This project came about, as usual, by accident. I was rooting through my box of IC’s for another project and came across a chip that I must have ordered sometime in the past and forgot about: the MSGEQ7, a “Seven Band Graphic Equalizer” chip. Not the best name — the chip doesn’t do any sort of equalization; it just analyzes an audio signal to generate information that can drive a display.
When I looked up the datasheet, it dawned on me that I had ordered the chip at one point with the intent of making something along the lines of a sound organ. Now that I had looked it up, though, I thought it would be more interesting to make bar-graph display that I could integrate into some future project.
This is a typical application for this chip and some quick web surfing turned up a few descriptions of arduino-based projects that put the chip to just such a use [1,2,3,4]. Between their descriptions and plenty of sample code, it didn’t seem like that big a task to roll my own.
So, let me describe what I did. The overall goal was to take an audio signal, feed it to the MSGEQ7 chip, and have it essentially break the signal into seven frequency bands, i.e., take the signal and display it very coarsely in frequency domain — sort of a poor man’s FFT.
Details are below, or skip right the demo video to see a working version of the display.
I think it is due to a reshuffle of Austrian SOTA summits, but according to the current database, there is only one summit in the Vienna (Wien) region, WI-001, Hermannskogel. I guess that made the choice of which peak to activate easy.
The Hermannskogel is the highest point near Vienna, and up to World War I, served as the cartographic zero point for Austria-Hungary. The Habsburgwarte, pictured here, is a rebuilt stone tower that sits on top of the hill and sports a variety of antennas and radomes.
For my last summit activation in Spain on this trip, I had two enticing options: first, I could aim for some of the ten-point peaks that lie along ridges or I could activate a peak for the first time. There are two good prospects in the first category: the peaks of Valdemartin (EA4/MD-004), Cabezas de Hierro (EA4/MD-002), and the Asómate de Hoyos (EA4/MD-006) all along one trail, and it looks like that trailhead could be reached by taking the ski lift up from the Estacion de Esqui de Valdesqui (presuming it runs in the summer). Similarly, Najarra (EA4/MD-013) and Bailanderos (EA4/MD-011) lie along a trail, which could probably be accessed by parking at 40.82797N x 3.83015W. In fact, it might be easier to reach Asómate de Hoyos by continuing west from Bailandreos rather than east from Cabezas de Hierro.
Predictably, I went for the first-time activation of EA4/MD-053, Cabeza Arcon. This is in no way a technically difficult peak, so I assume that it was recently added to the list of summits.
Looking at SOTAmaps, several associations overlap to the north of Madrid. I realized that without really going too far out of my way, I could visit a ten point peak in the EA1/SG association, which would put me over the top for gold level on the SOTA mountain explorer award. I’m not that much into awards, but why not? Having flown 8000 km to get here, another 20 km on the road is a drop in the bucket.
Recently, I attended a conference in Madrid and had another one scheduled a week later in Vienna. Instead of flying back to Madagascar between them (insane), I decided to take a few days leave in Spain (sane and fun).
There are plenty of mountains within an hour’s drive of Madrid, and many of these peaks are found in national parks. Just to the other side of that central range is the historic city of Segovia, so I booked a hotel a few kilometers outside Segovia.
Between Madrid and the hotel, I identified Cerro del Castillo (EA4/MD-052) as a target of convenience. It is a four-point summit in a region full of ten point summits, but I thought that I could do it in what remained of the afternoon after checking out of the hotel in Madrid and picking up a rental car at the airport.
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 (the construction of which was described in an earlier post): 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).