[time-nuts] Oncore, Trimble Antennae

[Lux, James P]

On 10/21/08 9:31 PM, "Chuck Harris" <cfharris at erols.com> wrote:

> Tom Van Baak wrote:
>>> Both the Trimble and Motorola modules use active antennae with 5V power
>>> - what I don't know is whether they are the same polarity.
>>
>>> all my trimbles and oncores have +5 on center, ground on shield...
>>
>> I'd be interested to know if any antennas are in fact the other
>> way around. Never even considered that.
>
> It would have been fairly trivial for them to put a bridge rectifier
> before the amplifier's power stuff, allowing for either polarity.
>
 But not so trivial to provide the DC blocks in the ground side of the coax.
The LNA is almost certainly some MMIC with RF ground==Vss

And, don't forget that these are cost sensitive devices. 4 diodes and their
installation and board real estate costs money, as would the extra couple
capacitors for the DC blocks, etc.
Jim