Another Project Saved from Perdition

The picture at the start of this is of the 55MHz DDS VFO I bought off eBay a while back. When I got the documentation on it, I bought another one. Today I hosed it up to the power & set up the encoder & some of the switch wires.
     To say that this box is cool is to be way too reserved.
     The fact is, even as small as the board is & with only the six push buttons on the board, adding the shaft encoder opens up a huge pile of options & functions.
     Using the buttons & the encoder I can adjust the IF offset, change the display offset for the VFO for different modes, kick in the RIT, adjust & save 19 memory, lock the display & encoder, switch between two VFOs & probably a pile of stuff I can't remember right off.
     And I didn't have to build it!

Now the reason I'm going on so fevered about this little board, aside from the things listed above & the fact that I didn't have to build it, is the simple fact that for about $60 anyone can have a kick-ass DDS VFO that will fill the need for most modern day ham radio DIY projects.
     And yes, there is a "But wait! There's more!" to this.
     I recently found by going to the vendor's online eBay store that the vendor also has a larger DDS VFO board that includes a keypad frequency input, a bunch of controls under the display that the user can hose to whatever they want. Like a volume control, a drive control, an IF bandwidth control & similar stuff.
     Basically it's a front pane for a radio.
     Which is a dangerous concept in my head, but for me waiting for the vendor to post on their eBay page that they also have the guts of a receiver or transceiver that will hose into either of the DDS boards to make what I'd guess is a pretty reasonable radio for hams or whoever else thinks they can build their own.
     Which includes loonies like me.
     And which is, to my mind, a lot less goofy than building scale models of turbo-jet military airplanes and posting the take-offs and landings on youtube.
     And although I'm not a bettin' man -- 'cause I ain't bought a lotto ticket in a damn long time, including not buying one for the recent megamillions -- I'm holding crossed fingers & a lot of other superstitious stuff in hopes that the Asian vendor of this board (and it's big brother) will come up with the rest of the guts for a decent radio.
     And now, if you'll pardon me, I gotta get back to wiring this puppy up into a box that presently holds a monoband receiver that drifts 30kHz in an hour & some. 'Cause, 'cept for the drift, it's a damn nice receiver. That will need a transmitter . . .
     Which will be easier for me to reach for than a scale SR71 that I won't be able to fly around here 'cause the local AFB will pick it up on their radar & my house will disappear in a puff of high explosive & rocket launches.

Moving into Digital Times

One of the joys of retirement is having the time to try doing things you always wanted to do but didn't have the time or the patience or space. Of course, it helps if you have the money, which retirement does not exactly provide. But you can – as in my case – have the time and, since I'm stupid enough to think I do, have the space.
      The big deal projects from my former days of employment involve either putting together a travel ham radio station that will get through airport security, building a receiver & transmitter that work well enough for me to use them upon occasion, and proving to myself that I can still dream up weird crap using bits and pieces of other people's ideas, kits or whatever.
      Add to this what Nick Kennedy calls “The Endless Receiver Project” and you get the idea.
      Well, you get the idea if you're familiar with the TDA1072A IC, a 16 pin DIP that has all the stuff necessary to build an AM receiver that tunes from DC to maybe 50MHz. I came across this chip years ago, amassed a collection of 'em, got boards done up & set out to build the receiver with either the usual 455kHz IF or another IF running in the MHz range.
      I was surprised at my success.
      And so it is all these years later – perhaps as many as 15 – and having stolen a bunch of ideas from Nick, that I am still fiddling with this chip and building receivers that either replicate my old Hallicrafters S38E and S38 or manage to be pretty reasonable CW receivers with the MHz IF and a fiddle-de-jiggered crystal IF. In fact, one version is so good at CW that you can't even hear Radio Habana on it. So that was successful.

But wait! There's more!

I recently got the idea that it would be cool to build a general coverage receiver using this IC. It looked easy. All I had to do was jigger up a set of switchable LCs to tune the range I was shooting for: AM broadcast band to the high end of 10m, 500kHz through 30MHz.
     Which works great in the head, pretty easily on paper and not so much in reality.
      First, there's drift. I have versions of this beast that drift up to 10kHz from turn-on over a 2 hour period. Totally unacceptable unless you're into moving the knob every couple minutes.
      Then there's fiddling with all this LC stuff to get a set of bands that at least cross each other a few 10kHz between band edges. No sense having a radio that has open spaces in the GCR spectrum I want. Add that to drift and you get some good calculational gymnastics.
      Undeterred I started building the GCR box at 455kHz IF. Came out pretty nice, once I got all the LCs figgered out &c. Except that it's a mechanical nightmare that – by way of my buggering up the band switch board design – has successfully put a partially function radio in a very rugged box sitting on the shelf behind me with the other lost cause designs so far attempted. At which point I discovered DDS.

