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[aprssig] FREQ Object Formats

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Mon May 7 23:41:15 UTC 2012


On 5/7/2012 7:25 PM, Bob Bruninga wrote:
> The example "FFF.FFF +" is only listed as an example in the SECOND 10-byte
> field, which ONLY applies to a separately explicitly listed frequency.  It
> is NOT part of the original FFF.FFFMHz format.  What I was referring to
> below, is that it is also NOT parseable as part of the "xyz" part of an
> OBJECT NAME either.
>
> Let me say it again, the only parsable offsets are +xxx or -xxx where xxx is
> in 10's of KHz.

Wait, are you saying that the table below isn't just EXAMPLES of the 
nuggets of information that can be transmitted in a frequency comment, 
but are EXPLICTLY the ONLY combinations that are LEGAL?  I surely didn't 
read it that way and was under the (apparently mistaken) impression that 
a frequency specification comment could include any combinations of:

FFF.FF MHz or FFF.FFFMHz
FFF.FFFrx
Tnnn or tnnn
Cnnn or cnnn
Dnnn or dnnn
1750
+nnn or -nnn
+ (and by extrapolation) -
Rnnm or Rnnk
(and maybe more)

and if I wanted to I could build a packet that said:

146.850MHz Toff -060 R20m PCARS Repeater

even though that particular sequence is not explicitly listed.  Did I 
completely miss the boat on this one?   And if so, then the 
specification, IMHO, definitely needs quite a bit of clarification work 
if any ones-and-zeros literally logical programmer is expected to pick 
up on what's legal and what's not.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PS.  From http://www.aprs.org/info/freqspec.txt:

>      1st 10-BYTES  Frequency Description
>      ----------    -----------------------------------------------------
>      FFF.FF MHz    Freq to nearest 10 KHz
>      FFF.FFFMHz    Freq to nearest  1 KHz
>
>      Examples:
>      146.52 MHz Enroute Alabama
>      147.105MHz AARC Radio Club
>      146.82 MHz T107 AARC Repeater (Tone of 107.2)
>      146.835MHz C107 R25m AARC     (CTCSS of 107.3 and range of 25 mi)
>      146.805MHz D256 R25k Repeater (DCS code and range of 25 km)
>      146.40 MHz T067 +100 Repeater (67.8 tone and +1.00 MHz offset)
>      145.50 MHz t077 Simplex       (Tone of 77.X Hz and NARROW band)
>
>      2nd 10-BYTES  Optional Added fields  (with leading space)
>      ----------    -----------------------------------------------------
>      _Txxx RXXm    Optional PL tone and nominal range in miles
>      _Cxxx RXXm    Optional CTCSS tone and range in miles
>      _Dxxx RXXk    Optional DCS code and nominal range in kilometers
>      _1750 RXXk    Optional 1750 tone, range in km, wide modulation
>      _l750 RXXk    Optional 1750 tone narrow modulation (lower case L)
>      _Toff RXXk    Optional NO-PL, No DCS, no Tone, etc.
>      _Txxx +060    Optional Offset of +600 KHz (up to 9.90 MHz)
>      _Exxm Wxxm    East range and West range if different (N,S,E,W)
>      _txxx RXXm    Lower case first letter means NARROW modulation
>      _FFF.FFFrx    Alternate receiver Frequency if not standard offset
>      _FFF.FFF +    Alternate Frequency and standard shift

Which would even mean that a 1750 tone must only express range in 
kilometers, and never miles?   I don't think you really mean that....




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