Tech-out of the Xiegu XPA125B Auto Tuner + Amplifier

Today we take a look at the Xiegu XPA125B QRP Amplifier and Auto Tuner hooked up to the Icom IC-705. This amp will work with a variety of QRP rigs including the new Lab599 TX500, Xiegu G90, Elecraft and Yaesu Rigs. Does it do the thing?
🛒 XPA125B to IC-705 Cable: geni.us/asMqoFl
🛒 XPA125B: geni.us/b8hwf
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[@Blaculo]

I've got this with a G90. My homebrew dipole had bad swr, so I got to see all of the error messages right off the bat. Thanks for these two videos, I learned a few things for future attempts.

[@temporarilyoffline]

Thanks for watching. We are all learning together.

[@Tonylovesjazz]

Will it work with a Xiegu G90+XPA125B+Xiegu GSOC?

[@W9HJBill]

I have that very combination and it ROCKS! I used to have a 7300, which became my "backup" rig when I got my FTdx-101MP, but when I got my 705 for POTA work, but sold the 7300 and got the XPA-125B for when I want to do 100 watts in the park or if something happens to my 101MP.

[@temporarilyoffline]

Smart Plan!

[@radiotype]

Man I just picked both the amp ans 705 up. Does your switch bands correctly?

[@temporarilyoffline]

No, the 705 doesn't speak the xiegu band switching language. I think we can make a box to do it...one of these days.

[@W9HJBill]

@@temporarilyoffline Sounds like a Raspberry Pi project in the making.

[@temporarilyoffline]

@@W9HJBill indeed!

[@Frank_K4FMH]

Another great video, Steve. I have this same equipment (plus the X5105). I was concerned about the reported issues regarding the keying circuit in the IC-705. George KJ6VU built a buffer circuit for his 705. I purchased a purpose-built one for this transceiver-amp pair from W7RF. 73 K4FMH

[@temporarilyoffline]

Hello Frank! I briefly saw there was a buffer option, but not what the problem/failure scenario was. Can you share?

[@Frank_K4FMH]

@@temporarilyoffline This is mostly a FUD issue for the XPA125B possibly but more serious for amps in general. There’s a set of threads on the keying circuit on the 705 groups.io list. See both Kevin Loughlin’s KZbin videos on this general issue and his HRCC appearance. George Z on Ham Radio Workbench built a buffer amp for his 705. It’s not n the Blog at HRW’s website. Both are for the 45 watt MX-P50M amp from China. I also have one of these too and want to be able to swap rig-and-amp setups with the xpa125B. I also have an x5105. Thus, since a damaged keying circuit on the 705 requires a trip to Icom, FUD let me to W7RF’s buffer devices. Hope this helps! 73

[@agoraphobicadam1171]

A friend of mine has that amp with his Xiegu G- 90 and he loves it.

[@temporarilyoffline]

I'm pretty impressed so far... except for the manual.

[@craftsman123456]

I'm thinking of getting this from my 705. I am currently using a Z-100Plus and a MX-P50m and have found that that when switching from say 20m down to 2m the Z-100 does not seem to go into a full bypass mode. Even when turning it off or selecting bypass mode. I have to disconnect the PL-259s from the tuner or I can not transmit in 2m or 70cm. With the XPA125 are you able to turn off the amp/tuner and still leave it connected and still use 2m and 70cm?

[@DonDegidio]

Hi Steve, As you increase the input, once the output hits a plateau back off the input and let the output fall back about 5 watts or so. Increasing the input with very little change in output will lead to splatter as the transistor is now operating out of it's linear range. Nice demo on how little input the amp needs for very good output power. You and the family stay safe. 73 WJ3U

[@temporarilyoffline]

Thanks Don, I did try to show that in the video a little, but there is always so much more to say than the time allowed in the format. Hope all is well in your neck of the woods!

[@radiotype]

One thing about that amp is it’s super low drive. I’ve found about 3-4 watts seems to safely drive the way to close to 100 watts.

[@WH6FQE]

I just received the XPA125B last week to go with my X5105 and was shocked at how heavy it was. They definitely lied about its weight when advertising it, lol. Cant wait till next week when my IC-705 comes in and I can pair it up with that one.

