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Reviews For: FlexRadio FLEX-6400M

Category: Transceivers: HF Amateur HF+6M+VHF+UHF models - non QRP <5W

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Review Summary For : FlexRadio FLEX-6400M
Reviews: 23MSRP: 2999
Description:
The FLEX-6400M places the most used controls right at
your fingertips. Controls are labeled for intuitive
operation and designed to minimize hand motion for the
most common operations. Occasionally used controls are
easily accessible on the large touch screen display
bypassing the complexity of multi-function buttons and
multi-level menus found on other transceivers. Like
modern smartphones and tablets, capacitive touch control
is provided on the large LCD display for intuitive pan,
zoom, tune, and menu operation.
Product is in production
More Info: http://www.flexradio.com/amateur-products/flex-6000-signature-series/flex-6400/
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
34.3234.4
K1OYQ Rating: 2023-03-12
Great Radio but not at full potential Time Owned: more than 12 months.
I've had my Flex 6400M since 2018 and I love its overall performance. This radio is one of the best I've owned and it is full featured. It can not be beat in terms of easy remoteability. SSDR is a real pleasure to use and the display is excellent. Tech support is very prompt and good, unless it turns out to be a Flex software issue. Then you have to wait for the next firmware update which takes a lot of time. I don't feel this radio is working to its full potential due to Flex Radio concentrating its resources on non-amateur contracts. There is so much that this SDR platform should be capabible of, but it isn't. Owners are constantly providing a wish list of performance improvements to Flex, but they don't seem interested in improving the product. Their motto is New Software = New Radio, but they don't live up to the hype. They are very slow to fix software/firmware issues and the fixes seem to introduce more new issues. They haven't introduced any new features in years. This is getting to be very frustrating and Flex Radio's credibility is deminishing in my opinion. Would I buy it again? I'm not sure at this point. I'm in the market for a new rig and I'm really questioning if I should stay with Flex. Guess I'll sit down and make my list of pro's and con's and see where I end up.
G2YT Rating: 2023-03-04
Terrific to use with SmartSDR for Mac Time Owned: more than 12 months.
I bought the Flex 6400M and Flex PGXL amplifier specifically because I wanted a remote station that I could operate from my Mac using SmartSDR using Mac OS. Being completely new to remote operation and SmartSDR I found that 'getting under the skin' of the Flex 6400M/SmartSDR took some time. It was, for me a fairly steep learning curve. The plusses are that I find it easy to use now (although I now realise that I would have been better served by the basic 6400 because I never use and never will use the knobs and buttons on the radio). Another plus is that I really like the SmartSDR for Mac. I edited this review March 23 because I had previously commented that I had a significant ‘frying’ noise on RX which I never get on my IC7851 (or other radios I have used). The latest firmware update early 2023 seems to have largely addressed this flaw and has made significant improvements to my ability to receive weak signals on a noisy band. It still gives the impression of a slightly noisy RX by comparison to the Icom, but is significantly improved and worth an overall increase in my ‘star’ rating for this radio from ‘OK’ to ‘Good’. The dynamic range of the Flex receiver is unquestionably excellent.

Transmitted audio of the Flex is good, providing good clean communications grade audio with plenty of punch, particularly when used with the compression/processor. I had been using a low cost CM500 Yamaha ‘gaming’ type headset connected to the Mac but recently I went cordless with the Apple AirPods Max. Super quality headset for use with a Mac/SmartSDR for iOS, if a rather costly. Super audio reports from the Apple headset.

As a dedicated Mac user I was really irritated to realise that I had to buy a Windoze PC in order to configure the PGXL linear amplifier and TGXL ATU to be able to 'see' it on the SmartSDR for Mac (and to download and install PGXL and TGXL firmware). Mr Flex... not everyone has a PC and I didn't want to buy one! Marcus DL8MRE who wrote SmartSDR, the App for Mac (and PC) told me that he would be very happy to write a program to allow the PGXL and TGXL to be configured using a Mac, and that all he needed was to be given the go-ahead by Flex Radio but the guys at Flex radio clearly had no interest in permitting this to happen. When I asked them they told me that they took this suggestion "under advisement" with no further explanation - US English I think for “we're not going to do this so don’t waste your breath asking”. I fail to see what Flex Radio would have to lose by not permitting this. I wonder if the main obstacle is an inability on the part of the manufacturers of these ‘Genius’ devices (4O3A in Montenegro) to incorporate this ability?

