|Parts, panels and rear panel board, front panel board, QSK board, main circuit board|
I finished building my Hardrock-50 (with QSK option) about a week ago and have been using it daily since then. Actually, I'm not quite through with it since I still have the built-in autotuner to install. The instructions recommend successfully building the basic amplifier first, before adding the autotuner, so that is what I've done.
Once the tuner is installed and configured I plan to make a video of the amp's operation using both keying modes (PTT and carrier-operated relay keying), with rigs that have a PTT out and others that don't. For now though, some thoughts:
Why the HR-50 and not the Elecraft KXPA100?I had initially considered Elecraft's 100-watt amplifier but ruled it out for a variety of reasons (including an issue with the ordering process itself):
1) HR-50's compatibility with a broader range of QRP rigs
|Even the boards contain instructions!|
A unique feature of the HR-50 is its ability to use a portion of the incoming RF to actuate the T/R keying. Most simple QRP rigs do not have a PTT out signal and would therefore not be usable with Elecraft's amp without some modification of the rig.
QSK capability is given up when operating the amp in this mode but that is a fair price to pay in order to be able to use my old HW-9, QCX, Hilltopper and other such rigs with this amp. Like many hams, I have a small collection of QRP kits assembled over the years - the ability to use them as 50-watt radios is quite appealing to me.
Radios that do have a PTT out can be used with this amp and retain their QSK capability. This includes rigs like the KX2, KX3, FT-817, etc. These particular rigs can also be configured in such a way as to cause the HR-50 to follow band changes. This requires an optional plug-in circuit for the DB9 jack on the rear of the HR-50 and, for the KX2, a single TRRS cable going from this plug-in to the KX2's AUX jack.
Info on the HR50 paired with the Elecraft KX2 is here.
2) Cost vs. effectiveness
Driving a 100-watt amp to full output with a 5 watt radio represents a 13dB increase in output power.
|Completed amplifier board|
The main use of my HR-50 will be with the Icom IC-705 which has recently become my do-everything rig: CW, digital, park activations, 6m monitor, etc.
3) Portable operation/battery life
The other use of the HR-50 will be for portable operation, activating parks, etc. where I'll most likely use the KX2 on CW. Band conditions recently have been very poor, especially for QRP operation - newer battery chemistries now make portable operation with 50 watts almost as convenient as 5-watt operation was a decade ago. With the HR-50 only drawing 140 mA during receive, many CW contacts can be made with a small and lightweight 5AH battery. This would be less true with a 100 watt amp.
Building the Hardrock-50
The build, with QSK option but not (yet) the autotuner, took 8 hours. A large part of this was winding & preparing the toroids/binocular transformers and preparing various interconnections of small coaxial cables.
|Panel and QSK boards completed|
The manual mentions that many builders seem to have difficulty with T3. This is a binocular core with 10 turns of small wire on each side of the core. Then, two additional windings of one turn each, are inserted into the core as it is mounted onto the board.
|Completed toroids awaiting installation|
As much as I hate to admit it, it took me three attempts to finally get the windings compact enough within each side of the core for the wire to fit through for the fourth turn. This one component probably took me half an hour!
Almost all of the electronic components are pre-installed and, in addition to the parts mentioned above, the only parts for the builder to install are relays, a few trim pots, various headers, four MOSFETS and associated hardware, jacks and front panel buttons & display.
Instructions are clear and well illustrated with many color photos.
|Panels being attached|
Alignment of the completed HR-50 is a simple process requiring only a multimeter to adjust the bias of each MOSFET. Once that was done, the two halves of the case were screwed together, the serial number sticker was applied to the ginormous heatsink and the kit was finished.
The Moment of Truth. With the new amp placed downstream from my Anan-10e transceiver and a WM-2 QRP wattmeter, and an antenna tuner and dipole antenna on its output, I fired up the works on 40 meters. The PTT output on the transceiver was attached to its corresponding input on the HR-50. The front panel menu on the HR-50 showed the keying method chosen (PTT), the band selected, temperature (selectable C or F) and supply voltage.
So far, so good.
I set the transceiver's output to two watts and keyed it. The HR-50's display then showed my SWR (1.0) and power out - 61 watts!
|Two watts in provides 61 watts out on 40m|
I made a few contacts with FT8 on various bands and the HR-50 exceeded my expectations. A few days later I attached a dummy load to the HR-50's output and, with the driving transceiver's output set to two watts, made the following measurements on all bands 6-160 meters (60 meters is available only with the built-in autotuner installed - later) with a supply voltage of 14 VDC:
6 meters - 56 watts
10 meters - 65 watts
12 meters - 67 watts
15 meters - 71 watts
17 meters - 65 watts
20 meters - 43 watts (5 watts drive needed for 50 watts out)
30 meters - 44 watts (3 watts drive needed for 50 watts out)
40 meters - 61 watts
60 meters - 50 watts (measured after installing ATU option described here)
80 meters - 68 watts
160 meters - 60 watts
I built the HR-50 over a two day period and it was a refreshing change from the type of construction of a typical QRP transceiver. For those who don;t like winding toroids, they can be purchased pre-wound for $30. This will shave 2 hours from the build time but I think I value my completed kit more due to having accomplished all the steps myself.
I am very pleased with everything about the kit, from customer support to final performance, and I look forward to operating it with a variety of rigs on both FT8 and CW, at home and afield.
Knowing what I know now, I would buy this kit again, without hesitation. And no, that's not an advertisement, just an honest assessment. I paid full price for the kit (as I do for everything mentioned on this blog).