Direct Digital Synthesis has been around since Marconi. Seriously. In Bucher's Marconi-sponsored Practical Wireless Telegraphy there's a whole back section on how to build a set of rotating arcs, aligned so that their damped pulses build a somewhat sinusoidal wave form. DDS.
      Of course, nowadays we have computers to do that for us and thanks to advances in technology, we can build those computers into outrageously tiny boxes. Lots of folks have messed with 'em, some even building them up in kits or combining DDS bits in radio designs and selling them as kits. KD1JV has a whole pile of neat things with DDS in 'em. Some of his designs and the designs of others are available in kits from Doug Hendricks' Kits. And you can get a pretty fancy DDS kit from N3ZI, among other doodads.
      Or, if you're lazy or have essential tremor or are otherwise kit-building challenged, you can get a Chinese guy to build you a box of DDS VFOs and then spend a couple weeks figuring out what the hell all those plugs and sockets on the board are connected to. And once done with that, you will realize that you have just bought the front panel of your $800 entry-level ham radio transceiver.

Which is just about where I'm at now.

Of course, I am also at the point where I have a couple 455kHz IF drift boxes, a nominal GCR with N3ZI's DDS VFO runnin' the works with a 4.915MHz IF & am well on my way to having the Chinese DDS VFO runnin' another version with a 4.915MHz IF.
      In the last two cases, I've built up a band switch/preselector system to do the front end filtering of the receiver mixer input, a function that more than likely I could chain drive off the data info from the DDS control IC, if I knew what I was doing and was willing to fiddle with that much more of what has become a very complicated project.

So what's this get me?

Good question. I guess it gets me proof that (a) I'm stupid enough to think that now that I'm retired, I have the time, patience, wisdom & money to waste on this sort of silly shit, (b) that I am still capable of building a radio by dint of what I think I know about radios, (c) that what I end up with will satisfy a need to say I built the damn thing(s), (d) that I'm preparing for a helluva estate auction, or (e) all of the above and then some.
      I'm going with (e).
      In the end – hopefully before I snuff it – I'll be able to hand one of these boxes, presuming they still work and radio signals are still in the air as they were in my youth (as in: analog vs digital), to one of my progeny with the admonition that the box in question will not be something to puzzle over at the estate auction.

But wait! There's more! I'll even include a CD with an operating manual in PDF format!

Dragon-Ball Z-Match

Somewhere in the grand eloquence of the InterWebs there is already a record of my having put the station first in a spare bedroom with antennas in the attic, then moving all that to a converted outhouse and finally, moving it all back into a spare bedroom with antennas hosed up with remote switches &c back out in the former outhouse. So them details you can find elsewhere, if you're interested.
     Yeah, I know: I am imagining that I actually have a readership, another narcissism to which we are all drawn in these days of instant FaceBook fame & all those book reviews we do for Amazon.
     Tough.
     But the story continues with the final addition of a remote control Z-match that will handle the crap spewed by my HF radios and a rehabilitated SB200 amp. And the story of the amp is almost as boring as this tale, so I'll deal with that later.
     Suffice it to say that I have taken the Z-match circuit that I first cribbed from the InterWebs maybe ten years back and modified the part sizes so I could run 500W through it. The first two Z-matches were designed for QRP, since I was whacked about that at the time. For QRO – which was 100W max for some time – I used either an SG-239 or an LDG auto tuner (I went through two of 'em), an Elecraft T1 autotuner (only blew on of those up) and the AH4 that hoses up to the Icom radios.
     The low power QRO tuners worked really well. I found the SG-239 to be the most easy to use, mainly 'cause it's set up for the user/owner to dream up the distances between the tuner and the rest of the radio stuff, along with advice on a tune/lock/reset doodad for real and serious remote control. The LDGs were interesting 'cause they're made to do interesting things for power levels under 20W. Same-same the T1, although it's not as easily remoted. But in the end, if I was going to run more than 100W (or under 20 with the Elecraft & one of the LDG tuners), I needed something a bit more husky.
     Making the decision began with the T1 dying on me at the beach vacation complex. Took me a couple minutes to finally determine that I was off the air with that box.
     Lucky for me, I had dragged along my rather arcane lookin' home-brew Z-match.
     This was an obvious learning moment.
     For all the nice things you can say about an automatic antenna tuner, QRO or not, you're still stuck dealing with a machine the controls of which are not exactly in your paws. If the automatic parts of the tuner are controlled by some AI thingie in the box, it can make up its mind a bit far from what you'd even be willing to try. And if the AI thingie in the box quits, you have a nice circuit board with a bunch of useless parts on it. You're off the air.
     Now any manual antenna tuner demands an operator with paws. And most of the time, such antenna tuners have husky enough parts to at least let you know when you've reached the design limits by arcing across capacitor plates or between turns on a coil. And of all the tuner designs that I've messed with, the Z-match beats all the other knob-twistin', coil-switchin', variable efficiency boxes by more than a marginal distance.
     Two knobs, most of the time, take care of all your needs.
     Thus the decision to figure out how to build a QRO Z-match, with QRO meaning anything up to and maybe even a bit past 500W.

