GPS Feeding Multiple Devices?

[yaknamedjak]

Hi all,

Sorry that I've had a few posts in this particular forum, I'll probably have more as I gear up to upfit my vehicle.

Does anyone know if it's possible to have a GPS receiver, like the MR-350PS4, feed both a scanner and a laptop?

I'd like to have a strong GPS signal for mapping on my CF-18 but also feed a 536HP.

Interested to hear of any solutions you may know of.

Thanks in advance.

 

[yaknamedjak]

Panorama Splitter

Anyway, Panorama (it's actually an accessory for the Sharkee) makes a "splitter" which can feed two GPS receivers from a single antenna (it only sends power from one receiver).

W5PKY suggested I look into this splitter from Panorama.

After looking at it, since it has FME connections, that would mean this would have to go between the antenna/module and the receiver, is that correct? In which case it wouldn't work with the MR-350PS4 since that is an antenna/receiver-in-one?

Ideally the solution would take the serial connection provided by the MR-350PS4 and give me two, one that could go to the CF-18's serial port or serial->USB converter and one that would go to the BCD536HP..

This may be naive, but is the solution as simple as getting the PS/2 connection to RS232 (with power linked in there to power the GPS device) and then an RS232 splitter, one to each unit? I'm guessing it might not work since it seems like there's a Tx side to the GPS that they would have to fight over.

 

[mmckenna]

Yeah, so there are two different things going on here:

You can either split the GPS RF signal from one antenna to two receivers. The Panorama product will do that. The trick to these is that the GPS Receiver sends voltage (usually, but not always, 5 volts DC) up the coax to power the amplifier in the base of the antenna. The splitter needs to feed that voltage from only ONE of the receivers to the antenna.

The other option, and the right one in your case, is that the receiver is INSIDE the antenna and it just feeds the RS-232 data signal down the wire to the computer. You'll need to feed power from ~something~ to the receiver in the antenna base, and split the RS-232 signal out to the scanner and the PC. I've heard (but never done it myself) of simply "T"ing off the RS-232 feed. From what I've heard, the data signal is usually strong enough on short cable runs to allow splitting it like this. I'm sure you could shop around and find an official RS-232 splitter.

So, you'd need to decide what you want to do. Do you use one antenna, one receiver and feed the RS-232 signal to two different devices?
-or-
Do you use one antenna and split it off to feed two separate receivers?

That decision is up to you.

 

[mmckenna]

I'm guessing it might not work since it seems like there's a Tx side to the GPS that they would have to fight over.

The GPS is receive only, so the computer/scanner would only be listening to what the GPS receiver is sending out. You could theoretically just hook up ground, power and RX data. 3 wires would be all you need. I did this with a Kenwood amateur radio I used to have. I built a small 12vdc to 5vdc adapter and used that to feed power to the GPS receiver/antenna puck that sat on the dashboard. The ground/5 volts fed up to the receiver. The RXD and Ground came back down from the GPS receiver/antenna to the same little project box and then fed out to the radio.

 

[Project25_MASTR]

Here is an interesting idea. Take your GPS receiver, convert it from serial to IP and then multi-cast it with tcp. At your laptop you'd just need to utilize a virtual com port. At your scanner, you'd need to reconvert that IP traffic to serial. Fairly simple, Id use a Mikrotik RB450 and set its serial port up as a serial server then another serial server to interface the scanner.


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[jonwienke]

It would be much simpler to buffer the RS-232 input to multiple outputs. The GPS puck output may not be able to drive multiple inputs on its own.

 

[yaknamedjak]

So many interesting ideas

Yeah, so there are two different things going on here:

You can either split the GPS RF signal from one antenna to two receivers. The Panorama product will do that. The trick to these is that the GPS Receiver sends voltage (usually, but not always, 5 volts DC) up the coax to power the amplifier in the base of the antenna. The splitter needs to feed that voltage from only ONE of the receivers to the antenna.

The other option, and the right one in your case, is that the receiver is INSIDE the antenna and it just feeds the RS-232 data signal down the wire to the computer. You'll need to feed power from ~something~ to the receiver in the antenna base, and split the RS-232 signal out to the scanner and the PC. I've heard (but never done it myself) of simply "T"ing off the RS-232 feed. From what I've heard, the data signal is usually strong enough on short cable runs to allow splitting it like this. I'm sure you could shop around and find an official RS-232 splitter.

So, you'd need to decide what you want to do. Do you use one antenna, one receiver and feed the RS-232 signal to two different devices?
-or-
Do you use one antenna and split it off to feed two separate receivers?

