Sunday, March 31, 2013

THE STORY OF AN ANTENNA


     I have mentioned my fit-to-the-space G5RV antenna, but never tried to show the whole thing.  So I shall:
     Here's the entire antenna in a kind of Cubist perspective, from the 2x4 post at the back fence, to the swing tree, to the next pol, up over the roof, to the feedpoint and "X" that carries the balanced feedline over the roof peak to the TV antenna pole on the chimney and, finally, past the front roof peak to the tall tree in the front yard. 

     It's a huge image -- click to see it more closely, if you'd like.

Saturday, March 30, 2013

STANCOR 10P UPDATE 4: LABEL

     I made a perfectly enormous scan of the front panel label of my Stancor 10P, with an eye towards cleaning it up and having a local silkscreen outfit make a new one.
     Alas, they're only accepting .eps files, so I'll have to pull it into Visio, draw over the top of it using matching fonts as much as possible, delete the scan image from underneath, save it as a .dwg, pull it into another drawing program that will read .dwg and spit out .eps, and haul that off to the silkscreen company, along with an accurately cut (and possibly drilled) sheet of aluminum and the original label for color matching.  So that may not happen very quickly, since I have to beg time on the drafting/drawing software.

     The old one has been straightened, polished and waxed.  It'll do fine for now.

     N.B., the alert eye will notice that the microphone gain goes to 11.

Wednesday, March 27, 2013

STANCOR 10P UPDATE 3

     I decided to clean the front panel and apply a little liquid furniture polish:
     This is an hour after dabbing on and dabbing up any excess.  The line between protected and exposed finish is a lot less obvious.

Tuesday, March 26, 2013

STANCOR 10P PROJECT UPDATE 2

     The chassis is stripped down about as far as it's going to be.  I still need to clean it up a little more, add some more pre-tinned ground spots and replace the user-installed octal crystal socket with an original-style five-pin.*

     Front panel is off, the label plate has been polished and straightened and I'm pondering what to do about the panel itself.
     You can see the original gloss and color where it was protected.  A clear-coat overspray would probably bring the exposed portion to a close match to original -- but it's likely a careful application of furniture polish would, too, and the polish is a lot easier to remove (as long as it contains no silicone).

     Here we have the parts sorted out in yes, an egg carton (and a tuna tin!).
     Mostly new, some salvage.  The RF choke, variable capacitor and filter choke go back in; the jacks almost certainly; the" Standby" switch, maybe; the potentiometer and power switch will be replaced.  I haven't picked up a fuseholder yet.

     Current worry, the blobs of wax where the primary leads emerge from the power transformer windings.  This could either be from the installation of the (now removed) brute-force line filter, or it could be indicative of problems despite ohmmeter readings that look okay.  Can't tell until the power is applied, and I'll be doing that with a light bulb in series -- a smallish one.  If the bulb lights up brightly, back to the drawing board.  Or checkbook.
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* There's no reason to do this in order to use "modern" post-WW II crystals -- the distance between the grid and plate or cathode pins of a five-prong tube socket matches the spacing of an FT-243 crystal well enough.  The old "doorknob" crystal pins were spaced for cathode and grid; so you wire K or P to G, and you have a dual-purpose socket.  Stancor did use "empty" socket terminals for tie points and perhaps that was the reason for the mod.

Monday, March 25, 2013

INDIANAPOLIS TELEVISION PREHISTORY

     I once worked in the building that was the first purpose-built TV station in Indianapolis -- studios and transmitter both -- and I didn't even know it.

     Oh, my coworkers shared the rumor that, "P. R. Mallory Co. had built it for TV experiments before WW II but abandoned it before making any progress," but that wasn't even close to the whole truth.