[@temporarilyoffline]

I've been really happy with mine

[@falsedragon33]

When you press the knob to bring the power setting up, touch hold the power setting on the screen. It will then take place of the default function for that knob, and you don't have to click to access it.

[@temporarilyoffline]

Good Tip

[@kylezeringue5673]

Steve, best video on this amp/tuner I have seen. When I next feel like spending the $$ I'm in. It was easy enough to get the point of the on-screen current draw you added w/o you having to say it.. On 160 I got a bit of a pucker factor when you started at max 705 power vs starting low. I thought you might be forced to add smoke! THANKS! 73 KZ4PIX

[@temporarilyoffline]

It would have been a much shorter video if I smoked it ;-) Thanks for watching!

[@lyledal]

Spent some of the annual bonus on one of these plus the L4001 cable. It's on the way. Looking forward to putting it to use.

[@temporarilyoffline]

Excellent, you have a G90 or an X6100?

[@yv6eda]

Great video Steve! Did you made a video to use G90+XPA125B? Thanks, Jorge

[@temporarilyoffline]

Not yet. But it's on the list!

[@CapeCodCNC]

Good thing they were joking about smoke replacement, Lucas (the prince of darkness) Replacement Smoke has been on backorder for over a year!

[@temporarilyoffline]

I hope they were joking

[@radiotype]

I have this exact setup. Works great. The only thing a little iffy is the auto band switching. It kinda scares me it’s super slow to switch bands.

[@temporarilyoffline]

The xiegu radios switch bands a bit better.

[@user-up6ug2ek2q]

What is the dummy load for. I’m a new ham.if understand correctly you need multiple antennas for VHF/UHF,HF and so on. Can you have all your antennas set up. Is there a switch to put all your antennas on so you can switch from one antennas to make it easier to go to different frequencies?

[@temporarilyoffline]

The dummy load absorbs all the power output I'm making so I don't disturb the world by "kerchunking" every band in this test. Some RF does get out into the world, but not enough to make much difference. You do need an antenna for every band you want to work on. Some antennas can be used on more than one band. We sell an "End Fed Half Wave" kit that will operate on 4 bands. Most VHF or UHF antennas will work on both 2m and 70cm because of the harmonic relationship they have. At the end of the day, its all about what you intend to do and what makes you happy. I love building and testing antennas and propogation myself. Yes, you can find antenna switches to use multiple antennas with a single radio. Welcome to the hobby!

[@KeepEvery1Guessing]

Thanks. Too bad about 1A receive current (though, since there are no decimal points in its current display, who knows what that really is). It would be nice to not spend a lot of POTA battery on it while listening. I don't suppose that your power supply has a current meter with more resolution? I also wonder if the ATU uses latching relays, of it it uses battery to hold a tuning. And I wonder if the auto band switch works with the x6100. If you mentioned that, I'm sorry that I missed it.

[@temporarilyoffline]

I'll be doing a power draw comparison soon. Just got the gear for it. In the meantime, if you have an X6100 and the L4001 cable: kzbin.info/www/bejne/hmPLoJuiZrdmhNU

[@pogot1799]

Steve Thanks for your insights :) KD9UOB - Can you elaborate on the XPA125b auto band switching please. I have a 705 on order and am planning on running it remote control with the xpa125b amp. My hope is that i can have the amp running and simply have it respond to my 705's band changes and also tune itself too when I key up. Is this Possible ?? Gear in the basement / Me in the deck with Beer !!! Any comments welcome

[@temporarilyoffline]

The XPA125b is designed to work with all Xeigu radios and the FT-817 from Yeasu. The icom will work, but not in "auto" mode as the icom doesn't send the signals to the amp that tells it what band it should be on. I wouldn't run the amp remotely though - you can't turn it on/off remotely. I think it would be possible to put an arduino off the cat port to read the frequency and then send the amp the right signal - also to grab the PTT signal and send that through. It would get interesting when you want to actually use CAT though. I've been thinking on it.

[@DaninVirginia]

Have you had any issues with using 705+xpa 125 with digital modes such as WSJTX or Winlink?