Since originally writing this review I have edited it because I had been struck down by the dreaded ‘corrupted SD card’ which has been discussed quite a lot on the Flex forum and seemed to be quite common. 10/10 to Flex for the way they sorted this problem. I reported this problem to the Flex help desk and got assistance from Tim in the USA at the help desk within minutes (thank you!). I had a new SD card sent from Flex in Germany to me the following day by courier which was simple to install and completely fixed the problem. This was apparently a firmware bug which had surfaced and seemed to strike at random. I am impressed with the level of support offered by Flex. I never have a problem when a company has unforeseen problems… its how they DEAL with those problems which defines my opinion of the company and so far, very good.
N4BRJ Rating: 2023-02-11
Love mine Time Owned: 6 to 12 months.
Coming up on a year of ownership and for the first time I'm not looking to see what's new out there.

SmartSDR for Mac is brilliant. It's written by a 3rd party so it's not free like the Windows version but it's worth every penny. SmartSDR for iOS is also available and works great on iPad and iPhone.

I specifically chose the "M" version because I like having a traditional style radio with knobs. Big bonus for the 8" multitouch display.

Some have grumbled that the radio's firmware and OS is stored on an internal SD card. This is offset by the fact they use an industrial SLC (single level cell) card instead of consumer grade MLC cards (google SLC vs MLC for the difference). Replacement cards are available from Flex if it fails. If you're worried you can always clone your card and have a backup on hand.

Coupled with an INRAD M629 microphone I've received multiple unsolicited compliments on my transmit audio. I run my receive audio through a pair of BOSE Companion 2 desktop speakers and couldn't be happier with the results.
W0YVA Rating: 2021-10-27
Best I have ever owned! Time Owned: 0 to 3 months.
I bought the Flex to replace my current transceiver, an ICOM IC-7700. To compare the two is absurd; the Flex is, in a word, amazing! I know there are plenty of reviews out there describing in great detail all it’s features, specs, etc., so there is no need for that here. I’ve been playing ham radio since 1954 and have had a LOT of radios, including some mighty fancy ones and none even compare to this technology. In short, if you’re looking for a new toy and can afford it, buy a Flex. I am not interested in SO2R or remote operation which the Flex handles nicely; I just wanted a current technology transceiver. Furthermore, Flex support is nothing short of amazing in addition to a massive Flex ‘community’ that is a wealth of information. Oh, and remember, the Flex is a computer with a screen and radio built in so be ready for that. It doesn’t ‘turn on,’ it ‘boots up’ and that takes a couple of minutes. Different from your Boatanchor - HI. Also, unlike the old days, you need an Internet connection. Lastly be ready for a fairly steep learning curve - but even that is great fun!
G0CGL Rating: 2021-09-17
One of the best SDRs despite some flaws. Time Owned: 3 to 6 months.
The 6400M replaced an Expert Electronics MB1 SDR that was my transceiver since 2016. During the past 5 years I twice reviewed the MB1 on eHam and on both occasions I gave it only 4 out of 5. That radio replaced an Icom 7800. I noticed with the MB1 that its receiver was noisier than the 7800 and that it lacked sensitivity on 6 metres. A distant 6 metre beacon could be received at S3 on the 7800 but not at all on the MB1 until I started using an external 20dB preamp.

On installing the Flex, I immediately noticed lower receiver noise, markedly so on some bands compared to the MB1, in fact reminiscent of the IC-7800. I checked the beacon. It was S5 and in the clear. A re-check with the MB1 and not a sign of it until switching in the preamp, when it was then S3 in a lot of noise. The difference on 6 metres with the 6400M is staggering and also, to some extent, on 10 metres and 12 metres as well. On most bands FT8 decoding is superior presumably due to the lower receiver noise, the additional decodes coming from the -22 to -26dB signals that the MB1 does not hear so well. On 160 metres not only is there lower noise, I also noticed that the Flex transmitter is much cleaner. I suspect that the MB1 has a design fault on 160m and indeed there is a new MB1 model this year with hardware improvements for Topband. But it is twice the price of the 6400M.

The 6400M has a low noise preamp of up to +32dB in 8dB steps. It is ideal for 6 metres as it does not increase the band noise which is naturally very low in my rural location. The other high HF bands, 10 metres to 15 metres, benefit similarly from the high gain and low noise preamp. With my last radio I was restricted to a noisy +10dB preamp.

I really like the 8-inch panel display and that its usefulness is retained in ‘SmartControl’ mode when the radio controls are in sync with SmartSDR, displaying the VFO frequencies with all the metering and access to the master menu. Local access from the panel or attached computer, or indeed any other device on my LAN, is straightforward. In the 5 years of owning the MB1, remote was never satisfactorily made usable and was left in an unfinished state. Other features that the manufacturer claimed would be forthcoming for the MB1 did not materialise either such as ALC for an amplifier, diversity receive and transverter support. All these are available on the Flex.

