DEM5O-28CK $29s

6M Transverter Kit
Description& Requirements

The DEM50-28CKis a 50 Mhz. transverter

kit with a 28 Mhz. IF. It requiresa 13.'lY,
5A supplyand a TXIF drive level between+0 and +23dbrn.The cornpletekit consistsof 3 sub-
assemblies.
ThernainPC boardassernbly, (DEM50-28K),thehybridpowermodule,(M57735), andthe-
kit, (DEM50-28HK).Eachsub-assembly
hardware may be purchased separateor in any combination.

DEM50-28K (Main PC board assembly)gl75

The PC boardassernbly is aprox.3.5" square.It is cornpletely

assembled
with surface
mountconstruction. Theboardis alrnost"NO-TUNE'.Theonly adjustrnents thatmayneedto be made
wouldbetheLO frequency andtheRX pre-ampandthisshouldonlybea tweaktbr everyDEM50-28K
is factorytestedto meetthe following specifications:

100rnw outputpoiverat50 Mhz. with +0dbrnof 28 Mhz.IF drive.(400mw Inaxoutput)

> 1 7 d b c o n v e r s i ogna i n ( 5 0 M h z . t o 2 8 M h z . ) w i t h < 1 . 0 d b N f
L.O frequencywithin + l- | khz.(22 Mhz.)
All spuriousernissions

The DEM50-28Kcontair,rs
the following built in featUres:

Ad.justable TXIF and FO(IFattenuation.(approx. 23 db rarrgc)

Higlr level rnixer.(t-11 dbrnLO)
GaAs FET RX pre-arnpbiasedfor a high 3rd order intercept.(Crunch-prciof'!)
Separate IF and RF inputsand outputs.
'fR
Relaycontactsfbr exrenlal switchingor biascclntrol.
All necessary circuitryfoi"theM57735hybridto provideapror. 20 rvattsof linearoutput.
Built in power lneterfor easeof set-upwhen usedwiih M57735 hybrid.

DEL-50-28HK (Box and hardware kit) $45

Although the DEM50-28HK i, llo, ,,"..r.ury tbr the operationof the transverter,it does
rnakethe cornpletionof the transvertervery easy.The contentsof the kit are as follows:

i - Hanunon{i159088castaluininulubox. (pre-drilled)
1 - H c a t - s i n ka p r o x4 . 5 " s q u a r ex 3 4 " h i g h . ( p r e - d r i l l eadn d t a p p e d )
4 - BNC paneljacks(IJG 1094U)
3 - RCA paneljacks arrdgnd. lugs
4 - fiber v/ashers
4-4() hardwarefor PC hoard installation
6-32 ltardwarefor hvbrid instaliatiolr
J

N o . 1 8 s o l i dw i r e
3 - lil00 pl'capaciii:i's
 ASSEMBLY INSTRUCTIONS

The assenrblyinstructions
assume thatyou havepurchased the DEM50-28CK,whichis
rhecomplete kit with PC board, hardware kit, and M57735 hybrid. Pleasereadall instructions
and
familiarizeyourselfwith the components,procedures, If you wish to usethe optional
anddiagrarns.
Pin Diode T-R switch (DEM50-28KPS) pleasefollow thoseassembly now.If not,continue.
instructions

1. Mountall off the connectors in the pre-drilledbox. Followthe diagrambelowand

startwith the RXIF connector first. lnstallandtightenthemoneat a time. Be sureto installthe
gnd. lugson theRCA connectors on the insideof the box. AIso, if theoptionalPin DiodeT-R switch
is to be used,installthe 3/8" gnd. lug on theTXRF BNC connector.

T O 7 W/ O U T C C V E R

OOOooOo
3/8" 3/8" 3/b" 1/4" t/ 4" 3/8" 1/4"
R Xl F RXRF T Xl F KEY AUX TXRF*13.7v
DNC DNC DNC RCA RCA DNC RCA

2. Placethe PC board insideof the box, then cut and fit the brassstrapsthat will
attached thehybridmountingscrewsto thePC boardmountingholes.Drill clearance holesin bothends
of the brass.Beforemountingthe PC boardin the box, checkfor any straymetalin the box or metal
that may be stuckto the bottomof the PC board.Also checkfor any leadsof componentsthat may be
protrudingthroughthe bottornof the board. Now nrountthe PC board, ind hybrid to the box
and heat-sink.Remerrberto placethe fiber washersbetweenthe PC boardandbox, andto applysome
thermalcompoundto the hybrid beforeboltingit into place.The thermalcompoundis important
becausethehybridwill needto dissipate aprox.30 - 40 wattsof heatwhenit is runningat full power.

