I would like to ask is it normal for a watt meter showing pep watts to show a wattage difference switching from a antron 99 to a 3 element gizmotchy beam. When my brother is using his amplifier putting out 1k there is a 200 watt pep difference that will show on the meter. The beam shows 200w more output over antron 99 . There also is a difference between the two antennas without output amplified. I thought that a meter would show only true output going out and antennas could cause no difference but it shows a difference. Can swr cause this possibly . Thank You Jimbo165
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Wattage difference between antennas
- Thread starter Jimbo165
- Start date
First of all, what kind of meter are you using? Unless its a powered PEP meter its about as much use as a chocolate fireguard and you need to use a constant tone to get an accurate reading. That is why you should really do it on a carrier mode such as CW.
Secondly yes SWR can make a difference. Importantly common mode RFI can also skew the readings. Lots of things to do with the antenna can skew readings which is why you test into a dummy load. Has he adjusted plate and loading on the amp for each antenna assuming its a tube amp?
However assuming SWR is within tolerance and if its a tube amp the plate and grid currents are right then don't worry about it. The difference between 800W and 1kW is barely even 1/4 of a S point and not going to be noticed by the receiving station.
Secondly yes SWR can make a difference. Importantly common mode RFI can also skew the readings. Lots of things to do with the antenna can skew readings which is why you test into a dummy load. Has he adjusted plate and loading on the amp for each antenna assuming its a tube amp?
However assuming SWR is within tolerance and if its a tube amp the plate and grid currents are right then don't worry about it. The difference between 800W and 1kW is barely even 1/4 of a S point and not going to be noticed by the receiving station.
Copy and paste from Walt Maxwells book "reflections"
." Contrary to our prevalent, deeply ingrained belief, it is therefore not true that when a transmitter delivers power into a line with reflections, a returning reflected wave always sees the internal generator impedance as a dissipative load and is converted to heat and lost. It can happen under certain conditions of pulse-type transmission; for instance, if the generator is turned off after delivering a single pulse into the line while retaining its internal impedance across the line, the returning pulse wave will be absorbed.
"THIS IS THE PART YOU WANT TO UNDERSTAND HOW THE DIFFERENT ANTENNAS CAN MAKE A POWER READING VARY EVEN THOUGH THE POWER IS NOT INCREASED OR DECREASED FROM THE TRANSMITTER."
" But if a conjugate-matched generator is actively supplying, power when the reflected wave returns, the reflected wave encounters total reflection at the conjugate match point and is entirely conserved, because it never sees the generator resistance as a dissipative terminating load. This is because the source and reflected voltages and currents superpose, or add at the match point, just as if the reflected power had been supplied by a separate generator in series with the source. And since the source voltage is generally greater than the reflected, the sum of their voltages yields a net current flow which is always in the forward direction.6 The reflected power adds to the source power, deriving reflection gain which compensates for the reflection loss suffered at the mismatched termination.
." Contrary to our prevalent, deeply ingrained belief, it is therefore not true that when a transmitter delivers power into a line with reflections, a returning reflected wave always sees the internal generator impedance as a dissipative load and is converted to heat and lost. It can happen under certain conditions of pulse-type transmission; for instance, if the generator is turned off after delivering a single pulse into the line while retaining its internal impedance across the line, the returning pulse wave will be absorbed.
"THIS IS THE PART YOU WANT TO UNDERSTAND HOW THE DIFFERENT ANTENNAS CAN MAKE A POWER READING VARY EVEN THOUGH THE POWER IS NOT INCREASED OR DECREASED FROM THE TRANSMITTER."
" But if a conjugate-matched generator is actively supplying, power when the reflected wave returns, the reflected wave encounters total reflection at the conjugate match point and is entirely conserved, because it never sees the generator resistance as a dissipative terminating load. This is because the source and reflected voltages and currents superpose, or add at the match point, just as if the reflected power had been supplied by a separate generator in series with the source. And since the source voltage is generally greater than the reflected, the sum of their voltages yields a net current flow which is always in the forward direction.6 The reflected power adds to the source power, deriving reflection gain which compensates for the reflection loss suffered at the mismatched termination.