Thursday, December 5, 2019
Wednesday, December 4, 2019
On the heels of Sunday's note on a CR kit build and last week's copper penny CR, here's an article about of the other end of things, a Zinc Negative Resistance CW Transmitter over at the wonderfully named and yet sadly neglected http://sparkbangbuzz.com This involves construction of the closest thing to a DIY transistor any of us are likely to see, so it's worth a look just for that alone.
sparkbangbuzz reads like a cross between a grimoire from a medieval alchemist's shop and a selection of tech reports from ACME Development Laboratories, but there is some heavy scientific lifting going on there. Lots to investigate in the coming years.
Tuesday, December 3, 2019
Monday, December 2, 2019
Sunday, December 1, 2019
OK, let's get this part out of the way first: I am a complete sell-out, and officially now have no ham geek cred. That's right, I built a crystal radio from a kit. But let me say why: I needed an easy win about now, and didn't want to start my experimentations with a flail. Besides, I was all fired up after last week's post about Minimalist Radio. When I went looking around for parts (and I did, I swears it!), it was just about as cheap to buy a kit. So... off to the races.
With that out of the way, the kit is the Picard radio from Borden Radio Company, by way of retailer MTC Radio at this link. Here's the Bordan product page, scroll down to the right kit. Then scroll down to the next kit, a ready-to-rock foxhole radio featuring a razor blade detector, all screwed to a scrap piece of pine board. So Borden's got some geek cred for selling these, and getting them out to aspiring radio geeks. Also, as I found out later, Borden's got a respectable line of hard-to-get parts for the next DIY go-round, up to and including WWII vintage razor blades, all at a very cool URL: http://www.xtalman.com
So now for the two big questions: How well does it work? Um, it gets the in-town 5,000 watt WMEJ, about 3 miles away, all too well during the day, and doesn't have enough selectivity to hear anything else. In the evening, when they turn their power down to I dunno, maybe 250 watts or so, it is possible to pick up 50,000 watt WWL from nearly 50 miles away (they were talking about – surprise! – sports). So, for something so incredibly simple, it's a complete success.
Second big question: How well did it come together, both structurally and aesthetically? Not bad, in a pre-WWI sort of way. Take a look:
Design dates to the mid-point of the interval between Now and the War of 1812.
The two alligator clips attach to ground (black) and a random wire receive antenna (red). The entire build was easy, if a little english had to occasionally be applied to various parts to make them fit. The key thing during construction is patience: to wind a nice tight coil with all 75 wraps, to use the recommended clear spray on the coil after wrapping (it keeps things glued in place), and to wait a couple of days for the clear spray to completely dry. The rest is a snap, requiring only steady hands and a few basic tools.
Speaking of winding the coil, yes, this kit requires that you wind the coil, and that you wind it neatly. So even though it is a kit, it does require some skill and patience to build. Mostly the latter though. I guess that does restore at least some geek cred.
Back to its performance, it's not bad, but I can't wait to take it on an upcoming camp-out. Up in Desoto NF, at the location we've chosen, there are several mid-watt stations at 15 to 20 mile distances, and of course WWL off over the horizon. It's going to be interesting to see how it does when there's nothing in the immediate neighborhood, swamping all other signals.
Enough already. You can read more about crystal radios at Wikipedia. It was fun to build, fun to test, and now it goes back into its box until the campout. Again, when it picked up WWL out of New Orleans, that was enough to declare it a success.
I'd been wanting one of these for a while. It's just a clock. Well, really more like two clocks in one:
The nice thing is that it auto-sets using a radio time signal from WWVB, which makes it literally the most nearly perfect thing in the entire house. After that, the other features are dual local and Zulu time displays; a backlight bar across the top to momentarily turn that on; and a nine-and-a-half minute countdown timer that does exactly one thing, namely, remind a long-winded ham operator to call out station ID in slightly less than the legally required ten minute interval. Like the backlight, it works at the press of a button and does its job without fuss or complicated user interface. Seconds are included in the display as well, a small but handy feature when setting another clock against this one. One more thing worth mentioning is that the display is usefully large. The main numbers are slightly over 1" high, easy to read across a long desk or even across a small room.
The clock was a snap to set up. Insert two AA batts, switch on the time signal receive, push-button cycle around the two clocks to their respective time zones, and give it five minutes to sync to WWVB. And that's it! I've had coffee pots with electronics that were more complicated to operate. Hats off to MFJ for getting the UI right on this one: simple, to the point, and only what the job calls for.
Note the lack of extraneous, complicating functions. No alarms (beyond the one-button fixed timer), USB jacks, Bluetooth interfaces, etc. When it comes to devices such as this one, less is more. Other small electronic manufacturers would do well to follow MFJ's lead here on UI design.
Reviews over at eHam are mixed. The chief complaint is that it eats AA batts and sometimes has trouble syncing with WWVB. The first is a non-issue because with rechargeable batts it's no expense, and for whatever reason this clock synced right up with WWVB. In sum, neither problem applies here, buy YMMV.
Manufactured by MFJ (feature tour and third party review videos at the link; worth watching of you're considering buying), and you can get it at a slightly discounted price from MTC Radio. Five out of five stars, highly recommended!
Saturday, November 30, 2019
Got into the Port St. Joe (FL) repeater with no trouble at all, then heard a station in Largo on 146.52 MHz (the 2m common calling channel). It was a little statickey, but perfectly readable. 430 miles, straight across the Gulf. No, this is not reliable comms by any means – VHF station-to-station limits out around 10 or 20 miles under usual conditions, due to the curvature of the Earth – but it was something out of the ordinary and a lot of fun.
These things happen in the calm, clear weather a day or two after a cold front passes.