Monday 30 October 2023



Yu Hongbo reminds me in many ways of Hans Summers and Boris SapundzhievThey are all electronic geniuses capable of coming up with amazing radio designs in compact form factors which perform superbly. They are small scale manufacturers - virtually self-builders! There are no mass production facilities here - these things are put together by hand - by them, without the benefit of a huge assembly line in a factory somewhere.
Despite being such incredibly busy people, they also find time to respond to what must be a constant stream of pesky customer queries. Nothing is too much for these people, it seems.

So when I learned about Yu's FX-4CR QRP SDR Transceiver, I was very excited by the idea of trying one out, so I set about finding a deal on a used one and before I knew it, there was one sat in my shack. I love to try out new radios and finding used bargains or doing ‘swaps’ permits me to do this without losing money (and I quite often make a little when I resell - although it can be a game of swings and roundabouts).  

It's a good job that I was looking for a used FX-4CR because at the time of writing, getting hold of new stock is like searching for the holy grail! There's a big waiting list. 

Please note that if you wish to order one of these, ONLY DO SO by placing an order directly with Yu! Don’t be tempted to buy anywhere else (unless it’s a second hand seller in your region). Here’s a link to a video of a guy who bought elsewhere…

This is the one I bought secondhand…

The FX-4CR is very compact and will literally fit in the palm of your hand and weighs just over 400g.  Size is so important to me when it comes to a QRP radio and they don’t come much smaller than this, apart from the (tr)uSDX,  which is a great little budget radio, but it obviously can’t compare to the FX-4CR.  It comes in a small Pelican style carrying case which really adds to the perceived value of the kit and demonstrates a high level of customer care (in my eyes anyway).

When you handle the radio for the first time, you are struck by the absolute quality of the build - this thing is beautifully engineered and well thought out. Yu obviously takes great pride in the fit and finish of his products - there are no unsightly gaps between panels. The screen and buttons are all perfectly centered in their case apertures. Even the supplied power lead is top quality and comes with a Velcro-Tidy instead of a bit of twisted wire.

XT60 connector for the radio

The interior of the radio exhibits equally high standards of construction and design. I know nothing about electronics, but I can recognise build-quality and Yu's attention to detail is obvious for all to see. Even the toroids are secured to the pcb with nylon screws - most manufacturers wouldn't even give them a second thought or at best, they'd use a glue gun. It’s built to survive a few knocks and drops.

This amazing little transceiver is a full blown SDR covering 10 bands from 80-6M and is capable of wireless digital operation thanks to built-in bluetooth and soundcard (if you prefer to connect a USB cable to your computer for digital work, you can do that too).

The TFT full colour screen is extremely crisp and sharp but it's not a touch-screen. Even though I have become used to touchscreens, I still don't find it a hardship when it's not available on radios like this - the screen is too small for touch operation anyway and you very quickly get used to using buttons instead.

The radio's panadapter is a really handy tool when out working in the field and you'll be amazed at how readable it all is despite the screen being just 2 inches in size. Needless to say, if you are a person who uses reading glasses, you will need  them when using this radio. 

There's a 48kHz slice of the band on display which makes it easy to spot signals adjacent to the tuned frequency. Please note that none of the photos and videos online express how very usable the screen actually is.

The operation of the FX-4CR is very well thought out and there's little use for the printed manual - it's really quite intuitive (but read the manual anyway lol, because some buttons have hidden functions and are mode-dependent). The buttons are a good size, well labelled and even backlit! The rotary dials have a good feel and are multi-functional as you'd expect. It doesn't take long to learn the functions of the buttons.

Surprisingly, the built-in speaker is really quite good!! It's obviously not bassy, but it produces a very crisp, loud audio which is perfect for outdoor operating. Most radios of this size require an external speaker to be connected, but not this one.

The supplied microphone is good too - small and neat. It's worth noting that the FX-4CR actually has a built-in mic too (in case you one day forget to pack the mic).

The receiver is very sensitive and the filtering is good too. Bear in mind that this radio will almost exclusively be used for outdoor activities which means there’ll more than likely be a great take-off point and a decent antenna - in those circumstances, the FX-4CR will perform every bit as well as any other radio out there. It's only when you wish to detect the most distant and weakest stations that you might wish you'd spent four times as much money on something else.

