one of the most common problems that can befall
an lcd, in my own experienceat least, is the loss of the displays usefulness
because one or more of the segments no longer darkens. most numerical lcds are
made up of seven individual line segments as shown in fig. 1. the electrical signals that darken these
line segments and thus make up the complete numeral, can be interupted,either
permently or temporarily, by poor contact between the pc board, the elastomeric
connector and the glass lcd itself.
25 wpmc
when the contact is lost, the display can dim,
or one or more segments can completely disappear. if this happens, some people
think that the entire display needs replacing. there's a chance you may not
need to replace the entire dislpay, however. many times the display sandwich
can be disassembled, the individual parts thoroughly cleaned and then carefully
reassembled. i have found that denatured or isopropyl alcohol cleans the parts
well.
20wpma
the term noise limited means that the noise
level in the receiver increased for that measurement in such a way as to cause
the audio output to be all noise with no tone , for a two tone measurement , or
to increase by 1 db , in the case of blocking . practically , the only time it
is a consideration is when you are comparing receivers of similiar performance
levels .
20wpmb
one troubleshooting step is to determine the
power threshold that causes the rfi
before and after each step . if you do something that makes the rfi appear at
50 watts rather than at 20 watts , of transmitter output , you know that you
did something that did have an effect . you can then try a better version of
the same fix , more turns on the ferrite , etc. if this makes an additional
improvement , you are on the right road .
20wpmc
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15wpma
if a rfi problem is caused by rf getting onto
the outside of a transmitters feed line , a filter of this type will help
suppress it . this rfi scenario arises only when susceptible equipment is much
closer to the feed line than it is to
the transmitting antenna . this could happen in an apartment location .
15wpmb
world distance records at 1 0 gigahertz and
higher are all held by portable stations in europe , australia and japan .
properly equipped north american operators could match any of the existing
marks with a careful choice of location and operating conditions . the hawaii
to california path probably provides the best opportunity to extend the 1 0
gigahertz record .
15wpmc
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