Any cell antenna inside pictures?

Hi, I saw an antenna lying on a desk nearby and snapped a pic for you I didn't look at the specs, but looks to be a dual-band 900/1800 GSM antenna. Of course the plastic housing that would protect it has already been removed, saving you the effort of climbing a tower and cracking one open yourself

Here's the front, you can see the antenna elements (the squares) are bigger for 900 and smaller for 1800. The size needs to be directly proportional to the wavelength, so antennas for higher frequencies (ie: smaller wavelengths) can be smaller compared to similar ones on lower freqs (with larger wavelengths):

Front of antenna:


Back of antenna:

 

Very nice. Why does the 2nd from the top look to be shielded?

 

You're welcome, bitte schön, palun, payzalusta ...uh, sorry, that's as far as I go with languages :O

Good question. Don't know, probably to focus the beam towards the center. I didn't look at the specs, and the antenna will probably be gone tomorrow, so I can't really give a full run-down. Was just a quick snap on my camera phone when passing someones office... like some WA spy, ha-ha

 

Ah-Ha!!
No wonder PIM (passive intermodulation distortion) is such a big problem in these antennas. I have always wanted to disassemble one of these babies myself. You can see the RET motor turns a plastic screw that's connected to a long (probably nylon or PETE?) rod. This in turn tilts each of the antenna bays.

So, moving metal antenna parts = excellent chance for PIM noise. Not terribly surprising by the way... Aside from the wideband response, this must be a huge challenge for the manufacturers to overcome.

Can one surmise that the white coaxes are for 850 (Cellular) and the red ones for 1900 (PCS), or vice-versa? Also, I assume those are power dividers on the flip side?

 

Sure
.......

 

There's two kinds of tilt, electrical and manual. Electrical tilt can be done remotely by someone sitting in an office. Electrical tilt means shifting the antenna elements to point slightly downwards. Mechanical tilt means someone climbs up the tower and physically pushes the top of the antenna outwards so that the whole antenna is pointing downwards.

With physical tilt, if it's a dual-band antenna (ex: 850MHz and 1900MHz) then both bands will be affected by the tilt (ex: if you mechanically tilt the whole antenna downwards by 6° both 850MHz and 1900MHz will have this tilt). With electrical tilt, you can tilt just one band without affecting the other (ex: you can tilt 850MHz by 6° and leave the 1900MHz at 0°)

Also note that mechanical and electrical tilts are not quite the same in terms of radiation pattern. Electrical is kind of more narrow and centered, while mechanical is more round and fat. Hard to explain. I had a nice picture somewhere explaining the differences but I can't seem to find it :O