Ramsey Electronics Stereo System RXD433 User Guide

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!  
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.  
 
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  
 
RXD-433 4  
 
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  
 
RXD-433 6  
 
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  
 
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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