Connecting external CAT controlled devices such as amplifiers, auto-ATUs and dynamic antennas is made very easy by using the USB cable facility. Flex has their own CAT and audio transport systems thus obviating the need to use external 3rd party software. I do have to say though that DAX, whilst clearly outperforming VAC, is not as robust as the TCI protocol used by Expert Electronics, 5M contest, JTDX, MSHV and so on. Exact setting up of digital mode software and the Windows sound system, together with the minimising of DPCs in the computer, are necessary or else DAX is vulnerable to distortion or artefacts on TX.

There is such a plethora of very useful 3rd party applications that work with Flex. My favourites are Swisslog logger that puts Spots to the panorama coloured by needed, worked and confirmed and which adequately deals with Slices (the Flex name for receivers) to log the active frequency; SDC Skimmer which I have used for the past 5 years as it is free and can be used either instead of or as a compliment to the Afreet CW Skimmer; SDR-Bridge (needed for SDC); and FR Stack with which I have the supported Elgato Stream Deck with a fully loaded profile that makes operating the Flex a dream.

SmartSDR is the only software that has CESSB built in, achieving the equivalent of an extra 2.5db output on SSB. In ESDR2, the software used by the MB1 and SunSDR radios, receiver optimisation is relegated to near last place in the priority list for features, with TX being overly endowed by numerous user configurable parameters. The 6400M achieves at least the same quality of transmit audio without all that drama while receive gets all the settings needed to make the radio perform how you need it to no matter what the circumstances are on the bands. I have read of complaints about the efficacy of DSP functions such as the noise blanker, noise reduction and notch. Not so here I must say because they all work well. But if you operate in a high noise environment then it might be a different matter. Often though, challenging environments require nothing more than the operator’s extra attention to the facilities at hand. The DSP functions seem no worse than any other radio I have used and to further compliment them with AGC-T and superb filtering, including filter shape programming, and most operating conditions should be catered for. The software guide user manual runs to over 200 pages. The radio deserves more than one thorough read of it in order to obtain the best results that it can achieve.

Contrary to other reviews on eHam, I do not have a frying hiss noise. Also, my 6400M has almost none of the failings noted by a reviewer back in December 2018. Flex must have improved the hardware in the interim and also this year there have been significant updates to version 3 of the software.

In contrast to Expert Electronics’ ESDR2, settings in SmartSDR are much more customisable and easier to deploy. This includes AGC, especially the excellent above mentioned AGC-Threshold which undoubtedly contributes towards the superior receive performance, filtering, information display and the Multiflex method of switching clients which is something that is practically impossible in ESDR2. I caution though against watching any You Tube videos about PowerSDR, the software previously used by Flex. You will wonder why the best features of PSDR were not incorporated into SSDR.

My favourite mode is CW and the 6400M performs admirably. There is a built-in CW memory panel (CWX) for macros. The filtering is excellent even down to 50Hz and the adjustable APF works very well too. With the M model, there are front panel function buttons that can be programmed for APF, CWX macro sending and many other non-CW parameters such as NB, ANF, diversity RX, VOX, etc.

You quickly realise the importance of the bandpass filters that the Flex has and which are so superior to SunSDR radios. For some reason 60 metres does not have a band pass filter associated with it and when on that band you see ‘WIDE’ show on the panorama. This band is as noisy on the Flex as all bands are in the MB1. Fortunately, this does not stop DX working on the band.

FlexRadio support is good, there being a superb community forum in addition to the proprietary help desk where you submit a ‘ticket’ and get assistance very quickly. New users though might find shortcomings with support. They are likely to have more than one question for the help desk. But only the first of those is answered, any others are rejected and only at that time are you told it is one question per ticket. I can see the need to close a ticket after one solution and not keep it open ended pending further solutions. But new users should be offered a complimentary system whereby all questions are given a reply in response to their submission with a note that outstanding problems should be submitted by tickets individually. The product is “flexible” but the company attitude to users’ needs, be that initial help or longer-term reporting of software issues, appears not to be quite so much. Owning a Flex is not just the radio, it is akin to a whole ecosystem and requires its support to be comprehensive enough to cater for the first-time user as well as the more experienced.

No radio is perfect and the 6400M has some quirks. It is very easy to knock the inner knob of the front panel’s concentric pairs when adjusting the outer ring, for example to accidentally change the mic gain when adjusting the output power. They are too loose and need some tension. On the MB1 the knobs click into indents when turned which is much better when there exists an inner and outer pair. With the Flex you must quickly learn to be dexterous and avoid unintended nudges of the wrong control.

