The FAT5 project is a 100 watt Class E AM transmitter from Dave GW4GTE and Eric GW8LJJ, dating back to 2011. The name derives from Dave’s desire to design a 100 watt AM workhorse using contemporary FETs to rival the ubiquitous AT5, a widely used war surplus boat anchor for low band AM.
Don W6JL’s 50 watt FET amplifier is a popular afterburner for FT817s and other QRP rigs and exciters. Don won the QST Homebrew contest in 2009 with this design. The amp offers a useful order of magnitude (12dB) power lift over QRP levels, and apart from the power FETs can be built from an averagely stocked junk box. The FETs are commonplace and cheap — they can be bought for as little as 98c each!
This year I tackled Feathertop as an overnight walk, leaving the car on the side of the Alpine Highway near Diamantina Hut at 1645 on Saturday 19th Jan 2019, after having driven up from Melbourne. It was about an hour later than I’d hoped for, but a daylight savings sunset time of 2032 gave me nearly 4 hours in the warm but cooling air to get to Federation Hut. The walk in along the Razorback Trail was in good conditions, but I was carrying my SOTA kit and camping gear, not well optimised, way too much weight, and it all started to hurt in the last hour. I met at least a dozen summiteers on their return leg, some looking like troops limping back from a battle, a few considerably worse for wear. More on this later.
September 2018: I ‘met’ Owen KJ6AKQ on Twitter, I cant recall exactly how or when, maybe 6 months ago. He was a KJ6 who had landed (with family) for work in Melbourne, with a KX3, a real ‘ham sensibility ‘, and an obvious desire to get back into the hobby. But living in an inner city townhouse was going to cramp his style somewhat. After finding how to take out a VK3 callsign he registered VK3EAR. Callsign, rig, but no antenna. I knew he was itching to get on air when he started calling CQ on Twitter.
The remarkable compact transceivers of Peter DK7IH inspired me to dream up a compact transceiver of my own. This project would be an experiment on a shirt-pocket scale — not as dense as some of Peter’s rigs, but small on my scale. Starting with the PLL VFO/controller along the familiar lines of Raduino (Arduino Nano and si5351), I sketched out a physical design, and it became clear that the display choice would dictate the size of this module. Where small displays are concerned, there’s only one option … OLED.
After completing a 6-band SSB/CW QRP transceiver (Summit Prowler IV) I found myself thinking about a more compact QRP SSB/CW rig for SOTA, with two of the main day-time SOTA HF bands (40/20m). The design driver this time was to try a different ‘form factor’ — I wanted a rig with a narrow and long case, such that it would easily slide inside a backpack, and on a summit sit vertically against a rock or be hand held. All my SOTA rigs so far use both front and back panels for connections and controls, so they need to sit level on a horizontal surface. As most rocks or tree stumps are low, you can’t easily read the display. Some designers get around this by putting the display on the top of the box, a sensible adaptation but one that makes the rig look like a flounder. Because I spend a lot of time building and using these radios at home on the shack bench as well as on a summit, I wanted a design for use in both situations.
Eamon EI9GQ’s book (‘Building a Transceiver’, RSGB 2018) started me down the path of another modular transceiver project. For this build I wanted to continue working with surface mount but without the compulsion to pack it all in tight. More space and the freedom to replace a module later. It would be a Shack Sloth rig (a base station), not a Summit Prowler, so the space, weight and power budget shackles fell off from the start.
Remembrance Day Contest is a 24 hour amateur radio operating contest conducted each year by the Wireless Institute of Australia, to commemorate those Australian licensed amateur radio operators who lost their lives in World War 2. It is ‘designed to encourage friendly participation and help improve the operating skills of participants‘, and is held on the weekend closest to the 15th August, the date on which hostilities ceased in the southwest Pacific. This year it commenced at 1pm local time on Saturday August 11th.
I recently cut this small piece Veroboard to hold two vertically aligned miniature potentiometers on a receiver front panel. The three soldered tracks to the right allow connection of the audio signal to the volume control using shielded twin conductor cable. Very standard stuff, I’ve been wiring up audio amplifiers to volume controls like this for about four decades. But this one wouldn’t work. It has a fault — it’s there, in the picture above, right in front of your eyes… can you see it?
New Adventures On The Low Bands
Amateur radio experiences with VK1DA
Amateur Radio and unrelated technologies
Amateur projects for the radio draftsman. Hardware, software, electronics and test equipment for the radio amateur
Homebrew electronics and a bit about a Tandoor oven
Homebrew Amateur Radio and Electronics.
For Ham Radio Experimenters
Amateur Radio and Stuff