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.