The spread spectrum system is a type of encryption, that makes
converstation or content very difficult to monitor using a scanner.
The voice signal is sent digitaly over an array of frequencies in
segments, or sent digitaly on one carrier, but split in to phase
shifted sements. In either case, there is a key value for the
tracking of the signals in order to decode them. The contents may
also be encryped in their content. There are different levels of
spread spectrum. http://www.sss-mag.com/G3RUH/ will give some basic
technical information about spread spectrum processes. Even with the
home type cordless phones using this system, it is very safe to give
out credit card numbers, and talk about personal things. A number of
years ago the spread spectrum system was limited to military use only.

As for the 900 mHz phones verses the 2.4 gHz phones, the 2.4 gHz units
may be suseptable to interferance if used near to a microwave oven,
and some types of computer systems. Normaly, I would not want to
mount the base unit of any phone within about 3 to 5 feet of a TV set,
microwave oven, or computer. Using the handset to within about 2 feet
to a microwave oven may produce some interference in the phone.

The 2.4 gHz phone will normaly have more range for the same amount of
power than the lower frequency phones. They are more expensive, and
the low cost ones are generaly not very good. The 900 mHz phone is a
better value if you want to stay in a low budget type of phone.

As for the 2.4 gHz units, the battery in the handset tends to not last
as long as the lower frequency phones when in use. These generaly draw
about 20% to 30% more power from the battery when in use. Therefore,
there is less talk time. During standby, the power consumption may be
about 10% more. This is why the people say they can talk longer on
the 900 mHz units.

If the battery is allowed to run down about once or twice a month this
is good for the battery, and it will not have the tendancy to easily
develope battery memory problems. On the average, the cordless phone
batteries will last about 2 to 3 years, if they are let to cycle down
from time to time. If you keep topping up the batteries all the time,
or leave them on charge constently, it will wear them out faster.
Many of these phones do not have very high quality charge regulation,
and after the battery is on charge for too long, it may be slightly
over heated. The expression we use is the customer is "Frying The
Battery".

In the cordless phones, from what I can see from the point of view of
servicing a few, and using a number of models, I found the Panasonic
units to be excellent. Some models of the Seimens are also excellent.
The Sony ones are also very good. I found the lower cost ones to
generaly be more noisy, and more suseptable to have fadeout, or less
stability. There are some very good models made by V-Tech, GE, and a
few others, but their pricing comes close to the previously mentioned
more expensive names.

In any model, it is good to have spread spectrum, or some type of
encryption. This will ensure that the conversation on the phone is
private. There are many sophisticated scanners on the market that
anyone with some extra dollars can purchase. Your cordless phone
range is limited to itself due to the lower cost of the technology
employed. You would be very surprised to know how far it is really
radiating if you were to use a good quality scanner.

Some of these phones can be picked up by a scanner as far as several
miles away! It is more comfortable to know that when someone tunes in
your phone on a scanner, all they can hear is a bunch of data noise,
and not a conversation, or not to be able to connect up an A/D
converter of some type and start to listen to what you are talking
about! For privacy, encryption, or at least spread spectrum is a must!

As for safety, all phones sold in the UK, EC countries, USA, Canada,
and many other associated countries must meet very strict
specifications for radiation from radio frequency emissions, and
electrical safety.

Some of the frequency bands are just above or below cell phone
carriers, and or amature radio bands. There normaly should not be any
interference, because the newer phones are generaly designed with
intelligent frequency selection, unlike the much older models. They
are in their own alocation of freuquency bands. They also should not
interfere with each other.

At this time, I would think that the 5.1 gHz phones are not such a
good investment, unless you specificly have a use for this level of
cordless phone. It is supposed to be a cut better than the 2.4 gHz
phone, and should not have any interference from microwave ovens, and
or the TV set, or even the computer. But, the cost is very high at
this time for the small difference.

Jerry Greenberg
http://www.zoom-one.com

--


lcoe wrote in message news:uATQa.69453$Ph3.7172@sccrnsc04...
Followup-To: sci.electronics.repair, also, FF:2lbs of TacoBell Condiments (you haul ;-)
.........

i am looking at some of the newer Uniden offerings w/two handsets and
wonder how much/if i will gain anything over my current setup which
actually works well(900Mhz SS Vtech) these past 5yrs. the batteries
are finally dying so have an excuse.

there is a plethora of new frequencies, with some advantages to each,
including 2.4, 2.4DSS, 2.4DEST, 5.4 in about that order of cost/performance.

so the Question: the range maybe less on 2.4 and i do _not_ have a problem
w/interference, does it make sense to make just one step up? ALSO, does
Spread Spectrum mean "digital handset" link by definition? if yes, i would
be going back to analog w/2.4Ghz.

Thanks (!) to my favorite (3) ng's, --Loren