WIRELESS RF LINK
RECEIVER/DECODER
MODULE
Ramsey Electronics Model No.
RXD433
Need a data transmitter or receiver for your remote wireless
application? These compact units are perfect for any project;
car alarms, door openers, home security, you name it!
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SAW Resonators for high stability – no drift!
Compact size with low current demand.
433 MHz license free band.
Sensitive superhet receiver with RF LNA.
Automatic tuning – no manual adjustments.
Operates on 5 volts DC.
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THE RXD433
This wireless RF receiver/decoder has a 4 bit data output that will match the
data sent by the encoder, TXE433. The output is CMOS compatible when
the unit is run on +5 volts.
The demod bandwidth is selectable by the placement of jumpers on the
circuit board. The table on the schematic shows jumper positions for
different bandwidths. Narrower bandwidths will give slightly better range at
the expense of more limited constraints on battery voltage tolerance over
time and more limited operating temperature range. For most applications,
the 4800 Hz setting will be best.
The “decoder address select” allows you to use one transmitter to control
different receivers by giving each receiver a unique address. The decoder
chip has internal pull-up resistors making it a simple matter of grounding the
address select pins to match the grounded pins on the transmitter/encoder.
These outputs are also CMOS compatible when run on +5 volts.
The receiver/decoder unit additionally has a “data valid” output. This output
goes high when the “decoder address select” matches the encoder’s
address select. This is convenient place to connect a “data valid” LED
indicator to show at a glance when the receiver is decoding. The schematic
below shows how such an LED can be connected.
ANTENNA CONSIDERATIONS:
The simplest antenna consists of a piece of wire approximately 6 to 7 inches
long. If you desire more range you can try a ground plane antenna or a
Yagi such as the Ramsey 4004 model. The antenna should be tuned for the
433 MHz band for best operation.
RXD-433 • 3
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RXD-433 • 4
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Data lines: Access your data here.
Data output will match data input to
transmitter.
DV: Data Valid line. Attach your op-
tional LED circuit or other data valid indi-
Address lines: Ground individual
lines to match transmitter address
lines.
GND: Attach
your power
supply
ground
here.
V+: Attach
your +5 volt
source here.
Demod bandwidth select: Jumper as
shown in chart on schematic to change
bandwidth
Antenna: Attach your
antenna here.
A0 through A7: These are the address lines. Individual address lines should
be tied to ground to match the TXE-433 transmitter address lines. Lines not
tied to ground can be left open.
A through D: These are the data output lines. The output from these lines will
match the input to the TXE-433 transmitter data lines.
DV: Data Valid. Output goes high when the “decoder address select” matches
the encoder’s address select. See text on page 3.
RXD-433 • 5
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RXD-433 • 6
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The Ramsey Kit Warranty
Please read carefully BEFORE calling or writing in about your kit. Most problems can be
solved without contacting the factory.
Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too!
All Ramsey kits will work if assembled properly. The very fact that your kit includes this new man-
ual is your assurance that a team of knowledgeable people have field-tested several "copies" of
this kit straight from the Ramsey Inventory. If you need help, please read through your manual
carefully. All information required to properly build and test your kit is contained within the pages!
1. DEFECTIVE PARTS: It's always easy to blame a part for a problem in your kit, Before you con-
clude that a part may be bad, thoroughly check your work. Today's semiconductors and passive
components have reached incredibly high reliability levels, and it’s sad to say that our human con-
struction skills have not! But on rare occasions a sour component can slip through. All our kit parts
carry the Ramsey Electronics Warranty that they are free from defects for a full ninety (90) days
from the date of purchase. Defective parts will be replaced promptly at our expense. If you sus-
pect any part to be defective, please mail it to our factory for testing and replacement. Please
send only the defective part(s), not the entire kit. The part(s) MUST be returned to us in suitable
condition for testing. Please be aware that testing can usually determine if the part was truly de-
fective or damaged by assembly or usage. Don't be afraid of telling us that you 'blew-it', we're all
human and in most cases, replacement parts are very reasonably priced.
2. MISSING PARTS: Before assuming a part value is incorrect, check the parts listing carefully to
see if it is a critical value such as a specific coil or IC, or whether a RANGE of values is suitable
(such as "100 to 500 uF"). Often times, common sense will solve a mysterious missing part prob-
lem. If you're missing five 10K ohm resistors and received five extra 1K resistors, you can pretty
much be assured that the '1K ohm' resistors are actually the 'missing' 10 K parts ("Hum-m-m, I
guess the 'red' band really does look orange!") Ramsey Electronics project kits are packed with
pride in the USA. If you believe we packed an incorrect part or omitted a part clearly indicated in
your assembly manual as supplied with the basic kit by Ramsey, please write or call us with infor-
mation on the part you need and proof of kit purchase.
3. FACTORY REPAIR OF ASSEMBLED KITS:
To qualify for Ramsey Electronics factory repair, kits MUST:
1. NOT be assembled with acid core solder or flux.
2. NOT be modified in any manner.
3. BE returned in fully-assembled form, not partially assembled.
4. BE accompanied by the proper repair fee. No repair will be undertaken until we have received
the MINIMUM repair fee (1/2 hour labor) of $25.00, or authorization to charge it to your
credit card account.
5. INCLUDE a description of the problem and legible return address. DO NOT send a separate
letter; include all correspondence with the unit. Please do not include your own hardware
such as non-Ramsey cabinets, knobs, cables, external battery packs and the like. Ram-
sey Electronics, Inc., reserves the right to refuse repair on ANY item in which we find ex-
cessive problems or damage due to construction methods. To assist customers in such
situations, Ramsey Electronics, Inc., reserves the right to solve their needs on a case-by-
case basis.
The repair is $50.00 per hour, regardless of the cost of the kit. Please understand that our techni-
cians are not volunteers and that set-up, testing, diagnosis, repair and repacking and paperwork
can take nearly an hour of paid employee time on even a simple kit. Of course, if we find that a
part was defective in manufacture, there will be no charge to repair your kit (But please realize
that our technicians know the difference between a defective part and parts burned out or dam-
aged through improper use or assembly).
4. REFUNDS: You are given ten (10) days to examine our products. If you are not satisfied, you
may return your unassembled kit with all the parts and instructions and proof of purchase to the
factory for a full refund. The return package should be packed securely. Insurance is recom-
mended. Please do not cause needless delays, read all information carefully.
RXD-433 • 7
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Price: $5.00
Ramsey Publication No. MRXD433
Assembly and Instruction manual for:
RAMSEY MODEL NO. RXD433
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
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