GSM and CDMA antennas?

Thanks for all the theoretical info. Though in the real practical world, things can be quite different.

 

The data is measured, real data, not theoretical. Actually I intrepret the results as being consistent with what bobolito saw in his stubby vs internal test: 0 to 4 dB is within the errors of the data I mentioned.

It also seems to support what AnthroMatt's nice data showed between extended and retracted data when in a call: the difference was only 1 to 2 dB; also within the data set measured by the mgfr's.

It does point out how variable an internal's gain can be even in a controlled professional test. All of the 3 antenna types will vary in performance as we whip them around our head or hold them horizontol or whatever.....however, they are likely to get worse, not better.

Sigma, you started an interesting thread with one question. Thanks, I learned alot from it.

Best,

 

I also think this was a very informative thread. I learned a couple of things as well.

I took an 8260 apart and saw the internal antenna. It is nothing more than a couple of flat odd shaped golden plates. Therefore, unlike an extendable antenna, they can't polarize vertically because they are not shaped vertically.

 

This is known as the harmonic of the wavelength. Whichever fraction of the wavelength the antenna itself represents can determine the antenna's ability to receive or transmit - 1/2 wavelength is longer than 1/8 wavelength and therefore has more surface area. Using the formula, an 850Mhz carrier has a 35.3cm wavelength. 1/2 wave is 17.65cm, 1/4 wave is 8.825cm, and 1/8 wave is 4.4125cm. Antenna dynamics are subject to many variables, including the body's interference as stated above, but a retractible antenna increases the length of the antenna and a stub cannot. Moreover, the antenna is only half of the circuit - the ground relative to the phone is the other half. Thus the extended antenna on the VX4400, for instance, should represent a 1/4 wave antenna. Hopefully, I got this all right... it's been over 20 years since I had antenna theory.

Basic Antenna Facts

 

Found this as a follow-up.


Retractable Antenna

The retractable antenna, usually a monopole type, is commonly used in hand held devices so that the antennas size can be minimized for portablity. The retractable antenna uses a single radiating element and assumes that the ground path is referenced to the outside of the device. The resulting radiating pattern is subject to distortions and pick-up as the ground element is dictated by relative position to the RF source and its associated ground. Retractable antennas can be configured as ¼ and ½ wavelength increments with gain increasing for the longer wavelength dimensions. The retractable requires a single conductor RF connection to the radiating element. Special concern for a retractable antenna is the connection of the RF signal to the radiating element. Loss of signal can arise due to improper coupling to the antenna element. A helical stub is sometimes added to the exposed end of the retractable antenna to act as the radiating element when retracted and a pseudo ground when extended. The retractable has average performance and lower gain than a dipole for the same size of the antenna.


Stub (Helical) Antenna

The most compact antenna configuration, the helical antenna offers the smallest size with respectable gain. The helical antenna uses a single wound coil, the element is still sized for ¼ and ½ wavelength increments. While gain increases for the longer wavelength dimensions, the physical size of the resulting coil has limitations on the effective gain. The helical requires single conductor RF connection to the radiating elements. The helical has good performance for the size of the antenna.

Found it here....