The Most Important Amplifier In Ham Radio

The title is a pretentious joke, but there is a kernel of truth in there.

A few days ago I wrapped up my HobbyPCB HardRock50 amplifier build, and I'm in the process of testing it with a variety of QRP rigs. So far so good with the Yaesu FT-818 and the Icom IC-705, and testing with the Elecraft KX2 is coming up. Right now I'm updating the external interface for the IC-705 that is manufactured by HobbyPCB, an interface that allows the amplifier to follow band changes on the radio and trigger tuning cycles

Earlier today I created a video showing the start-up procedure when using the amp and the IC-705 interface with the IC-705. The video shows how the IC-705 interface controls band switching (via Bluetooth), tuning and amp triggering. The interface works quite well, but it is an extra cost item ($70 as I have it configured) from HobbyPCB. Note - you DO NOT need this interface to run the IC-705 with the amplifier - the interface just takes care of the band switching and tuning duties, something you can do without the interface. You just have to do those tasks manually, and it's not at all difficult. 

I'm quite happy with the output. Signal reports from fellow hams are good, and I'm easily getting 50 watts PEP on sideband when driving the amp with 3 watts of output from the radio.

Building this amp was, as it's popular to say today, 'a journey', and I've outlined much of it in earlier postings. This is the second of these amp kits that I've built, and I learned a LOT on the first build. The reason I built this new amp is because the previous amp kit was an early model (shipped in 2014 but never built) and it had some issues regarding the ability to interface with the IC-705. I figured I'd start with a clean slate (and somewhat improved soldering skills) with a current production kit from HobbyPCB that included the internal tuner board. While this is not a tough kit to put together, it took me several months to get it done as work, family commitments and other factors got in the way. 

One of the hiccups was a blown capacitor on the amp board, which the manufacturer put down to it being a tantalum cap with known tendencies to let out the smoke when voltage is first applied. Jim Veatch, the owner of HobbyPCB, said they are likely going to switch capacitor types on the next production run. He cheerfully sent me two replacement caps. The job to replace them gave me the convenient excuse to buy a hot air re-work station to get the remains of the old cap off the board, get things cleaned up and the new cap in place. 

Poof!
Luckily the damage was limited to the blown capacitor

Getting set to replace the blown capacitor

Another issue was the maddening discovery that the mounting holes for the tuner board had been mis-drilled in the case - basically they were drilled 'backwards', but you don't immediately know that until you go to mount the tuner board in the case and button everything up for testing - it just doesn't fit, and too much forcing can result in some bent connector pins (don't ask me how I know...). Again, Jim at HobbyPCB got back with me and let me know that their recent production runs had the holes on some of the cases drilled improperly, and he's only finding them when people like me bring up the issue. He offered to replace the case but I had to ship the old one to him first, or he could send me a template that would allow me to drill my own holes in the proper location. I opted to go the template route.

So, I can't emphasize too much that this is a 'hobby' build - the instructions are very good, and on-line support is good (Jim answers emails promptly and very courteously), but you are still likely to run into glitches like I did. This is where the hobby aspect comes into play, and you're kind of expected to do your own troubleshooting. Adversity builds character, right? But HobbyPCB also states that the price of the kit includes a working amplifier, so if you get it all together and simply can't get it working you can ship it off to Jim and he'll diagnose and fix whatever's wrong, for free.

The IC-705 interface module - a box that connects between the amp and the 705 and allows
automatic band switching and tuner operation. It's basically an Arduino board with a Bluetooth
interface. I just got through soldering in the add-on board that drives the tuner in the HardRock50
(the lighter colored board in the upper right)

Another challenge for those of you not used to running bootloaders is updating the firmware. Your kit will likely ship with a slightly outdated firmware version. Updating the firmware isn't tough, but you have to install a bootloader on your computer and run the update from there. It's a well documented procedure, but might put off those with limited computer skills.

Last, although everything about this amp and the add-on components like the tuner and control interface are well documented, the HobbyPCB website is something of a dog's dinner in terms of organization, and HobbyPCB has some dead links and pointers to outdated files out there. They need the help of a good web developer.