The DX Spot display is limited to 10 tiers or rows with Spots that cannot be displayed hidden behind a ‘+’ sign that has to be clicked to reveal unshown Spots. That is so unhelpful. If vertical screen space is available, it should be used. Spots do though carry useful information: mouse over a Spot and I can see whether it is a duplicate for the mode and band, receiving this information as it does from the logbook. SDC Skimmer Spots can be a unique colour to identify them from DX Cluster Spots. That is all good, but the restricted display of them is silly. SmartSDR does display extremely well on a 4K monitor and Flex should recognise this and not waste the extra screen space these monitors provide.

Rear panel connectors: my footswitch and Antlion Mod 4 microphone that I used with the MB1 do not work without adaptors with the Flex. In common with most accessories, they come with TRRS (stereo) jack plugs but the Flex will only accept TRS (mono) and RCA plugs. It is a surmountable problem but annoying nevertheless. Some Flex users criticise the back panel positioning of the microphone and headphone inputs when all other manufacturers use front panel connectors. I do not find this too much of a problem because I am settled in a ‘plug-in and forget’ scenario. But if changing these accessories is often necessary, the design would be an inconvenience.

Then there are the Windows OS update issues, historically problematic to the integrity of SmartSDR and CAT / DAX, that have supposedly been fixed in the latest software version. I updated Windows 10 21H1 with the 2021-6 KB4023057 update and got a blue screen on launching SmartSDR. I had to remove all old COM ports and reinstall them. It is vitally important when using a Flex radio to have a recently saved W10 image and to back up CAT + DAX settings and profiles. Fortunately, I had done so. Having these back-ups also meant that it was very easy to transfer SSDR and all its settings to a fresh install of Windows 11. I will say though that none of the numerous updates to Windows 11 so far have given rise to any CAT or DAX failures. Maybe I was just unlucky that one time.

In Europe at least, Flex has a poor reputation for reliability of their products. Clubs and Societies that I belong to have their own discussion groups and forums. All of them in the past few years have detailed several times various hardware reliability issues encountered by new Flex owners. In Europe, the Flex repair centre in Germany has its own poor reputation. This had put me off buying a Flex radio until June ’21. I had noticed that Flex had taken assembly and quality control out of the hands of external parties and I persuaded myself that the chances of having a defective radio on receipt were now much less. Unfortunately, that was not to be the case with the radio exhibiting audible clicks on tuning the main VFO. It had been supplied with a mechanical fault and had to be returned to the dealer, ML&S in the UK. They found it to be due to a loose securing nut, probably as a result of vibration during transportation. I must say Flex pay only lip service to the quality of the packing. They use just two foam inserts in the box that leave especially the bottom of the radio vulnerable. Also, their packing is not enough to suppress vibration. I added a lot of extra polystyrene packing when I sent it back to the dealer.

The above is a shortlist, some may call it a long list, of quirks or failings that I have found. Are they deal breakers? For me they are not and, in any event, the pros of the radio vastly outweigh them. It is very easy to justify your expenditure on a new toy by giving it a 5-star review, regardless of the truth. However, with the Flex 6400M there is just so much to like. It really is amazing. When I sit back and take it all in, I realise that I am glad not to be using the MB1 anymore and very happy to be using a Flex. The bottom line for me, a DXer, is can it put more DX in my log than my last radio? Yes, most definitely. If I could give it a 4.5 rating, that would reflect my true experience with the radio so far but it is worth more than 4 so I have given it the full 5.
IK0OZD Rating: 2021-03-08
IF "YOU REALLY WANT TO CHANGE" RADIO THIS IS AWESOME Time Owned: 3 to 6 months.
I had many RTXs in my life, this is not the best neither the worst. This is an excellent radio for all the people who are tired to have all the usual icom, yaesu and Kenwood. Is a new way to do something. If anybody really wants to change the way to do radio, this is the possible way
W1XYZ Rating: 2020-11-10
Good transceiver for SSB and AM, easy to use Time Owned: more than 12 months.
"Easy to Use" is the operative word for the 6400M which I have had for over a year now, operating with MacLoggerDx on my MAC based station B. I also have a 6400 that I use remote, and an ANAN 8000DLE which is station A. I've had the pleasure to be able to use these two stations simultaneously and the remote station also.

