Question about Power measurements

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Luca66
 

Posts: 123
Joined: 16 Apr 2022, 13:02

Question about Power measurements

Post by Luca66 »

Hi Guys I have a question to ask

I noticed that the output power measurements made with a dummy load applied to the antenna connector

they provide substantially different results when a small impedance transformer for wire antennas is applied instead of the dummy load.

In practice, what happens is that with the 50 ohm dummy load applied, the power efficiency reading is about 3 Watts with 70% efficiency.

By replacing the dummy load with a small impedance transformer for wire antennas, the power measurement rises to about 3.6 Watts with an efficiency of 72%.

I am sure of the quality of the measurement of the instrument (OLED) inside our small transceiver as I have verified by measuring the voltage across the dummy load that the watt indication is correct.

For the sake of completeness of information, I report that the measurements were carried out with a 12 volt power supply and between the transceiver and the small antenna tuner I use an rg58 cable of about 30 cm.
DL2MAN
 

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Re: Question about Power measurements

Post by DL2MAN »

What is your question, then ?
You observed, that your output Power changed, when your load changed from 50 Ohms to unknown.
When you change the load, the behavior of your PA Stage will change.

73 Manuel; DL2MAN
Luca66
 

Posts: 123
Joined: 16 Apr 2022, 13:02

Re: Question about Power measurements

Post by Luca66 »

DL2MAN wrote: 25 May 2022, 07:29 What is your question, then ?
You observed, that your output Power changed, when your load changed from 50 Ohms to unknown.
When you change the load, the behavior of your PA Stage will change.

73 Manuel; DL2MAN
Hi Manuel, thanks for the reply. Obviously, by changing the load applied to the transmitter, the system reacts accordingly. In my case what I observe is that with a 50 ohm dummy load I get a power and when I connect an impedance adapter that always shows the transmitter 50 ohm the power increases. Because? They are always 50 ohms in both cases.
DL2MAN
 

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Joined: 30 Dec 2021, 19:18
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Re: Question about Power measurements

Post by DL2MAN »

Let´s assume both really are 50 Ohms (Which I doubt):
Your Dummy Load is in most Parts resistive, while your Antenna System is a complex Impedance constisting of L,C and R.

73 Manuel; DL2MAN
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