[Elecraft] dBi dBd correction

[Guy, K2AV]

The way the regulation reads, hams are being told they can put 50 watts PEP
on an antenna, up to the gain of a dipole, and call that 50 watts ERP. 
Higher gain must be referenced to the dipole and the 50 watts reduced
accordingly. 

For mobile stations there is no mention of the idea that a LESSER antenna
may have the 50 watts increased. 100 watts appears to be in excess of
regulation.  Stated another way, 50 watts max regardless, unless the antenna
has more gain than a dipole in which case power must be reduced by a factor
representing the gain of that antenna over a dipole.

The whole thing is really interesting since there are really precise
definitions of ERP elsewhere in FCC referencia.  By the regular definition
of ERP 50 watts into a dipole for 5.3 MHz at 108 feet over medium ground
will have an ERP of 328 watts.  At 50 feet the ERP is roughly 200 watts. 

We had best be very careful with our privileges on 60m, because all FCC
would have to do is enforce regular definition of ERP and the same dipole at
108' would take seven and a half watts to obtain 50 ERP at pattern max.

73, Guy

It may also be that whoever wrote the reg was having a brain f**t at the
time, and they just haven't discovered it yet.

The max pattern gain and takeoff angle on a dipole



Joe Subich, W4TV-4 wrote:
> 
> 
> 
>> If my recollection is correct, 0 dBd is 2.15 dB greater than 
>> 0 dBi in the dipole's favored directions (perpendicular to the 
>> radiator).
> 
> Only in free space ... when a horizontal dipole is placed 
> above ground all of the radiated power is concentrated in 
> one hemisphere.  Since both the E and H fields are confined 
> to the single hemisphere, the resulting "gain" is 6 dB more 
> than the free space gain or 8.17 dBi (1.25 + 6.02).  
> 
> 73, 
> 
>    ... Joe, W4TV 
>  
> 
> 
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net 
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ron 
>> D'Eau Claire
>> Sent: Wednesday, May 06, 2009 5:32 PM
>> To: don at w3fpr.com
>> Cc: elecraft at mailman.qth.net
>> Subject: [Elecraft] dBi dBd correction
>> 
>> 
>> Yeah, I misread the rule. I thought the rule was saying a 
>> dipole was 0 dbi, not 0 dBd! Didn't make sense to me.
>> 
>> Gus, KB0YH also caught my mistake.  
>> 
>> Tnx for un-kinking my brain Guys!
>> 
>> 73,
>> 
>> Ron 
>> 
>> -----Original Message-----
>> 
>> Ron,
>> 
>> The FCC regulations for 60 meter power is referenced to the 
>> maximum lobe 
>> of a dipole.  Sooo --
>> That should be "0 dBd" (gain/loss relative to a dipole) 
>> rather than "0 
>> dBi" (gain relative to an isotropic radiator).
>> If my recollection is correct, 0 dBd is 2.15 dB greater than 0 dBi in 
>> the dipole's favored directions (perpendicular to the 
>> radiator). For those not familiar with an isotropic radiator, 
>> it is a point 
>> construct in free-space that radiates equally in all directions.
>> 
>> 73,
>> Don W3FPR
>> 
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