On the transmit side, you can dial in anywhere between 100mW and 20W output which is amazing for such a tiny radio. On full-tilt, the metal case does get hot and without additional cooling, digital work is restricted to less than 5W - a sensible precaution.

I’m going to fit some heatsinks to the top of the case like I did on my EE ColibriNano (pictured below). The Nano (an SDR Receiver) gets incredibly hot and is very uncomfortable to the touch. Even though Expert Electronics assure owners that the Nano is designed to cope with such temperatures, fitting those little heatsinks genuinely cools things down and makes you feel happier.  There are rumours that Yu is going to offer some sort of fan solution for the FX-4CR which may allow the radio to use more power in digital modes (or at least keep it cooler).

Circles show hot-spot locations

Watching an online video by the popular Temporarily Offline Ham Radio vlogger Steve, it's clear to see that the FX-4CR has a large heatsink plate below the RF PCB and you can see how the heat is transferred away from the PA into this aluminium block. The only criticism is that there's no external heatsinking, but then I've not heard of anyone actually suffering any overheating issues.


For the CW operator, you may want to know that only semi breakin is available, but on the plus side, the filter is good and the T/R has full adjustability. Early production models had some hardware and firmware issues affecting CW operation which resulted in Yu offering full refunds or free replacement PCB’s. Thankfully, all that is behind him now and he has to be commended for not shirking his responsibilities.

I’m not a morse man, so I can’t comment further on the radio’s performance in this mode. I have just bought a paddle to start the journey, but it’s going to be quite some time before I’ll be on air,😂. 

To be honest, for digital and CW work outdoors I would much more likely to be found using a QRP-Labs QMX or QDX, so the FX-4CR’s performance in these two areas is not as much a concern to me as it might be to you

Okay, so everything's quite positive so far - what about the negatives? Well for comparison I may sometimes refer to the Xiegu X6100 because it's a similarly priced HF radio and I've owned one. 

Some people will complain about two specific things about the FX-4CR - no internal battery and no internal tuner. Internal batteries are little more than a convenience to me - I almost never use them except for just playing around at home looking through the settings or using a radio for morse-practise without transmitting. When I go outdoors to play proper radio, I always use my 13.2V Lifepo4 battery. The X6100 has batteries built-in but they don't last two minutes and there seems to be an issue with the BMS which makes the whole thing a bit of a faff.

The lack of a tuner is perhaps a more valid complaint, but then again, my £1400 705 doesn't have one either! And let's face it, most internal tuners are pretty poor anyway, so a few years ago I invested in a tiny 20W Elecraft T1 ATU and that has always been my "go-to" tuner for any outdoor activity. It's super fast, super light and could tune a string vest.

Onto the testing. Connected to an EFHW at home, it was an absolute doddle to pull in signals and get 55-to-59 reports from operators across the globe on just 10W. People were impressed with the modulation and were even more impressed when I asked them for a second report on 5W with barely any change to my signal. This is exactly what I love about QRP transceivers - making great contacts with people who themselves are often using 100-1000W. My IC-7610 is virtually an SWL station these days, lol.

Out in the field, the FX-4CR continued to please. I took it to the site of ROC B/G-0444 to continue my BUNKERS ON THE AIR activation from last week. I'd previously used my IC-705 with an AlexLoop, so this time I thought I'd use the FX-4CR with my SotaBeams 20/40 Linked Dipole. The noise floor was ZERO!! It’s so quiet around here.

The dipole is simple and quick to erect using a TACTICAL-7000HDS mast and within minutes I had spotted myself and was managing a mini-pileup with the FX-4CR easily pulling in signals and earning me a long string of complimentary reports.

During the activation I was trying to find things about the radio which annoyed me, but I just couldn't. It's pretty much perfect for me. The only thing that I would love to be added is a 500Hz Tuning Step. So many operators work in-between a 1kHz frequency for some reason and the 500Hz step makes it sooooo easy to flick through the band. Please, please add one Yu 🙏

Once the Bunker had been activated, I relocated to an area on the edge of the Forest Of Bowland which gave me a good height advantage and provided a take-off toward the west From here I sought out some proper chinwags to see how well the radio coped with extended TX. Everything went perfectly well and although the temperature of the case climbed, it remained "comfortably warm" - certainly no hotter than the X6100 under similar loads.


