Sunday 10 March 2024



Having previously posted about building the Radio-Kits Explorer, now is the time to switch it on and see if the magic smoke is released.

I had followed the instructions and run all the tests listed in the instruction guide. Thankfully, everything seemed fine and to spec, so I finished off the last bits of construction and got it ready for full operation. For the first switch-on I used a 12V 600mA psu and plugged it in. The radio lit up and made radio-like noises. No smoke!! ๐Ÿ‘

I connected an EFHW and checked the receive capability of the Explorer and I'm happy to report that everything is working really well! Thankfully, there was a contest running , so there were lots of SSB signals to listen to from all over the world. The narrow CW filter worked well too down at the bottom of the band. So far, so good! ๐Ÿ‘๐Ÿ‘๐Ÿ‘

Then I plugged the Explorer into a computer and Windows saw the device and assigned it a COM port ๐Ÿ‘

The PA BIAS adjustment was odd. It is set by default to 100, which is too low. When you select the option, the radio goes into TX (no RF) and the red LED lights up. The current draw went from 154mA (RX) to 285mA and adjusting the BIAS made no difference - it's supposed to increase the current draw and you keep rotating the dial until you've added about 40mA to the initial reading you got. 

Odder still, every time I return to the BIAS menu option, the figure has defaulted back to 100. I assumed it would maintain the adjusted level, but it doesn't. Apparently, this is normal but I’d personally prefer it to remember the figure. The reason Steve forces it to default to 100 is in case an owner changes the PA transistor. If I had to change the transistor, I’d probably do a full reset anyway.

The end result is that the radio isn’t transmitting. I tested it in CW mode on a straight key and every time I keyed-up, I saw a current draw around 280-290mA and the Power Out reading on the radio's screen was 0W. ๐Ÿ˜จ 

I wrote to Radio-Kits and Steve said he'd put together a list of things to check. 


Steve emailed back promptly and gave me some things to check...

With a 13.8V input and the receiver set to measure bias current (SYS MENU - TX BIAS - 100 - red led on), Point-1 should be around 13.8V and Point-2 should be 0V. They were both fine๐Ÿ‘

Next up was a resistance measurement between Point-1 and Ground (with the power supply disconnected). It should be 890 Ohms - it was ๐Ÿ‘

Next was the bias voltage. This involved setting the bias figure to 300 and measuring the voltage at Point-3. It should be 2.1V and it was. Voltage at Point-4 should be 1.5V and it was. ๐Ÿ‘

Next, Steve wanted to know the voltage at Point-5 (the PA transistor Gate) with the bias setting at 300. It should be 2V and it was. ๐Ÿ‘

He also wanted to know the current being drawn by the radio if the bias setting was increased to 400. The current didn't alter at all with the increase from 300 to 400. In fact, the current stayed the same even if I increased the bias setting to 1000 ๐Ÿ˜ฎ

If you're an outright beginner and you're not exactly sure how to use your multi-meter to measure current, see the diagram above. Be sure (in this instance) to pick the mA port on the meter. 

By this time, it was getting late into the evening, so we called it a day. Steve signed off with a note about the PA transistor, saying to check the voltage reading on the metal tab which backs onto the case and he also mentioned the connections on the T2 windings. I'll leave it for tomorrow.



I checked the voltage on the transistor’s metal tab and it read 13.8V which was correct. At this point, I took note of Steve’s suspicion that the output transformer (T2) wires might not be making contact.

Checking the wires with a continuity tester, everything seemed fine, but I decided to reflow the solder joints anyway and boom - it worked! Thanks for your guidance Steve!!

With the radio showing a solid 5W into a dummy load, I rebuilt the radio and started to run some on-air CW tests. I connected an EFHW and used my Elecraft T1 tuner to get a good match. During the tuning process, I saw the output power vary between 1.5W and 6W. This prompted me to ask Steve if the Explorer had any built-in SWR protection and the answer was no.

He followed it up with a reassurance that it won’t fail as long as it doesn’t get too hot. The Elecraft T1 usually finds a match very quickly, so I’m not too worried about that, but obviously, you need to be cautious when using data modes such as FT8.

Once I’d got the radio matched to the antenna, I started to put out some CW TEST messages and within a minute or two of sending, spots appeared on the Reverse Beacon Network as far away as 1,100 miles away into Eastern Europe. Conditions were very poor tonight, so I was quite happy to see those. 

Later, I tried again and managed to make 3 contacts in the USA, over 3,500 miles away! I’ll try again at the weekend from a better location.  I also need to find a suitable microphone to run some SSB. 

While I've been fiddling around with the Explorer (especially during the testing phase) I thought that the radio would benefit from a Power Switch - so I fitted one!

I'd noticed that the PCB had two contacts marked power-switch and I asked Steve how these could be used. He explained that one simply needed to cut the track in-between the contacts and then route a switch to it. The problem, he said, was which switch to use and where to put it.

