Ham Radio - Looking at the MX-P50M HF amplifier for QRP radios.
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- Опубліковано 30 вер 2024
- An overview of the amp, and some testing to see how much current it draws.
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You're wearing a sweatshirt in June! Clearly you're no longer in Arizona!
Oregon
@@loughkb Thought so.
Hi Kevin
I bought one of these last year and use it occasionally. The board is exactly the same as your unit with the unmarked MOSFET. My results according to my Daiwa power meter shows the power output, using my FT-818 at 5W constant carrier in, is a maximum of 30 Watts across all bands except 10 Meters that is at about 25 Watts. I have not put it on a spectrum scope so I'm not sure about the distortion mentioned. It does get quite hot when using FT8 or other high duty cycle modes for more than 5 minutes or so. Many thanks for your great videos. 73
VA7DGT
"Unmarked" or "scraped off" Chinese parts are very often new and quite usable, but are slightly out of spec parts that escape from the factory via the "back door". In the case of PA modules, it's usually that they don't quite meet the full output power, linearity, or bandwidth specifications. The company that is having them made in China, demand that their name and logo must not appear on them before disposal, to protect their reputation. Small equipment manufacturers will buy these to reduce costs, and (hopefully!) will weed out the worst during production and test.
Great theory but these parts went out of production more than twenty years ago. IT may well be that these were out of production parts that Motorola though had been scrapped but in fact were diverted. Since Motorola as a serious radio MFR basically no longer exists , I can't understand the scrape off business. MOTO sold off many of their high quality power RF templates to MA COM. Perhaps MA COM legally can have these out of spec parts pulled ex market as they have taken over the legal clout. But would they care .. they no longer make or support the part which seems to be a late sixties design. it is highly likely some of the parts are board pulls , often boiled off in PCB oil (nasty stuff ) and because the buyer knows the parts can be traced by the date codes he wants to muddy the waters as much as possible. it is all highly highly dodgy.
Rock that HTX-202! I still love mine, though it doesn't get used a whole lot since I got my FT-4XR
Would you know how to take off the black cover that tighten the power wires and signal wire? I’m trying to tap the the wire but it’s really tight.
Hey Kevin,
I missed where you said you bought this amp. Could you give the information again, please?
73
I purchased the same amp 3 years ago. It's available on both eBay & Amazon. On eBay search on "QRP Amp" and you will see a bunch of them for sale from different sources. Most are coming directly out of China or Hong Kong, although, sometimes you will see some from a US source (still all made in China). They vary in price from about $150 to $200 usd. There are at least 2 different designs showing up for sale, but both look to be about the same product. 73 Paul NA9M
@@paulkinas7926 Thank you!
Nice simple design. I like that. I wish someone made a similar amplifier but class E so it's more efficient, using less battery power and generating less heat. QRP Labs has a $26 power amplifier kit that provides 26dB of gain so you'd need an attenuator on the output of a 1-5W QRP radio, as the PA kit is designed to be used as the power amplifier for a transceiver kit. With a 20V power supply the amp can provide a solid 20W out, although it's closer to 10W with a 12V supply. QRP Labs sells low pass filters for $4.60 each, and if you want to select them conveniently they have a $16 relay board that will accept five of the LP filter modules. I might build the dedicated 40W version of that to give my Phaser transceiver kit a 20W output.
If you want 160m operation with the MX-P50M, you could always put it in 80m mode and add a 160m low pass filter in line with the output.
The ferrite output transformer may not have enough inductance or saturation margin to support 160M. Worth a try, but the current draw and heating may be higher. --N2GX
Fine if you do CW. Class E amps can't used for SSB, See QRP Labs website,
The schematic looks like a piece of crap. Up top right is where a fuse would be but the poster/s logo has covered it up. The switching system for the relays is obscure. It appears the relay coil power comes down via the LED which is rubbish. I think this is obscure on purpose.. and to fill out the utterly rubbish drafting "Filters in here ". As a trouble shooting document the schematic is next to worthless and at $150 USD I 'd expect a lot better and make a complaint. If the description on Ebay has manual , it's a lie.
