There are a few, but they are usually $$$ and not as available 2) run them at much less than full load.

I'm currently testing two GE CP3000AC56 supplies running in parallel with load sharing for my 1500 W LDMOS amp. These are 3000W supplies. While a single one will run my amplifier, using two in parallel is much quieter.

The GE is a nice supply and seems RF quiet. One thing I like with GE compared to the Eltek is that I was able to find a complete data sheet for nearly the same model. The datasheet gives all the information on pinout, setting the default voltage, enabling load sharing, I2C programming information, etc.

Tor N4OGW

[WB2VVV]

Any of the 48V switching PSU are going to be acoustically noisy if you run them near their max power, even if they have a temperature or load controlled fan. They are designed to be used in places where nobody cares about the noise. If you want something quiet, then either 1) find one without a fan. There are a few, but they are usually $$$ and not as available 2) run them at much less than full load.

I'm currently testing two GE CP3000AC56 supplies running in parallel with load sharing for my 1500 W LDMOS amp. These are 3000W supplies. While a single one will run my amplifier, using two in parallel is much quieter.

The GE is a nice supply and seems RF quiet. One thing I like with GE compared to the Eltek is that I was able to find a complete data sheet for nearly the same model. The datasheet gives all the information on pinout, setting the default voltage, enabling load sharing, I2C programming information, etc.

Tor N4OGW

That's a very interesting approach Tor!

Can you share the details of your load sharing parallel connection between your two power supplies and your PA?

[N4OGW]

It's pretty easy to load share. Most of these rectifier units are designed to slot into a power shelf and share power among many separate units. For my units what I did:

1. set both for 50 V out default (5 k resistor from "Margin" pin to "Logic ground" pin). You also need "Remote ON" to logic ground and "Interlock" to the negative output to enable the psu.
2. connect outputs in parallel
3. connect single wire between "Ishare" pins of the two units

The data sheet is linked from Mouser part number 894-CP3000AC54TEPZ-F. My units are "AC56" with default output voltage of 56 volts, but otherwise seem identical to what the datasheet for AC54 describes. Standard 0.1" header connectors fit the signal pins; for the power output I made some connectors from bits of squashed brass tubing- you could also solder directly to them. A mating connector is available but would require making a pc board.

Tor N4OGW

[WB2VVV]

Here is another version of the VK Amps DC Switching Power Supply Filter, this version is a little more compact with a single pole versus a dual pole filter layout. I installed this single pole filter board inside the Volts and Amps meter box, on the wall across from the ammeter shunt.

https://flic.kr/p/2o9YFrn

The meter box is in-line with the DC wiring between the power supply and the RF deck, and sits on the RF deck so the meters can be monitored.