Well I looked around and bought some single-pole, single-throw, latching, push-button switches on Amazon and when they arrived, I discovered that they were much too long and would touch the PCB, so I simply fitted one of the fixing nuts above the fascia plate and one below. I then splayed the legs out and hey-presto, it fitted perfectly! If I can find a lower profile switch later, I'll swap it out.

I opted for a white colour to match the writing on the radio fascia. I think it adds a real convenience to the radio and saves you from repeatedly plugging/unplugging the power plug.

Modified with Power-Switch

I also made some other tiny mods which obviously make no difference to performance - it's purely cosmetic - but it personalises the kit you've just toiled over. Apart from the heatsink and the power switch, I also swapped out the case screws for some stainless-steel low profile cap-heads from ACCU. And finally, I fitted a black aluminium knurled finish tuning knob.

Oh, just for convenience, I also fitted a kick-back stand to angle the radio up toward me. These are actually sold as Laptop Stands and I've used them lots of times on portable radios. 


I do plan to make one more mod and that relates to the Mic Bias option. Inside the case there's a link which you fit a small jumper to if you want to introduce a 5V bias to the microphone for electret mics. I think I'll fit a small slider switch to the side of the radio to bypass the need to open and shut the case if you want to switch mics.

At the time of writing, the manual didn't include any diagrams showing the connector configurations, so I've knocked together a sketch below...

More testing... 

Obviously, I'm a Foundation License holder with no fancy test-equipment and even less expertise. All I can do is look at the Explorer from a practical end-user point of view and maybe compare it to a couple of other similarly priced radios.

To give a radio the best chance of working to it's maximum ability, I always test radios from a quiet location, where the noise floor is low and the take-off is good. I have a holiday home on the edge of the Forest of Bowland, so no better place to play radio! 

I decided to head up to a slightly elevated location called Bodie Hill above the Port of Lancaster. This place overlooks Morecambe Bay, out toward the Irish Sea and beyond. It's a great take-off point and it's also a beautiful place to work from. It's weird how you can see ships floating above the houses at Sunderland Point. One of my favourite places to operate from, not least of all because there's loos and cafe's not too far away ๐Ÿ˜‚

Because I'm working a single band, I setup with a 20/40 Linked Dipole from SotaBeams - it can always be relied upon for great results as long as you've got the space to erect it. If I didn't have the space required, I'd use my Super Antenna MP1 Vertical on a tripod.

The first thing that I normally notice when I switch on a radio here, is the stony silence, but the Explorer has around S3 noise with no antenna connected. When I was at home, I'd blamed the local QRM, but no, it was the same here too. Now bear in mind that it may be due to my build-skills and not the radio. Or it might just be the way the S-Meter is setup ๐Ÿคท‍♂️.

As I tuned around, the incoming signals negated the need for a super low noise floor anyway - almost everyone was S5 to S9+ anyway and boy, did the signals flow in - it was a busy day on 20M.

I tuned to the CW portion of the band and put out some CQ TEST messages to see how far my signal was being spotted on RBN. I spent a few minutes doing this, changing the frequency each time. I'll download the report later.

To use SSB I plugged in a TNT microphone that I'd hurriedly made up to suit the jack-plug configuration of the Explorer - I was using a non-electret mic on this occasion. I found someone calling CQ and went back to him, unsure if the mic was actually working. He came back to me immediately, confirming that I'd got the wiring right, lol.

He gave me a 59 from Bykovo, Russia, which I think was more of a bouquet of flowers than a true report, but I took it anyway. He certainly wasn't struggling to hear me.

Next up was a contact in Lithuania, followed by two Germans, an Italian and an American guy in Austin, Texas! I got great signal reports from everyone, apart from the Texan, who gave me a 4/0. Despite this, I was talking with him longer than any of the others, so he had no problem copying me. He was very impressed with the fact that I was using a kit-radio and asked for the manufacturer's website.

After a few more SSB contacts, the rain started to pour and made a cold day, colder! I was happy that I’d tested the radio sufficiently enough to draw conclusions on its performance, so I packed up and headed back to the caravan.

Back home, I was interested in trying out different mics and I tried to alter the mic-gain, but Steve informed me that it's not variable - it's fixed by R29 at 100k. So I will have to spend time playing around with other mics which means cutting connectors off and fitting new ones ๐Ÿ˜จ 


Let me preface this by saying that I really enjoyed building this kit and I am really pleased with the finished product, including the form factor and that blue case. It is not a compact radio like a (tr)uSDX or a QMX and doesn’t try to be. In fact, its size makes it A) unique in the marketplace and B) easier to build. In contrast, QRP-Labs seem to have gone to great lengths to keep the QMX as small as their QDX by using a 6-layer pcb and construction methods which can make the build quite a challenge (although their instructions are second to none).