That decision is up to you.

So yeah my initial idea was to try to "T" off the RS-232 feed....a little worried that I'll get all the parts and it won't work, and I'll wish I had just bought another GPS receiver. If I were going to be doing a bunch of installs or was really concerned about limiting the roof holes, I would probably be willing to invest that much time and money into it, but wondering if two GPS units is just the most time(and possibly cost)-efficient solution here. Not ruling this method out, though, since it seems like the simplest on paper.

The GPS is receive only, so the computer/scanner would only be listening to what the GPS receiver is sending out. You could theoretically just hook up ground, power and RX data. 3 wires would be all you need. I did this with a Kenwood amateur radio I used to have. I built a small 12vdc to 5vdc adapter and used that to feed power to the GPS receiver/antenna puck that sat on the dashboard. The ground/5 volts fed up to the receiver. The RXD and Ground came back down from the GPS receiver/antenna to the same little project box and then fed out to the radio.

Good to know. Yeah, if I weren't future-proofing this install for my laptop going in, (even though the install should be happening this month, I'll probably wait to ride around with my laptop until the summer when I'm running more EMS calls) then I would go this route with just a few wires and a 12v to 5v solution near the scanner.

Here is an interesting idea. Take your GPS receiver, convert it from serial to IP and then multi-cast it with tcp. At your laptop you'd just need to utilize a virtual com port. At your scanner, you'd need to reconvert that IP traffic to serial. Fairly simple, Id use a Mikrotik RB450 and set its serial port up as a serial server then another serial server to interface the scanner.

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THIS is a cool idea. Up my networking alley. Outside the box. I like it. My only concern would be additional parts, additional cost, additional parts of the puzzle that can fail. I could definitely see this being more advantageous if I had more than just two devices.

It would be much simpler to buffer the RS-232 input to multiple outputs. The GPS puck output may not be able to drive multiple inputs on its own.

I can't say I know how this would be achieved, sounds simple and interesting though.



Overall, right now I'm wondering if I just spend the extra $65 or so and get another GPS to throw on the roof. For a total of $150, I can have two MR-350s, one with a RS-232 adapter and the other with a USB adapter....what do you guys think? It's a little pricey, but it may save time, headaches, and shipping costs if the badass manual splitting solutions go bust. It would be another hole in the roof, bringing total to 2xGPS, 2x4G, 1/4 wave UHF, 1/4 wave VHF, and the tri-band Laird WPD....getting closer and closer to WX4EMT's roof, HA.

 

[mmckenna]

Depends, how critical is the GPS function to you?

If you are uncomfortable just splitting the RS-232 line, then a second receiver might be a cheaper solution rather than purchasing the Ethernet gear, active splitter, etc.
All are good ideas, but take a look at the costs before making up your mind.

Even a puck on the dashboard will work well. Did this in one of my trucks and never had an issue with it. My current work truck is set up this way.

 

[AK9R]

I've had good luck splitting the RS-232 signal from a GPS receiver to multiple devices. For several years, I split a Byonics puck-type GPS receiver to a Kenwood TM-D710 APRS radio and to a laptop computer. Just T-tap the RX and GND lines coming from the GPS receiver. I used a 12 volt power supply from Byonics to inject 5 volts DC into the power lead of the GPS receiver. Worked great!

 

[Project25_MASTR]

THIS is a cool idea. Up my networking alley. Outside the box. I like it. My only concern would be additional parts, additional cost, additional parts of the puzzle that can fail. I could definitely see this being more advantageous if I had more than just two devices.

If it were me, I'd use a Mikrotik RB450 for routing/switching/receiving the Serial data and then something like a Moxa serial server on the scanner and virtual com adapter on the computer. Then just connect everything via cat5 or wireless if you'd rather use a wireless capable board for routing since Mikrotik is fond of supporting 12V inputs.


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[N9JIG]

I use a single Uniden GPS receiver for 2 scanners just by use of a DB9 splitter I made.

I used to use a single GPS receiver on 4 scanners, a Kenwood APRS radio and a laptop, again with a homebuilt cable just parallel wiring the cables together. I never had an issue with this at all.

 

[bfperez]

I use this software on my laptop to feed multiple programs and/or devices from a single GPS receiver:
GpsGate - GpsGate Client for Windows - GpsGate Client

It can take Bluetooth directly in addition to just about any NMEA sentence speaking GPS device that connects to a COM port.