The way this station is set up, I have two runs of about 75 ft in double-shielded Ethernet coax taken from service at the university from which I retired. The two runs, along with a big pile of confusing control cables, go from the pipe chase that heads the upstairs bathroom bathtub/shower to the former outhouse & part-time ham radio shack.
     Out in the shack I have built two boxes containing what are called either toggle-relays or ratchet-relays. The coils on these beasts trip a ratchet kind of like a on/off/on pushbutton. One pulse they close alternate contacts. Another pulse and they go back to what they were before the first pulse. Thus they do not need constant voltage & current to stay in whatever switched state I want. I discovered, after I bought what I thought was a reasonable number from Roger's digs, that they're rare little beasties and they're very expensive. That and the kind I have don't seem to exist any more. Bummer.
     At least I have enough of 'em to make a six-hole antenna switch for the HF antennas and a four-holer for the VHF/UHF antennas. (And yes, I know switching HF is a whole bunch less fussy as VHF/UHF. Gimme some credit for at least trying. And no, I don't do moon-bounce of run QRO stuff on VHF/UHF. What I can hear is good enough for me.)
     So with this switching system, I can pick out either fixed-frequency antennas, such as the 4BTV I got for Christmas or the 30m/17m vertical that I made out of beat up CB vertical parts and some hardware from DX Engineering. And for the tunable beasts, well, that's why I have all those extra control cables running out there.
     I tune the tower as a shunt-fed vertical on 75m. Works pretty good too. Consistent good reports from the Late Nite Radio/Old Hippies on the Air gang. I originally hoped to switch it between two shunt lines for 40m and 75m but I found the relay chosen (one of those then-inexpensive toggle relays) turned into carbon powder running more than 100W. Lesson thus learned has tempted me to build a motor-driven doodad to switch those load lines. Ain't gotten that far yet. The tower, however, has its limits.
     It doesn't do 60m or 160m or any of the other bands that are interesting in these days of low sunspot counts.
     For that I need an old friend antenna: the open-wire-fed, balanced feed dipole lash-up that was my antenna of choice (my choice or not) for many of the first couple decades I wasted money on the air. And when we put up the tower last summer – we being KD8HCV, non-ham Dale Goubeaux, a few admonitions from my youngest and with my wife biting her nails – I made sure to put a yard-arm and pulley at the top of it with which I could haul up any antenna wires I wanted.
     At which point we get back to the QRO Z-match.

High power RF, I learned many times over the four decades I've been doing this – requires lots of space or expensive vacuum. Capacitors that work great for 5W or 20W have a tendency to arc and melt when pressed past their design limits.
     Which is why I was sooo damn happy to find a split-stator, dual-gang 40-475pF capacitor in Roger's stash for only $40-odd bucks. That made things very easy.
     If you look at the schemo above, you'll note that the frequency-dependent part of the Z-match's transformer requires a dual-gang set up. Try finding one of those. I did for a long time and figured I'd just end up putting two Ten Tec 400pF high-voltage variables on the same shaft or ganged with a toothed belt. The discovery at Roger's made that shopwork project unnecessary.
     Which left only the coil, something that I didn't feel like building more than maybe twice on a good day with no Ls in it. So I bought some time back a 4-inch diameter toroid of #2 material.
     I went with the #2 'cause I figured my main intention was to get 160m through maybe 15 and that'd be good enough. If I'd wanted to be fussy, I'd have used a toroid of #6 material, which is more suited for tuning between 60m and maybe even 6m. I know this 'cause my two QRP Z-matches use the #6 material and they's just super good. Wanting to have 160m meant I'd have to go with #2, which, obviously, I did.
     Which left only the gauge of wire to consider. And having just resurrected a much-abused SB200, I'd learned that wire sizes under #12 are like asking for trouble. So I went to PowerWerx's webpage and ordered a chunk of #10 wire.
     And when the wire arrived, I discovered something: winding #10 wire is like trying to straighten coat hanger wire. And yet, after a couple hours of consideration, I managed to get the core wound with the #10, layered with fiberglass tape and the secondary – for which I only had a bit of #12 – on taped up.

I've never been good at estimating how much energy it takes to do things, which means that I'm not good at estimating what's gonna happen to various parts when they're stuffed with lots of energy. So when I stuck the finished Z-match out under the tower & hosed it up to the pitiful remnants of earlier open wire projects, I didn't expect to see the system fail so quickly.
     When I hauled the box back inside and opened the beast up, my nose told me something was up.
     I let all the smoke out.
     Well, if not all the smoke, at least a fair batch of it.
     And I'd burned the enamel off the windings in a couple places. Which meant that my investment in #10 magnet wire had, one might say, gone up in smoke.
     My back up was a chunk of #10 multi-strand wire in a Teflon jacket. More hard to wind stuff.
     So I tore off the magnet wire, rewrapped the core and rewound the Teflon over where the smoked stuff had been. I wound the first 10 or so turns close, twisted in the tap, wound the next six or seven open, so the secondary could lay between 'em with space to not burn up again, and then wound the last ten or so turns a bit less than close-wound until I had the previously used 27 turns on the core.
     Then it was “back in the box, bitch” and off to try it out.
     I found that the Teflon wire, by dint of its being insulated, even close-wound makes more inductance than the enamel, which had been nominally spaced out across the coil. So I could tune the antenna through to about 1.2 MHz, way past 160m. So I took off a few turns at the top and tried again. Got to 1.650 MHz with that. So I hauled the box back in, took two turns off the bottom and suddenly I was good.
     The lowest frequency I could hit was about 1.75 MHz. The highest? Well into 6m. And where once tuning 20m had been seriously problematic, now it was just a tad closer to not too frustrating.
     With that, I'm done with it.

