Why don't TDMA extend and CDMA antennas do extend?

I'm not sure I understand. Are you asking why the CDMA phones have antennas that are retractable and the TDMA phones do not? If that's the question I don't think it's a matter of technology as much as the manufacturer's preference and design. I have a TDMA phone that the antenna is retractable and I have one that is not.

Tom

 

i don't know the exact answer, but i do know that it is technology related.

CDMA technology requires an extendable antenae and TDMA does not. I'm sure it has something to do with how the phone searches for the signal or something..

Look at the carriers...all Verizon and Sprint phones (CDMA) have retractable type antenaes....

 

I always wondered that myself. Nokia 5185 retractable-5165 stub, Startac 7868 retractable-7897 stub, Timeport 270c retractable-280 stub.

I guess the designers figure more gain is needed for CDMA networks.

Hman

 

here's a good link abou the differences between CDMA and TDMA:

http://www.arcx.com/sites/CDMAvsTDMA.htm


I didn't see anywhere where it specifically says why one needs a retractable antenna and one doesn't...however, it must have something to do with the way the signal is decoded by the handset..

i posted a question in another forum that Steve Putner (the author of that website) frequents...maybe he can give a more definitive answer..

i'll let you know.

 

and just to throw in my 1.5 cents (after depreciation, state and federal tax and everything else)

The Nokia 2160, now a faded memory along with dinosaurs, did have a retractable antenna.

Also, it is possible to find CDMA phones that have stationary antennas.

 

<< and just to throw in my 1.5 cents (after depreciation, state and federal tax and everything else)

The Nokia 2160, now a faded memory along with dinosaurs, did have a retractable antenna.

Also, it is possible to find CDMA phones that have stationary antennas. >>




probably a better way of phrasing the question is "Why can TDMA have internal antennas and CDMA can't?"

as far as I know, there are no CDMA phones with an internal antenna.

 

I'm not 100-percent sure, but I think this one:
http://www.pc-ephone.com/

Just found this in another forum:
Nokia 8270

 

<< I'm not 100-percent sure, but I think this one:
http://www.pc-ephone.com/

Just found this in another forum:
Nokia 8270 >>



i forgot about that 8270 just being announced....but i believe that is a 1900mhz digital only phone. And I would bet that that pc thing is digital only too (but it clearly has an antenna in the picture

I got this response in another forum, which I believe answers some of the question, but doesn't seem to answer it fully:

Your question is quite interesting indeed and I am not sure if I can answer it to you 100% correctly. Here we go.

The reason why CDMA phones usually have a retractable antenna because it's optimized for the AMPS part. Since AMPS works on the 800 MHz and the optimum antenna length for AMPS or for any 800 MHz operating phones would be about 7 inches. Since what AMPS is transmitting over the air is purely radio wave with no encrytion or anything like that, so the sound quality would purely base on the signal strength. It would be better for a dual band/dual mode CDMA phone to have a retractable antenna to work well on the AMPS part, not to mention that many dual mode CDMA phones out there are operating in a less than optimal power (i.e. less than 600mw) in analogue mode.

Why does TDMA phone doesn't have an antenna then? This is because TDMA, as the name states, is a DIGITAL system. The voice is being encoded and transmitted over the air. Even there's a loss of data due to the weak signal, the CODEC has already included a error correction algorithm that would compensate the loss of data to a certain extent. As long as there's enough data to be decoded, the sound quality would sound identical when there's a super strong signal and a quite weak signal. Although IS-136 still has the analogue mode built in it, it's not often to be used in today's market. (AT&T and Rogers AT&T has a quite extensive digital coverage already). Because of the convenience of having a stubby antenna, manufacturers tend to customize the phone toward to customer's needs.

Hope this helps.


It would make sense to have a retractable antenna for the analog side of things, but according to his reasoning, TDMA manufacturers don't care about the analog reception of their phones. Which seems like a bad idea to me. Yes digital is the majority, but there are still many places when all you can get is analog.

Anyway...i think this get's closer to the answer, but it seems like something is still missing...

 

he also implies that CDMA isn't digital....at least that's the way it sounds: "This is because TDMA, as the name states, is a DIGITAL system"

so the more i read this answer...the less it really answers for me...

 

Both TDMA and CDMA are digital systems. The difference is how the signal is presented. CDMA: Code Division Multiple Access. TDMA: Time Division Multiple Access.

 

True, the poster that seemed to infer that cdma isn't digital didn't quite express him/herself clearly.

The original question was why do most (if not all) cdma handsets have antennas that extend. I think the issue can be laid to rest now that the Nokia 8270 has demonstrated that the technology is not the base-reason for this. We still haven't gotten clear and concise explanations as to why most cdma handsets have extendable antennas. I have a feeling Bill Radio might know the answer or at least an intelligent guess. I don't feel it is a big enough issue to bug him about.

Kevin

 

<< True, the poster that seemed to infer that cdma isn't digital didn't quite express him/herself clearly.

