Thursday 15 December 2022



There's a lot of people out there who remain very happy with their analogue radios but quite fancy dipping their toes into the pool of SDR Transceivers. They don't, however, fancy paying big bucks for the privilege. And who can blame them - SDR technology has really shot up in price due to the world economy and the ongoing silicon chip shortage. Thankfully, there's a very cheap option and it's also a really very good one too - the FLEX-1500 160-6M Transceiver.

For the newbies who are new to all this talk of SDR, I should perhaps point out that broadly speaking, there are two types of SDR radios - the ones which require a PC to work and those which don't. Originally, Software Defined Radios always needed to be connected to a computer - all the operational side of the radio was controlled via a computer program - the unit itself had no buttons or dials - they were all onscreen and you clicked the controls with your mouse and keyboard.

Later, SDRs were introduced in the traditional radio form with a built-in display, buttons, knobs and dials - but you could still connect them to a computer if you wanted to and benefit from the "big screen" and the advantages of the software.

The Flex-1500 is one of the former types - the only button it has is an On/Off. Everything else is controlled by your computer.
When it was launched over ten years ago, this was a bit of a marvel. A fully featured, Direct Conversion, QRP multi-band, multi-mode transceiver in a small form-factor with fantastic performance and amazing control software. It was priced around $700 at the time and provided many hams with a budget-gateway to the world of Software Defined Radio.

In 2022 it's possible to pick one of these up for around £200 if you're not too bothered about cosmetic appearances and don't mind printing your own manual from the internet. Needless to say, if you find an absolute minter in original packaging with accessories, then you may pay more.... 

The Flex-1500 is a very compact radio and takes up little space in the shack. In fact, you could use it just about anywhere - in the conservatory, in the garden, in a park, basically anywhere that you can attach it to a laptop and an antenna. 
The connectors are simple and well placed. On the front you'll find the On/Off switch, a USB Socket, Headphone Socket (stereo (inserting a mono jack-plug will cause damage)), an RJ-45 Mic Socket and a Keyer Socket. On the back you have the BNC Antenna, 13.8V Input, FlexWire I/O, and three BNC's for Transverters and Reference-In.

Even though this little marvel is getting on a bit,  it's no slouch in 2022 and is still very much relevant. Being an SDR it was regularly being updated via its superb software - PowerSDREven at launch, this software was pretty darned good, but it was nowhere near as good as it is right now.

When Flex Radio decided to discontinue the 1500 (for reasons that absolutely no one understands), someone from the ham community decided to pour themselves into improving the software further still. That person is Darrin Kohn (K9ENS) and his work has taken the Flex-1500 (and 3000 & 5000) from strength to strength over the last few years. His software can be downloaded along with a whole host of useful files, documentation and videos at his incredibly informative website

Before we move onto the software, let's just quickly look at the spec of the radio itself. The Flex-1500 has a usable receive coverage of 490kHz to 54MHz and a transmit range of all ham bands between 160M and 6M. It's a shame that the receive coverage doesn't extend to the LW section but from what I understand, you can add bandpass filters to facilitate this.

The power output is 5W PEP (3W AM) which in my experience is more than adequate to make contacts around the world using nothing more than a wire for an antenna. Personally, I use a 40-10 EFHW at home and even though I've seen people refer to end-feds as "dummy loads", I've found them to be quite the opposite. The main antenna I use for outdoor QRP activities is the SotaBeams 20-40 Linked Dipole - again - another great performer.

The physical dimensions of the radio are 7" deep, 4" wide and just over 2" tall. It weighs around one and a half pounds (680g), so it's an extremely portable device - ideal for POTA and suchlike. One has to bear in mind that in addition to this small device, you also need a LapTop and a power supply of some sort, so that soon adds up to a small rucksack or large laptop-bag.


Pretty darned good! For a small amount of money, you have got a powerful radio on your hands, with good sensitivity and selectivity and some pretty amazing filters and noise reduction.

The PowerSDR software (currently V2.8.0.262) offers so very, very much in terms of features and functionality and it's all pretty intuitive too. Even though there's a hell of a lot of options onscreen, everything is well laid out and there's an immense amount of customisation available too, if you're the type who likes tinkering with such things. Darrin Kohn's  website is absolutely brimming with information and there are many YouTube Videos to flatten the learning curve.

