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[wxsig] Hobby Boards Barometer

Dave Barton dbarton at nettally.com
Thu Apr 10 23:47:14 UTC 2008


I tried searching the TAPR archives and found one reference to the 
problem  from Mr. Brown, N5KUK, but nothing further.  No rush, Mr. Beal, 
not a high-priority, I am just curious.  The APRS specs allow for the 
digit, I assume, since it is displayed on the log files. 

Dave
AI4GF


will at beals5.com wrote:
> Folks:
>
> There is a lot of history on this!  Like everything else it was a conpromise. I'm on a trip now, but can see if I can dig them up this weekend.
>
> will 
> Sent with thumbs from a PDA
>
> -----Original Message-----
> From: John Yost <k3yjp at yahoo.com>
>
> Date: Thu, 10 Apr 2008 10:10:12 
> To:TAPR Weather Station SIG Mailing List <wxsig at lists.tapr.org>
> Subject: Re: [wxsig] Hobby Boards Barometer
>
>
> I am using a T238+ with the TAPR X1W-1 barometer kit.
>
> I see the same behavior, the local display in inches
> of mercury seems to be ok but loses the resolution
> when sent to aprs.
>
> my .02
>
> john
> K3YJP
>
> --- Ken Brown <Ken.A.Brown at noaa.gov> wrote:
>
>   
>> The problem with the pressure reading only reporting
>> whole millibar
>> readings is not in the barometer but in the T238
>> code that converts
>> the reading received from the barometer to the
>> millibar reading
>> transmitted.  At my station, n5kuk, I have two T238s
>> each with a
>> Bray barometer. One is on APRS and one is a test
>> unit on the bench.
>> Both exhibit the same problem. The problem is seen
>> on the APRS output
>> but not on the displayed value in inches of mercury.
>>  I use the APRS
>> T238 as a standalone with it's own tnc and radio. 
>> On another APRS
>> station with WinAPRS the nice weather graph clearly
>> shows the stair
>> step of the pressure reading. My units are T238 and
>> not T238+.  On
>> the bench unit the reading were noted on the rad
>> RS-232 output that
>> would go to a tnc in APRS service.  Both T238 units
>> running the latest
>> firmware.
>>
>> Ken, n5kuk
>>
>> Dave Barton wrote:
>>     
>>> More information on this issue.  This web site, 
>>>
>>>       
> http://www.wxqa.com/callsminmax/index_callsminmax.html,
>   
>> has logs of 
>>     
>>> T238+ weather stations.  I've only checked a
>>>       
>> handful of T238+ stations, 
>>     
>>> but I have found a couple of stations which seem
>>>       
>> to to have the same 
>>     
>>> issue as mine, N5KUK and K3YJP-4.
>>>
>>> There is another station, KA1GEU*, *that has a
>>>       
>> normal range of first 
>>     
>>> decimal places.  However, his station is reporting
>>>       
>> via the Internet, not 
>>     
>>> radio.
>>>
>>> I'll try to find more examples after work today. 
>>>       
>> Now I wonder if it's 
>>     
>>> the modem board?
>>>
>>> Dave
>>> AI4GF
>>>
>>>
>>> Gerry Creager wrote:
>>>       
>>>> I'll have to get some sleep, then check but I
>>>>         
>> think the APRS spec, and 
>>     
>>>> therefore FindU, resolve to 1 mB.
>>>>
>>>> More's the pity.
>>>>
>>>> gerry
>>>>
>>>> Dave Barton wrote:
>>>>         
>>>>> I am puzzled by something.  I recently bought
>>>>>           
>> and hooked up a Hobby 
>>     
>>>>> Boards barometer (B1-R1-K) and it seems to be
>>>>>           
>> working OK.  One thing 
>>     
>>>>> I am seeing is that the barometric pressures
>>>>>           
>> reported by FINDU almost 
>>     
>>>>> always have a .0 for a decimal millibar value. 
>>>>>           
>> In other words, 
>>     
>>>>> 1016.0, 1017.0, 1018.0.  I have occasionally
>>>>>           
>> seen xxxx.1 or xxxx.2, 
>>     
>>>>> but never xxxx.3 through xxxx.9.  My FINDU plots
>>>>>           
>> (AI4GF-4) have a 
>>     
>>>>> very jumpy barometer chart.  The barometer is
>>>>>           
>> supposed to have a 
>>     
>>>>> resolution of 0.007 in.Hg.
>>>>>
>>>>> I looked at the raw packets and the anomaly is
>>>>>           
>> reflected in the raw 
>>     
>>>>> packet.   I have the latest firmware, 1.15.8R.
>>>>>
>>>>> I saw a suggested mod of a resistor in parallel
>>>>>           
>> with R1 but have not 
>>     
>>>>> done that because I don't quite understand the
>>>>>           
>> mod.  Could this 
>>     
>>>>> problem somehow be related to not having done
>>>>>           
>> the mod?
>>     
>>>>> 73, Dave
>>>>> AI4GF
>>>>> Tallahassee, FL
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>>
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