Re: The Ultimate Cellphone

bostonresident@aol.com wrote in news:fohss3l45dnu1j66mlfm25e07jii2n9ich@
4ax.com:

> http://www.sparkfun.com/commerce/pro...roducts_id=286

Cool! I like it!

For the beach houses of friends on Edisto Island, SC, where calling the
35 miles back to Charleston used to cost $4.20/min from the rinkydinky
rural phone company that had a stranglehold on the island, I used to
disconnect the POTS from the houses and plug a "data interface" into a
hard-cased Panasonic 3W AMPS cellphone. The interface provided a normal
telephone loop and ringer voltage for all the touchtone phones in the
house, complete with dialtone that was intended to make a phone line
computer modem think it was plugged into Ma Bell. The bagphones were
located in an upstairs bedroom with the best access to the roof, where I
erected a small TV antenna mast with an 11-element 800 Mhz paging
antenna beam pointed in the direction of Charleston, but specifically
aimed to null out roaming to Savannah, GA. This gave the beach house a
Charleston telephone number and no long distance service back to the
city, bypassing the ripoff LD rates from Bubba's Telephone and Tire
Company.

When the AMPS line got a call, the interface rang all the phones and you
simply picked up, as usual, to answer. To make calls, you picked up,
got a dialtone from the interface, then pushed the buttons to dial the
number.

When they left the Beach House, they unplugged the interface and antenna
and put the phone back in their car where it acted as a mobile phone all
week until it was time to go to the beach house again. The benefit to
this was they were charging it off to their businesses, making the beach
house phone bill zero...(c;

Thanks for the memories....I'd love to sit one on a table in a
restaurant with no explanation to anyone, then have it ring and take a
call, just to see the priceless looks....(c;

Too bad the Motorola M800 (CDMA)/M900 (GSM) is such a scam:
http://www.alltelsolutions.com/solutions/m800.html
I bought one on Alltel because they said it would vastly improve rural
coverage over the toyphone V60i I was carrying at the time. It's HUGE,
giving you the ILLUSION of power. The "handset" is the skinny part with
the coil cord. The keypad/display ISN'T the handset, though it looks
like it is. The keypad/display is fixed to the massive unit, making
dialing in the car near impossible with one hand. Voice commands made
it usable. Then, alas, reality set in.....IT'S JUST A TOYPHONE IN A BIG
BOX! The damned transmitter is the same 150 milliwatt toyphone
transmitter the tiny phones uses, not a 3W powerhouse that would make
better phone calls, especially to AMPS towers in the country.

I returned it for refund the next day, quite pissed off it was all a
lie.

I have a full mobile repeater to a high gain colinear 800 Mhz antenna in
my stepvan service truck that DOES give me plenty of power to make calls
in the boonies where I sometimes work. Just walk inside the steel cabin
and notice how your bars climb as you pass through the door...(c;
http://cellantenna.com/repeater/cae50cel.htm
A 9db colinear 800 Mhz antenna is magmounted to the roof outside.
A simple 1/4 wave magmount 800 mhz whip is stuck upside down to the
ceiling over a file cabinet so I don't hit it with my head to couple to
the antennaless toy phone inside.
It turns NO SERVICE into FULL SERVICE, even with data out in the
boondocks...(c;

On 2008-03-05, Larry <noone@home.com> wrote:
> Too bad the Motorola M800 (CDMA)/M900 (GSM) is such a scam:
> http://www.alltelsolutions.com/solutions/m800.html
> I bought one on Alltel because they said it would vastly improve rural
> coverage over the toyphone V60i I was carrying at the time. It's HUGE,
> giving you the ILLUSION of power. The "handset" is the skinny part with
> the coil cord. The keypad/display ISN'T the handset, though it looks
> like it is. The keypad/display is fixed to the massive unit, making
> dialing in the car near impossible with one hand. Voice commands made
> it usable. Then, alas, reality set in.....IT'S JUST A TOYPHONE IN A BIG
> BOX! The damned transmitter is the same 150 milliwatt toyphone
> transmitter the tiny phones uses, not a 3W powerhouse that would make
> better phone calls, especially to AMPS towers in the country.

I see they're selling them in Northern Ontario, Canada, where I used
to live, with the amplifiers intact, though the price is not nice. See

http://www.neilnet.com/Products.asp?pid=67

The rural areas north of there make rural areas in the eastern US look
positively crowded so, while they've been turning AMPS off there too,
it seems like they've also been turning up the output power on the CDMA
towers in really remote areas to make up for that. 3W CDMA is guaranteed
to be better than 3W AMPS.

Dennis Ferguson

Dennis Ferguson <dcferguson@pacbell.net> wrote in
news:slrnfsua9v.4g.dcferguson@akit-ferguson.com:

> it seems like they've also been turning up the output power on the CDMA
> towers in really remote areas to make up for that. 3W CDMA is guaranteed
> to be better than 3W AMPS.
>

No it's not over long distances. FM will work for 100 miles if conditions
are right. No digital signal, no matter what it's modulation scheme looks
like, including CDMA, will make a long trip without timing errors and
multipath reflections causing it to crash. It's just not gonna happen, no
more than a 20 watt wifi running high speed to a big tower at the tv
station.

