[NLRS] RF read water meters

[Dr. Gerald N. Johnson]

There is a click at 4 second intervals. I'm beginning to see how they 
get 10 years battery life, those transmissions are SHORT. I set the 
receiver to WFM so probably 250 kHz bandwidth. The strongest click was 
around 914.4 and it down a lot at 914.150 and 915.3.

10 years is 5,256,000 minutes. A duty cycle of 1.76 msec per 3.98 
seconds is a toyal transmit time of 2324 minutes, almost 39 hours. That 
seems like a practical battery life, presuming the controller sleeps on 
nanooamps.

That module has an FCC ID GIF 2006B which google hasn't yet turned up.

First item in the FCC file is a letter requesting confidentiality.

The test data says it can be set for 911.65, 915.45 and 921.25 single 
frequency or frequency hopping. That the transmission is 1.76 
milliseconds every 3.98 seconds.

https://fjallfoss.fcc.gov/eas/GetApplicationAttachment.html?id=739649

If we figure sending 8 digits ID and 8 digits data as BCD we need 32 
bits for each, plus at least one byte for sync and one for EOT, so 80 
bits. That's 44.4545 kilobaud. Or we could fit in 98 bits in that time 
period at 56 kbaud. If the data was pure binary converted to decimal in 
the display the range of 8 decimal digits takes 27 bit for each part. 54 
total, still probably 8 bits sync and eot for a total of 70 bits in 1.76 
msec is 39.325 kbaud. An odd speed but good for keeping the data 
proprietary. 60 speed 5 bit Baudot teletype (like the model 15) was 
45.45 baud.

The FCC Id submitted spectrum shows two peaks off the center frequency, 
I may not have been patient enough to find both. And the center 
frequency stability may not be quite crystal controlled.

So to learn what those new installations are doing, go to the meter 
transmitter and find the fCC ID and go to:
https://fjallfoss.fcc.gov/oetcf/eas/reports/GenericSearch.cfm and search.

73, Jerry, K0CQ

On 7/21/2012 3:10 PM, David Donaldson wrote:
> Yes that was my thought.  Put the antenna right on the unit.  I would
> think there should be some noise rise.
>
> Dave
>
> David Donaldson
> Burnsville, MN
> WB7DRU
> Navy Mars:NNN0AXK
> Skype:wb7dru
>
>