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Radiation and power output
1. EM (HM) Field:
Reactive Near Field (1 : 2π)λ = 350m.
Radiating Near Field (1 : 2π)λ to 4λ = 350m to 8800m.
Far Field = > 8800m.
2.Radiation
EIRP (effective isotropically radiated power) product of power supplied
to an aerial and its gain (hypothetical).
ERP (effective radiated power) product of power supplied to an aerial
and its gain relative to a half wave dipole.
EMRP (effective monopole radiated power) product of power supplied to an
aerial and its gain relative to a short vertical aerial mounted on a ground
plane.
3. Norm
The Radio
Regulations define:
In a perfectly
conducting plane area
1kW EMRP
means 300mV/m FS in 1km distance
1kW ERP
means
222mV/m
1kW EIRP
means 173mV/m
Measuring the
fieldstrength (FS) the radiated power is determined by
Peirp = 0,0111( E
• d)2
-P in W, E in mV/m, d in km
0, 0111(300 • 1) = 1000W EMRP
0, 0111(222 • 1) = 547W ERP
0, 0111(173 • 1) = 332W EIRP
If
EMRP, ERP and EIRP have to be compared the
following factors are in use:
0,547 = 547/1000
(ERP/EMRP)
0,61 = 332/547 (EIRP/ERP)
1,64 = 547/332 (ERP/EIRP)
1,83 = 1000/547 (EMRP/ERP)
3,01 = 1000/332 (EMRP/EIRP)
The overall view:
ERP = 1,64EIRP
ERP = EIRP/0,61
ERP = EMRP/1,83
ERP = 0,547EMRP
EMRP
= 3,01EIRP
EMRP
= 1,83ERP
EIRP = ERP/1,64
EIRP = EMRP/3,01
4.Efficiency of aerial
Efficiency according to the progr "grndwav" = 0,06%.
( Rloss = Rrad/efficiency = 0,05/ 0,0006 = 83Ω. Rrad
see loadcoil )
5.From TX pwr to radiated pwr
a)Ropex 156W
b)home brew 600W
EMRP = TXpwr • efficiency
a,)EMRP = 156W • 0,0006 = 94mW (ERP = EMRP/1,83
= 51mW)
b,)EMRP = 600W • 0,0006 = 360mW (ERP = 197mW)
6.From aerial current to radiated power
a,)
I = 1,5A aerial current. 1,52 • 0,05 = 112mW EMRP
b,) I = 2,8A aerial current. 2,82 • 0,05 = 392mW EMRP
Remark: The HF thermo current meter is not calibrated.
And now the truth:
7. From FS to radiated power
FS measured with calibrated receiver ESH3 and loop HF12-Z2 (R&S equipment for standard FS measurements).
P eirp = 0.0111(E • d)2 - Watt, mV/m, km - .
FS of DJ8WX signal measured in a distance of 1,806km:
a,) 1,5mV/m
b,) 3,2mV/m
a,) EIRP = 0,0111(1,5 • 1,8)2 = 0.0111 • 7,25 = 81mW
ERP = 1,64 • 81 = 132mW.
b,) EIRP = 0,0111(3,2 • 1,8)2 = 0,0111 • 33,2 = 368mW
ERP = 1,64 • 368 = 603mW.
Remarks abt some short transmitting tests:
I modified the aerial, see "New arrangement of aerials" < arrangementofaerials> .
The FS in 1,8km distance changed from 3,2mV/m (70dBµV/m) to 4,5mV/m
(73dBmycroV/m) using the home brew TX:
b,) EIRP = 0,0111(4,5 • 1,8)2 = 0,0111 • 65,6 = 728mW
ERP = 1,64 • 728 = 1,194W.
Newly change: The power output has been increased. The FS changed from
4,5mV/m to 5,4mV/m (74,6dBuV/m):
b,) EIRP = 0,0111(5,4 • 1,8)2 = 0,0111 • 94,5 = 1,05W
ERP =
1,64 • 1,05 = 1,7W.
TX power output = 2020 • 0,0006 = 1,2kW.
ERP has to be 1,0W .
So TX power output decreased.
Measurement of power output
Measurementequipment:
Dummy load DC - 2GHz "SPINNER" 1kW(30dB) 50Ω, reflectionfactor
0,04.
Meters R&S URV5 V, W, dBm, dBV display and oscilloscope OS5020P.
Insertion unit R&S URV-Z2,
9kHz - 2GHz, 10V.
The power output of the two transmitters
a)Ropex
b)home brew
have to be examined.
1. With an oscilloscope the voltage is measured at the transmitter
output and on the assumption that the impedance is 50Ω the power output
is calculated.
1.1 TX output is connected via 80m RG213U to the aerial system. The system
is tuned to maximum of aerial current:
a,) 147 Vpkpk • 0,707 = 104Vrms
I = U/R = 104 / 50 = 2,1A
N= U • I = 104 • 2,1 = 218W
b,) 283Vpkpk • 0,707 = 200Vrms
I = 200 / 50 = 4A
N = 4 • 200 = 800W
1.2 TX output connected to dummy load "SPINNER" Z50Ω:
a,) 125Vpkpk • 0.707 = 88,4V rms
I = 88,4 / 50 = 1,768A
N = 1,768 • 88,4 = 156,3W
b,) 248Vpkpk • 0,707 = 175Vrms
I = 175 / 50 = 3,5A
N = 3,5 • 175 = 612W
2. Measurement with URV equipment:
a,) 155W
Check: I = √ (N/R) = √ (155/50) = √ 3,1 = 1,76A
U = I • R = 1,76 • 50 = 88Vrms.
b,) 605W
Check: I = √ (605 / 50) = 3,46A
U = 3,5 • 50 = 173Vrms
Summary.
155W and 605W are the correct results. Calculations from FS to radiated
power and via efficiency to TX output power are (almost) confirmed by those
results. So what about the results 218W and 800W? Unfortunately I can not offer an absolut value for the TX output
current because the HF current meter is not calibrated. The Vpkpk measurements
are correct. The other factor, the impedance, must be wrong. I changed the
matching point at the TX side of the loading coil again and again. The
situation did not alter.
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