If you've looked at the pictures, you might be wondering what I used to box this beast up. Answer's simple: PVC. The body of the box is a 10” chunk of high pressure PVC pipe salvaged from a university project. The end pieces – well, the entire innards – is chunks of PVC sheet that I bought from Small Parts.com. I used a saber saw to cut out the disks that form the end panels and the mounting surface for the two drive motors. A table saw cut the main chassis down the width to slide into the pipe. And the end of the pipe sealed shut was cut slightly larger than necessary, chamfered around the edge to slide into the pipe with reasonable force and then glued into place with good ol' fashioned PVC glue. Some of the innards is reinformed with pieces of PVC sheet either screwed into place of glued there.
     The motors came from Hong Kong. I found 'em on the Virtual Village. One is a 2 RPM motor (driving the frequency tuned part) and the other is a 4 RPM (input capacitor; it's a bit too fast on some bands). I cobbled together a PCB to control the motor direction through a relay. Got three boards made inexpensively at ExpressPCB.com, which gave me a direction control motor for the shunt feed to the tower as well.

All together, I'm happy with the way this beast works. Yes, it's huge, all things considered, and it does resemble the remote tuners that I saw and used with the WRT2 transmitters on the USS Saratoga (may she rust in peace) nearly 40 years ago. The final installation will come this spring, when the snow is gone and I can finally get out to the garage to torture pieces of angle metal to build a X-frame cradle for the beast. Gonna lash it down between the tower and the wall of the shed. And put up some legitimate open-wire feed. Then it'll be even more kick-ass. And come next winter, I'll have no excuse to avoid the 160m contests.

If only I could figure out how to pay for a 160m amp . . .
 

"In my day . . . ЦЩ-Мйр always Strйggle!"

Back in the days of old, when there were Commies – yes, real Commies, not the fake ones that Glenn Beck goes all toad about – radio amateurs had the occasional honor of having a QSO with their ham radio counterparts in the USSR. And every year there was a contest put on by the Central Radio Club of the USSR in Memory of E. T. Krenkel, which contest was CQ-Mir, or ЦЩ-Мйр. The contest was held in May, of course, as a talking point for Lenin's revolution. ЦЩ-Мйр gave Russian hams a chance to contact as many DX stations as possible (perhaps before the Organs arrived in the early morning hours, as was their way at the time). The contest gave DX hams a chance to work as many Soviet oblasts as they could, which contacts could lead to a nice diploma from the ЦРК attesting to the facts.
     The contest was called ЦЩ-Мйр for two reasons, both of which relate to the meaning of the Russian word мйр, which means, among other meanings, peace and world. (The word also can mean universe, kingdom and system.
     So if you were into the contest, you could say that it was a contest put together by the Soviet ham radio organs to show the Soviet Union wanted peace, or peace with the world, or that the Soviet Union wanted, as even Glenn Beck, even as a child, would have recognized easy enough, the world.
     Those were the days, sure.
     Now all the little bits of the former Soviet Union are full-fledged, if not totally independent countries. Well, except for the ones with lots of oil, but that's another problem. For the Russians.
     All the places that used to have the formerly easy to catch Soviet call-signs (like UQ and UP and UT &c) have their own call-signs. UQ2- (Latvia) is now YL-, UM8 (Kirghizia, now Kyrgyzstan) is EX-, UP2 (Lithuania) is now LY. And Croatia, once part of Yugoslavia (YU) is 9A-, while Azerbaijan, formerly UD6, is 4J-4K.
     And yes, I know the US call-sign system is a veritable alphabet soup of guess and hedges.
     The fact is, you don't hear that many of the Russians on the air these days, at least not with CW and the watchful eye of the Organs hanging around Post Box 88, Moscow. Sure, there are Russian hams on the air, even if they've all gone digital and now works MFSK and DominoEX more than most gringos.
     And the ЦЩ-Мйр is now under the aegis of a completely different group of organs.

