Amateur Radio Report Card

AUGUST 1965
Curing Distorted
RTTY Patterns
The simplest means of tuning in a RTTY
signal is with a scope. Most homebuilt converters
obtain the mark and space signals directly
from the toroid filters fee ding the d iscriminator,
similar to the circuit of Fig. 1.
However, the main d rawback in using
this method is that the scope p attern is sometimes
distorted as in Fig. 2-A and tuning is
difficult.
0}
:
~
'00 <
A Rl\
FILTER
0 6 6 ETC 21 25 'V
,
VER TlC.lI,L
I,.. PU T
SCOP E
MARl< S1G"'Al,.
,
~
ALA NCE -
.0 3 35 ETC. :::!: _ SPACE
'"
T : FI LTER ,
2975 ""'
DISCRIMINATOR
HoqlZO!IITAL
I...PUT SCOPE
S",,"CE Sl~"'L
•
HE
GROUNDED
(but not quite in time)
F'G
If the converter is working properly an FSK
signal will be only slightly ellip tical, as in Fig.
2-B. In tuning in a mark or space signal the
patterns should be similar to Fig. 3-A and
3-B.
The distortion can often be cured by putting
two IOO-K resistors in series with the
toroid filters feeding the vertical and horizontal
inp ut of the scope.
FIG
2A
FIG 26
CD8
FIG 3.11
FIG 36
SERIES
COAXIAL
RELAYS
$;..
2~4d~••1 Y.
L... thl.. 9 ••.
Another cause can be ringing taking place
DK150 _C2C
somewhere in the unit as a result of poor layout
of the converter. All circuits should be
4 Standard Models, AC or DC,
UHF, N, BNC, TNC or C Conn.
run in a straight line and under no condition
should an input circuit be located close to its
output circuit. Also-remember that aluminum
is a poor shield where wiring is done
close to power transformers, chokes, input .. UNCONDITIONAL
GUARANTEE for
transformers, and mark and space filters, so
one year. (We
keep the low level circuits away from such
will repair If
faulty within 1
hazards.
yea r.)
With care we can obtain the kind of performance
stated in T U designs and our tuning
.. For a eatalot of
complete line of
eouial relays, STANDARD RELAYS:
write :
DK60-2C and DK60-G2C -
becomes a pleasure with a clean scope pattern.
PRICED f"RO-" . . . . $ 12.45
Be N U on RTTY.
. . . K4GRY DOW-KEY CO•• Thief River Falls, Minn.
Outstanding lavorite for a mate urs ... Ve rsatile com ­
binations fo r indust rials! Lo..... \'SWR less t h a n 1.15:1
from 0 t o 500 mc. LOW LOSSES .•• High Contact
Pressures. LOW CROSS·TALK through use o r patented
" isolated connector" a rrangement. HIGH POWER RATlNG.
All coils e nca psuled in epoxy resi n fo r quieter
oper a t io n and r esista nce t o m oisture.
* All R elays available in
weatherproof b oxes fo r
experior installat ion.
* Ga naed. multiple position
switch arrangement aV:Jllat:le
for remob~ contr ol 5eJection
01 antennas.
DK60. DK60-G,