A 3.2 Watt RF Amplifier from AliExpress

This is a less than $20 amplifier from China. It made 3 Watts at 7 MHz and about 1 Watt at 700 MHz.
Links:
www.gswagner.c...

[@pstonard]

Nice review, thanks for presenting it. Another test you may consider is to input a CW signal and use your Spectrum Analyzer to measure the output harmonics. If this amplifier is to be used as a transmitter final stage it is important not to radiate our-of-band. The solution is to construct a low pass or band pass filter to attenuate the harmonics to be legal. Note the FCC rules: §97.307 Emission standards. ... (d) For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission.

[@acestudioscouk-Ace-G0ACE]

Thanks for making this video. Interesting and useful.

[@bjtaudio]

You can run them at or below 12V with a modest drop in performance. You can adjust the power output by simply dropping the supply voltage with just 1mw of input, works well up to 500Mhz. If a small pie output attn pad say 1.3db is installed the antenna can be removed for short periods without damage to amp as it has at least some load on it works for up to 30dbm out, the trick is limit voltage and the current drawn to prevent destruction of output amp.

[@robertlong2531]

Big thanks for finding this little gem and reviewing it.

[@valetech8751]

Thanks for the review. So would you recommend this for QRP HF operations?

[@raadkamil1756]

Thank you so much

[@user-dk5pl1dg7r]

1 is sbb2089z (or similar) 2 is rqa0004 (or similar).

[@stevestrivia-bystevewagner4852]

Thanks! Steve

[@keyboarderror1]

@@stevestrivia-bystevewagner4852 I've fixed dead ones with an SBA-5089 for the driver and a PD85004 for the output. Just for the list of options.

[@_nemo171]

Great!

[@ericlindal8008]

Nice video.

[@leonsebel9237]

Hi Steve ! Thank you for the video, I'm looking into buying this amplifier for a small RF project. What is the name of the connectors/cables that you use to hook up the amplifier to the source and antenna ?

[@stevestrivia-bystevewagner4852]

For work on the bench, I use SMA connectors, male or female as required with RG174 coax. It has some loss, so long cables (10 ft or more) are avoided but I like the flexibility. www.ebay.com/itm/143494709575 Similar diameter is RG316 but sort of stiff. www.ebay.com/itm/143955791825 Beware of RP-SMA, they are for special use and will not fit regular SMA devices. Steve

[@leonsebel9237]

@@stevestrivia-bystevewagner4852 Thank you very much, that is some great information right there

[@oilsmokejones3452]

My question exactly because I have the 1 watt model....thanks for asking..

[@Voiceguitar]

Hi Steve. I am seeking an RF amplifier that can input 250mw and boost to 3 watts+. Frequency range is 470-480mhz. Do you have any recommendations? Thanks!

[@awalfarouk8200]

What do you want to use it for I can help you in specifics

[@jpdesroc]

Do you think, with small modifications this amplifier could be used in the MW band (500Khz to 1700Khz) ? Thanks.

[@stevestrivia-bystevewagner4852]

I nont thik so. Steve

[@DeeegerD]

Haven't heard you mispronounce components in some time 😅. Perhaps this would make a good amp for a home brew qrp transmitter?

[@inkits1]

Steve whats the input drive required,?

[@grzesiek1x]

is it worth it? I don't trust AliExpress in complex circuits, buying simple staff like diodes etc. is ok for me but I am just looking at some original RF amplifier from Mouser for less than 1$ which has a gain about 22 dB for 2.2 GHz

[@F_Tim1961]

The aD 8009 Video amp chip is your friend. It won't go to GHz but it will produce up to 350 mW of clean AB class oput power into 50 R with about a 20 dB gain, right across the HF spectrum and a bit less at 52 Mhz. It can direct drive an RD16HH RF mosfet in Class A biasing through a capacitor 0.1 uF MML type with no coupling transformer .

[@fotografm]

Please could you measure the linearity of the amplifier to see if it can be used for ssb and measure the harmonic output ?

[@ltlt6117]

I have some problems!!! How rf power amplifier works I have a walkie talkie that have a rf power amplifier module inside and powered by 7.5v and have 5watts of power into the antenna How this is happening? We know our antenna have a impedance of 50 ohm so if: I = v÷r P= v × I I= 7.5v ÷ 50ohm=150mA P=7.5v×150mA=1.12 watts So why ican see 5watts in my power meter

[@watson946]

Output impedance of the PA transistor in your radio will not be 50 ohms, it will be less. There will be some impedance matching to bring it up to the required 50 ohms for antenna. Try reading about impedance matching PA stages👍

[@leonsebel9237]

Hello Steve ! I have another question, what type of antenna should I hook up to the RF out side of such amplifier ? Is there a certain type that I should use ?

[@stevestrivia-bystevewagner4852]

That depends very much on the signal frequency. Steve

[@leonsebel9237]

@@stevestrivia-bystevewagner4852 Thanks Steve for your answer ! Since it's a FM amplifier I'm looking into 90Mhz to 110 Mhz. Is there a type of antenna or length that would be optimal for those frequencies ?

[@oilsmokejones3452]

I've had good luck using shortened mobile CB antennas for FM broadcast freqs...as Steve says ofcouse longer or shorter for different frequencies..at this power level perfect matches are not essential but then again the closer the better..hint: 100 mhz wavelength is 3 meters or 9.8 ft...1/4 and 1/2 wave dipoles usually work pretty good..

[@DeeegerD]

No link to this on ali or ebay?

[@n1kkri]

Do you know what Class Amplifier it is?

[@F_Tim1961]

It's class A . all MMICs work as Class A... that's part of reason for the heat generated.

[@johndavis1465]

The 2nd amplifier is a MOSFET not a MMIC.