Back in the days of yore, it was very uncommon to tune across any part of the RF spectrum – amateur, commercial or whatever – and not find a couple stations on the air. This was particularly the case with 40m and, especially in the morning or on towards evening, 75m or 20m. On the lower bands it was mostly folks talking, having the usual techno-speak and weather report conversations that make up most of ham radio's conversational base. On the bands more suited for DX-chasing, like 20m or 15m, rarely could you tune through the band and not hear a Russian or high-powered gringo station.
     Now, as most folks will easily admit, 75m is pretty quiet almost all day. Weekends, sure, more folks are on the air, but you can't call it “crowded band conditions” any more. More like open space to stretch out with that 6kHz wide, over-compressed, over-driven but high-fi audio that some hams have taken as the holy grail du jour.
     Part of this is because of the loss of the Novice band spaces, I suspect. Once you don't need CW to be a ham, and once your privileges get changed 'cause the license you got ain't the license you bargained and studied for, why bother, right? Sure.
     At the same time we all must admit that much of what ham radio offered as a communications system among electronic & RF techno nerds has been usurped by the InterWebs. Skype beats fading SSB signals any day of the week. You can't beat meeting at 10:30 am with a gang of similar nerds in high-fi, effortless InterWebs telephonism. No fading. No distorted AF (well, at least not that you'd admit). No fancy license studied for and test taken. None of the stuff that went into getting on the air with a gang of folks on 75m every Friday night before the bars filled up and you had nothing to do with nobody but your radio friends. As in: “Why bother?”
     Which is pretty much where we are today.
     The collapse of the Soviet hegemony brought an end to the good-ol'-days ЦЩ-Мйр contest as surely as it freed up a pile of call-sign prefixes for nations formerly suffocated by the now less than vibrant hegemony. And once the Russians discovered that they'd been missing out on a lot of stupid stuff now found on the InterWebs, well, that was the end of that old chummy talk about it as well.

Simple fact is, ham radio has changed and has been changed monstrously by the advances of technology. The touch-tone pad on your average 2m HT is about as useless as a cat with no teeth. The cell-phone has taken care of that. The 75m traffic net that once traded messages from one station to another so the folks back home would know that Junior had arrived at US Naval Training Center San Diego (boot camp) are now email messages formed up just as the radio grams once were and bulk-sent from a small corner of the boot camp complex. If the state gets covered with a blizzard and the family claiming Johnny Student as their son is worried about his condition in the weather event, all they have to do is call him up on the cell or text him on the iPhone. Who needs the National Traffic System?
     Nope, the Russians ain't on the air like they were once. The bands are as open and uncrowded as they'd be if half of ham radio suddenly fell to narcolepsy – despite Gorniak's grumbling on 3675kHz every Friday night like clockwork. Radioteletype has been replaced by MFSK, DominoEX and computerized versions of the old German Empires Hellschreiber system. Even CW itself has been subsumed into a computer program.
     And Gorniak's favorite radio don't even have a knob on it . . . 'cause it's a computer, dammit.
     And your audio still sucks.
     Even the long-time ham radio publications have dropped like flies in a freezing rain. The only few left are published by special interest groups or supported by national ham radio clubs. In Gringolandia that's the ARRL's QST. The SIG publications are small and usually published quarterly, like the QRP ARCI's QRP Quarterly or the British QRP clubs SPRAT. After that it's all on the web, yo. Just go to the site and read it in a PDF.
     Yep, it ain't like it used to be. And those of us still able to remember what it was like running a Johnson KW matchbox to a wire draped out the window and hung in the trees might wonder if it's worth the effort & electric bill. Me, I tend to think it's just as cool as it once was, but I say that for a couple simple reasons.
     Playing with the electromagnetic spectrum as most hams have to admit they do, even in the most minimalist of views, is still fun. Challenging nature to cut your conversation off, even it it's with Gorniak's criticism of your audio, is yet a trip. Runnin' low power is fun 'cause it challenges you to be inventive and address fundamental problems like antenna construction and transmitter design. But you can say the same for high-power ops.
     Sure, my essential tremor makes CW a challenge – especially for the guy on the receiving end – as much as it makes a challenge of just getting on the air for a friend whose post-stroke therapy includes getting on the air every week with friends.
     The size of parts these days is nearly criminal to the bifocal and shaky-hands brigate. Building your own stuff is more expensive and certainly more trying. But the technological advances of SMD and even smaller through-hole parts have made it possible to build a remotely-tuned Z-match with robot motors doing the knob twisting. Computer technology's wedding to RF design has made it possible for a radio with 99 memories, two VFOs, DSP audio filtering and solid-state QRO to be called an “entry grade rig.”
     Hell, I barely had one VFO and never had all the filters on my “entry grade rig” of some 40 years back!
     Which I guess brings this all around to still finding fun in playing with the electrons. CW, at least to me, should always be run by hand. I have no use for & refuse to QSO with someone using a computer to generate what they think is faultless CW. I say that 'cause, if I wanted to have QSO with a computer, I'd turn on this one and let it play surf & wind noises to me all day. SSB – even with Gorniak's critiques of everyone's audio – is fun 'cause I can filter the hell out of it with a simple DSP doodad in my entry grade transceiver. And hosing the computer up to the radio now gives me all those digital modes that used to take up square yards of space in the shack, all of it replaced by a much abused former classroom computer bought surplus.
     I do miss the ЦЩ-Мйр contest, at least the way it was back in the days of yore when CW was hand sent. I miss the trip of running a radio that was, even for its time, minimalist. But I do not miss the overly crowded bands, the huge number of folks who thought they had to run QRO 'cause they had antennas made out of wood and bits of solder encased in black electrical tape.
`     Nope, it ain't what it was but the nowadays stuff I have in the shack challenges me to build that tuner and make it work without flaming out the entire backyard.
     Ham radio's still fun. Even if Gorniak's audio still does suck.
     