The Explorer construction/user guide is perfectly adequate for seasoned kit builders, but I’d say it’s a bit lacking from a novice’s point of view. Having said that, the designer acknowledged this and is about to make some alterations.

The radio does not have a bootloader, so there’ll be no firmware upgrades available through the USB port - something we’ve all become familiar with in recent years, to the point that we now expect it.

Ergonomically, I’d say the radio is lacking. There’s only one controller and that makes some tasks a bit laborious. I was quite shocked to find that you cannot change the Tuning Step unless you use CAT Control ๐Ÿ˜ฎ, although the Explorer does feature Progressive Tuning, where the tuning rate increases the faster you spin the dial. I’m not sure how much would be involved in a redesign  to include a second encoder or additional function buttons, but I’m sure it would make a huge difference to the enjoyment of the radio.

Performance-wise I found the receiver to be quite sensitive and selective when fed with a good antenna in good conditions. It was definitely better than the (tr)uSDX but not massively so. 

In terms of value for money, I guess the Explorer doesn't do well compared to the competition. For less money, you can buy kits which provide you with five times as many bands to play with, more modes, lower power consumption, better ergonomics, a built-in microphone, ptt/morse key, morse decoder, memories, swr bridge, colour screen, firmware upgrades and more!

It sounds like I’m not very happy with my purchase, but the fact is, I’m glad I bought the Explorer and for me, it’s a keeper. As I said previously, I love building these kits and have made something that is just that bit different.  If they bring out a V2 with a richer feature list and better ergonomics, I’d buy that too!

But I’m not normal ๐Ÿ˜‚ Most people buying a kit-radio would be doing so to save money and they’d be keen to get the best feature-set for the least money. This is where the (tr)uSDX really makes sense. So too does the QMX, even though it currently doesn’t include SSB (although future firmware upgrades will add it). If your main modus-operandi is CW, then the QMX would easily win out here, thanks to its click-reducing envelope shaping.

Anyway, I’ll be keeping my eye on the Radio-Kits website and look forward to any new additions to their range.

If you have any comments, please leave a note below and try to include your callsign.

73, Tom, M7MCQ.


I have been testing microphones and experienced a rather big issue. For some strange reason, my transmissions sounded DREADFUL!!! I had the power output on the Explorer extremely low and was listening in on my RGO ONE. Every time I keyed up and spoke, the audio was shockingly bad.

I couldn't understand what was going on, because I was calling CQ all last weekend and had been getting great reports!

I approached Steve and explained what was happening - he was baffled like me. He asked if there was power out when I spoke into the mic and I told him, yes. He said he'd give it some thought and get back to me.

I returned to the radio and transmitted some more, but this time I turned the VFO dial on the RGO ONE - boom - it was then that I discovered the Explorer's VFO Calibration was out by 70Hz ๐Ÿ˜ถ

Lesson learned - RTFM! Well in all fairness, I didn't really think I'd need to calibrate the VFO after reading this part of the manual...

VFO Calibration Frequency calibration will already be close due to use of a TCXO but may be improved if required.

I should, of course, have checked though. All my fault.

73, Tom, M7MCQ


Fraser MM0EFI said...

Although I have no plan to buy one of these, I hugely enjoyed reading about your experiences with the kit build, the testing and operation of the radio.
Cheers, Fraser MM0EFI

Fraser MM0EFI said...

Although I have no plans to purchase one of these kits, I hugely enjoyed reading about your experiences with the build, testing and use of this radio. Really well laid out article(s).
Fraser MM0EFI

PE4BAS, Bas said...

Hello Tom, what can I say about this. Excellent blogpost, very detailed. Not to forget I've got the idea this kit is supported very well. Steve did help you a lot as far as I can read. Excellent results as well. I think for those that buy this kit it isn't just a money thing. It is just a fun kit, even more when you build it and modify it to your needs. Well done! 73, Bas

VE9KK said...

Good morning Tom very nice run down of the trouble shooting and so it goes with kit building. The best is the smoke test worked out to be negative. I agree with Bass and the support you were offered was greet. The only kits I have ever built was from Elecraft. The KX1, 2x K2's and the different test kits they offer. Its always great kit building as you put it together, test and adjust it and then take it out to play.
Very good post of the steps and the final on air testing.

MadDogMcQ said...

Thank you very much Bas! It sure was an enjoyable kit and Steve was quick to respond when I told him there was an issue. Despite a few shortcomings, this is an enjoyable superhet and I think it will become a popular kit to build.

73, Tom, M7MCQ.

John AE5X said...

Well, you've got me motivated to start my build but I hit the road tomorrow. Thanks for all the detailed info and photos!


MadDogMcQ said...

Thank you so much for visiting the Blog Fraser and for your very kind comments - it’s appreciated!

73 de Tom, M7MCQ.