     Recently, I was looking around the website of the incredible Early Television Museum and stumbled across a link to W9XBI/W9XMT, an experimental station put on the air in Indianapolis by Jerry Smith in 1938.  His "studio" was the family living room and depending on one's source, the transmitter was in the basement or that same room.*

     W9XBI was transmitting genuine, 441-line electronically-scanned TV, the same thing Farnsworth, RCA, Philco and GE were putting on the air in Philadelphia and New York City.  It was on what was then Channel 3, 60 to 66 mc/s. Programming wasn't much -- a camera pointed out the window, or a test pattern, maybe amateur dramatics from students at Butler University; but it worked and in 1944, local electronics manufacturing giant P. R. Mallory Co (yes, the Copper Top people: the battery business grew so big, they dropped or spun off everything else) bought the station, changed the call letters to W9XMT ("X" for "experimental" back then, and if "MT" wasn't "Mallory Television," I'll be surprised), and built a beautiful new building and tower at 30th St. and Kessler Avenue.  They also set up several employees with TV receivers.  With Jerry Smith still running the station, they proceeded to do television -- a lot of test patterns and shots of the street, but studio programs as well, using Mallory employees and Butler students.  (Go to the W9XBI/W9XMT link and scroll to the bottom for the page for an idealized look at the building.)

     I don't think the basic layout was ever changed; when I worked there, twenty-mumble years ago, it was airing religions programs, with a long, skinny control room looking into a very large production room/studio, a little newsroom/announce booth off to one side and a "junk room" used for storage behind the control room, just about the right size for Mallory's W9XMT transmitter.  It was an odd layout for a radio station, but nearly perfect for a small TV station!  The expansive windows seen in the Mallory ad were mostly glass brick; it had a kind of a blockhouse ambiance in the inner core of studio and control room.

     W9XMT was experimental, non-commercial, and by 1947, Mallory decided it had run its course and shut the station down.  They told Jerry Smith if he could find a buyer, they'd sell the station, but it never came to pass.

     In August of 1948, WXLW radio went on the air from the building and tower, on 1590 kc/s.

     In the spring of 1949, WFBM radio got into the TV business, making a splash by televising the Indianapolis 500 live for their inaugural TV broadcast.

     That same year, WXLW received (or purchased, as there's a "WABW" on the frequency in 1945) a license for an FM station, WXLW-FM, on 94.9 mc/s.  By 1950, it had moved to 94.7 mc/s and was pushing 20 kW into the ether, but FM was a money-loser and at some point prior to 1955, they dropped the license; either it was sold to WFBM or they filed on the frequency, I haven't been able to find out which.  As WFBQ, 94.7 is still on the air and I'm pretty sure it has turned a tidy profit in the years since 1949.

     But this story is not quite over.  In March of 1952, an application was filed for Indianapolis' second commercial TV station by "Television Indianapolis, Inc.," with stockholders including P. R. Mallory Co., WXLW and Butler University.  They received a license but withdrew their application, and it fell to WISH to be the second commercial TV signal in town in June of 1954 -- with WTTV Bloomington  (November 1949) and WLBC Muncie (April 1953) well ahead of them.

     I can't help but wonder about the backstory to the Television Indianapolis license application.  It's unlikely I'll ever know past what I have pieced together here, but with Mallory providing the tech, WXLW the commercial savvy -- and hey, that studio building! -- and Butler the stagecraft and actors, it was something of a W9XMT reunion.

     I wish I'd known all this when I worked there for a few months between better-paying jobs.  Many years later, through an unlikely hamfest coincidence, I purchased the old Hallicrafters SX-28 HF receiver that had been in the rack (and working!) in WXLW Engineering and got it running again.  It's waiting on desktop space in my basement hamshack now.  Was it part of WXLW's original setup -- or did they inherit it from W9XMT?
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* WFBM's "From Crystal To Color" [the WFBM Stations, 1964] says basement.  The ETVM website says living room.  David L. Smith's "Images of America: Indianapolis Television" [Arcadia Publishing, 2012] doesn't break the tie either way.

Thursday, March 21, 2013

STANCOR 10P UPDATE

    In the summer of 2011, I acquired a Stancor 10P transmitter in complete-but-modified condition.  Lately, it's been bothering me that I don't have an HF, AM ham transmitter that works, despite owning three of them and having a long-standing breadboard project to build another.

     The 10P looked like a good place to start.  It's the smallest of the lot, doesn't run a lot of power, and uses standard tubes.