Got Signal?

Two things about ham radio that make it such an interesting adventure are (1) home-brew & kit built gear, and (2) buying used home-brew or kit built gear and recognizing therein that the quality of what you buy is only as good as the quality of the builder's desire to make it work.
     At which point it goes without saying that buying used home-brew or kit build equipment is either the result of an estate auction or the builder finally giving up on undoing all the shoddy work that went into building whatever it is that's up for sale.
     And all that explains the SB-200 amp sitting on my desk, basically unusable, that has held the floor down under the desk for the past three years. I spent $275 on it being here, not counting shipping costs. It was a hard luck case of sorts when I got it, but at least it came from a place where the seller had taken the time to test the amp before boxing it up to sell. As the advert said, “Good output on 15m and 10m, fair on 40m and 80m. You fix or use as-is and save! Tubes are good!”
     Which is exactly what I got.
     The box had been built before the day of solid state transceivers and thus needs modified for radios that were not designed to switch relay voltages of 130VDC. Back in the day of tube radios, this was no problem. But new transistorized radios won't take that sort of power switch arrangement. Thus, I had to add a board to use with the Icoms. And I had to rebuild the power supply, which fortunately was available as a kit. After all, the amp was sold by Heathkit from around 1964 through 1978 as part of the Heathkit SB-series of transceivers, receivers, transmitters & accessories.
     I went through a bunch of Heath gear when I first got into ham radio back in 1969, starting with the SB-310 shortwave receiver, which I soon modified to give me 15m ham receive coverage. I used a DX60 transmitter, a home-brew T/R antenna switch and a TenTec KR40 keyer for my entire time as WP4DKA. Then I built a SB401 transmitter and tried to use it with the '310 for a while. I also ran a used DX100 transmitter, a behemoth of drifty VFO, chirpy signal CW/AM gear that disappeared into some void between 1973 and 1975 when my first son was born.
     All that stuff had been replaced by a TenTec Argonaut somewhere along the line and the Argonaut went on the shelf when I built my last piece of Heath gear, an HW101 that died during a blizzard around 1977 or 1978.
     So now, surrounded by Icom radios – all of which are very nice, easy to use and, so far, high quality & trustworthy gear – my decision to get a used amp was driven more by idiocy than reason. Idiocy because I just want to have a strong signal when I get on 75m every Friday night with the ex-radio hippies and late-night-radio leftovers of the once thriving Ohio Valley Teratology Net. And maybe talk to my cousin in Pennsylvania who lives in a RF noise hole and has to run a kW to get a signal over to Ohio mid day on Saturday or Sunday afternoons, something that hasn't worked for a while 'cause my signal is buried in the noise at Keith's location.

But back to the amp.

First thing I did was buy a power supply rebuild kit from Harbach Electronics, which set me back $75 and a couple days of patient building. I later added in the low voltage keying board so I wouldn't fry my Icom radios running the amp. (I have yet to hose the amp up to the radios 'cause, well, that's the rest of the story.)
     In the process of getting the amp running I've had to redress some cabling and give a serious long look at the tank circuit and the tubes in the RF deck. What I eventually found was disheartening.
     Whoever had this amp last modified the hell out of the band switch circuitry.
     First, the high end of the HF section was wired backwards, so the 10m tap fell into place before the 15m tap. And someone had moved the tap on the 10m section of the tank circuit to what can only be guessed at being 11m, although the placement is more suitable for something higher in frequency than 11m.
     Confused work there.
     Then the padding cap that get switched in to the tank circuit on 75m is on the 40m position of the band switch, which makes 40m tune way the hell off somewhere else.
     This misplaced padding cap position was tossed in because the point and switch contacts on the 75m position of the switch is, for want of a better term, gone.
     So what I end up with is an amp that won't work on 40m and barely makes sense of 75m, should I be nuts enough to use it only there. Which I could, I will admit.
     But I bought a five band amp and I want a five band amp.
     So now I'm adding on the bill the $35 it costs to replace the mangled switch section (not counting what it would cost me to have someone take the switch out of the box and take it apart so a new section could be laced into place).
     Then there's the quality of craftsmanship that's missing from the ass of the amp, on the input section to the tubes. And there the list is simple.
     First off, all the bypass caps have long enough leads on 'em to snag a fingernail.
     Then there's the strange wiring of the input circuitry, some of which is part of the build instructions but about which I have serious disenchantments.
     That's 'cause one of the tubes runs hotter (as in the plate gets redder) than the other. And that may be caused by something not done up right or completely failed in that section of the box.
     So there's that.