The rf seems to be a salvaged part that has been stripped of the manufacturing markings some manufacturers require that salvaged components be stripped of their markings if resold
@70 Roadrunner a certain amount of rubbish. these are not Mutistage amps. BUT the do seem to be out of UHF old analogue 900 to 950 Mhz phone towers units.. scrapped. Which makes you wonder how much life is left in the components as sold. WoRSE I can't find replacement NEW parts as in NOS anywhere not RFParts and not UTSource . It is huge risk buying these given the status of the main part in the amp.
I've got one and it seems to work ok. Opened it to have a look and it has an unmarked part too. It's good that they don't get too hot, which is just as well if the PA module isn't bonded to the case and won't be getting the best out of the heat sink that's available. But Mats Bengtsson makes a point about gain compression, thermal issues could be part of that.
Kevin, very interesting Amp. I want to see how you make it work on the mcHF clone that you have so will be interested in the next video on it. Once you have that, you can use the mcHF for some FreeDV contacts ;)
Love this video! Im gonna buy one. Thanks Kevin. 73
Have you encounter Hams that tell you that the MX-P50M doesn't need modifying? They just plug it into their IC705 and it works. Could it be the signal from the relays might have much more smaller amounts of current so the the radio can handle it?
No. But I've heard from several that confirmed it did not work out of the box.
I built an amp using this same design (kit from eBay) about a year ago. The higher efficiency comes from it being a straight class B power amp. Most name-brand rigs use a class AB power stage, and so are cleaner, but draw more current. With proper filtering I didn't have any problems with the output on the kit (assuming the transistor bias is set correctly), but I was never happy with the input SWR. I had to run the tuner on my QRP rig - but otherwise it worked fine. The build quality of yours is certainly better than my kit :)
Thanks, I just had one delivered last week, glad you did this review...
Most of these are made with mosfets pulled from recycled parts...
weeew, that doesnt bode well.
Good review and good to see you still kicking around.
The current draw difference was more than I expected. Thanks for this.
i dont mean to be so off topic but does any of you know of a way to log back into an Instagram account?
I somehow lost my login password. I appreciate any assistance you can give me
@Royce Johnny instablaster =)
@Andy Aarav thanks for your reply. I got to the site on google and Im in the hacking process now.
I see it takes quite some time so I will reply here later when my account password hopefully is recovered.
@Andy Aarav it worked and I now got access to my account again. Im so happy:D
Thanks so much you saved my account :D
@Royce Johnny You are welcome =)
I know this is about a year old but I have a question. I have one for my 817 also but both lights on the front panel are lit up. Do you think I have a dud or a crossed wire in the accessory plug? I’ve tried to diagnose it but I just get aggravated and put it away. Any help would be greatly appreciated!
Maybe a short in the connector? Those are tricky to solder on.
Dennis&Charlie 😺👋
Just noticed some peculiar. I have not modified the amplifier yet. But when I Key on FM I get the 40 watts. Although when I do SSB then I don’t get any additional wants. Was that your experience?
In FM mode the transmitter is putting out a carrier at full power continuously. In SSB mode, only the brief audio peaks will produce full power. If you have a peak hold meter, you'll see that you're hitting full power. (Just for very brief moments.) Speech varies over time quite a bit. That's normal.
@@loughkb Thanks. I've been learning a lot about radio power and how it relates to the different modes. Thanks for the tips.
I got one of these for my 818. The thing that bothers me is the keying cable at the back. Does anyone know how to connect it to the 818…?
In my video on fixing the amplifiers keying, I show how to connect it to the FT-817. The same wiring as the 818. I talk about the wiring around 7 minutes into the video.
ua-cam.com/video/k8dwJMOdEMI/v-deo.html
Top Video 73 de DE2TRF
The 120 Watt power rating would DC input not RF at ~50% efficiency would be about right, giving around around 60 Watts RF. This was born out by your DC measurements
Good video Kevin! Generic parts are par for the course. It cost less and it is about making money... 🤷🏻♂️de WO0E
I prefer a one box solution. I hate lots of little boxes and connecting wires. I have all three rigs that you have. Rather than have to downgrade a station because of insufficient current, I would rather increase the current capacity (bigger solar panels and bigger batteries) and use the FAR more capable IC-7300. Trying to tune around the bands with the FT-817ND is a pain in the butt - but it's fine for mountain topping.
