Assemblycont’d
Thisallowstheboardtoremainflat duringmostoftheconstruction.Followingthisorderwill alsofacilitateinitialcheckout.Thechokes
will beselectivelyinstalledtoallowforcheckoutof varioussectionsofthecircuit.
Checkout will followthisorder…
Verifyproper+5vdcbeforepoweringanydevices
Install L2, PICandPLEDandcheckdisplayforproperPICoperation
Install L1, L3,U5,U7and U8andverifyproperoperationofADC
Install L5andU4andverifyproperpowerdetection
Install L7andverifyproperfrequency counteroperation
Install U6and verifyproperserialportoperation
Theabovechecks willrequireonlyaDVMand theCalibration screensexcept forthepowerdisplaycheck.Tocheck thepowerdisplay,
you will needatransmitterandcompletedcoupler. I will list expectedcurrentdraininredateachstepsothat youcan verifythat
nothingisshortedineachsection.
TocalibratethepowerreadingsoftheLP-100willrequireaminimumofanaccurate50-ohmdummyload and ameanstomeasurerf
voltage. ACantenna typeofloadisnot generallyagood choice. Thedummyloadwillneedadiodepeakdetectoroutputoryouwill
needacalibratedoscilloscopetomeasurep-prfvoltageacrosstheload.Analternativewouldbeanaccuratereferencewattmeter.
Tocalibratetheimpedancegainandphasedetectorsyouwillalsoneeda25or75-100 ohmdummyload.Thiscanbeeasilymadeup
outofinexpensive3W,5%metaloxideresistors,suchasusedinmyLP-200 ortheElecraft DL-1.Thiscalibration canbedonewithas
littleas1Wofpower.
Alternatively,youcanuseapairof50 ohmdummyloadswithcoaxadapterstoallowthemtobeparalleledtoprovide25 ohms.SWR
calibrationrequiressettingoffsetandslopeadjustmentsfortheAD8302gaindetector.Calibration oftheAD8302phasedetector
requiresadelaylineofknownelectricallength. Youcangetprettyclosebyusing ahighqualitypieceof polydielectricRG-58,and
calculatetheelectricallengthindegreesusingthefollowingformula…
Phase=(360*L*F)/(984*VF)
WhereDelayisindegrees, Lisinfeet and FinMHz. VFwouldbe0.66forpolydielectric.Anyconvenientlengthofabout5-10’is
acceptable,whichwouldprovideadelayof~39to78degreesat 14MHz. Youwill findmoreaboutcalibration inthe Calibration
section.I amcontemplatinganinexpensivecalibration kitinthe$25 range,whichwouldincludeaswitchabledummyload PCBand
pre-cutdelayline.IwillalsocalibrateanyassembledLP-100kitfree ofchargeif you willpayround-tripshippingtome.
You willneedthefollowingtoolstocompleteassembly…
30-60Wadjustablesoldering iron
60/40alloysolder….020”diameterrecommendedforthermalpads
Needle-nosepliers
Wirecutters
SmallPhilipshead screwdriver
Razorknife
DigitalMultimeter
NOTE:TheLP-100iswhatIwouldcall anintermediatelevelkit. Ifcareistaken,you shouldhavenodifficultybuildingit. Iwouldpegthe
assemblytimeat about8hourstotal,alongwithsomereadingthrough themanualinadvance, and sometimeforcalibration.Takeyour
time, and double-check yourwork.Itissomewhatdifficulttocleanlyremoveincorrectpartswhichhavethermalgroundpadsonthem.I
foundinthemanyboardsI haveassembledthatthethermalpadswillaccept solderwellifyouplacethetipoftheironatthejunctionof
thepad andwire. Extraheat mayberequiredonthesepads,however.Iplantoeliminatethethermalpadsonthetopoftheboardand
add moreviastocompensateonfutureboards.