All in all, it looks from the figures and frustration that I could just as easily have bought a higher-priced, probably better-constructed, used amplifier. I could have bought a fresh off the factory floor amp, if I had been interested in buying one of the cheaper – and notorious by their cheapness – amps that run tubes familiar to anyone who's been playing radio since 1969.
     Which brings up the other part: I have another amp, a Heathkit Warrior HA-10, that I got more or less as a “please take this off my bench and make it go away” deal.
     Took that one apart – it was way easy to do – and built it back up again. Used it for a long time over the solar maximum of the late 70s and early 80s. Worked the world, seriously, with that amp, a TR7 and a home brew three-element beam on top of a 40 ft tower.
     Then we moved to the new digs and that was the end of ham radio. At least until the past couple years when it became possible to remotely control antenna switches, antenna tuners & similar bits and pieces that make it more fun.
     Which brings us to today: two Icom radios and a used SB-200 that needs serious therapy.

By the time I clean up the wiring mess in the tank circuit area, rebuild the entire input section at the tube sockets & replace or repair (if possible) all the broken bits and pieces, I'll have spent almost as much in resurrection as I did making the box appear on my porch.
     But that's the way it's gonna have to work, if I want the amp to work.
     I've done it before.
     It ain't easy, however.
     Every single component in the radio has to be vetted. Can I trust this piece? Is it the right value now, if it ever was? And what about all these improvements to the design that have shown up since the beast went out of “production” a bit over thirty years ago?
     That is a good question. The hot tube may be part of a design feature that was discovered by a ham in Holland. Another guy in the US collected a pile of useful mods and improvements that sound interesting. But mods are like Communism. They sound good on paper. But . . .
     Will they work?

And truth be told, as my 65th birthday approaches, I am less than enthusiastic about sticking my hands inside a piece of radio gear, let alone guide a soldering iron in there among the plastic and wire.
     The plate voltage for the amp is around 2.3kV. Twenty-three hundred volts.
     I took 750V across my arms once. I remember screaming.
     I doubt I'd remember anything if I crossed 2.3kV. They' sweep up the ashes and thrown me in the oceans so I could swim with my family every summer.
     I don't have the steady hands that I once had either. Two hands to plant a screwdriver tip in the head of a screw. That kind of thing.
     So there's that to consider.
     But I spent my money and, goddammit, I want the amp to be amplifyin'!
     And I'm tired of hearing W9BS tell me I'm weak and that I need a signal.
 

A Book Not About Radio

Well, I done finished writing my book. There's an advert for it in the sidebar. You can order it online from the link provided. But I have to tell you two things: First, it's about time travel, mean monkeys, friendly cats, two guys from the future trying to fix things up so the future goes on to be what it is supposed to be. All that. And secondly, if you find anything wrong with it, like misspelled words and bent story lines (which I already know about, being as how it's PostModernist fiction), don't tell me right away. Read it all the way through. Jot notes down in the margins or on the back blank pages or something. Give it some time.
     Give me some time.
     Then tell me.
     See, I went through a ton of frustration on this project. The biggest problem was having to read it again and again, looking for typos and blown up sentences and stuff. It was wearying. And then there were all the little things like the same word used three times in one sentence to say one thing. Yeah, like that. And a huge amount of wasted space on adjectives. All of that stuff I had to find before I could say that it was "sell-worthy."
     And then there were the typographic problems. Widows and orphans and hyphenated words at the bottom of one page and the rest of the word at the top of the next. The usual stuff most people don't notice or if they do, they just figure it's the work of a rank amateur and let it go at that before giving up.
     I didn't want to come off looking like I didn't know how to paginate, see?
     I'd get all finished finding what I thought needed fixed and then I'd fix it and upload the changes to the site. Then I'd order another proof.
     Before that proof even got halfway out the shop where they print 'em, I'd find stuff that I'd missed which had gone on in the upload that I was waiting proof on. So when the proof got there, I knew I had to fix all the stuff in the proof that I'd found before receiving the proof. And then there were the things I found from that proof which, upon being fixed and again uploaded, led to more errors.
     I think I went through four proofs getting to where it is today.
     And just today I found a mistake on the back cover, a small typographical one, a matter of an apostrophe, that I will have to fix when I find all the rest of the stuff that I didn't find this time or that time or any time before.
     Yeah.
     It was a pile of more frustration going through all that than it was just writing the damn thing. And even there I had help, as noted in the previous posting. At various points in this long dance around frustration, I often thought that, if I hadn't put this much effort into it already, I'd just give up. Seriously.
     So there I was -- and here I am today -- trying to not make something for the public offering that looked like my amateurish hand set penny dreadfuls, even if the penny dreadfuls that I've printed for the Amalgamated Printers' Association are pretty much the source of what's in this book.
     But at least it's done.
     You can buy a copy if you want. I'm sure by the time it's been around for a while -- presuming I get more than one reader total -- that I'll have found time to go over it again and find even more stuff to fix than most readers will take the time for.
     And therein lies the problem: I have finished this one. There are two years of penny dreadfuls already printed for the APA membership, two of which are stories of their own, stories which have proven to be source material for another book, just as the earliest two penny dreadfuls were the source for this book.
     Yeah.
     I'm already working on another one. There must be something wrong with me.
 