[@temporarilyoffline]

None, but I wouldn't run it at a full 100w or if I did, I'd be watching the temperature guage.

[@Echo_Hotel]

Having trouble with mine and a 705. Did you hook up to the ACC port? It won’t tune well and won’t put out or even try to draw any power.

[@temporarilyoffline]

The amp needs a cable connected to the SEND/ALC port. It should tune with only RF input

[@RicSpivey]

The draw on this amp is a lot better than I thought it would be, that makes it a lot more attractive

[@RicSpivey]

Omg I just got to the "replace smoke"... I spit my coffee out lmao

[@temporarilyoffline]

I've been under the impression that QRP rig+ QRP amp = lower power draw than 100w rig alone.

[@DonzLockz]

Is it worth it, does it still work?🤔 Have you tried to upgrade the firmware? The operating manual is shocking!😆 If I get the X6100 with this amp, I think I may aswell get the Yaesu FT-991A.🤷‍♂️ I think I'll do more radio from home than Pota. I'm probably more keen on digital modes than phone atm.👍

[@temporarilyoffline]

The amp works great. There is no firmware to update to (I tried). I've been happy with it.

[@Qwiv]

eBay seller noted you need to buy a buffer for the keying cable in the ic705 interface. Any thoughts on that? Hate to have a separate box with this amp and the 705…

[@temporarilyoffline]

As of yet, I haven't needed it. I need to talk to some trusted friends and find out. If you do need one, I'll get it, do a video and explain what I learned.

[@Paddy_Roche]

Just came back to watch this again before buying it tomorrow. I might wait if there is a problem. What do you think Steve? Should I buy for the 705, where would you get the Buffer for the cable? Confused here, lol.

[@temporarilyoffline]

You can find the buffer and the 705 cable on eBay, you can always buy the buffer after the amp arrives if it's needed. I'm hoping to get answers tomorrow.

[@temporarilyoffline]

@@Paddy_Roche Link for cable and buffer: ebay.us/IOGGwP

[@gregmihran8616]

Great demo, thanks for putting this video together, but ... at $530, big box and 7 pounds (!!), I really don't see the use case with this amp unless all you have are QRP rigs. I love my IC-7300 for POTA ... and it has a great handle too (including 100 watts and an auto-tuner) for an all-in-one package for $1K. And it does QRP too :) 73 my friend / KJ6ER, Silicon Valley

[@temporarilyoffline]

You must have gotten the fancy 7300, mine doesn't have a handle :-( I have another video in the works. I don't really see this as a portable amp, other than maybe checked luggage while I listen to shortwave during the flight.

[@gregmihran8616]

@@temporarilyoffline LOL Steve ... ya inflight shortwave would be fun :D I admit it, I spilled another $36 on HRO for the handle but this is a dedicated 7300 for portable ops and I use it on every POTA. Seriously, I really want to buy the IC-705 but am such a QRO guy. I use portable resonant antennas so the auto-tuner is less important for me but am waiting for a small, backpackable amp. At 9 pounds, the 7300 will never find itself in my backpack for remote POTA or SOTA. Btw, I just found your channel a week ago and enjoy your videos. Keep up the great work. 73, KJ6ER

[@lrobie123]

the wifi capability is what drove me towards the IQ 705 so the radio is near where the antenna comes in the house and can access the radio from multiple home office locations in the house or from work. no need to be attached to a computer

[@gregmihran8616]

@@lrobie123 Roger Roger Irobie. I actually just bought an IC-705 two weeks ago! I want to do 'official' QRP POTA activations now and am putting my backpack together. Very cool how you've configured your radio via WIFI, I'll have to check that out :) 73 KJ6ER

[@lrobie123]

@@gregmihran8616 Please note, I am using the Icom RS-BA1 remote control software to connect over my mesh wifi network at home to the Icom 705

[@rttakezo2000]

I am presuming the higher wattage reading on the external meter is due to harmonics.

[@temporarilyoffline]

It could be, or it could just be not properly calibrated. I use that external meter as a "note the change" meter.

[@W9HJBill]

Unable to turn on the XPA-125B ... if you use an Astron RS-35M power supply. Seriously, although it says it does 25A continuous and 35A surge, but if I plus the amp in to the Astron, the Astron goes into overload condition when I press the power on button on the amp. Strangely, I have to run it from my LiFePO4 battery.