3. Usingthe boarddiagrarn,rnakeall necessary RF and IF connections to the BNC

connectors usingthe #18solidwire. If you areusingtheoptionalPin DiodeT-R switch,do not attach
the RXIF and the TXRF connectors.Keepthe connections as shon as possible.Connectthe Red wire
to the 13.7VRCA jack andconncctthe Blackwire to the groundlug on the sameconnector.After
decidingwhichkeyingscherreyou will be using.selecteitherthered/whitewire (PTT to GND) or the
white/bluc(positivekeyingvoltage.4-15vdc)andconnect it to thecorrectRCA.iack.ThelastRCAjack
is for the aux. contactsin the relay.Its Your choice! Wire it tbr Norrnallyopenor closedduring
transmit,or don't usedit at all. Thenfinally installthe 1000pf capacitors on all of the RCA jacksto
ground.Theywill bypassRF from the DC lines.Recheck all of you connectionsandbe sureall of the
hardwareis tight.Trirn andSolderthe leadsof the hvbridlast.
 TEST AND OPERATION

Unlessyou havedamagedthe PC boardduring assembly,it shouldbe readyto fire up!

Make the appropriateconnections betweenthe transverterandyour 28 i|'dhz.IF rig. Connectthe 13.7V
to a power supplyor batterythat can supply 10-15VDC @ 5A..Terminatethe RXRF connectorwith
a 50 ohm load of somesort. (Ant., signalgenerator, 50 ohm pad, etc.) and listenfor noisein your
receiver.The noiseshoulddiminishwhenthe loadis disconnected. You cannow adjustthe RXIF pot
to minilnizethe RX noiseleveland to keepyour "S" meterat a reasonable level.Again this is your
preference. Now testtheTX side.Connecta dummyload,powermeter,or Ant., thatcanhandle30{
watts, to the TXRF connector.Then pre setthe TXIF adjustmentpot for maximumattenuation.(turn
it full clockwise)Key your if rig and listen for the relay to click on the transverter.Now slowly
increase thedrive levelon your IF rig while watchingthetwo LED's on thePC board.The first LED
will be at maximumbrilliancearound750 rnw. If you run out of drive controlbeforethe secondlight
comeson, startto adjustthe TXIF pot on the PC board.The secondLED will startto light aroundthe
7 watt level and will max out around15-18wattsoutput.The secondLED will not be as bright as the
first. If everything is OK at this point, thetransverteronly needsa TR switchto completeyour system.
WARNING!!!!!!!!!!!!!! SomeM57735arecapable of producingmorethan30-35wattsof outputpower.
At this level the SSBqualityis undesirable. It is recommended to limit the outputby adustingthe fiIF
attenuatorto somewhere under20 wattsfor phoneoperation.Be carefulwith those"HOT BRICKS!'

OTHER OPTIONS AND IDEAS

1. The TX power LED's may be moved off of the board and mounted in the die cast
box. Justde-solderthem, drill holesto mount them, and run wires from the board to the LED's. Be
sure to bypassthem for RF with a similar cap. that is usedon the RCA connectors.Keep the wires as
short as possible.

2. A ON/OFF switch may be mountedon the box. The red wire from the RCA
connectormountsto the DC inputof the Hybrid andthenit travelsto the restof the board.Disconnect
the red wire that feedsthe restof the boardand connectit to a switch.This will switchoff the circuit
boardbut will leavethe DC poweron the hybrid. That is all that is needed.You could switchoff the
DC powerthat is goingto the hybridbut you wouldneeda switchthatcouldhandle5 Amps min.

If you encounterany problems,pleasecontactthe Down Eastfactoryor me direct. Thankyou for your

purchase, and havefun on the bandsl'73, Steve-N2CEL

DOWN EAST MICROWAVE

9 5 4 ,R T 5 1 9 ,
Frenchtown,NJ 08825
Tol 908-996-35 tt4
Fax 908 -996-3102
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