[600MRG] transmitting power

[Eric NO3M]

Shouldn't the peak antenna gain per modeling also be factored into the 
calculation?

The formula I use is:

EIRP(W) = TPO(W) * n * G(a), where:

n is efficiency -> R(rad) / R(feed)
G(a) is antenna gain factor -> 10 ^ (G(dBi) / 10)
G(dBi) is antenna's peak modeled gain

In most cases, a vertical monopole will have 2-3 dBi gain resulting in a 
power factor of 1.6 - 2 (or a further lowering of transmitter power).

Experimental operators that had previously been running at 5W "ERP" also 
now have to reduce output power by 1.64 to comply with the 5W "EIRP" 
limit, which is about a 2dB reduction:

EIRP(W) = 1.64 * ERP(W)

73 Eric NO3M

On 10/27/2017 02:24 PM, Rudy Severns wrote:
> Just a heads up on transmitter output power measurements.
>
>   
>
> Like many of us with experimental licenses I’ve had to dial back transmit
> power, 6 dB in my case.  To estimate my radiated power I’ve been using a
> measurement of transmitter output power and the efficiency of my  antenna.
> I derive my radiation efficiency using the ideal antenna Rr from NEC divided
> by the measured input resistance from the antenna.  This gives a reasonable
> estimate of efficiency.  My amplifier has a power output meter which I was
> using but recently I was able to acquire a Bird 4410 directional wattmeter
> with the 200-535 kHz slug (4410-1).  I discovered my transmit power was
> about 20% lower than what the Bird was reading!
>
>   
>
> In the past I’ve seen the Bird 200-535 kHz slugs for Bird wattmeters but
> they are marked “10 kW”, which is a tad high for me so I gave them a pass.
> That rating is what you might get in a Bird model 43 which many of us have
> but the 4410 has a dial-in divider which will take the power level down to
> 10W!  If you are a ham flea market habitué keep your eyes open and grab one
> if you see it.  Later if you have a chance to beg,  borrow or steal a 4410
> you’ll have a very good estimate of output power.
>
>   
>
> This is of course not the only way to estimate output power but it’s really
> handy if you get the chance.
>
>   
>
> 73, Rudy N6LF
>
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com