[@temporarilyoffline]

I ran an RS-25A in this test. I wonder if you've got an issue with your 35m?

[@W9HJBill]

@@temporarilyoffline very possible. I used to run my 7300 on it but now I only use an FTM-100D on it since I got rid of my 7300 in favor of an FTDX-101MP, which has its own power supply. I may have a look at it more in depth.

[@EdStyer]

I'm kinda new at this...I have a 705. What do you use to connect the IC 705 to the XPA 125B? Thx in advance.

[@temporarilyoffline]

There is a custom cable (easy enough to make on your own) that is 3.5mm (headphone) on one side and 6pin mini din (ps/2 keyboard) on the other end. You can find them on ebay

[@tonyconstabile63]

@@temporarilyoffline I'd like to make my own but cannot find that the pinout is. I've searched everywhere! Help! XPA125b to IC705

[@temporarilyoffline]

@@tonyconstabile63 This is what I could find... and it ain't much... Page 6 of the XPA125B manual, Page 18-1 of the 705-Advanced manual... My cable was sent from another ham and I can't really say its right or wrong...so use this at your own risk, This is how my cable tones out: Tip: Pin 2 Ring: No Connect Sleeve: Pin 4, Pin 5, Pin 6, Outer Shell Using this pin guide: bit.ly/3k10Bl2 There is some talk of a de-bounce buffer or something that I'm chasing down. If I get any useful information one way or the other, I'll share it in a future video. I'm still trying to figure it out. I have a high risk tolerance and like fixing broken tech, so I'm ok if my cable turns out bad. YMMV.

[@temporarilyoffline]

@Tony Constabile Here is a link to a pre-made cable on ebay also: XPA-125B to IC-705 Cable: ebay.us/wyQ33z

[@brianhendrix]

So do you still think this amplifier is still a good purchase at $650 (currently) for my new Xiegu G90?

[@temporarilyoffline]

I think its one of the better 100w amps out there in this price range. I've used quite a few. I would like to try the MiniPA-50, or the RMItaly would be the next upgrade (but $$)

[@KA4UPW]

Did you make a video using the amp with the x6100?

[@temporarilyoffline]

Yes, one with the cable from the ic-705 before they made the L4001 and another with a custom made amp cable. They make a great pair.

[@KA4UPW]

@@temporarilyoffline I havent found these videos. Just purchased the x6100, the cable and the amp. Delivery will be in a few weeks

[@temporarilyoffline]

@@KA4UPW custom cable: kzbin.info/www/bejne/hmPLoJuiZrdmhNU

[@temporarilyoffline]

@@KA4UPW x6100 with simple cable

[@rickpinelli1586]

How would you set the Xiegu amp to run FT8?

[@temporarilyoffline]

Once you get everything connected, turn the power down on the radio and run through a tuning cycle to make sure you have a good/safe match on your antenna/radio, then engage the amp and start transmitting. While you're transmitting, you can turn up the power until you reach your desired output (or can't get anymore output).

[@rickpinelli1586]

@@temporarilyoffline Thank you!

[@powind-zi8ik]

I have seen someone on TikTok use 705 to control XPA125B to automatically adjust the band, but I don't know how to do it.

[@temporarilyoffline]

I have the gear. But I haven't made the video yet. Stay tuned!

[@dudeski934]

Will the radio turn the amp on and off

[@temporarilyoffline]

Not that I have seen so far.

[@kevinkc3onohelijeepworld953]

N9tbe checked into the toad net tonight strong 10over into pa. 😉 maybe chat with him about his antenna. I’m sure with your 811h we should get you into the net from Wi 😉

[@temporarilyoffline]

It should, just have to make some time between the minutes to get on.

[@kevinkc3onohelijeepworld953]

@@temporarilyoffline yea totally understand. Can’t believe how dark it is when I get home at 6pm. I Hate switching times around 🤔😫

[@lblerg]

Why are you putting double the suggested power into it. Are you just trying to kill it?

[@temporarilyoffline]

I'm demonstrating the amps built in safety circuits so that people are aware of what happens. They are quite good.

