WEST U.S. -- gsm repeater

[danmck]

I am looking for a recommendation for a repeater for my house in Baja. The GSM carrier is Tel Cel. I can get an intermittent signal at my garage but not at my house which is 100 feet lower on the cliff. I am considering erecting a mast to mount an antenna for the repeater(s) on my garage. I would also like a VHF antenna or repeater on the same mast to hear local fishing and boat chatter. Any advice for having these two on the same mast to minimize interfearance problems? I am tech savy but not so much on wireless.

[COtech]

I'd suggest putting the VHF marine antenna (an omnidirectional, perhaps you can cover ocean and gulf!) at the top. Next down would be the PCS (1900 MHz) unidirectional antenna, a Yagi is readily available, perhaps twenty to twenty-eight elements. The rear end of the PCS Yagi's boom would be mounted to the mast (or tower leg), aimed at the neighborhood TelCel tower site. The coax for both would then come to your garage.

The repeater should live in the garage, so it wouldn't need a weather-proof box.

Next comes a second PCS Yagi, which need not be as long and directional as the one pointed at TelCel. This is the one to point at the house downhill. We want to have as much isolation as possible, between the two PCS antennas, so that they can't feedback into each. (Think of a microphone picking up the sounds from a PA speaker, and squealing and howling.)

You may be able to place the mast on the side of the garage away from the house, using the garage to "shade" the house directed antenna from the cell site directed antenna.

If geometry permits, a right-angle (or more) between the two PCS antennas' azimuth should work. You'll get more isolation too, with the difference in the antennas' elevation, with the house antenna depressed to aim down the cliff.

Think about it as if it were a same channel in-and-out television repeater station, on a ridge crest. You put the receive antenna not on the crest, but twenty or thirty feet down on the TV station side. You put the transmit antenna on the community side of the ridge, twenty or thirty feet down from the crest, so there's sixty or ninety feet of granite in between. No chance of feedback here! The repeater shelter is on, or near the crest, either side (closest to the access road).

Use the best, low-loss coax you can reasonably obtain, in dB per 100 feet at 1900 MHz. I don't know where you will put your marine radio receiver, garage or house, but if going down to the house use the same good stuff (at 158-162 MHz) for the longer length.

I wouldn't advise you on specific equipment, you'll see other threads of messages on that here. I wanted to make you aware of the necessary design philosophy.

COtech
amateur radio Extra class N4BKN
former engineering ops WMC-AM/FM/TV

[danmck]

Thanks for the info COtech. That sounds pretty straight forward. A couple more questions. The house is about 200 ft over and 100 ft down the hill. There is line of sight to the palapa roof of the house. The BDA I am intending to use is 100 mw. Is that enough power?
2. My neighbor is about 600ft away and may want to sponge off my repeater. If I split and point a second yagi at him will that reach? Will it reduce my coverage?
Lastly can I paint the yagi to match the house to help it blend in?

[COtech]

Yes, 100 mW is plenty since you'll be using a directional antenna over that 223' hypotenuse.

You'll want to investigate "power dividers", to add a second antenna on the house(s) side of the repeater. This is more than just a T-connection, because the characteristic impedance is constant on each port, matching the coax for best power transfer of both transmitted and received signals. Typically come in 50 and 70 ohms, and you'd want a 2:1 model.

Yes, you'll be sharing your house side coverage by adding your neighbor. Your signal will be cut in half (down -3db) by an ideal power divider, but you can compensate by using more antenna on the house(s) side of the repeater (tightening the beam down from flood to spot, in effect, for each house).

This ups the complexity, and deserves more of a "link budget" calculation, to be more certain of a good installation. You'd be moving from a "rule of thumb" to more of a "designed" solution.

Yes, you can paint the Yagis, but shouldn't they match the garage that they're mounted near?

COtech

[Born2Fly]

Hi,

I'm looking for a gms repeater system that could be set up on top of a mountain, and have a 2-3 km range at line of sight between the itself and the cell phones (should support about 20 active gsm cell phones).

Its a temporairy setup for workers in deep valleys. We intend to set the system up with 12v batteries and a solar panel.

Can anyone recommend a repeater of this type?