[RFI] Passive Cellphone Repeater?

Christopher Brown cbrown at woods.net
Sun Apr 17 11:00:28 PDT 2011

Go spend about about $100 on a small UPS.

Passive is possible, but you would need.

Exterior and interior antennas matched to the bands used by the cell
carrier.  Note, _bands_, not band.  Most carriers will be running one
high, one low (example, 800/1900), but the specifics vary with
technology type (GSM v.s. CDMA) and specific carrier.

A very short run or very low loss coax (low loss at up to 2Ghz).

Ideal external antenna placement.

A _very_ strong signal.

I have seen this done several times, but they fell into 2 groups where
is worked...

1) Line of sight and a stones throw from the tower with omni on roof.

2) Farther away with perfect line of sight to the tower with a well
aimed high-gain directional on roof.

As I said, get a small UPS to support the DSL modem, pico-cell, etc.
Much cheaper than the required gear for a passive.

On 4/16/11 1:54 PM, doc at kd4e.com wrote:
> It seemed to me that someone here will know about this ...
> We are in a steel building and have been using a Samsung
> Internet-GPS black box to generate a cellphone signal.
> However, whenever there is a power glitch (three times
> today due to high wind gusts in the area) we lose the
> connection.
> If we go outside we can get a signal off the tower.
> SO ...
> Has anyone rigged a passive repeater using a gain-type
> outside antenna and an omnidirectional inside antenna
> with only coax connecting the two back-to-back?
> It seems as though that may be more reliable than the
> black box device ... if it works.

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