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Text File
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1996-02-19
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7KB
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124 lines
SHORTWAVE ON A LIMITED BUDGET
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My ancient S-38E Hallicrafters shortwave receiver died some years ago. I
did not realize until then how much I depended on foreign short wave
broadcasts to keep in touch with world events and to get the news before (!)
it was hot. I could not see spending $75 and up for a new commercial
receiver so that left as the only alternative build-it-yourself converter
kits.
The October 1989 POPULAR ELECTRONICS feature article told how to build a
sensitive shortwave converter using an old car radio and 6' or shorter
antenna and about $10 worth of parts. This had to be too good to be true. I
passed up buying the issue at the time and regretted it later, after the
issue was gone from the stands. Fortunately, the article was reprinted in
the 1990 POPULAR ELECTRONICS Annual. This time I bit. The converter seemed
simple enough to build as there was only a bare handful of parts involved
and nothing tricky such as winding your own coils. Even etching the printed
circuit board was not mandatory since you could haywire the thing on a
piece of perfboard, or so the article claimed. Just to be safe, I ordered
the complete kit of parts, including etched PC board, but less crystals,
from the supplier listed for the sum of $10.50 postpaid.
Prior to the arrival of the kit, I had looked for a used car radio at a Ham
Radio flea market. They seemed to be selling in the range of $1 to $10 per.
I bought a fancy one for $5, and as an afterthought, a "junker" for $1.
(Used car radios are available at flea markets, yard sales, and swap meets.)
The kit arrived in the mail a couple of weeks later. Building the kit
itself took all of 20 minutes, no big deal. Figuring out the hookup to the
car radio was something else again (see enclosed text file CARRADIO.TXT for
instructions). Of course I also had to build a 12-volt, nicely filtered
power supply to provide the juice for the radio and converter (see enclosed
text file POWERSUP.TXT for construction of this).
All right. Everything was built and connected. I cheated and used a longer
than recommended 10' length of speaker wire strung along the ceiling (I was
building it in my basement so I wanted to improve my DX luck). Turning it on
and holding my breath... I was greeted with a loud burst of static that
turned into that old familiar CW beeping as I twirled the dial, and yes,
gabbling in foreign languages, now Spanish, now German and French. The thing
worked!
The converted car radio is surprisingly sensitive. The article claims it
can "outperform most under $150.00 shortwave radios". This may well be the
case. In several months of casual listening I logged all of the following
stations: Radio Sweden, Radio Sofia (Bulgaria), Radio Beijing (China),
Deutsche Welle (Germany), WWV time signals (U.S. Bureau of Standards),
Radio Netherlands, Radio Budapest, Radio Moskow, Radio Havana, KUSL (Salt
Lake City, Utah), Radio Canada, VOA, Radio Japan, Radio Austria, BBC, VAE
Dubai (United Arab Emirates), Radio France, Swiss Radio, HCJB (Quito,
Ecuador), Radio Yugoslavia, Radio Denmark, Voice of Turkey, Radio Vilnius
(Lithuania). Not bad for a total expenditure of about $16.
So, how do you, gentle reader, build one of these babies yourself? The easy
and recommended way used to be to send a check for $10.50 to the SMALL PARTS
CENTER for the postpaid kit...
Unfortunately, I have been informed by Carl Evans of Greenfield, CA, that
the Small Parts Center is out of business. You'll now have to build it from
scratch, no great task as it turns out. Try DC Electronics (address below)
as a parts source.
Parts needed are an NE602AN frequency converter IC, an IF transformer, and
the caps, resistors, and the diode, as well as some kind of circuit board.
You need in addition to this a crystal (if you want to tune more than one SW
band, you need extra crystals). If you can't find crystals at your favorite
electronics store (even Radio Shack sells 'em), you can order them from
Jameco, Digikey, or a host of other mail order suppliers. You can usually
pick up assorted crystals at a Ham or Computer show or flea market for
between $ .10 to $ 1.00. See enclosed file XTAL.TXT for more info.
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A highly recommended source of NE602/s: DC Electronics
($2.50 ea.) P.O. Box 3203
Also try their "NE602 Experimenters Scottsdale, AZ 85271-3203
Package" (cat.# 602EXP) @ $7.95. 1-800-423-0070
Digikey, JDR Microdevices, Mouser Electronics, and other suppliers now also
stock the NE602. Fortunately, it is no longer hard to find.
The IF transformer, a 10.7 Mhz submini, can be ordered from Digikey, part
no. TK1501, at about $2, or from DC Electronics, part # 42IF126 at only $.60
each. It can even be pulled from an old transistor radio (it is marked
GREEN), but this requires specialized desoldering tools, and even then the
operation is extremely delicate (NOT recommended). The rest of the parts,
the caps and diode, can probably be found in your junkbox, or if not,
purchased from a supplier for only a few cents each.
Note:
A CAR radio works best. Another type of radio might not work as well because
of the interference from local broadcast stations that might be picked up
since the case is unshielded and because the infamous loop antenna in most
AM radios is optimized for pulling in Broadcast Band signals. However, I
have gotten perfectly acceptable results from an old AM clock radio that I
hooked up with a SW converter. This saves about half the cost of the
conversion and the end result looks nicer. The details of converting an old
table-model or clock radio, or even a portable transistor radio are given in
the file AMRADIO.TXT.
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I would be interested in getting in touch with other SWL's (shortwave
listeners) and also finding out what you think of this particular project.
Your questions, suggestions and/or criticisms would be welcomed. If you want
a reply, enclose an SASE please. If you have successfully completed the SW
converter project, a $2.00 contribution would be greatly appreciated.
M\Cooper
3425 Chestnut Ridge Rd.
Grantsville, MD 21536
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email: thegrendel@gcc.cc.md.us
Again, happy DXing!