A good example of what happens is to simply put a new digital ATSC TV set
in your car and start driving towards the TV tower transmitting the signal.
Consumers are gonna be really pissed when they find out digital TV simply
LOCKS UP as soon as the vehicle it's in starts moving because it cannot
tolerate the changing phase-timing errors. No more Car TVs for us!

Turning up the cell site power isn't the problem in the country. The phone
starts out with a 150 milliwatt transmitter into an almost non-existant
antenna. The ERP, effective radiated power, is LESS than .15 watts...MAX!
I don't care what kind of hype you put on it, 150mw on ANY system isn't
going to go far in the finest conditions. Put it in a pine forest on 800
or 1900 Mhz and IT WON'T MAKE IT OUT OF THE TREE ATTENUATORS and digital
sales gimmicks and dreaming won't overcome basic RF physics and
propagation. A toyphone will NEVER give service over a couple of miles in
the treed countryside.

POWER is our friend! Drop by any broadcast station and see our friend
doing what it does best....

On 2008-03-06, Larry <noone@home.com> wrote:
> Dennis Ferguson <dcferguson@pacbell.net> wrote in
> news:slrnfsua9v.4g.dcferguson@akit-ferguson.com:
>
>> it seems like they've also been turning up the output power on the CDMA
>> towers in really remote areas to make up for that. 3W CDMA is guaranteed
>> to be better than 3W AMPS.
>>
>
> No it's not over long distances. FM will work for 100 miles if conditions
> are right. No digital signal, no matter what it's modulation scheme looks
> like, including CDMA, will make a long trip without timing errors and
> multipath reflections causing it to crash. It's just not gonna happen, no
> more than a 20 watt wifi running high speed to a big tower at the tv
> station.

That's silly. I think you probably have personal experience with CDMA
receivers receiving signals over distances and 12,000 or 16,000 miles from
50 Watt transmitters moving fast enough and far enough from the planet's
gravity field that the receivers have to make corrections for relativistic
time dilation effects, since that is what is in a GPS unit (and I'm trying
not to mention the digital signals they're apparently still getting from
Voyager I, which is out of the solar system and probably 10 billion, with
a 'b', miles away by now). The only difference between the CDMA in your
GPS receiver and the CDMA in your cell phone is that the information rate
for the cell phone is a couple of hundred times higher.

The comparison between CDMA and FM (or anything and anything) is all basic
math. In both cases you have transmitter power, transmit antenna gain,
path loss and a receiver antenna gain, and since RF is RF in both cases
the only modulation-dependent question becomes, do you have enough signal
power at the receive antenna terminals, compared to the noise, to usefully
demodulate that particular kind of signal? For cell phone CDMA you
require a 6 dB S/N (or, more accurately, Eb/N0) ratio to be useful, for FM
you need 12 dB (according to the ARRL) or 16 dB (according to Qualcomm, may
be self-serving) to have anything worth listening to. If everything else is
equal the CDMA signal will have a 6-10 dB advantage, which is enough to
win every time.

> A good example of what happens is to simply put a new digital ATSC TV set
> in your car and start driving towards the TV tower transmitting the signal.

So you are picking digital HDTV service, which packs way more information
than analog TV (just compare the pictures when you aren't moving) into
less RF bandwidth, and saying that since the digital receivers don't
(yet?) do as well with certain signal impairments that the digital stuff
is crap? Information rate matters, and the comparison you are making isn't
in the ball park of apples-to-apples. If you want a comparison which is
closer to apples-to-apples why not try, say, CDMA and FM phones, whose
information rate must be close since they do about the same thing with
about the same quality.

> Turning up the cell site power isn't the problem in the country. The phone
> starts out with a 150 milliwatt transmitter into an almost non-existant
> antenna. The ERP, effective radiated power, is LESS than .15 watts...MAX!
> I don't care what kind of hype you put on it, 150mw on ANY system isn't
> going to go far in the finest conditions. Put it in a pine forest on 800
> or 1900 Mhz and IT WON'T MAKE IT OUT OF THE TREE ATTENUATORS and digital
> sales gimmicks and dreaming won't overcome basic RF physics and
> propagation. A toyphone will NEVER give service over a couple of miles in
> the treed countryside.

Attenuation in the trees is the same for both CDMA and FM at the same
frequency, the only question in either case is how much signal, and how
little noise, you need left over at the antenna terminal, for it to
do something useful. Some modulations need more signal, some can get by
with less. CDMA can get by with less while FM needs more, so CDMA wins.

As for cell site power, note that cell phone transmissions are
bidirectional and the transmission paths are (almost) reciprocal,
so the necessary power in each direction is about the same. The reason
a 3W analog phone is useful is because the tower is willing to spend
3W talking back to the phone. A 3W CDMA phone won't be useful, however,
if the tower thinks it will only be talking to 200 mW handsets and
won't adjust its own transmit power above that. For higher-power
phones to be useful for anything you need higher-power towers.

I linked to a picture of a 2W CDMA phone; they exist. For that to be
useful you need cell sites willing to spend 2W to talk back to the phone,
so you need to crank up the power at the tower transmitters. When you've
done that, however, you'll have a system which, given the same antennas
and same RF path, will do better if you spend your 2W on CDMA than
it will if you spend your 2W on FM. That's all the physics says
about the modulation-dependent part of this.

Dennis Ferguson