At the higher location I was going to transmit some "CQ TEST M7MCQ" morse messages and see how far my signal was reaching on PSKREPORTER. Unfortunately, the FX-4CR doesn't let you store messages in memory, so I had to use my paddle to do it manually. Maybe message-storing could be something to add to the next generation models?

The radio performed really well as a QRP Field Rig and not once did I think "Oh I wish I'd brought my IC-705 instead".  Okay, so the 705 has a bigger screen and VHF/UHF but it's 3X more expensive and it’s over twice the size.

This fabulous SDR radio costs around £450 and as I've said before, you cannot pay Ford prices and expect Rolls Royce performance! But you can expect high quality and superb value for money - and that's exactly what you get with the FX-4CR. It’s a fun radio and you feel like you're a part of a great adventure with Yu in the background, constantly looking to make improvements through firmware upgrades. He listens to his customers and responds to their comments and suggestions wherever possible.  

For a stand, I used some self-adhesive pop-out stands from Amazon. I've used them on all sorts of radio gear (and other) and found them to be reliable and strong.

Needless to say, any little niggles tend to annoy some people and they want fixes now, now, now, so you'll come across the odd keyboard warrior who blows things out of proportion. You only have to look at other independent radios such as the superb RGO ONE QDX  or tr(u)SDX which have all been 'works in progress' and have grown into something far greater than how they originally started.

Fitted with alternative knobs

The great thing about the FX-4CR is that 98% of everything works extremely well and 2% awaits further improvement. The X6100 by comparison  has quite a few serious issues which are very annoying (bluetooth, wi-fi and squelch virtually unusable (and we'll not even talk about those birdies 😮)) plus you have absolutely no confidence in them ever being addressed by Xiegu, which is very poor considering they’re such a big manufacturer and their products are sold by big retail outlets across the globe. When I buy from a large retail outlet, I expect a finished product!!

There's a pride of ownership with the RX-4CR.  Somehow it's more than the sum of its parts. I can't quite explain it - I'm just glad I became part of the club! It suits my modus-operandi perfectly.

So in summary, I very much like the FX-4CR and look forward to being part of its development and growth. I also like that the radio has 20W finals because (to my mind at least) that means I can operate SSB at a full 10W if I need to, without worrying about being at the limit of the PA.

Some features aren't fully implemented yet, but it's early days and no doubt there's a lot more to follow in the coming months.

It's never easy investing hard earned money into a company 5,000 miles away, but when you get assurance from so many other customers that a producer is talented, honest and communicative, it really helps.

We've all occasionally experienced cheap, fake products from China and many people have been ripped off by unscrupulous overseas retailers, but let me assure you, that's not the case when you buy an FX-4CR from BG2FX. Buy with confidence (but only through his website)!

In case you were wondering what the little house-logo was about (which I've embellished here), Yu explained to me that it serves as a reminder of his humble beginnings living in a rural mud house, where everything was a great challenge and it represents the start of his journey to where he is now 💗

Here's a video-review by Bob Nagy...

