My longish term goal is to build the LBS transceiver described by N6QW and KK6FUT (who I see is now AI6YR) and I am methodically working my way through that project.
However, I am not above taking a shortcut for instant gratification along the way. Remember the 80-meter Sudden Receiver variant I built a few weeks ago? Well, not much use for it in my current location. It occurred to me that I could gut the 80-meter parts of it and use the NE602/LM386 core as the rest of a very minimal direct conversion receiver for a more useful band, say 20-meters. So that’s what I did and long story short, it worked.
Over the last couple weekends, I put together an RF signal generator based on a AD9850 DDS module controlled by an ATmega328 microprocessor. In this entry, I describe both physical construction and the arduino sketch underlying its operation. The most recent versions of both code and schematic are archived on github.
On one hand, it probably doesn’t make too much sense to try to refine the MMM: it’s more an oscillator demo than a building block of any more complex radio, but there are a couple variables that I thought would be fun to explore: choice of transistor, supply voltage and emitter resistor value. Tables and pretty x-y graphs follow.
Over the summer, I managed to get back to Virginia just in time for ARRL Field Day with the Vienna Wireless Society. The trip itself wore me down – I had just spent a few weeks in the US, returned to Madagacar for a week (just long enough to get back on local time), and then back to the US for Field Day. However, because my brain was still on East Africa Time, I was unusually perky for the midnight to 8 am shift on 80m.
Our best year yet
Our numbers were just compiled and reviewed at the last club meeting; a really polished analysis is available online. This year we did much better than last year; this year’s score of 12,302 points blew past the club’s 2009 all time record of 10,958 as a class 4A station. We essentially doubled the QSO count from the prior year, with all four stations pulling hard through the night to keep up the rate.
The 80m Madagascar Mighty Mite was suffering from “a tree falls in the forest but nobody hears it” syndrome. Eighty meters is a tall ask for Madagascar — there aren’t that many hams in the coverage area, and given local noise, I doubt any of them can hear well on 80m. It would be a long wait for a signal report about the on air performance of the MMM. Clearly, the thing to do was to create a mate for the MMM, the Madagascar Mighty Mite Mate (MMMM).
In keeping with the philosophy of back-to-basics rockbound simplicity, I decided to build an 80m version of the Sudden Receiver originally described by George Dobbs in SPRAT, and reprinted in 73 (October 1991, page 8, available online thanks to the Internet Archive).
I thought my 200mW Madagascar Mighty Mite (MMM) would benefit from some sort of afterburner, so I dusted off a project shelved in 2011: the Texas Topper amplifier. I had built based on a design by Chuck Carpenter and kitted by Rex Harper. I ran into a couple problems back then, including some difficulty getting the bias right on the mosfet at the heart of the amplifier. In another brilliant move, I managed to burn out said mosfet by grounding it while trying to get it and its heat sink to fit into a metal box.
Over the last few years, there have been a spate of postings from homebrewers taking inspiration from the Soldersmoke podcast to whip up various incarnations of the Michigan Mighty Mite, a very simple rock-bound QRPp transmitter. I’m a little late to the party, but here’s my story.
My final SOTA stop on the way back to Washington, DC from Indiana was at Mount Davis, the highest point in Pennsylvania. Arriving towards the end of the day, I did not take advantage of any of the hiking trails from around the mountain, but followed signs directly to the parking area. A path leads around to a metal observation tower and a path continues past the tower to a sort of rock garden with some informational plaques. Not far from the tower’s base, there are some large boulders, where I set up the radio.
Yes, yet another Sugarloaf. I guess sugarloafs were very popular for long time and people saw them wherever they looked. I activated this Sugarloaf on the way back to Washington, DC from Indiana. This and several other SOTA summits are clustered near the Ohiopyle State Park. I have camped and white water rafted there a couple times in the past, but due to time constraints, I didn’t have much time to hang out in the park proper on this trip.
On the way back towards Washington, DC from Indiana, I passed again through Ohio, this time to the south of the outbound route. I had targeted two SOTA peaks near Ashland, Ohio: W8O/NE-001 (Noblet Benchmark) and W8O/NE-003 (the Ashland County High Point). I did get to both sites, but only activated the former one. Both are discussed, below.