I have it send the same input to a physical COM port for my scanner and several virtual ones for things like MapPoint, Streets & Trips, and Street Atlas.

For fun, I also use the logging so I can open in analytic programs that show max/min/average speed, elevation, etc.

It can also do various IP based sharing modes - I was playing with one laptop serving the receiver output to another computer running the software as an IP client and outputting that signal via virtual com port to Streets & Trips.

 

[yaknamedjak]

Depends, how critical is the GPS function to you?

If you are uncomfortable just splitting the RS-232 line, then a second receiver might be a cheaper solution rather than purchasing the Ethernet gear, active splitter, etc.
All are good ideas, but take a look at the costs before making up your mind.

Even a puck on the dashboard will work well. Did this in one of my trucks and never had an issue with it. My current work truck is set up this way.

It's starting to look like it would be cost efficient to test the RS-232 split even if it doesn't work. One of the counties I run in is very rural, GPS and mapping on the laptop is definitely helpful, I have awful coverage there on my cell with AT&T, but it's not like it's "tracked by dispatch" critical.

If it were me, I'd use a Mikrotik RB450 for routing/switching/receiving the Serial data and then something like a Moxa serial server on the scanner and virtual com adapter on the computer. Then just connect everything via cat5 or wireless if you'd rather use a wireless capable board for routing since Mikrotik is fond of supporting 12V inputs.


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This is definitely a sweet and badass solution, looking at cost though the RB450 seems like it's $70+, that's before the receiving/serial server. In that case I'd probably just plop another MR-350 on the roof.

I've had good luck splitting the RS-232 signal from a GPS receiver to multiple devices. For several years, I split a Byonics puck-type GPS receiver to a Kenwood TM-D710 APRS radio and to a laptop computer. Just T-tap the RX and GND lines coming from the GPS receiver. I used a 12 volt power supply from Byonics to inject 5 volts DC into the power lead of the GPS receiver. Worked great!

I use a single Uniden GPS receiver for 2 scanners just by use of a DB9 splitter I made.

I used to use a single GPS receiver on 4 scanners, a Kenwood APRS radio and a laptop, again with a homebuilt cable just parallel wiring the cables together. I never had an issue with this at all.

Thank you both so much! These are the confirmations I was hoping for.

So, if I were to take the BR305-RS232 , and get this voltage converter for it, then plug in a serial splitter like this I should be in business?

Two questions:

1. Looks like the BR305-RS232 has a male PS/2 connector, doesn't the GPS receiver also have a male PS/2? So I'd need a PS/2 turnaround?

2. Is it ok that that power supply will put out 3A, or is that dangerous since the GPS takes mA? Could I run the GPS *and* a USB port or two off it?

Thanks again, all.

 

[yaknamedjak]

I use this software on my laptop to feed multiple programs and/or devices from a single GPS receiver:
GpsGate - GpsGate Client for Windows - GpsGate Client

It can take Bluetooth directly in addition to just about any NMEA sentence speaking GPS device that connects to a COM port.

I have it send the same input to a physical COM port for my scanner and several virtual ones for things like MapPoint, Streets & Trips, and Street Atlas.

For fun, I also use the logging so I can open in analytic programs that show max/min/average speed, elevation, etc.

It can also do various IP based sharing modes - I was playing with one laptop serving the receiver output to another computer running the software as an IP client and outputting that signal via virtual com port to Streets & Trips.

This sounds awesome, thanks! So much to learn. I will definitely check it out.

 

[Astro_Spectra]

A single RS-232 output will have no problem in driving two standard RS-232 loads like those in your laptop and scanner at the typical speeds used by GPS devices (19,200 bps or less). At higher speeds you might have issues with long leads.

Where this typically doesn't work is with marine electronics which often use opto-couplers for isolation or with other non-standard '232 driver/receiver implementations.

 

[AK9R]

Byonics GPS5, Byonics GPAC, plus the serial splitter you showed (assuming that it's wired as a Y-splitter for the RS-232 lines).

Byonics - GPSs

 

[yaknamedjak]

Byonics GPS5, Byonics GPAC, plus the serial splitter you showed (assuming that it's wired as a Y-splitter for the RS-232 lines).

Byonics - GPSs

While that seems like an easier setup, I'd like to stick with the roof-mounted GlobalSat MR-350, would rather not have anything on the dash or hanging out of Troy console.

 

[wx5uif]

I've got the serial output from my gps running four devices. I just used the RX line into all four. No need for the TX.