Running two Fine Offset stations in close proximity

[brassing]

Does anyone know if you can run two Fine Offset stations close together - i.e. within wireless range? Do the remote unit and the base station pair in some way? (I realise that even if it was possible I would still need to couple them to different PCs.)

The reason I ask is that at my sailing club it might be interesting to monitor the wind at 10 m and also the actual conditions on the lake. (I could fix a station to one of the marks. It might not survive the cormorants trying to perch on it though!)

If the answer is no, can you run two copies of Cumulus linked to two different weather stations on the same PC?

[Gina]

Does anyone know if you can run two Fine Offset stations close together - i.e. within wireless range? Do the remote unit and the base station pair in some way? (I realise that even if it was possible I would still need to couple them to different PCs.)

Yes, you can. I have done. And yes, the console (base station) "locks on" to the transmission (from remote). It tends to take several tries to get the second console to lock on to the second transmitter - it will lock onto whichever transmission it "sees" first. To get a console to connect to a transmission it needs to be powered down - disconnect USB and remove a battery. Reconnect batteries after a short time. When you're sure you have the right signal you can reconnect the USB. You will need to be able to differentiate between the two transmitter stations, of course.

[daj]

I was just about to reply and say that I thought Gina had done it, but not sure how...then you appear as if by magic.

[Gina]

[brassing]

Thanks Gina. I'll store that info away for future reference.

I'm quite impressed that Fine Offset have built that feature in. It must mean that either each remote unit has a unique preset code or that the remote negotiates a code with the base station and remembers it. Or it might be they negotiate a wireless channel - in which case there might be a limit to how many stations you can run together - not that I intend to try more than 2

I must say I think Fine Offset have done a great job on the cost engineering - producing a low cost station that still does a good job (mostly) and has most of the essential features. Its certainly much more than a toy.

[Gina]

I'm not sure it does anything clever like pairing and it doesn't change channels. There is no communication from base/console to remote/outdoor unit. I think it just waits until it's nearly time for the next transmission then "listens" for it. So two (or maybe more) stations can interleave their comms. It means you have to have the transmissions at different times and if you can't separate the two signals you may need to power down (take batteries out) one transmitter briefly. I had to do that once.

To repeat myself in case you/anyone missed it, I have used two independent stations for testing. One is my main weather data gathering station and I often use the second as a testing system. Usually with the test rig on the dining room table. I can separate the two when synchronising because the indoor unit is a lot warmer than the outdoor one (at this time of year anyway).

[mcrossley]

I think what is required is lightly different Gina, he wants to run two transmitters to two receivers.

I think you will have problems, you can probably get the receivers to lock on to the correct transmitter (eventually!), but because of timing drifts, I suspect that the two transmitters will end up transmitting at the same time for extended periods. This would be a recipe for disaster.

[Gina]

I think what is required is lightly different Gina, he wants to run two transmitters to two receivers.

I DO run two transmitters and two receivers when I run an independent test.

Let me explain what I run etc... (This will take a while )

Number one system - main weather data gathering and presentation:-
Outdoor sensors, wind sensors on 20ft mast, rain gauge on a tubular steel framework about 2ft above ground both feed into the Stevenson screen mounted beside the mast at 5ft above ground and thence into the no.1 transmitter unit.
Indoors, console no.1 feeds my old laptop running G-Weather for Linux and feeding my weather website and banner in signature.

Number two system - test rig:-
Test rig uses the second complete station with separate computer running different software. The test rig has consisted of the wind sensors on their arm and one section of FO mast held vertically on a base on the table. I used a desk fan to produce air flow over the anemometer and wind vane. The cable from the combined wind sensors went through the test circuit to the no.2 transmitter unit, also sitting on the table. The second console was synchronised to the transmitter on the table and checked to see if it was reading 20+ C room temperature rather than the 0-10C outdoor temperature which was being received by the no.1 console. The second console was connected to my main desktop computer (AMD64) running slightly modified pywws linux software and uploaded to a separate page on my weather web site.

I think you will have problems, you can probably get the receivers to lock on to the correct transmitter (eventually!), but because of timing drifts, I suspect that the two transmitters will end up transmitting at the same time for extended periods. This would be a recipe for disaster.

The transmitter timing is controlled by a crystal so I think the timing will probably be about as accurate as a digital watch. They may eventually drift apart but I think it will take quite a long time.

[Gina]

I think the confusion arose because when I'm not running an independent test I usually resynchronise the second console to the outdoor transmitter and use the second computer system for software development or special rapid logging of the outdoor data. In this arrangement the test rig is cleared away with the batteries taken out of the second transmitter. So this is one transmitter to two receivers. (Table currently in use for development of new wind vane.)

[mcrossley]

Ah, with you now

[JabbaTHutt]

If these systems are running FM the receiver will pick up the strongest signal, if you could run some say RG6 tv cable outside near the onshore one and put a little stub of bared center cable near the transmitter and a stub near the receiver you could end up with passive antenna, you could do better if you knew the frequency of the transmitter you could strip each end and use the shield for the ground plane you might be able to leave it inside but as close to the transmitter as you could get it, it could do the job.

Then for the offshore one do the same thing but make sure the far end has some kind of sheild behind the antenna so it doesn't see signal from the onshore one and would see more from the offshore one

[brassing]

I take the point that there is no communication from base to remote, but they could still pair. If the remote creates a random code when it is fired up then the base station, when it is turned on, could remember the code of the first remote station transmission it receives and in future only respond to transmissions wth that code. Pretty simple to implement that in software I would have thought. Still, whether it does that or simply relies on listening at the expected time as Gina suspects, you still have the long term problem of what happens if the transmission times drift together. JabbaTHutt's idea of using coax would help there but it's a bit more work than I was hoping for.

I know it's quite fun trying to reverse engineer the Fine Offset but I suppose the real answer is to ask FO. Has anyone had any success contacting them about technical matters direct? (I notice that their site is currently down so I can't see if they have a support email.)

I like the idea of calling the on-the-water station "offshore" but in case anyone gets the impression of 60' yachts and G and T in the cockpit at sunset our sailing club is dinghies and windsurfers only and the lake is an old gravel pit