[time-nuts] GPS antenna splitter recommendation?

[Bob kb8tq]

Hi

Pretty much all the Mini Circuits splitters will pass DC. The only ones that 
don’t are the ones that show “goes to DC” on the data sheet. Those are 
resistive splitters. I’ve run thousands of GPS modules through a lot of different 
Mini Circuit splitters. None of the “right”. ones have ever had a problem passing
DC (or failed in any way).

DC blocking ports is generally a good idea. You can get “cable TV” dc blocks
for <. $1 each. They have F connectors on them so total cost to get to SMA
is more than $1. For a large splitter setup ( like say 64 ports … ummm … errr …)
that can be a lot of DC blocks. 

I tend to block all DC to the splitter and feed the antenna from a bias tee. They
also are pretty cheap. It eliminates a “single point of failure” when the device that
does pass DC gets unplugged. ( Actually it just moves to the bias supply wall wart. 
Practically the failure goes away).  The bias tee approach also provides a very tiny
improvement in lightning immunity. (you loose a 5V wall wart and not a GPSDO). 

=======

Devices with gain generally also have filters in them. We now are in a world that
has cheap multi GNSS / multi band modules in it. Both are already in production 
GPSDO’s. None of the filtered amps will pass multi band GPS / GNSS. Many of them
are sharp enough to take out Glonass based mulit-GNSS. 

Does this matter if your splitter is a $30 (delivered) sort of unit? Maybe not. It’s
all worth considering before you move up into the “hundreds of dollars” range. 

Bob

> On Apr 30, 2020, at 5:38 AM, Chris Burford <cburford1 at austin.rr.com> wrote:
> 
> I use a 4 port splitter from InStock Wireless, all with SMA jacks. You can
> view the specs here as well as browse for other configurations. To help with
> the attenuation factor use the lowest loss coax between the splitter and the
> GPS antenna. I'm using Times Microwave LMR-400 for just that reason.
> 
> https://www.instockwireless.com/gps-splitter-4way-SMA-gps410.htm
> 
> Chris Burford
> 
> -----Original Message-----
> From: time-nuts <time-nuts-bounces at lists.febo.com> On Behalf Of Frank
> O'Donnell
> Sent: Wednesday, April 29, 2020 19:18
> To: time-nuts at lists.febo.com
> Subject: [time-nuts] GPS antenna splitter recommendation?
> 
> I'm looking for a splitter to allow three or four GPSDO's to share my
> roof-mounted Lucent PCTEL KS24019L112C 26db GPS twist antenna.
> 
> I understand from scanning past threads that inexpensive splitters by
> companies like Mini-Circuits often turn up on eBay, but I'm having trouble
> narrowing down to one that will work for my situation. Can anyone recommend
> a specific splitter that wouldn't be too expensive?
> 
> Thanks much,
> 
> Frank
> 
> 
> 
> 
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