[@timdbl7804]

Thanks for the demo, Steve. Looks like these amplifiers start compressing well below rated output power (((

[@temporarilyoffline]

Help me understand: Compressing? I'm not familiar with that term.

[@timdbl7804]

@@temporarilyoffline It's when the amplifier is not amplitude-linear. For example, when the drive-power is increased by 20%, the output power increases less than 20%. It looks like these 125B amplifiers might have a design/build flaw; they seem to be hard into compression at less than the rated output power!

[@temporarilyoffline]

@@timdbl7804 Not that I'm smart or nothin... I always thought that was "efficiency", so I learned something new! From what I understand, you can turn up the drive... 1w> 10w>, 2w> 20w>, etc... then you get to a point where the amp isn't capable of any more output and 200w in won't get you >100w out, you're just creating (problems). Add to all that that the efficiency or compression is different for different bands. This amp does a good job of increasing my 10w to 100w... is there anything to be concerned about here or were you just making a note? Curious!

[@timdbl7804]

@@temporarilyoffline Efficiency is how good the amplifier is in converting the DC supply power into RF output power. For example, typically 100Watts DC supply input will result in about 60 Watts RF output; that would be quoted as an efficiency of 60%. I think you were meaning "gain"; for example, you drive the amplifier with 1 Watt RF from your radio, and get 40 watts RF output from the amplifier. So the gain would be quoted as 40, or more typically in decibels as 16 dB

[@temporarilyoffline]

@@timdbl7804 agreed. Vocabulary is hard - and there is a lot of it in this hobby

[@clesheanj]

What’s the cost on that?

[@temporarilyoffline]

The 705 is around $1k, the amp is around $600 and I have a discount code in the description

[@mdwestlund1]

Beautiful Family super dad . Lol.

[@temporarilyoffline]

Thank you!

[@Screamingtut]

steve if you convert 7# to Kg it is 3.2 Kg

[@temporarilyoffline]

So maybe they did the math wrong in translation? www.radioddity.com/products/xiegu-xpa125b ("Weight:1.6kg | 3.53lb") You can tell instantly when you pick it up that its not ~3lbs

[@Screamingtut]

steve I have sent you guys an email about my surgery.

[@temporarilyoffline]

I got it! Best wishes for a speedy recovery!

[@DeltaXray444]

Manufacturers really should put ground ports on everything radio.

[@temporarilyoffline]

Agreed

[@angelscomputers]

Xiegu makes cool products BUT their Quality Control is non existent. Bought one of those XPA125B and brand new out of the box the display was installed wrong. Cant see help of the numbers of the volts and amps. For my research I am not the only one as there are many out there. Good thing was an easy fix but I should not have to repair a brand new product mostly when have warranty void stickers.

[@temporarilyoffline]

I totally agree that all products should work out of the box. I get that there are a few times when things happen and then I expect average customer service (which is also pretty rare). Glad you got it fixed!

[@nigelgunn322]

How about you zero the MFJ meter before you test.

[@temporarilyoffline]

If it was zerod out, I bet you're the kind of person that would complain that it was made by MFJ instead.

[@r0naldzuccala198]

Sorry. Sorry but way to pricey. Also I will never buy xeigu product again. Please don't forget I was one of the suckered who bought the g. S. O. C. A complete piece of crap. I've heard enough about their upgrades that never worked correctly. Sorry but not impressed.

[@temporarilyoffline]

I can see that. They are a little overpriced compared to build quality/actual working feature set. I enjoy these from a tinker perspective, I don't think they were fun if I was just looking for a product that worked.

[@xxmrrickxx]

Do not buy a Xiegu XPA125B! This amplifier was originally introduced with a good design using a pair of RD100HHF MOSFETS to easily handle 100W. After a few years they started selling units using the a single AFT05MP075N rated for 75W without any change to published specifications. You can push these amps to 75-80W but they are now really 50W amplify to achieve the same IMD rating. For a company to engage in these unethical design practices, I'd strongly recommend to never buy any Xiegu products! This is the same practice that Huawei tried when they started to gain some market share in the US with their phones and tablets.

[@temporarilyoffline]

I have a couple more vids on this amp.