2) crip the two potted inductors at the end opposite the

7oo -Hz
ASSEI'IBLY PROl]EDURE FOR/UI{
l)
FILiER USiNG POTTED
ii]DUCIORS
fc. the follcwing par-ls bcfor.e s:arting the kit assqrbl:j
(a) a white gx4:tz-inch caj:dbcarC bcx ccnlaining a lr,.rlrj:ed DFm sHttch
riith four leads altacheC arC a 1/4" phone jack trstalled on lhe box slde;
(b) a separate cardbcard base tsq)ci:an li ]nstalled in Lhe bcx ,.rith five
pre-wired pclted rnductcr:s '*lth r.atchrog capacitcr:s and +-',o g/200-clnn t!.ar:ifcrners;
(c) tn-o separate arrd LnpotteC g6-r,q loroidal rnCuc+_or:s to be npdified by
rerpving turns lo 91ve the inductarce valuei r.eTrired bi L2 and L4;
(d) a l/4-rnch rnonc-phore plug axd cable;
(e) iour ::'rbber burpers ijrstalled cn the bc+-+-on o: lhe bcx;
(f) '.wc resislors for RI taped to the inejde of lhe bon cover; and
(g) a four-page set of asssnbly instructions.
2) crip the two potted inductors at the end opposite the
traisformers and firmli l:.ft up +-he assenrbly on the cardboard base.
Renove the carCboard base//inductcrs fron the box. L2 6 L4 are easier
tc lnstall with the cardboard base and induclors cutside cf +-he bcx.
3) For the L2 inductcr moCification, lahe one of the two unpotted
tcroiCal ioductors and nole that it has t,*c windings cn opposite
halves of the core lrjth a start lead (with sleeving) and a finish lead
(no sleeving). Using the fiaish leaCs on both windings, remove s5
turns from one winding and 55 turns from the elber Hinding (total
turn. removed: 130). On lhe leads with sleeving, carefully scrape the
filn insulalion until you see copper. cut the two finish leads to
abou! t'rc inches 1ong arld carefully scrape off the insulation to
within one inch of the Hinding. To mahe the center-tap, solder the
start Iead ot one'rinding to the finish lead of the other winding.
4) Modify the other indr_rctor in the same way for L4.
5) Using cE silicooe sealant, the two nodifled inductors, L2 and
L4, are glued side by side to the cardboard base I/4', behind L3B and
L3C, respectii'e1jl. CE silicone sealant is available in a 2.8 FL oZ
tube labeled "Household clue, CE Silicone I, IOOg Siticone Rubber
sealant, cIear," and stocl<ed in hardrare stores for g3 per tube. Lay
two circular beads of silicone eealant behind L3B and L3C and press
the L2 anC L4 inlo the sealant. position lhe inductcrs so the sleeved
leads can reach and be soldered to the two joined leads of C2 and C4.
The other tpro leads of the inductors are soldered to the open leads of
C2 and C4. See lhat the inductcrs do not move for about one hour unlil
the silicone sealanl sliffens. .q fuil cure occurs after 24 horrr.
6) connect the yellow ilrire from C3 (node 4) to the center tap of
L2. connect the orange wire from the junction of L3 and L5 (node 6) tc
the center-tap of L4, See Figures I and 2 for the node locations in
the schemalic and pictorial diagrams.
This completes the wirrng of lhe inductor/capacitor assembly.
Chech
-
114 -
(7) Return the cardboard base/inducto!: assembly to ihe box.
Insert the base so +-he end ,;ilh lhe lransfor:ners sliaes under the DPDT
swilch and then 1c*e:: the oppcsite end uj:lil 1t fu1tj, serts cn ihe
bo:tom of '-he box. lthtle lcHering the base, iush it torarCs lhe
side
wiLh Lhe phone jacJ: tc leave a 1,/9" cpenlng ajong lhe cpposite
si.le +_c
allc* lhe cover I1a:.rge tc fullj: seal tn lhe bcx.
9) Inser.t the phore plug cajrle th::ouqh ihe hole under ihe phcne
jacl. so that the sclid blacl< leaC has sufficien+_ length tha+_
i+- can
ccnnec+- to the grcunC 1ug of the phone jack. Eefcre sclCe;.ing
the
ground lead, tiqhtli wrap and tie scme lactng ccrC arcund the phcne
plug cable just insiCe the bcx to sei:ve as a s+_rain re.liei. Thei
the insulation off lhe solid blacl: lead of the phone plug ccr:d andstrip
crinp it 1n the hole of the jacll gr:ound 1ug, but do nct solder. as yer-.
S+-r1p the insulation from the t,rc transformer black gr:orxrd leaCs
aad
fr:om the L2/L4, c2/c4 single black ground reec and lnser+- these
three
leads intc lhe ground lug hcte cf lhe phcire jack. This completes al1
the grcuqd lead connections and they nolr may be soldered.