The biggest plus I can find with the 6400M is that it is dead simple to use. The very basic controls are similar to an old school analog transceiver and the connections to the computer, should you wish to do that, are easy to set up and work reliably. With that said I can comment that I prefer the setup with the 6400M as I can have the display of the radio going and then the display on my MAC running MacLoggerDX and WSJT-X which is very convenient and stable and is the main reason that I selected the 6400M. In non-digital operation I found some interesting things, however, that bear mentioning. The transmit audio is excellent on SSB and AM. AM is very good with the included EQ and all I had to do was plug in a good mic like a Shure SM-58 (not a "ham radio" mic) and got excellent audio without any outboard gear at all! Bravo! On 6M the transmitted RF is within specs but not all that clean, I noticed, not as clean as the other bands. ANAN's PureSignal technique ought to be borrowed by FlexRadio for sure to cure that.

The receiver is good but has some limitations relative to the ANAN, especially on CW and AM. For instance, there is no real noise blanking action on those modes. The Noise Reduction is also ineffective, compared with the ANAN 8000DLE (which is spectacular). The receiver and controls do not compare to the ANAN which has diversity receive operation built in - something that is simple to do but not found in many rigs! AGC is very well done and the VFO selections are easy and intuitive.

On CW, there is another issue in that the sidetone has no apparent adjustment from the front to use to zero beat, and the demodulated CW note has a grainy sound, like a low bit-rate channel might have. I haven't looked into it but it lacks the liquidy musicality of any analog CW receiver, which can be tiring. (this is with headphones, inboard and outboard audio) The selectivity of course is fantastic so if the tone is not something you care about then you will enjoy digging out the weak ones, even though it is not any contest against the 8000.

Customer service is good - I had a micro SD card that was apparently corrupted with too many overwrites in the Maestro module so I was mailed a replacement. I would have been happy to download and burn a card but they seemed reluctant to do that. I duplicated a card in case the new one went bad again and taped it under the lid even though I was told I needed a special medical-rated SD card burner to do it (LOL) by the company. It was kind of funny. Another issue that has cropped up is the internal automatic antenna tuner. This device does not work reliably on 160 or 6 meters, even with a modest 2:1 SWR. Sometimes it works other times not. In addition, the reflectometer in the rig (HW and SW, I presume) shows the right SWR at, say 20 Watts and then something else at full power. I get around that by turning the tuner off and may see if there is something that can be done.

What else? The global, Mic and TX profiles seem redundant to me. The menus on the Maestro are a little odd until you get used to them, with some things such as the noise reduction controls placed in odd locations, in my view. All in all I like the radio enough that I bought a second one for remote operation - a 6400 without the "M" - so obviously I think these are pretty good! Remote operation is very very easy. I do look forward to a future version with the CW problems addressed, but I am not complaining. Bottom Line: Easy to use, good performance especially on SSB and AM transmit, and MAC compatible. A few flaws prevent a fifth star but I'll remain a customer.
N2DTS Rating: 2020-09-01
Fantastic! Time Owned: 0 to 3 months.
I love this radio, the fidelity is fantastic, the display rocks!, its very easy to use and figure out.
My only real beef is the knobs are a bit touchy, everything else about it seems great for the price.
I love the ability to dial the filters in just how you want, the two separate slices (receivers) you can create and move around, how you can expand or shrink things on the screen.
The only issue I had was the power button, you just tap it to start the radio, if you hold it down till something happens, it gets the radio ready for software updates and that can hose things up.
Hold it down till it turns white and it does a factory reset.
Once you know that, the radio works fine every time.
Turn DC power on, tap power button and the radio starts.
I have had a number of new radios over the last year and this is the best by far.
Maybe its missing something for hard core contesting or top notch cw, but in general use the ergonomics are very good, fidelity is great, receiver performance is as good as it gets in this price range.
I prefer to use the radio standalone over the software in a computer, the screen and knob setup is that good.


K1OIK Rating: 2020-02-20
Good riddance Time Owned: more than 12 months.
I traded this for an Icom 7300 where the noise limiter works, where I don't have to wait 70 seconds to boot, where it doesn't crash or blue screen my computer, where updates are free, not $200, Also Flex owners tend to believe they are better than anyone else.
Although the Flex customer service is great.
KL4QG Rating: 2019-07-31
Best HF I owned Time Owned: 0 to 3 months.
Well having owned icom 7700 and 7610 and Ten Tec Omni 7
My new 6400M in league of it own very good receiver and clear audio with hand mic
I have RadioSport Headset with mic coming .
I can use 6400M without computer
Flex user group very helpful to new owners also

Buy Flex 6600M or 6400M it’s best HF radio out there
Joe