Subject: Help needed with my A-level project - RF link
Date: Fri, 1 Nov 2002 20:02:52 -0000
NNTP-Posting-Date: 1 Nov 2002 20:02:55 GMT
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I'm an A-Level student who is currently contructing my end of year project.
I intend to
build a simple RF transmitter, and reciever to send digital data. The
digital data is going
to have a maxmium frequeny of about 500KHz, and the carrier is going to have
around the 50MHz mark (Is this an approiate frequency? Tell me). The data is
going to be
amplitude modulated onto the carrier wave,as this is within my ability.
Currently I intend to use a dual gate JFET ( the only FET with two gates in
our school) to
mix the LO with the digital signal. After this I'm going to put a bandpass
filter which will
reject unwanted frequencies created by the mixer. Then the signal is going
into the input of
an amp, then to an antenna. This is hopefully the end of the transmitter
section of the
project, tell me otherwise.
The reciever is going to consist of a tuned circuit, to only accept the
frequency my data is
on, then it is going into a mixer. The mixer will be a dual gate FET, and
will have an input
from a LO and the RF signal, so that the output after it has been filtered
will have a lower
intermediate freqency. This intermediate frequency will then be fed into a
demodulate the AM signal into a digtal one. Then the siganl will be fed into
trigger to clean up the signal.
I want to know if the approach I going to use is approiate for this project,
and if not i
want to know where I am going wrong.
The data I'm going to be sending is going to be in the form of 8 bits at a
time. So for
example if I send BYTE A:"1 1 1 1 1 1 1 1", then send BYTE B:"0 0 0 0 0 0 0
0", how can I
prevent the reciever from picking up a mixture of BYTE A and BYTE B (e.g. "1
1 1 1 0 0 0
0")? Will i need to synchronise the digital clocks on the transmitter and
As an A-Level project, it does not have to work properly, or work at all.
What I want is to
get the theory behind the project correct, and have a basic schematic of all
which make up this project, e.g. mixer, filter, amplifier.
I would appreciate any comments on how to improve this design, or any help