     A closer look under the chassis revealed extensive mods -- the 6J5 oscillator tube replaced by a 6AG7 (which would provide more than plenty of drive for the poor 6L6 PA!), the 80 rectifier replaced by a 5Y3,* five-pin crystal socket swapped for an octal, extra components, and a rather casual attitude towards things like making good soldered joints, lead dress, and similar items.  Much of the wiring was old and the newer stuff was a bit, well, sub-optimum.

     It seemed best to clear it all away and start over.  I'm about half done.
     The bigger holes in the back of the chassis were for an SO-239 socket (replacing one of the two ceramic feedthroughs for RF output) and a pair of feedthrough capacitors on the incoming AC line.  I'll have to make some small plates to hold a replacement RF output feedthrough and the line-cord grommet and a fuse (probably a 5x20mm "Eurofuse," as the holders are tiny.  It's not period but it's a minimal change.)
      It should look like this:
     Comparing the two, it appears the original builder of mine didn't have a hot enough iron to tack ground connections directly to the chassis (but tried anyway), and later on, bolted-in ground lugs were added.  My smaller American Beauty iron can solder to the chassis -- there's a test spot over to the left in the upper photo, near the 5-pin coil socket.

     Here's the front panel.
    The hole below the meter was for a B+ test point, which I have removed.  A hole plug will fill it; I could patch the panel but matching the original paint color would be almost impossible.  I'll polish the control-label plate, which will help minimize the scratches.
     It's small.  Scale may be a little hard to grasp -- the "Key" and "Mic." jacks are standard 1/4" types.

     For completeness, here's a top view.
     I'll try to post updates as the work continues.  Ohmmeter checks of the power transformer have me hopeful it's still good.
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* I'll probably keep the 5Y3.  Essentially an octal-base twin to the '80, they're a bit more affordable and easier to find.

Sunday, March 17, 2013

SOLDERING IRON ROUNDUP

     Soldering irons: you can't solder without one.  Some people can't solder with one, either, but that's another story.
     Shown above, most of my stable.

     Left to right:
     A nice butane-heated portable; this one's a Wahl but you can find the same thing marked for other brands.  Puts out plenty of heat and works well, though a really high wind can be a problem.
     Antex fine-point iron, one of the very best tiny irons out there.
     Hakko dual-heat. 30/60W 20/130W (!).  This is an excellent general-purpose iron for electronics work, though they warn you to not hold the high-heat button down too long, lest you melt the grip!
     A pair of small Wellers, inexpensive general-purpose soldering irons and my go-to model for years.  The solid-copper tips do get eaten up over time but you can file 'em down until they get too short for even that.  If you can only buy one iron and you want to purchase locally, this may be your only option  That's fine -- they work well.
     Next, a big Hakko, 60W or more.  The "handle" unscrews and can be threaded over the tip for storage and transport, very handy.
     Even bigger and my general-purpose iron for tube-type radios, an American Beauty 75W.  This is an industry standard, one of the best irons made.  Tips are solid copper.
     Speaking of copper, here's the soldering copper again.
     Last, an absolute warhorse, a 225W American Beauty.  The guy who was selling it had several and said they all heated up.  I'm not in a huge hurry to try, but this will solder chassis together, if needed.

     Not shown, soldering guns.  I own two and use them in disassembly; I  find them too awkward for serious building.  Plus the tips are small, which means they cool down when you solder.

     Also not shown, torches.  I have a couple of small butane torches, which will do a lot of small work.  I'd own a MAPP-gas torch, but I have access to one at work. (MAPP gas these days isn't the real thing but it's still hotter than propane.)

    You'll note that most of these irons -- I think all -- have copper tips.  There's a reason for that.  While a well-known bench iron has used plated iron for years and tout its durability,* if the plating gets damaged -- say, by using the iron tip to undo some solder-soaked knot on a terminal in a 60+-year-old radio -- it's just about impossible to restore.  Copper, you just file down.