Technical Specifications  

  • Transmission frequency range: 3.5 - 29 MHz, 6M.
  • Receiving frequency range: 465 kHz - 50 MHz 
  • Operating Modes: USB, LSB, CW, AM, FM 
  • Frequency Steps: 10 Hz, 100 Hz, 1 kHz, 5 kHz, 10 kHz, 100 kHz, 1 MHz  
  • Antenna impedance: 50 Ohm  
  • Operating temperature range: -20 - +40℃  
  • Voltage range: DC 9 V - 18 V (please keep the maximum voltage below +16 V for long-term  operation: About 14 V is recommended)  
  • Power Consumption:  Transmit: (maximum power) ~ 2 A;  Receive: ~ 220 mA. 
  • Overall size: length 107 mm, width 65 mm, height 43 mm  
  • Weight: (radio only) 0.46 kg  
  • Filter Bandwidth:  SSB: 1.5 kHz, 1.8 kHz, 2.1 kHz, 2.4 kHz, 2.7 kHz, 3 kHz  CW: 50 Hz, 100 Hz, 200 Hz, 300 Hz, 500 Hz, 800Hz  FM: 5 kHz, 10 kHz  AM: 6 kHz, 9 kHz  
  • Power range: 0.1-20 W continuously adjustable  
  • Spurious emission suppression: -43 dB  
  • Carrier suppression: -50 dB  
  • Microphone impedance: 2.2 k Ohm  
  • Audio output power: 1 W  
  • Receiving sensitivity: -120 dBm  
Functional Characteristics:  
  • ☆ 2.0″TFT display screen 
  • ☆ Spectrum display and waterfall plot  
  • ☆ Dual VFO operation (VFO A and B) with split mode operation  
  • ☆ Internal USB sound card with serial communication via USB  
  • ☆ Adjustable DSP digital noise reduction  
  • ☆ Ultra wide input voltage: 9 V - 18 V  
  • ☆ Quick switching among various frequency bands and convenient operation 
  • ☆ CAT control over USB 

73, Tom, M7MCQ.


Philip Neidlinger said...

Good review!


MadDogMcQ said...

Thanks for visiting the blog Philip and thanks for your kind comment.

73, Tom, M7MCQ.

Anonymous said...

Great article!

Anonymous said...

It’s a quite pleasing and honest review, I might add. Well done!!!

PE4BAS, Bas said...

Very nice review. It shows well how Yu is doing the best he can to build a radio that will last. I've read reviews from AE5X as well. It is no doubt a very nice radio though personally it is not what I would buy. Luckely for Yu there are many that are really interested in his radio. 73, Bas

Anonymous said...

Excellent review Tom ;)
Gary - G7TOK

MadDogMcQ said...

Thanks all and thank you for visiting my blog - much appreciated.

73, Tom, M7MCQ.

MadDogMcQ said...


Tom I’ve enjoyed your blog observations with a variety of radios - your thoughts are what had swayed my opinion of the ic705 over the KX2. But a couple of thoughts where we disagree (FOR ME) the FX-4CR has really fantastic rx picking out signals that are completely inaudiable on other transceivers (yaesu ft857 Icom 718 & 706iiG Xiegu x5105 and x6100) it’s on a par with the yaesu ft891 but different (better copy on the speech but with more noise - I turned the MGC up to 60, it’s usually 32, to 40)
what’s for sure is that it hears stations that it can’t work with only 20w.
That said there’s no way the other radios could either.

For low power radios there’s not much point in using an ATU - it robs tx power so I only use one when I don’t have access to a resonant antenna, or as my contingency if my EFHW breaks. I don’t put every signal through an ATU trying to get the SWR from 1:1.8 on a resonant antenna down to 1:1.0 sone people do and it sounds like you loose more tx out than you gain in the lower SWR above 1:2.5 maybe…

I honestly can’t think of a better compact radio the build quality (and internals) is designed for outdoor operation but not quite in the way that the lab 599 tx500 is , more in the way that the Elecraft’s aren’t.

But what’s so special about it that stands head and shoulders above the Elecraft Icom and Yaesu rivals is the ability to natively run off 4 18650 2600mAh Lithium ion batteries with out a buck converter or rectifier again stealing energy so you can run 17v lossless right down to 12.8v that’s nearly 11w of useable power. Whereas the same 2600mAh 18650 batteries in 3 cell packs offers only 7.8w - in the field it feels like it lasts twice as long. For me that makes this the go to radio.

Thanks for your input Graham!

Regards, Tom.

TerryB said...

Very comprehensive and enjoyable review. I agree that it's REALLY hard to find any faults with this radio.

MadDogMcQ said...

@TerryB : Thanks for visiting the Blog Terry and for your kind comments. When some people see the radio, they think I'm out of my head for spending £450 on what they perceive to be a cheap Chinese radio. They have no idea of just how good this thing is, or just how well built it is.

Thanks again for joining in the discussion.

73, Tom, M7MCQ.