Vorläufig / Preliminary, work in progress
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RF Amplifier 2W
In Chinese shops you can buy for about 7 EUR an RF-Amplifier module with an advertised output power of 2 W.
On the right is a picture of the module.
Unfortunately it looks like, that I got a bad clone, explained further down.
Let's see with some measurements, if it does so.
- Supply voltage:DC 12 V (typical 0.3 - 0.4 A)
- Working frequency: 1 MHZ-930 MHZ,
- input and output impedance: 50 ohms;
Maximum input power: 0 dBm (1 mW)
Maximum output power:
- 2.0 W (33 dBm) low frequency (10 MHz)
- 1.6 W (32 dBm) IF end (512 MHz)
- 1.0 W (30 dBm) high end (930 MHz)
- 0.8 W (29 dBm) high end (1000 MHz)
- Size: 48 x 48 x 13 mm
I use the following equipment:
Adjustable Power Supply with current limiting.
Attenuators 6, 20 dB (SMA connectors)
RF Wattmeter RW-151D, company Kuranichi Keisokui (5, 25, 150 W full scale)
RF Testgenerator frequency 10 MHz, output power +13 to -23 dBm at 50 Ohm, waveform: sinus (tinySA).
nanoVNA-V2 Vector Network Analyzer.
DSO Hantek DSO5072P
- Coax cables to connect
The input power was varied between -16 dBm to -22 dBm
The gain factor was about 15.4 dB (920 MHz) to 46. dB (10MHz)
Maximum output power (clipped) was 1.0 W = 30.0 dBm = 20.0 Vpp (10 MHz)
Maximum output power (sine) was 0.5 W = 27.0 dBm = 14.2 Vpp (10 MHz)
Supply voltage: 12 V
Current draw was about 0.25 A (3 W)
Power efficiency was 17% to 33%
See following the DSO screen shots from the output signal:
The left screen shot shows the 10 MHz sine drive at Vcc = 12 V, on the right you see the FFT, just 20 dB to the second harmonic. The output power at 50 Ohm is 0.5 W.
The left screen shot shows the 10 MHz over drive at Vcc = 12 V, on the right you see the FFT, just 15 dB to the second harmonic. The output power at 50 Ohm is 1.0 W.
With the Vector Network Analyzer nanoVNA-V2 and some attenuators it was possible to measure the frequency response.
See below the measurement setup:
See below the the frequency response measurement:
While testing the amplifier, I found that the heat sink gets pretty hot. So, I measured with an IR thermometer the temperature at the Power Amplifier Ground with 48 °C at 21°C room temperature. The RF output was 0.1 W (930 MHz) at this time. At 1.5 W (10 MHz) the temperature is only 34 °C at 21°C room temperature, because of the better efficiency.
I assume that it will give no problem with over temperature in normal use.
The very different measurement values compared to the specifications let assume, that this board is a bad clone.
The Amplification curve on the right I found in a news group nanovna-beta-test. It corresponds with the Specification of this amplifier. Therefore I bought 3 boards at Aliexpress.
Unfortunately the Frequency response measured is way off the vendor Specification.
I checked the data sheet of the semiconductors. The first is a SBB2089Z, labeled BB2Z. The S21 value (Amplification) of 20 dB is flat within 1 dB from 50 to 850 MHz.
The second one could be a RD01MUS2B. Then it is understandable, why the amplification at 930 MHz is so low.
Within the measured values this amplifier is useful, especially considering the price. You just have to consider, that it is not a broad band linear amplifier.
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-- RudolfReuter 2020-12-19 22:13:07