[time-nuts] GPS splitter

ziggy9+time-nuts at pumpkinbrook.com ziggy9+time-nuts at pumpkinbrook.com
Sun Jun 18 16:06:48 EDT 2017

+1 for satellite splitters as a low cost option. But as others have mentioned, you do need to use a little care. Some are 'DC isolated', but that can mean diode OR’ing for each port (all ports DC pass) and not a DC block. And they often don’t have the frequency response (many satellite splitters only say 1GHz or 1500MHz).

The Radio Shack 4 way splitter I started with was just such a device. One input, four outputs, DC pass on all ports with diode isolation. It worked OK, as long as all GPS were 5V antenna types. Adding a 12V receiver was suddenly a problem as my antenna is 5V, along with the other receivers.

The best satellite splitter choice (for me) was a DirecTV SWIM 4 way unit. It’s rated 2-2150, has DC pass on one port. So I could connect my somewhat deaf 12V receiver with an inline amp on one of the DC block ports, and a 5V unit on the DC pass port. Each receiver was happy. A picture of one is at <https://images-na.ssl-images-amazon.com/images/I/41EWn-NoJlL.jpg <https://images-na.ssl-images-amazon.com/images/I/41EWn-NoJlL.jpg>> Easily found and cheap, 2, 4, or 8 port models exist.

BTW, putting each splitter on the network analyzer proved that the DirecTV unit had lower loss and better port to port isolation than the Radio Shack unit (no surprise really). I ran this way for quite a while until I uh… ran out of ports. I now have a GPS Networking 8 way with ‘proper’ DC block and load on each port which works well too.

Just as an aside, does anyone have any thoughts on the noise contribution of the diodes in the Radio Shack splitter (or similar)? It’s device dependent of course, but I wonder if it’s enough to be a ‘significant’ contributor.


> On Jun 17, 2017, at 12:07 PM, Chris Albertson <albertson.chris at gmail.com> wrote:
> On Fri, Jun 16, 2017 at 8:54 PM, Clay Autery <cautery at montac.com> wrote:
>> This brings up some interesting questions:
>> I am assuming since this is a receive only situation, it will follow
>> approximately the same rules of physics that dealing with satellite
>> antenna installations.
> And guess what?  Satellite TV splitters work.  They even have the answer to
> "how much attenuation" printed right on the splitter and they come with F
> type connecters you can use the recommended TV type antenna cable too.
> You can buy them with DC blockers too.  All this stuff is low cost because
> it is mass produced  by the billions
> Yes, it's 75 ohm not 50 and the splitters a 2+ GHz but it works just fine
> if your antenna has the right gain. The splitters don't high pass the
> signal.    Trimble actually recommends using the 75 Ohm TV cable and
> supplies it with their kits.
> Sometimes a GPS receiver will raise an "Antenna Alarm" if it does not see a
> DC load but you can turn those off with a serial command
> -- 
> Chris Albertson
> Redondo Beach, California
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list