To TB1-1

Follow the photos to lay out and install the remaining top panel pans, the positioning of which is much less critical than the need to keep Q9 cool.

Except for the short ANT/GND and Y1 wires, connect the PC hoard to top panel components as shown on the schematic diagram or parts overlay. Hinge the board over and mount it to the lop panel on metal spacers, and then connect the short wires to TBI and S2. Check to ensure the coppcr side oi the PC board is not touching any panel components like potentiometers or jacks: astly. install Q9 to the heal sink using a heat conductive insulator pad and 6-32 Teilon or nylon screw or a TO-22G transistor mounting kit, to couple the flange thermally hut not electrical!) to the heat sink slab.

Power Supply

A suitable power supply far the SP-10, one supplying 18 to 28 VDC at 1 amp, Can be as \imple as a DC wall adapter or a pair of 12V batteries wired in series. There's no need for a fancy, electronically regulated unit, Precise regulation, where needed, is already supplied by U2. The external supply should, how-e\er. he beef) enough to hold its output voltage within 20%, going from ke\-up to key-down. For example, a source measuring 25 VDC should drop no lower than about 20 volts when you close the key. The no-load input can be as high as 32 VDC; be\ond that point, protection /ener D10 ma> conduct and if it does, it will probably short circuit tn the process of protecting ihe SP-10 from overvoltage.

If you wish to build a power supply from scratch, the classic transformer-rectiller-filter arrangement shown in Fig, 4 will w ork just fine. Regardless of the power supply you choose, be sure to provide an inline luse in the plus lead running to TB I - L Stan off with a i -amp 14 73 Amateur Radio Today * January 1996

l use if possible and, if all goes well, upgrade it to 2 or 3 amps for normal ioperation. This conservative approach to liring up new, untested equipment will minimize casualties should anything be amiss.


The operating frequency of the SP-10 is controlled by a single crystal in transmit and receive. With crystals, you give up the ahility to wander (or drift!) around the band in exchange for excellent frequency stability, intrinsic dial readout (frequency is marked on the crystal) and simplified project tune-up, requiring very little test equipment. For the beginner, or the old-timer into "radio karma," crystal control is a g*xxi wa> to go.

The actual crystal is a thin square of quartz too fragile and sensitive for direct handling* Rather it is mounted in a holder which, depending on type, plugs into a crystal socket or is wired diiectly into the equipment. The octal crystal socket on the SP-10 accepts two of the popular fT-243 holders, having a pin spacing of .486" and a pin diameter of ,093/' T>pes HC-17 and Petersen Z-9 are also compatible, in general, any fundamental crystal with a frequency in the chosen band will work if you can adapt it to plug in. For example, even the miniature HC-18 holder with leads instead of pins may be wired to the base salvaged from an unneeded octal vacuum tube, w hich will then plug in.

Photo C The SP-10 at an angle

Getting crystals is like ordering pizza. Unless you are buying a stock or popular frequency, they are tailor-made by a manufacturer upon receipt of an order. Thai's why delivery can sometimes lake 2-3 weeks or more; you must allow for lead time! Some manufacturers require the Yl specifications provided in the Parts List while others will do the job if you merely order "amateur-grade crystal4' and specify the frequency.

If you're a Novice, don't crowd the edges of your subband when ordering crystals, unless you have the means to ensure the crystal you're using is "in-bandThe reason is, a general purpose or amateur-grade crystal ordered tor, say, 7102 kH/.. may actually put out on 7100, It's a matter of manufacturing tolerance and circuit correlation. If in doubt, give band edges a wide herth.


The key to a smooth, uneventful tuncup is to do a careful job during

Tfr TTJt t ti*

SPADE LUGb twtf y


LAMP RS27;:1 1110

Photo C The SP-10 at an angle

Fig. 5. Terminating RF detector.

construction. Having done your hesu let's see if it works! On the PCB, set R f 9 Bias and R42 Sidetone each to midrange. Connect the power supply to TBl-l (+) and TBI-2 (-) and a 50-ohin dummy load with relative power meter or wattmeter in line to TB1-3 (coax shield) and TBI-4 (center conductor). Lacking this test equipment, build the simple terminating RF indicator shown in Fig. 5 and connect it to TBI-3 and TBI-4. This gizmo provides a suitable resistive load for low power transmitter testing, as well as a visual (and thermal-it gets warm to hot!) indicator of RF output.

Plug a speaker into J2, Insert a crystal into the socket and select it with S2, Sw itch on power w ith SI. close the telegraph key and adjust T1 for maximum RF output indication. Adjust R42 on the PCB for desired sidetone level. Replace the dummy load w Uh an antenna or signal generator at the crystal frequency and adjust C23, T2, and T3 for best reception.

Radio Ts50s
Fig, 2. PC Board foil pattern.

Some paticnce is called for with the antenna method; you may need to wait for a signal strong enough to he heard through the as yet unpeaked front end. A temporary clip-lead jumper from the anode of D6 to the upper lead of C34 may help by allowing you to get T2 and T3 in the ballpark first. Then remove the jumper to peak C23 and touch up T2 and T3,

On the Air with the SP-IO

Like all modern transceivers, the SP-IO prefers to see a 50-ohm antenna sy>-tem with low SWR. The classic half-wave drpole comes close to ideal without the use of extra matching techniques. Other antennas like the G5RV or random wire will require an antenna tuner to provide an acceptable load. If operation into a less than perfect match is unavoidable, it might be wise to reduce the operating voltage from, say, 24 VDC to 18 VDC. This will reduce the adverse effect (Q9 overheating) of a somewhat high SWR.

