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MegaWatt vs. Chinese Imitation 30 amp switching power supply comparison


Ham Radio Nerd
Apr 14, 2002
In an earlier thread about the various switching power supplies available on Amazon, there were questions posted about the difference between the authentic American made MegaWatt 30 amp supply and the cheaper Chinese imitation supply. I've purchased both supplies and used them extensively with my Elecraft K3 and can now report on the major difference.

First, here are links to the two supplies in question:

MegaWatt 30 amp switching power supply:
Amazon product ASIN B00JZBE97U
Chinese 30 amp switching power supply:
Amazon product ASIN B00D7CWSCG
The two supplies look identical, although the Chinese supply does not include an AC power cord. However, the performance difference is significant: The MegaWatt has no "hash", while the Chinese unit has terrible "hash". I took pictures of the interference on the Panadapter that shows the difference visually.

First, here's the Chinese supply:

The slanted lines in the pic are heard in the receiver has a high pitched whine that slowly lowers in pitch and interferes dramatically with your RX signal. It can get so bad that it can wipe out the intended signal.

Here's the same frequency only moments later on the Megawatt Supply:

Notice that there is no slanted lines; only clean signals of the transmitting stations. That's because there is no hash. They say a picture is worth a thousand words, but in this case a video demonstrating the difference between the two supplies tells the whole story:


No surprise there. It seems more electronic products coming out of China are cheaply made and designed in regards to RFI. The American made one is remarkable especially given the reputation some switching power supplies can have plus it can be bought cheap!

Now it seems I may have a problem with some grow lights in my neighborhood causing strong RF hash where I can't run 40 meters. I wonder what hey might be growing? I have read about Chinese made ballast causing havoc on amateur bands. It is a shame products like these are allowed in this country that don't meet RFI standards anymore.

Nice video!
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Reactions: Megawatt
Great review Tim. I have the mega watt 40 amp and the cheaper amazon 30 amp power supply and both have been great, I only use them on 11 meter and don't get any noise that i can hear from either. I don't have your equipment to test or your knowledge on how to test as you have. My only question is is the mega watt truly made in the USA there is nothing on their web site or my power supply that states this, just wondering i know from all the reviews that you have done that you always try to be as accurate as possible. Keep up the great work.
My only question is is the mega watt truly made in the USA there is nothing on their web site or my power supply that states this,

On their Amazon page, a customer posted this question and they responded that they are made near Los Angeles.
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Reactions: jwilkers
You should see the inside if you want to see the difference. The $20 clone has 1/2 the parts inside. All the filtration and oscillation frequency control is missing.

OK, then I'll open them both up, take some pics and post for all to see.
John don't get me wrong , I have had a few questions for you in the past and was very happy with the quick response back. I have great service from your P/S, and it would be great to see the difference in the 2 supplies .
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Reactions: Oatmeal
You can see why this one makes noise. There is just about no filtering on the 110 input. Few caps and a tiny choke. The voltage double caps are way to small and so is the full wave bridge rectifier. This will cause an early demise. The amazing thing is there in no circuitry in the red oval area. The MegaWatt has a duel OP Amp to control over voltage shut down and MOSFET frequency control. It also controls crow bar instant shunt down on short circuit or over voltage. There is lots of filtering missing there too.
Two Power Supplies.jpg
Yes it's a 1987 that I have turned into a rock crawler sas in the front dual low range transfer cases, my son has a white 87 with 350,00 miles on the original motor. They are great little rigs.
Wow, wow, wow! Glad I came across this thread, because I recently recommended one of these supplies to a friend of mine that is a new ham. Good to know the differences and what to look out for.

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Reactions: jwilkers
Thanks megawatt! Glad I got one myself! The megawatt supply I have has been a workhorse for me. And now they have the larger supplies. A local near me just got one after his Astron 20amp supply just wasn't cutting it with his icom 728. He got the 50amp version and is one happy camper.

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