Whole Lot o' Crazy Stuff Goin' On!

Many years ago I got into searching for single-purpose ICs that would or could be used to make a decent radio. Just something to replace, say, all the tubes & shock-box parts in an old Hallicrafters S38 probably come off the factory floor when I was still in diapers.
     I came across quite a few ICs, actually.
     There's the TDA1072AT, which I will extrapolate on below.
     The TDA1572 chip is the gussied up version of the '1076 with a separate IF output for whatever uses one might dream up.
     There the TDA1083, which is everything you need for a receiver, including a small .25W audio amplifier. It's laid out a little weird but it looks like a promising trip. (I say looks like because I have ten of 'em and have yet to fiddle with a single one for any purpose at all. Limits.)
     Then there are a handful of other ICs, most of 'em Sony chips, many of which are no longer available except in vast quantities from warehouses here and there in the Orient or wherever. Among these are the TCA440, which is a pretty neat little RF/OSC/MIX/IF chip for which the builder must provide a detector & AF am circuit. If I could find a handful to play with, I'd be cool.
     The TDA1046 IC, identified on the website for the data sheet as "AM Empfängerschaltung mid Demodulator" also travels under the name of TDA4001, which is identified on its data sheet as "AM receiver IC with Demodulator." The chip is what it says it is, but looking at what information there is leads me to suspect that it wouldn't make a very good HF radio. The oscillator is only spec'd out for 1.5 MHz and the IF is shown only at 455 kHz. Still . . .
     And there's the TBA651, which is shown as a tuner & IF amp for an AM radio. Like the TCA440, this chip is the basic IF section of a standard AM radio. There's an IF output to a transformer in the design notes, with the output of the IF transformer being a simple diode detector feeding an external AF amp. Replace the diode with a product detector and it might make a good CW/SSB radio . . . if you can do that at the spec'd 455 kHz IF.
     The TAD100, an IC from the late 60s, is another of the "basic AM radio" chips. The datasheet suggests a circuit covering LW and MW bands. And a two transistor AF amp. Yeah, it's that old.

Out of the whole batch, the TDA1072 (and the TDA1572 version) is the most sensible of ICs to go with. First off the oscillator is spec'd to 50 MHz. And the IF has proven in experiments to work in the 4 to 9 MHz range. It has a detector bypass (which must be capacitor grounded to get any AF out of the detector) which in one online application provides for BFO injection. There are two AGC lines, one of which must be coupled to ground for the detector to work. And the chip has a mute line that must go to ground in receive.
     The next possible winner is the TDA1083. With this one you get a nominal mute line (which actually shoots between an AGC function or an AFC function; the IC is touted as a AM and FM receiver) & AGC. You get the ability to use an external oscillator (with a weird looking coupling mechanism that others have used successfully). And there's a pick-up point at the second of two IF amp stages to use an detector outside the chip itself (or to inject a BFO signal). And there's the .25 W AF amp, which is one less thing to fight with if you're like me. The only drawback is the way the IF system works and what to me looks like a kind of haphazard IC pin layout. There are a couple designs on the InterWebs using this IC, including one for a 75m SSB transceiver.
     Of course, if you don't want to play with one or two ICs to build a radio, then you've got the NE602/MC1350/NE602/LM386 circuit common to a whole list of tiny radio kits.

Now I started on this madness over ten years ago, at least to my reckoning. Over that time, other than amass a small fortune in ICs, some of which I parceled out to friends with greater levels of determination than I, I've done nothing with the idea.
     Then I found a design on the web from one of the original unindicted co-conspirators. That design, using a 4.915 MHz IF, seemed reasonable and, with as few parts as the design had, possible for my shaking hands and short attention span.
     Now, after months of burning things up and winding tiny toroids and all the other accumulated million aggravations that beset any project that I start, I've gotten to the point where I can say three things about the single-chip radio project:

• 1. It is possible to use the TDA1072AT chip to make a shortwave radio with nearly single-signal detection, even using 455 kHz ceramic filters. (I used a 455 kHz ceramic resonator for the BFO.)
• It is possible to get a reasonable CW/SSB system out of all this accumulated soldering, burning, cursing and quick turn down of the AF gain pot.
• If you want to build one of these, I'll be finished writing up what I've found – much of it with the help of my fellow unindicted co-conspirator – for eventual publication in some QRP ham radio magazine. And note that I said eventual publication. I don't do command performances any more.
• Oh, one more thing: I'm tired of working on this . . .

That being said, here's a picture of what happened the last time I messed with this design. It isn't that bad of a radio, really. The only problems I have – and they're problems that I feel are more owing to my klugish way of putting things together before I get out the real metal working tools – are oscillation & instability in the input circuit. And there's a small problem with the BFO injection level and more importantly, a bit of trouble getting the BFO frequency set solid. Minor stuff, right?
     After that, it's a good enough deal to listen to Radio Habana on, which was the original goal nearly a decade ago when I first got a bug up my kilt over this single-chip receiver madness.