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7/17/2019 A Miniature HF to VHF AM-FM Receiver Using the NE605
http://slidepdf.com/reader/full/a-miniature-hf-to-vhf-am-fm-receiver-using-the-ne605 1/2
BY
IRWIN
MATH, WA2NDM
MATH S NOTES
WHAT'S NEW AND HOW T USE
IT
A Miniature
HF
to
VWF
AMIFM Receiver Us ing the NE6 5
t seerns that every time we preserit a
circuit for a miniature receiver we get
lots of rnail, most of which is con-~pli-
tary an d indicates that this type of pro-
t "tickles a lot of fancies." I am
xactly why that is, but if that's
o spark homebre wing,
ngs that m ay be applicable to a ma-
portion of the hobby is, after all,
this mo nth we are pleased to pre-
The Signetics (now Phill ips) NE605 is
r m ixerilF amplif ier integrated
e used as the heart of a sim-
circuit to be described,
ip, will enable you to construct
and FM receiver that can
sed for local moriitoring or for casua l
le entry-level com-
ications receiver. Before proceeding,
ver, be aware of the fact that this is
edium -perform ance circuit, not the
F to 50 0 MH z for the front end is
sible, the noise figure is only
ly will not be received a s well (if at
) as with your H T or standard comm u-
low-noise tuned pre-amp ahead
he NE6 05 will obviously increase per-
but that will not be covered at
internal circuitry, limiting opera-
rna l local oscillatGr will be;equired for
t ime. However,
microprocessor-
igher frequency single-channel
imitations men tioned in mind , a very sim-
le receiv erth at may suit man y needs will
Fig.
1
is a schematic of the simple, sin-
AM receiver using
CQ
magazine
'
OpF
= 001
ceramic
L1
C1
resonate
t
desired
operating frequency
cerarnic filters
L2 CZ
esoriate at Vcc
55 KHz
below desired
operating frequency
Fig.
1 Simple HF to V HF AM/FM receiver.
necessary: the input, which will provide
sorne deg ree of selectivity, and the loca l
oscillator, which should operate at 455
kHz below the desired input frequency.
Choice for the absolute values for these
circuits will be left to the expe rimenter and
probably will be dedicated by what is in
the junk b ox. The two items labeled F L I
and FL2 are common, low-cost 455 kHz
ceram ic filters design ed for AM rad io use
and are readily available.
In operation, signals received by the
antenna are applied to the input of the
NE605. This input goes directly into an
internal mixer stage, which accounts for
the higher noise figure. Also a pplied to the
mixer is the lo cal oscillator o utpu t, the fre-
quency of which is determined by the set-
ting of L2-C 2. The difference be tween the
two is the IF frequency, 455 kHz, and the
two ceramic fi lters are u sed to provide a
narrow p ass-band IF amplif ier at that fre-
quen cy. You will note that the local oscil-
lator is tunable. If fixed frequency opera-
tion is desired, C2 and its parallel padding
capacitor can b e replaced by a crystal of
the appropriate frequency. L2 and the
,001 IF capacitor, however, must be left
in. If you use the variable-oscillator ap-
proach, be sure that C2 and its padding
2
CQ
August
998 Say
You
Saw
It n Q
7/17/2019 A Miniature HF to VHF AM-FM Receiver Using the NE605
http://slidepdf.com/reader/full/a-miniature-hf-to-vhf-am-fm-receiver-using-the-ne605 2/2
ke the tuning range too wide will result
ty. Keeping the range to 1-1.5%
The 270
p H
coil and 390 p F capacitor
o pins 10 and 11 form a quad-
ignal and provides recovered audio
7 is usually use dfo r a received
th me ter. As a result, its out-
o the incoming signal am plitude.
s output m akes a neat AM detec-
the AM a nd FM audio ou tputs
e are used to equalize
An LM386 au dio ampli-
e entire receiver operates from
ed from a 9 volt
is
tput level.
When building the circuit, take ca re to
ans short leads, keeping input and
ay from each other,
So-cal led dead-bug or
construct ion methods are f ine as
re careful. Overall results are
nt to a great degree on layou,t so
careful.
The com pleted receiver can be m ount-
ve the local oscilla-
equency may leakth roug h. This is the
Q that
tracks the local oscillator can reduce this
but that's some thing you will ha ve
play with. Regardless of what your
the NE605 is a chip worth
ith.
As a final note, we have not purposely
ed exact layouts or bills of mater-
whole point of building such a circuit
to cut an d try until you acheive results
8
1 East Arques Avenue, Su nny-
88-3409. Good luck and let
ow of your results.
73, Irwin, WA2NDM
It s a different kin d of ham m agazine.
Fun to read, interesting from cover to cover, written so you c an unders tand it. That s CQ. Read
by
over
90 000 people each mon th in 116 countries around the world.
It s mo re than just a maga zine. It s an institution.
I
CQ also sponsors these fourteen world-famous award programs an d contests: The
CQ
World-Wide
DX Phone and CW Contests, the
CQ
WAZ Award, the CQ World-Wide WPX Phone and CW Contests,
the CQ World-WideVHF Contest , the CQ U SA-CA Award, the CQ WPX Award, the C Q World-Wide
160
Meter Phone and C W Contests, The
CQ
World-Wide RTTY Contest, the
C Q 5
Band WAZ Award,
the CQ DX Award, an d the highly acclaimed
CQ
DX Hall of Fam e.
N o C o m p r o m i s e C o m m t r n i c a ti o n s
Q u i c k
M o u n t S y s t e m
f o r
m o b i l e H F I V H F u s
e
The
QMS
is rated for use
on
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7
miles 120km)
per hour.
GO-MOBILE ith QMS
The
Q M S
a mo bile system w hich is easy to instal l, i~npl-oves adiat ion
eff ic iency and provides frequency ag i l i ty witho ut m anu al adjustments. Th e
Q M S can be quick ly instal led for permanent or temporary use wi th out dam-
aging the vehic le 's f in ish. N o dr i l l in g or modifications are required, and
industrial suct ion cups, high strength straps and buckles give structural
integr i ty to the instal lat ion. Al l QMS systems inc lude an
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antenna. Fo r 100 ,200 or 500 watts, choose the Q M S w hich f i ts y our requ ire-
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QMS b2
cat. 55-47
includes the
SG-230 (200W),
1.8
to 30 MHz SG-303 9 H.
antenn:t
Q M S a 7 c a t .
55-49
includes the
SG-231
(1 0 0 W) . 1 .0
to MHz SG-307
7 St. anten na
OMS b3 cat.
55-48
includes the
SG-235 (500W ) . 3 .0
to
30 MIHz SG -303 9
ft. a n te n n a
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1 8 0 0 2 5 9 7 3 3 1
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SG C Inc . , P .O.Box 3526, Bel levue, 98 9 US
Te l : 425-746-63 10 Fax : 425-746-6384 or 425-746 -7173
Say You Saw It In CQ
CIRCLE 71
ON
READER SERVICE C RD
August
998
CQ
5