Good video Kev...I am off grid, and run my laptop on DC. I found online an DC upconverter..13.8 to 20 volts DC. I don't use an inverter for the computer, nor wifi stuff..all 12 volts. The DC upconverter are sold with a cigar plug, for use in a vehicle.
Tnks for the vid at the end you mention modes very quickly..... i'm only interested in AM mode use. I have and oldie Tube Transmitter/Receiver that has High 7 watts and low 1 watt outputs in AM only well CW too. i was wondering if how 1 watt AM input would work with this amp for 40 and 80 meters?the radio has a REC/Transmit switch and it "they" are a separate Transmitter and Receiver not a transceiver.jim
It would work fine. With one watt input, you'll probably see somewhere around eight watts out. With seven in, probably around fifteen to twenty out.
7W of AM input is above the rated input I would have thought?
Nice Amp but wonder how clean the TX signal is (harmonics) 73 m0wao
Thanks. I bought one for the FT-818ND. 73!
I don’t know, what next, a linear for QRP operations. 😂🍻🍻👍⚡️⚡️⚡️⚡️⚡️⚡️⚡️
Good to see you are going well now with new income. You were always a good and genuine guy. I wish you all the best. 73s
Hi Kevin,
Good video. That amp is a nice simple design. I like the idea of using diodes to keep both your QRP rigs available to key the amp without swapping cables. I think the SignaLink USB can be wired into the microphone jack for PTT control. That's how I use it with my Flex 1500. I could also use it the same way with my FT450 as they both have the same mic wiring, however I am using the ACC port on the FT450. I had to sell my NIB Flex 6400 and used Acom 1000 last week. My father left me with a credit line to pay off after his passing. The sale of those will give me a couple months cushion to decide if I need to sell my home. If I can get a reverse mortgage, that would solve the problem. Stay safe. 73 WB3BJU
Awesome video Kevin...Thanks for sharing! I need to get my FT817 fixed (won't power up) and back on the air...with a little amp :)
I went the direction of the Xiegu G90. Low current draw even at 20 watts and a fun rig to run too.
73 de N2NLQ
Congrats on confirming your expectation of non-trivial power savings with the new configuration, Kevin.
Do you think this could be used with the hackrf sdr?
Thank you Kevin. Nice video. 73 Clark KG7LOI.
Very neat. I might try and build a amp based off this type of design for some of the high bands. (6m,2m and 70cm) Considering the rating for the transistor.
Hello. Will this amp work with the Xiegu 6100 ?
Sure, but you wouldn't gain too much. In a follow up video I show that this amp will clip and splatter if you drive it in SSB with more than about 2.5 watts,
which produces about 35 watts.
So in SSB mode, it's only a 35 watt amp. Which makes sense, since you have to think in terms of RMS power when in SSB. In straight carrier modes like CW or FM, this amp will do close to 50 watts with 5 in. In RMS terms, 50 * 0.707 = 35.35 watts.
So the xeigu is already capable of 10 watts in CW, or 7 in SSB. (RMS)
This amp would give you 35 in SSB mode, RMS, still vocal peaking near 50, but it compresses a bit toward the ceiling.
@@loughkb Thank you for lots of good info !!!
Hi, great review. I have one of these to use with my X5105 when portable and 5W is not quite enough. It's best used with a resonant antenna then no tuner is required. 73
Have you looked at the Radiooddity PAX100 QRP amp they are selling for the XieGu G90?
Not as of yet.
Yo Kevin!:
Great video as usual, I agree about linearity concerns.. I'd like to know more about that unmarked mosfet. : ) Maybe a U.S. made amp would be better? I hope u consider a side trip up into Washington hopefully. Motor on! 73's!
de seeker/Jeff WA7LFP
RFParts in FL used to sell the MRF 186 as a new bare part. It was about Sixty USD. All gone now and he seems to have run out quite recently. Tim F in Nz.
It isn't "powder coated" it was "bad blasted." It is not over engineered and it cannot be driven to 120 Watts, it is operating from 14 Volts, not 28 Volts. Amplifiers are not triggered, they are switched. Several companies make an equivalent device to the MRF186.
