[time-nuts] Distributing GPS L1 signal to many GPS devices

[Bob kb8tq]

Hi

There are a number of MiniCircuits passive multiport splitters that show up on eBay
at reasonable (< $40) sort of prices. You can get eight port versions with SMA connectors
on them fairly quickly. Other connector types or higher port counts may take a bit of shopping 
and added cost. There are also 4 port versions that show up in the < $20 range. 

Cascading one 4 port into 4 eight ports gets you 32 outputs. You also have a bit of loss to deal with.

One way to deal with the loss is to run a “survey” antenna in front of the setup. Some of them have
50 db of gain (compared to the 20 to 30 db often seen in timing antennas). That will quite nicely make
up for the splitters plus some cable loss.

Another way to make up for the loss is to shop a bit for an amplifier that will do the job. There are a 
number of manufacturers out there. Some include filtering, some do not. A broadband amp with no 
filtering and possible open questions about 3rd order intercept ( = signal handling) capability can be had
for <$20. Something fancier with filters might be 5X that.

Indeed there is no need to stop at a 4 port on the front end. You can start with an 8 port and then
tack on 8 ports after that…..

Be aware that some sort of DC block probably is a good idea on each of the output ports. If you have
a (rare) GPS that freaks out with no DC into the antenna that also will need to be handled.

Bob

> On Sep 24, 2019, at 12:30 PM, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Currently, I have a symetricom antenna outside that feeds an HP58536A (4 port).  One of the output port daisy chains to another HP58536A's antenna port.  That gives me 7 ports total. Well, I need more.  I can simply daisy chain another one but it doesn't look like an elegant solution.  Besides, if I only turn on GPS on the last port, it will end up driving all of the active distributor amps.  Also, signal delay would be a concern.
> 
> I KNOW there are many folks here who has more than dozen GPSDOs.  How do you do it?  Obviously, buying an 8 port version is one of the solutions but what if I need to expand that?  My goal is like 20 ports for future craziness.
> 
> GPSDOs tend to grow during my sleep.  It must be because I started with just two.
> 
> 
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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