9) Connect the two leads from the bottom termioals ct the DPDT
switch to the B-ohm.rinding leads of T1 anC T2.
f0) Connect the lead from the s,ritch center terrninal next to T2 to
the lip lug of the phcne jack;
11) Connect the teaC from lhc other swilch centcr termrnat n.:xf to
TI to the phone plug cable with a white tracer. Mal{e a slrnple
connection of these two wires by tlristing the stripped end-together,
scldering them and then taping them to the sl.de of the box.
12) Tack solder one of the resistors provided acroes the top
terminale of SWf. Do not crilnp the leads because it may be necessary
to change the resistor until a suitable r,,aIue gives equal headset
voiume with the filter in or out. SLart with the 6.g_chm iaesistor as
Rl. If the audio volume is too loud l'ith fitter out (DPDT switch in
the down position) increase the resistance of RI untit the audio
levels are similar qith the filter in or out.
13) This completes the wiring of the filter l(it. Checl< the
ccrreclncs5 cf your wjring bi. comparing the mcasurerl node_to node
resistances (see Figs l and 2 for node localions) against the values
listed in Table l. Figure 3 shows the filler atteouation response.
14) Perform an aural checl. bi. ptugging the phone plug into your
receiver wilh the filter OUT and listening in your headsel while
tunirg in a ctl signal and adjusting r_he to:re for a ?OO-Hz note. l/t1th
the f1ller OUT tune on either gide cf the CI,t srgna1 and note that lhe
Cll audlo level does not change. Srrtch the filter IN and repea! lhe
procedure and ycu should hear significant altenuation at irequencies
belos and above the frequency cI the clt signal, This compleLes the
aural checj< of the CW iilter. your filter is now ready to use.
-214-
A E
1l: .+ll
Lr
r1
']I
ll
FiglJre l. Sche.oat ic diagrer llnd c€nponent values cf the 7OO-HZ Cy/ filter.
C1, cS = 0.630 uF L'1, L5 = 82 nll
C2, C4 = 1.00 uF L2, L4 = 51.? nf]
C3 = 0.210 uF
L3 = 246 nfi
f ig 2. pictorial d jagr$1 of lhe filter
a53scblv
rhe encircled
.r.,_"
n-t..i
rsrv,\, r,
Node-+-o Node Pesi5loj1ces
the 700-t'l: C{ Fi lter
cf
Nodes
Ccnponent Res i stance
Designation (otnE)110E
G'lD T1 Hi-Z wtnd:ng- 12
cl']D L1 + 1/2(L2)
to.7
6rD
L2
5.2
3{D
1/2(L2)
2.6 2_a
O.rD L3 + 1/2(L4)
26
F.cm To
1
2
3
4
5
7 G'lD
L4
B G,rD L5 + 1/2(L4)
I e.D T2 Hi-Z windins
2 4
L1
56L324
58L5e
? 3 L1 + 1/2(L2)
a 7 L5 + 1/2(L4)
5.2
1O.7
12
I
10.7
10.7
NCTES:
1.
Sec l.igure5 1 and 2 for the
rrode locations.
check your wi.ing using thc
fi lter
2.
reci5tonce value: in Lhi. Lible.
lf there is a significant difference between your ftEasured values
and the teble valucs, you have a
wiring error to find 3nd correct.
3, For accurate nEasureflEntg
Lrse a digital olrnrEte..
-314-
tn"",-i;'t;;;Jl"
6C
1r-lE
l1:l
l-+F
=
-1--L
,
RELATI\€
ATTENUAT
lol,l
(l6r trs.fom.s)
of a 5-Re5onator 700-11: c1{ Filter
re$ured i. q 215-olr test .y.tdBy: €d wetherhold, |V3NON, Anrcpoli., lO
0916 20 FEB ?003
E€
five 3?{tl lott€d
ltdr cl,t tilter
inductor! ad tro nEdified 35-fttl indu.tors
in a five-re56ato( iilte! cirdit.
rEL:(4r0) ?63
Cl,5:
,530 uF, c2,4= 1.0 0F,
L1,5:
3?
c3:
,210 uF
: 51,? trtl, L3 . ?c5 rfl
tilte! rE L€.i !.0 &, 3-& Bn: !?4 Ez
trtl, 12,4
3. Measured relstive attenuation of
700-Hz Cl{ filter. The 3-dB BIV is 274 Hz.
Figure
- the
DESI0N & FILTER
ED WETHERHOLD,
KIT
ASSE|IBLY BYr
W3NQN
Cotlyn Pl, Annapolis, t1D 2140'1
TEL: (410) ?68-0915 26 |'IARCI-I 2003
1426
-414-