MX-P50M Amplifier for Yaesu FT-817ND
September 22, 2015
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I had been debating long and hard on a higher power rig for HF portable use. I really enjoy running the Yaesu FT-817ND on 5W QRP and portable. There are times when conditions are just plain lousy and my signal clearly doesn’t get through the noise floor. A big goal of my portable station is for running off the grid in case of an emergency. There are times when QRP will just not get through. With this in mind I have often looked at getting an FT-857D which is a mobile /portable rig capable of 100W. Unfortunately, my budget just wont allow it. I started looking at amplifiers for the FT-817ND but cost remained an issue. I ultimately came across a Chinese made 45W amplifier on Ebay that is called a MX-P50M and comes with a cable specifically for the FT-817ND. The cost for this was $189 including shipping from Hong Kong. I have read some real horror stories regarding some Chinese made amps with most being nothing more than noisy CB amps. After a bit of research I came across some favorable reports on this unit from folks like VK2QR and GM4SLV. Check out these sites for some detailed measurements. I decided to take the plunge and order one about a week ago. I just received it today and unboxed it.
The amp was well packed and came with a DC power cable and an ACC cable but no manual. Setup with the FT-817ND is fairly straight forward. First thing was to add some Powerpole connectors to the DC supply line. I made this a “Y” connector so I can also plug in the rig’s power supply with the same cable. This cable connects to the amp to some sort of cheesy little connector which I will discuss in greater detail. The other cable connects the amp to the ACC port of the amplifier. There are two SO-239 connectors in the back, One of these goes to the antenna and the other to the radio. I connected an SWR/power meter to make some measurements and am using the magnetic loop antenna so I need to limit power to no more than 25W. The front panel has a band switch and a power/bypass switch. There are two LED’s one for power and the other to indicate transmitting. The entire unit is housed in a sturdy aluminum case with a heat-sink on the upper surface.
I hook up the coax, and the meter and the radio on a 15A 12V power supply. The amp needs only 8A at 13.8V to run at full power. I tune up the loop antenna and set the power output to 1W. I turn on the amp and….nothing….power light doesn’t light up….hmmmmm. I powered everything down again and checked the connections but still no power. On to the inline fuse holder on the amp power cable. This is a pretty weak cover and sure enough the 10A fuse inside was blown…hmmmmm. As luck would have it…no spare fuses…so off to Home Depot for a pack of 10A fuses. Insert the new fuse and power on and….nothing…check the fuse again and it was blown…aha!
Needless to say I was starting to think about how I was going to return this thing but decided to check all my connections. I unplugged the cheesy little power connector on the amp and sure enough the pins had bent. I straightened these out and made sure they made contact, replaced the blown fuse and this time…nice blue power LED light came on. Whew!
From here testing proceeded nicely. I set the band switch to 20m, adjusted the Magnetic Loop antenna for min SWR with the amp off and set the power on the FT-817 to 1W. Turning the amp on gave me about 15W. 2.5W on the rig gave me around 22W which is where I intend to run it. Total Power consumption is under 5A at this power level. Made a 20W contact on SSB into Nevada with no issues other than QSB on the band tonight. All in all I am favorably impressed with this unit. I’ll be doing some more testing with various power supply sources over the next few days. I am hoping that I can still run this on my solar power setup without excessive drain.My preliminary estimates are that with the 60W fold up solar panel used during full daylight availability in South Texas would give me 3AHr headroom over a 12 hour period with 10% transmit time at full power.