4
Building the Transmier
Y u will have n 5ced that this is a rather unusual kit. It has a printed circuit b ard
with ut any h les. We call it “Limerick C nstruc5 n” because it was designed by Rex
Harper, W1REX, f Limerick, Maine. It is a surface m unted b ard in that the c mp -
nents are m unted n the surface f the b ard, alth ugh the c mp nents used are
“thr ugh-h le” parts. This all ws f r ease f c nstruc5 n and easy c rrec5 n f any
err rs. The main b ard als has the fr nt and back panels f r the transmier. They are
sc red and can be snapped ff the main b ard. We suggest y u sm th the snapped
ff edges with emery paper r an emery b ard. The c mp nent parts are s ldered t
the t p surface f the b ard using the leads that w uld g thr ugh the b ard n a
c nven5 nal printed circuit b ard. The interc nnec5 ns between the m un5ng pads
are ready made but hidden by the black screen printed verlay. The designa5 n f all
the parts is printed next t the appr priate pads. Each sec5 n f the transmier
(OSCILLATOR, DRIVER, FINAL, LOW-PASS FILTER and KEY SWITCH) is als marked n
the b ard. The MUTE circuit c mp nents are m unted n the back panel. Any refer-
ences t t p, b m, le4 and right assume that the b ard is held with the printed text
the c rrect way, with the G-QRP Club l g in the centre right. T p is actually the Rear
f the finished b ard, and b m is, f c urse, the Fr nt.
It d es help t set ut all the c mp nents in the rder
f designa5 n. i.e. C1, C2 etc. The best way is t use a
small piece f p lystyrene t h ld the individual parts.
If y u are g ing t use this idea f r semic nduct rs, a
piece f aluminium f il wrapped r und the p lystyrene
will prevent any sta5c damage. D uble check the ca-
pacit r values—there is a l t f difference between a
101 and a 104 capacit r!
The building f the transmier d es entail winding f ur
c ils n t r id c res (TR1, and L4, L5 and L6), and an RF
ch ke f r the PA wired n a pig-n sed bin cular c re
(L2). The c res are the small rings that l k like miniature “P l Mints”. L1 and L3 are
pre-w und ch kes (c ils) that l k like fat resist rs. Winding the c ils is n t difficult; it
just requires a lile care and the accurate c un5ng f the number f turns. There is
ample guidance in the pages f this manual. It is a g d idea t wind TR1 bef re begin-
ning t add any ther c mp nents t the b ard. It is the m st difficult f the hand-
w und c ils as it has tw windings, a tuned winding and a smaller link winding.
TR1 is w und n the FT37-43 c re. This is the black c re - the ne with ut the yell w
c a5ng. The primary winding has 25 turns f the g ld wire. There is guide as t h w
t wind these n the next page. Each 5me the wire passes thr ugh the h le f the c re
c unts as ne turn. The turns sh uld be laid side by side and ccupy ab ut three-
quarters f the circumference f the c re. The link winding is 5 turns f the red wire
w und ver the centre f the main winding. Placement f the link winding is n t t
cri5cal – just guess the centre p si5 n.