The original question was why do most (if not all) cdma handsets have antennas that extend. I think the issue can be laid to rest now that the Nokia 8270 has demonstrated that the technology is not the base-reason for this. We still haven't gotten clear and concise explanations as to why most cdma handsets have extendable antennas. I have a feeling Bill Radio might know the answer or at least an intelligent guess. I don't feel it is a big enough issue to bug him about.

Kevin >>



The 8270 doesn't put the issue to rest. I believe the reason why this phone can operate with an internal antenna is because it's 1900mhz only. The external/extendable antenna is driven more from the 800mhz side.

Here's some further explanation lifted from a post from a user on another forum (i would credit them if I knew who it was):

"A possible explanation for CDMA phones to work with an external antenna would be, as I said, the analogue portion. The analogue transmittor in a CDMA phone is usually weaker than normal to conserve energy, that's why it's necessary for the phone to operate at an optimal situation to compensate the loss in the output of transmittor. Even in digital (CDMA) mode, the phone will transmit in lesser power if there's external antenna to help. Then that's perhaps another reason why there would be an external antenna for most CDMA phones: To conserve power and enlong the standby and talk time.

The reason why an 800Mhz operating phone require 7 inches long of antenna is that the wavelength of 800 Mhz is about 15 inches. Therefore, the crest occurs at 71/2 inches. However, since we don't hold the phone with the antenna stright up, therefore the ideal length for an antenna in 800 Mhz is about 7 inches. What that 7 inches is measured is from the bottom contact point of the antenna component to the tip of the antenna. The old analogue startac phone has an antenna in about 7 inches long. "

I believe this comes a lot closer to the answer than before. It's not a manufacturer preference as some people would argure (case in point is the Ericsson t60c & t60d- exact same phones but the CDMA version has an extendable antenna and the TDMA version has internal.)

I don't think there is an easy answer to this question- believe me, I've been trying to find it. But after doing a lot of reading and research on TDMA/CDMA, I think that CDMA has the external antenna for all the reasons mentioned here and probably a couple more that haven't been mentioned..

If someone does have an easy answer...i'd love to here it

 

The reason why Cdma antennas pulls up its because Verizon don`t buy phones with internal or fixed antennas(exept for the 1228c), all the Cdma manufactures wants to sell phones to Verizon because of the large . thats the biggest reason

 

<< The reason why Cdma antennas pulls up its because Verizon don`t buy phones with internal or fixed antennas(exept for the 1228c), all the Cdma manufactures wants to sell phones to Verizon because of the large . thats the biggest reason >>



and i suppose sprint has the same stipulation?

i don't buy that explanation.

 

I discount that as well.

 

those explainations would make sense except...
sprint does not use amps and operates at 800 and 1900mhz.
at&t's tdma also operates at 800 and 1900mhz.

so we need a brand new theory.

some things to consider...
my verizon phone works better with the antanae up even within a digital area.
if an antanae can retract, that means it would be very easy to make it internal.

 

<< those explainations would make sense except...
sprint does not use amps and operates at 800 and 1900mhz.
at&t's tdma also operates at 800 and 1900mhz.

so we need a brand new theory.

some things to consider...
my verizon phone works better with the antanae up even within a digital area.
if an antanae can retract, that means it would be very easy to make it internal. >>



While Sprint may not actually use AMPS, it's phones (at least some of them) are designed to roam onto AMPS. Also, Sprint is primarily a 1900mhz provider.

And because an antenna can retrack does not necesarrily mean it can be made internal. It means that the phone is designed to work at optimal performance with the antenna extended. You prove this point by saying your phone works better with the antenna extended even when digital.

I don't think we need a brand new theory...I think part of the answer lies in some of these responses, but I still believe that there is more to the answer yet to be discovered!

 

well at&t roams into amps as well. so the whole amps theory doesn't work.
and sprint is primarily 1900mhz so the whole wavelength theory doesn't work either. 1900mhz would require a shorter antanae than 800mhz.

though the wavelength thing may be true it still doesn't tell us why some carriers have retractable antanaes and some don't when they use the same frequencies.

the antanae is not in use when not fully extended. at least it doesn't appear to be. the antanae only makes contact with the metal it comes out of, when it is fully extended. the only way it would make sense to have an retractable antanae is if there is already an internal antanae that works along with the retractable part. if there is no internal antanae, there is no point in making a retracable one since an internal one would probably work just as well.

my best guess is that it's the carriers preference.

 

I know we've beaten this topic to death but here's the latest I have uncovered. I spoke with 2 different people from Motorola and both have told me there is no correlation between antenna and technology. The first guy works in the PCS division but isn't an engineer but did speak with them about this topic. He said it's customer preference that drives the antenna. Keep in mind Motorola's customers are not the end user though. The 2nd gentlemen is my neighbor who is an engineer and heads up the division working on the 1x technology. He's pretty knowledgeable and basically said the same thing. That there's no correlation and that it comes down to customer preference.

I understand that this is coming only from Motorola sources but logic would tell you that it would be similar at Nokia and others.

Tom