A few of the WorldwideDX.com members made me aware of some small, inexpensive switching power supplies being sold on Amazon and eBay and they swore that they were free of hash. After my unbearable experience with the MFJ-4275MV supply (original thread here), I was curious to find out myself if the $30, 30 amp switching supply on Amazon made for a better operating experience.
This is the product that I purchased on Amazon:
Amazon product ASIN B00D7CWSCG
And this is the MFJ-4275:
The Amazon unit doesn't come with a power cord, but must of us have those laying around to sacrifice. After wiring up the AC, I also wired up a DC cord for the rig, complete with Anderson power poles.
The first thing I wanted to find out was how bad the hash problem is on the $30 Amazon unit. I turned on the NaP3 Panadapter, used with my Elecraft K3 and took a print screen so you can see the hash present on the MFJ supply:
Note the circled slanted lines - that's the interference you will hear in the RX present on any of those frequency ranges. It sounds like a whistle going by and is quite loud.
This next screen shot was taken only minutes later after changing the rig over the the Amazon 30 amp switching supply:
As you can see, all of the slanted lines are gone. I've been using this supply for about three weeks now, and no matter what band I'm on, I hear no interference from the supply - a night and day difference from the MFJ unit.
I also developed a problem with the MFJ with the voltage varying significantly every time I turned it on. I had set the supply to 14 volts, but found it as low as 11v on occasion and as high as 16v! So far, the Amazon unit has consistently held the voltage I set it at (14v). I do notice about a 1v drop under transmitting at full power with the Amazon unit, but that is about the same as the MFJ supply.
All told, I couldn't be happier with this little, inexpensive supply and haven't found a reason why anyone should spend more money on a more expensive unit.
10/28/14 Update:
I found some hash with this unit and have posted details with a pic later in this thread: http://www.worldwidedx.com/threads/...upply-vs-mfj-4275mv.174465/page-2#post-500387
This is the product that I purchased on Amazon:
Amazon product ASIN B00D7CWSCG
And this is the MFJ-4275:
The Amazon unit doesn't come with a power cord, but must of us have those laying around to sacrifice. After wiring up the AC, I also wired up a DC cord for the rig, complete with Anderson power poles.
The first thing I wanted to find out was how bad the hash problem is on the $30 Amazon unit. I turned on the NaP3 Panadapter, used with my Elecraft K3 and took a print screen so you can see the hash present on the MFJ supply:
Note the circled slanted lines - that's the interference you will hear in the RX present on any of those frequency ranges. It sounds like a whistle going by and is quite loud.
This next screen shot was taken only minutes later after changing the rig over the the Amazon 30 amp switching supply:
As you can see, all of the slanted lines are gone. I've been using this supply for about three weeks now, and no matter what band I'm on, I hear no interference from the supply - a night and day difference from the MFJ unit.
I also developed a problem with the MFJ with the voltage varying significantly every time I turned it on. I had set the supply to 14 volts, but found it as low as 11v on occasion and as high as 16v! So far, the Amazon unit has consistently held the voltage I set it at (14v). I do notice about a 1v drop under transmitting at full power with the Amazon unit, but that is about the same as the MFJ supply.
All told, I couldn't be happier with this little, inexpensive supply and haven't found a reason why anyone should spend more money on a more expensive unit.
10/28/14 Update:
I found some hash with this unit and have posted details with a pic later in this thread: http://www.worldwidedx.com/threads/...upply-vs-mfj-4275mv.174465/page-2#post-500387
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