Ron W4BIN
LOL!
good vid Kevin, bet your glad you got out of Arizona when you did, really hot down there in many different ways. take care
A nice little amp. Thanks. N0QFT
I suspect the cas is extruded not machined
Nice little video. It's nice to see hams doing things like this.
Any chance of video showing how to wire up the Connector for a FT817?
A google search will turn up a few references. I don't remember where I found it, but it was in the top few hits on the search.
it remind me in the 1960 attitude!, the amplifier with a little secret
Might be interested in one of those to work with the ic-705.
Hi Kevin, I sent an email to your qrz listed email regarding this amp and an interface I built to allow the use of CAT control and the amp in the same port.
Hi, can I ask where you found the plans for this? Thanks 73 de KF7VUT
I would be very interested in seeing the harmonics of that amplifier.
Here is the data. gm4slv-geek.blogspot.com/2015/03/mx-p50m-amplifier-for-ft817.html
I run this amp on an 817 and got similar results when I checked mine.
My QRP radio has a built in antenna tuner. If using a linear amp would one still be able to use a built in tuner?
Nope. It's important for the antenna's impedance to be matched to whatever is driving it. The amp would be the last link in that chain so you would need a transmatch between the antenna and the amp and leave the radio flat.
Learn something every time Kevin, thanks and take care!
Kevin, Nice review and look inside the amp. I've had one of these for about 7-8 years now and it was used in my SOTA/WWFF radio pack with FT817, I now upgraded to KX3 but kept the amp and use it with a ELAD FDM DUO driving it with 5w which works with no real difference to when I was using IC7400.
One thing I have found that the plastic power connector was deformed and found it had melted the it together, so have cut out & replaced with powerpole connectors, I would recommend to do this as this could be an issue down the track if you use it on a more permanent basis. Cheers, Adam VK2YK
Awesome
Kevin, thanks for the video. I got the same amp for my RS-918, I am unsure of how to wire it to the accessory port. Can you clarify or post a diagram. I have not had any luck finding any info on how to wire this. Thanks in advance
I'll be addressing this in the next video. Along with a simple mod to allow the 918 to key the amp. It doesn't work out of the box due to a design problem in the amp.
@@loughkb looking forward to the video
Thanks for the video.
coldwar attitude
How does this compare to the Mini PA50?
MINI PA50 and similar are utter crap because they use SMPS Mosfets and over rate them so they are likely to fail.
@@F_Tim1961 It has Motorola finals and they are under rated.
I'm using this amp for the last couple of years, today after watching your video, i opened it up as well, and mine also is having same MOSFET like yours, not the Motorola one....one thing i did realise is that it runs hot atleast in my case when using full 45 watts..
I also have been running this amp for 2 or 3 years. I absolutely agree, the amp does get hot, not warm. hot... I ended up putting a small fan from a computer power supply to blow on the amp, and that helps a bunch....
What mode are you guys running when it heats up?
@@loughkb even on ssb while using 45 watts it does get hot..now im also using small external fan..
Great this one's 4 me!
will it work at all on 6 meters ?
Nope. The low pass filters on the output wouldnt pass 50 mhz
I really like mine, its a nice modular addition to my QRP go-bag in case I want to add a bit more power.
@@frankwc0o Cannot tell you where he got his, I got mine from eBay (HK) and I needed to pay import VAT (EU) - fast delivery though
That amp is terrible. If you check the linearity you will find that it works with more than 3dB compression which is totally unacceptable. More like 6dB compression. This is causing splatter (broad signal) and distortion.
The one I tested showed 20W with 1W drive and 45W with 4W drive, That is NOT linear. Should NOT be called Linear amplifier.
If 4W produces 45W then 1W should produce 11.25W (not 20W). Please don't use with more than 2.5W drive.
1dB compression is acceptable upper limit.
You mean the ones without the Motorola MRF-186 module, right?
This is interesting. Was the splatter you observed within the band or was it at a harmonic?
If the amp is used with an FT-817 on SSB mode, given that the FT-817 has no tx speech compression, I wonder if some compression provided by the amp is perhaps even good/acceptable behaviour?
Certainly think that operating with drive to keep compression around 1dB or less is a good rule of thumb.