So what's the use case for this amp? For me it's simply this - with the demise of portable all-band, all-mode 100 watt rigs like the IC-7100 or the FT-857, I am looking for more 'oomph' for both my IC-705 and my KX2. I love those rigs, but feel that they are limited by their 10 watt output, particularly when working voice. Let's focus on the IC-705 - an incredibly capable radio that brings together all the features anyone would need for portable operations. I consider 50 watts as something of a sweet spot for portable work. In most cases going from 50 - 100w output doesn't really get you much beyond greater power consumption. I also like the idea of the two components in separate packages. If I only want to run digital I can go out with just the radio and work at 10 watts. If I want to run voice, I can bring along the amp and push things up to 50 watts. With the internal tuner in the amp I can also leave the Icom tuner behind. It's all about options and capability.

OK, what about this silly 'most important amp in ham radio' claim? Well, here's the truth of it. To be an effective portable shack-in-a-box radio the IC-705 needs to put out more than 10 watts. This is particularly important if you want to use the rig for EMCOMM applications. Ten watts may be enough for digital modes, but for SSB it's not enough for reliable & repeatable comms. There are a number of solid state amps on the market that will work with the IC-705, but they generally fall into two categories - low cost, low output Chinese manufactured amps of poor quality, and high quality (and expensive) 100+ watt amps designed for in-shack use from companies like Elecraft, RM, ACOM and others. The HardRock50 is the only high quality, field portable, well supported and reasonably priced amp available for QRP rigs. This means the HardRock50 stands alone as an amplifier that can turn the IC-705 into a serious field radio for EMCOMM use. So while not the most important amp in all of ham radio, it is still the best option to turn your field QRP rig into an effective tool for reliable communications.

The next step is testing using a battery instead of a power supply - I'll test using a 12 amp hour LiFePo battery to see how long that holds up in field use. I'll also be testing with the KX2. So stay tuned!

W8BYH out

Pop Goes The Weasel

For the past two months I've been slowly working my way through the HardRock50 amplifier kit designed and manufactured by Jim Veatch at HobbyPCB. This is the second of these kits I've put together. The first one I bought off of QRZ.com last year. It was used, but new-in-the-box. The owner bought it from a friend, who had bought it from HobbyPCB. Neither of the two had the time to put the kit together so the last owner sold it to me at a significant discount. Everything was still in its factory fresh packaging. However, it was only after I got this kit that I realized it was an early 2014 vintage unit. HobbyPCB still supports them, but getting the amp to work with modern QRP rigs like the the IC-705 was going to be difficult. Lots of jumpering, some cutting of traces, etc. This unit works well with my Yaesu FT-817, but I still wanted something I could use with the IC-705. So, I bought a new kit from HobbyPCB and figured I could sell the old amp to help cover the cost of this new one.

HardRock50 paired with the Elecraft KX3

Construction of the HardRock50 is pretty straightforward, and Jim has tweaked the build instructions over the years to the point that everything is clearly described and diagrammed. Having already built one of these kits, this second build went quick and relatively easy. One of the upgrades Jim has introduced over the years is that a lot more of the components are now pre-installed at the factory. With the 2014 kit you got a bag of relays and instructions on how to stuff them on the board. With the current kit, the relays are already on the board. This cuts down on a lot of the tedious soldering. If you've soldered one relay, you've soldered them all.

Everything went pretty straight forward until I got to the step where you have to set the DC bias. There's a Rube Goldberg-esque setup in the manual that has you interconnect your power supply with your ammeter and the amplifier. I've done this a few times with my old amp, with no problems. Just take your time and follow the test lead and power connection instructions in the diagram.

OK, all cables connected and checked and re-checked. I reach over and hit the ON switch on my power supply and POP! Lots and lots of smoke coming out from under the board. Damn, damn, damn, damn, damn. I pull everything apart to get a look at the underside of the board and find that capacitor C36 - a pre-installed component, had popped. What the hell had I done wrong? I checked and re-checked my test lead setup, and everything looked good. But SOMETHING went wrong. The evidence was inescapable. Clearly I screwed up.

I contacted Jim and asked him if he had any ideas as to what could have caused this - something upstream in the build I had put in wrong? Maybe a solder bridge I didn't catch? Jim wrote back almost matter-of-factly,

"Tantalum caps have a habit of blowing the first time voltage is applied"

Oh really?! I'd heard 'tant caps' could be problematic. As the comedian Bill Engvall says, "Here's your sign".

So Jim is mailing me a new cap, and I'll report back on how well this one survives. At least this experience gives me the excuse I've been looking for to buy a hot air solder rework station.

W8BYH out