With its rather broad selectivity, it can be questionable whether or not signals heard on the SP-10 are close enough to your crystal frequency for a QSO. Those th;ii decrease in pitch and approach zero-beat with RIT control moved fully counterclockwise are \ery close. Others may be workable if the operator tunes around for your signal.

Though 10 watts is considered low power, it's right up there with the popular one-tube 6L6 transmitter (and countless variations) that propelled tens of thousands of hams into the ether in their early radio careers. The receive section I is certainly no worse (and probably better) than those tudrifty/ broad-tuning super he l Novice receivers we once cherished and still remember fondly. They did the job I And on most an> night the SP-IO can be your doorway into a won-| derful world of Morse and static, faceless names, exotic places, and colorful QSL cards—all the more exciting when you build the rig yourself!

SP-10 Condensed Parts l ist

CI-C-LCl I-C12.C18.C22. C25-C34

f$ee table 1 \ 023 4-20 pF irimiiïer, Mouser 24ÀA022 C56. C57 0.0015-fiF Mylar™ l>l MV2IM, ECG612 02. D^D8 IN9I4, RS 276-1122 i H 3.3V 5W aeœrdiode i IN5226B) W IN4Q01, RS275-1101 D10 33V IW /L*rt.T diode 11N4752A) L)l \ 9.1V _5W re* diode 11N5239R* J1 J2 mm closed circuit mini phone jack L1-L6 (see lable 1 )

Q f. PN22:2. ECG123AR MS 276-2CXn Q2 2N2219 A. ECG 128, RS 276-2030 M?r 1 ( ï2. ECG312r RS 276-2062 Q7 2NG027, ECG64Q2 QS 2N?m. PN2907A, HCG159 Q9 [RF5 30

RS 271-282 lt23, R47 10k auilio taper potentiometer,

RS 271-1721 RFC t 22-|iH coated.

Mouscr 43LS275 T1-T3 Mouser42IF123 T4 S Lums #24 e iiMe 1 a i re, miliar wound on tv- o FT>t M 3 i Amidon l cores TB i 4-Iu£ ien 1 îuial boanl Mou^x534-1190 U1 LM386 audio amp, RS 276-1731 LT2 7812 voltage regulator, RS276-1771 U3 MC3359P (Circuit Specialists) V \ Fuixlamenial cr> sial spceifv dt^ned frequency* panillet / 3Z-pF load, .005'ï tolerance. holder type FT-243. HC-17/U or equivalent

Note: Check the advertising in this magazine for parts suppliers. For a free list of parts sources for this project, send the author an SASH requesting SP-iOLST. PC boards and project kit for the SP-10 "Senior Spider" are available from Lectrokit, 401 w. Bogart Rd„ Sandusky, OH -44870 (no telephone).

Confirmed on page I 7 73 Amateur Radio Today 9 January 1996 15

Number 16 on your F&edb&ck card

by Phil Salas AD5X 1517 Creekside Drive Richardson TX 75081

I have been using a Ten-Tec 938 switching power supply for some time with my Kenwood TS-50S tor portable operation. This switching power supply is ven/ small, efficient, and lightweight {25 pounds ) and lets me operate my TS-5QS at 50 waits output continuously However, for base station use f wanted the full 100-watt output power capability of the TS-50S. A full 20-amp linear |»wer supply weighs three to four limes what the TS-50S does, ami is two-to-three times larger than the TS-5QS. It just didn't seem right to have a power supply that overwhelmed theTS-50S in size and weight. What I wanted was a small, lightweight switcher with 20-amp capability Unfortunately no one seems to make these at this time for amateur use, and commercial switchers are very e\;»enstve. Oh, what lo do!

L like many of you, receive lots oI catalogs of surplus electronic stuff through ihe mail. Many of tiiesc catalogs list all kinds of DC power supplies, both new and used. My favorite surplus epilogs arc frum Martin F Jones & Associates (407-848-8236), All Electronics Corp. (818-904*0524)^ and Hosfelt Electronics (80(^524^6464). 1 recently noticcd dial Marlin P. Jones & Associates was Lidvertising a 12-V1X' 20-amp actmstiKi i/_

switching power supply for only $49. This w as a used i ,ambda power supph thai is 9M x 4-7/8" x 2-7/8" and had a -flipping weight of only six pounds. This seemed great, but could it be made to operate at 13.8-VDC output? There was only one way to find out—so I ordered one.

"This surplus treasure turned into a 20-amp switching power supply that is smaller than a I S-5OS, weighs less than six pounds, and costs less than

A few days later the power supply arrived It is a used LambdaLYS-W-12 power supply rated at 20 amps continuous at 40 degrees C, 18 amps at 50 degrees C, and 15 ainps at 60 degrees C. The input to ihe supply can he 105-132 VAC at 47-63 Hz, or 130-160 YDC. 1 lis power supply has no switches, fuses, connectors, or indicators, Wt>en I removed the coven 1 round that ihe DC output connectors were #10 studs on the IV board, and the AC inputs were just pins on the PC board to v >lder a line cord to. Every!hina was voteg* AdM

DC Output o


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