[time-nuts] GPS antenna splitter

[Bob Camp]

Hi

From what I've seen, a 50 ohm load on the 8th port of an 8 port splitter does a pretty god job of doing the DC correction. No need for an inductor, everything matches up just fine. 

Since you have an amp in the antenna, you don't *always* need an amp in front of the splitter. A lot depends on how much cable loss you happen to have (and the gain of the amp in the antenna). With a modest amount of cable (< 50') eight port splitters seem to work pretty well. 

Bob

On Jun 29, 2013, at 4:34 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> Hi Bob,
> 
> On 06/29/2013 08:43 PM, Bob Camp wrote:
>> Hi
>> 
>> The auction sites are great sources of GPS splitters. I've gotten Mini Circuits splitters for much less than what they go for new. All of the ones I've seen do indeed pass DC.
>> 
>> One thing to consider - you may want one with an extra port on it. Some GPS cards are a bit sensitive to antenna current. If you gang up seven receivers, one may not see enough drain to turn off the antenna alarm. The simple answer is to terminate one port with a resistor to ground.
>> 
>> If you do need to inject DC, they make purpose built gizmos. You can also run one of the Symmetricom splitters that has DC blocking on all but one port. They tend to be expensive.
> 
> For GPS receivers needing more DC load, I've found that hooking up a DC load through a SMD inductor in series with a SMD resistor (150 Ohm is what I've used). I hacked that onto a BNC-T and it got a GPS receiver to work.
> 
> Strange that my hobby-hack is drive-by delivered to one of the major
> telecom operators, but it solved their problems. :)
> 
> A splitter should have a pre-amplifier.
> 
> Cheers,
> Magnus
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