With this type of SDR equipment, the software is everything and among SDR users, there's quite a bit of software-envy. You may have an Expert Electronics radio but prefer the look of the Flex software. You might have an Elad but fancy the Apache software. Well be in no doubt, there are plenty of people who would love to have the Flex software to play around with. It's very good indeed! And it's 100% free.

As you can see above, the two VFO's show their frequencies in clear and simple digits. These can be adjusted in terms of size and font and even the last three digits can have a separate colour. 

The central portion of the screen provides enough space to display a working map of the world and still have space for the panadaptor. On the left side are the often used buttons and sliders for quick adjustment. On the opposite side are the Band and Mode buttons. Many buttons have left and right click options.  

The lower section of the screen contains a host of other controls and any one of these panels can be relocated to give you the layout of your choosing. The level of customisation is incredible.

Apart from having all the radio's control-options onscreen, you can also have the PowerSDR software overlay the Weather, Lightning-Strikes, F-Layer, D-Layer, Cloud Cover and then there's the Spotter Map and even a Designator Map view. More could be added in the future.

The Spotting feature is quite extensive and Darrin has made it very easy indeed to choose a source and made it simple to switch from one to another. The thing I like the best is that the Spots are shown on screen relative to the LOCATION of the operator rather than the frequency they're on. So if you see a Spot over Africa, that's where his registered QTH is and all you need to do is click that spot and the radio will be tuned to that operators frequency and the mode changed as required. Fabulous! Of course, your own transmissions will be spotted too. 

PowerSDR includes an Audio Recorder (or a QSO Recorder as I like to call it). It's possible to not only record an active QSO, but also re-transmit it. 

Needless to say you can save the audio files for playing back at any time you choose. Additionally, you can create files for Calling CQ, etc and these can be programmed to transmit repeatedly with a timed delay between transmissions.

Because the file-format is a common type, it's easy to share these files online with other interested parties.

Rather strangely, PowerSDR also has a feature called TX WaterID which transmits your CallSign in such a way that it appears on the waterfall for all to see. It obviously has no practical value as far as I can see and I'm not even sure that it would be legal to use it - but it's there. 

You can also use the same feature to transmit a simple 24bit image. Again, why you'd want to, I don't know, but if that's your thing, knock yourself out, lol.

VAC! PowerSDR has two Virtual Audio Cables built-in which make it simple to interface with external programs such as N1MM+, CW SKIMMER, WSJT-X, etc. There is a very comprehensive configuration screen in PowerSDR's Setup menu.

As mentioned previously, this software is infinitely configurable and apart from being able to alter the colours of almost all the components which make up the interface, there are also a number of "skins" to change the overall cosmetic theme. Even the meters can be adjusted individually.

It's worth mentioning that the Flex-1500 does not have an SWR meter built into it. I use an external QRP SWR meter from MFJ and if I'm using a non-resonant antenna with an ATU, then I also insert an SWR BRIDGE to protect the PA during tuning. Some may think this is overkill but the last thing you want to do after finding a bargain radio like this is to see magic smoke coming from it.

Connecting the rig to my EFHW (which is not well sited), I soon started collecting contacts. Andy in Germany gave me a 57 and was impressed with the signal from my 5W radio. He was using 700W which earned him a 59 from me.

Other contacts rolled in and I was enjoying the user interface. My only negative comment would be that there’s a tiny spike when you drop the mic. I could see it on the waterfall and could hear it in one of the QSO recordings I made. I imagine that I’ll find the solution on the KE9NS forum.

When I enquired about my transmitted audio, people were quite complimentary which was good to hear, but there's an awful lot that you can do to "tailor" your TX Audio within the software and HERE's an excellent video guide on the subject by Nige Coleman (G7CNF). There are real benefits to experimenting with this.

Is in summary, I can say that the  FLEX-1500 has been a great purchase. Big radio fun for relatively small outlay. Punches WELL ABOVE its weight!

Maybe it's time to treat yourself to a Xmas Cracker...

I’ll update this post as I do more experimenting.

73, Tom, M7MCQ.


Anonymous said...

Wow, sounds very tempting Tom. Have been thinking of an sdr rx though.

MadDogMcQ said...
This comment has been removed by the author.
perlguy9 said...

Hermes Lite 2 is a pretty cool little SDR too..