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[aprssig] PHG - dBi or dBd ?

Patrick winston at winston1.net
Mon Sep 29 12:28:36 UTC 2008


Add emphasis to the "do not very accurately represent true coverage".... 
there's a digi to the west of me which says that it has 2-3 times the 
coverage that it really does, at least in the north and west 
directions...  part of the fun of the rolling hills of the area..

p

Heikki Hannikainen wrote:
>    Hi Chuck,
>
> On Mon, 29 Sep 2008, Chuck Kimball wrote:
>
>   
>> I've noticed that aprs.fi is using dBi for it's display of the info
>> provided by PHG.
>>
>> In looking through Bob's and most other references of PHG they only
>> specify dB not specifying dipole or isotropic.
>> So which is it?   Do I need to reprogram my digis with dBi numbers?
>>     
>
> The APRS Spec addendum 1.1 clarifies the specification that it is dBi:
>
>    http://eng.usna.navy.mil/~bruninga/aprs/aprs11.html
>
>    "The Antenna Gain in the PHG format on page 28 is in dBi."
>
> The PHG circles do not very accurately represent true coverage, so if they 
> *roughly* match with your mobile (half-sized circles) or fixed station 
> (full-sized circles) coverage, and if it's hard to reprogram the digis, I 
> wouldn't go through an awful lot of effort to change the configuration.
>
>    - Hessu, OH7LZB
>
>
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>   




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