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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Xiegu XPA125B Help


Reviews Summary for Xiegu XPA125B
Xiegu XPA125B Reviews: 1 Average rating: 2.0/5 MSRP: $549.95
Description: 100W HF 160m to 6m amplifier, 13.8V input, 2-5W input.
Includes ATU.

Frequency range: 0.5-54 MHz
Maximum output power: 1.8-30 MHz >110W / 50MHz >90W
Maximum ambient operation temp: 131 Fahrenheit(55
Celsius)
Gain: 13 dB (+/-2dB)
Spurious suppression: >50 dB
Supply Voltage: 12-15 Volt DC
Transmit current draw: @ max output 30A
Receive current draw: @ max 700 mA
ATU Frequency range: 1.8-30 MHz & 50-54 MHz
ATU Tuning range: 14-500 Ohm
Dimensions: 10.3 x 6.3 x 2.8 inches (Excluding knobs,
feets, handle etc)
Weight: 5.86 lbs(Shipping weight 8.82 lbs)
Product is in production.
More info: http://https://www.mfjenterprises.com/Product.php?productid=XPA-125B
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AE7EU Rating: 2/5 May 9, 2019 00:34 Send this review to a friend
Well built, but a major flaw prevent from being a perfect amp  Time owned: 0 to 3 months
Alright, I'll have to say for this review, I feel sorry for MFJ being the distributor on this. They have been reasonably responsive, and very helpful, but honestly, the big problem with this thing lies with Xiegu.

I wasn't really able to find much in the way of reviews for this thing, except for a few videos, and what looked like a bad photocopy of the manual. After understanding what I thought I might be getting, I took the plunge and bought one for my KX3, figuring I would need to just make a 2.5mm to Mini-DIN6 cable, the parts for which I had already. For half the cost of the 'pro' amp, seems like a good deal.

My first amp arrived with a cracked screen. I'm guessing thermal stress on the plastic window that is glued into the bezel. After corresponding with MFJ, they simply sent me a new one, along with a return label for the previous. Cool!

First off, the good: This amp seems to be very well built, aside from the issue I initially had. It's all aluminum, the edges are solid, and even if you drop it, you're probably not going to break anything off. Peeking through the ventilation, I can see MCX + coax going across the single board, and what little I can see inside seems fine. The power connector is a little cheesy, 2 wires in a 6-pin housing, but it works. I hooked mine up to an Astron SS-25M power supply, and it powered right up. I then used my KX3 to drive the system, and had intended to build a band interface eventually for the KX3, but just went with manual the first time around. Using a 2kW dummy load, I put the PA into passthrough mode, tested SWR to make sure the ATU on the KX3 was off, and make sure everything was 1:1 for solid connections. Per the manual, I adjusted the power on the KX3 to 1W, and band by band, got it to transmit a full 100W. Some bands required 5W, the most sensitive seemed to be 40m with only ~1.6 or 2W drive needed to get 100W output. The dummy load is actually a 40dB, 2kW bird coaxial attenuator in this case, so the other end went into a 50ohm terminated oscilloscope. I was going to do harmonic measurements/etc on this thing, but that brings me to the bad.

Minor bad, the manual it comes with is like they used a crappy 80's photocopier that was low on toner. Okay, get what you pay for, fine. The other minor bad, I found that sometimes I'd press a button and it felt sluggish for something to happen, e.g. power, etc.

Another thing that worries me, but didn't seem to be an issue and that I didn't fully evaluate is the heatsinking. This thing has a massive heatsink, excellent! Except, it has no fans, and the ventilation seems marginal. I figured there was at least a fan inside, but nothing. Upside, it's quiet. I didn't get to evaluate thermal performance.

The major bad: I began testing the keyshape waveform to get an idea for gross linearity. What I found horrified me. The XPA125B has a HORRIBLE TR delay. I would key a dit from the KX3, and see 10's of ms of 5W RF, then a pulse to 100W. After fiddling with my KX3 and finding the TX RF Delay function, I set it to its maximum, 20ms. I found that even with 20ms RF delay, the TR relay was being hot switched. I wish I could attach an image for this review. Here's where it gets worse: The delay from RF active (TX) to when the relay switched would vary by 25ms or so. So on some dits, I'd get 2-3ms of RF and then the TR switch, and on others, 25-30ms of RF before the TR switch. And this is with 20ms on the KX3 side. I know other transcievers only do 30ms delay maximum (IC7300). It turns out, you will need minimum 50ms TR sequencing to get this system to work. Which, for any kind of reasonable operation, simply isn't going to work with this system. I don't know about you, but I'd rather not risk my KX3's finals nor worry about replacing TR relays in the amp down the road due to hot switching. I also re-verified the functionality of the KX3's TR Relay, and that the relay was switching in a timely manner compared to the RF.

Now, I would like to note: The delay is variable, 25ms to 50ms. Because of the function of the front panel, and because it has a processor-based amp enable, I surmise that the XPA125B has a polling loop, instead of using an interrupt. I think this absolute showstopper problem could be easily fixed with a firmware update to using an interrupt. Which is why I give this a 2 and not a zero. BUT: I've been generous waiting for Xiegu to respond to my inquiry, and I didn't get warm fuzzies from MFJ about their response time either. So I'm going to give the benefit of the doubt and say this is a 2, for now, but I'm still sending this back. But, unless you have an external amplifier sequencer and use that can handle a 50ms+ TR delay, I highly suggest you check Xiegu's webpage (http://www.cqxiegu.com/en/index.php?m=content&c=index&a=show&catid=126&id=420) for a firmware update, and if anyone else can confirm that the firmware update would fix this problem.

If Xiegu won't or can't fix this problem, this review really should be considered a 1. Don't damage your radio.

It's a real shame this is turning out to be a dud. I'm certain the tuner, SWR meters, lowpass filters, and the amplifier design itself is perfectly good and well done (likely based off many years of public knowledge, and the application notes from Mitsubishi), but I'm not risking my radio any further to evaluate this.
 


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