     Also left out, a selection of little sponges in metal trays.  A damp sponge is an excellent way to keep an iron tip clean during use.  The "potscrubber" tip cleaners are okay but a bit aggressive.  I've also got a little block of sal ammoniac for the tough cases, and rosin paste flux for difficult-to-solder items; both very handy.

    You don't need a jillion soldering irons -- but it's nice to be able to select the right size for the job.
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* The main reason for the iron tips is their clever Curie-point temperature control.  You can select tips by temperature!  This has to be weighed against the need to treat them nicely, so it depends on your application

Thursday, March 7, 2013

TINY MORSE KEY

     In years past, J. H. Bunnell (the firm that developed the standard form of straight key used in North America) has occasionally done production runs of the miniature telegraph key they first manufactured as a souvenir for the 1905 reunion of the Old Time Telegraphers' Association; at some point, Bunnell even made a tiny sounder as well.  No mere watch-fob, both items work.

     Bunnell is not the only maker of very small, "Triumph"-pattern telegraph keys.  KA6IRL made "QRP J-38" keys for several years and when one showed up at a well-known auction site, I was the winning bidder.
     Here it is between two full-sized keys.  Just the thing for when you only want a short QSO or smalltalk!

Sunday, March 3, 2013

1:1 BALUN: NO LANGUAGE BARRIER FOR RADIO HAMS

A nice tutorial on building a 1:1 ferrite-core balun for amateur radio HF use by a Spanish ham, with all the information you need to build one yourself presented visually, like Roy Doty's "Wordless Workshop" series:

     (Bonus: includes the metal version of a cold 807!) In case pictures don't quite work for you, EA7IQZ kindly provides an English bill of materials in comments at YouTube.  His drawing -- which still-frames quite readably -- is especially good.  Oh, and the 2 mm enameled copper wire?  Close enough to #12 AWG (2.053 mm) that you can use one for the other.

     Variations and cautions: different ferrite formulations will have different saturation points and frequency coverage; I'd expect salvaged AM radio ferrite to be okay for 160 through 40  meters and maybe getting lossy around 20 meters. Power-handling should be okay up to a couple hundred Watts. You can (and should) test this before you glue up the housing by running some RF power through it into a dummy load for a few minutes, shutting it off and checking for heat, repeating the process at different frequencies (see below also) and power levels.  It is possible that with a really crummy ferrite rod, it might break or smolder, which would be exciting, but considering the most expensive part of the project is the PVC pipe and eyebolts, not a big loss.

     You can build air-core versions (I have one, somewhere, in a box with a nice toroidal balun, but I still haven't found them!), by scaling up the diameter and number of turns, but it's a matter of making a good estimate followed by cut and try.  If you own an antenna bridge, it's easy to build them, terminate the balanced side with a 50 Ohm resistor, and use the antenna bridge to check frequency coverage.  Power handling will be limited by wire size, insulation and coil form material -- PVC pipe is slightly lossy, polystyrene much less so.

Friday, March 1, 2013

SOLDERING COPPER

    Shown below is a soldering copper.  Good ones are increasingly rare; what has survived the sieve of time tends to be wobbly-topped, or chewed-up by harsh flux, or just beat-up.  This one is none of those things. It has a nice copper tip, solidly attached to the steel  haft.  Stamping on the tip reads "THE ELECTRIC MATERIALS CO. NORTH EAST, PA."  (Still around, with over 90 years in the business.) Plus a very large "2" which is probably tip weight in pounds.
   In use, you heat 'em up good and hot in the fire and the tip stays hot long enough to make a few connections.  Set it back down with the tip in the heat, wire up some more components, and by the time you're ready to solder again, it's ready, too.

     Proper use is something of an art -- keeping the tip hot but not too hot and not so sooty you cool it down wiping it clean is the kind of thing that can be learned only by the doing.  But zillions of electricians and radio-minded people did, once upon a time.  (According to their FAQ, The Electric Materials Co. will still make you soldering coppers (PDF!), though they have a $200 minimum order, which would be more than "several" even at current copper prices plus other materials and manufacturing costs and their profit.)

     My lodger and friend Tam found this one at an antique shop in New Hampshire and brought it home as a gift.  Good choice!