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작성자원더우먼가요 조회 1회 작성일 2021-06-19 12:48:07 댓글 0


RF 증폭기 예비보고서

RF 증폭기(amplifier)로 사용할 수 있는 CE(common emitter) 증폭기를 QUCS(Quite Universal Circuit Simulator) SPICE로 설계한다. 먼저 TR의 바이어스(bias) 회로를 설계한다. 바이어스로 설정한 동작점을 기준으로 소신호 해석을 수행한다. 이를 통해 CE 증폭기의 AC 증폭도를 계산할 수 있다.

RF Power Amplifier Construction

In this video I am showing how I built an RF power amplifier for my HF amateur radio experiments. This amplifier puts out up to 37 watts with one watt input on the lower Amateur Radio HF bands
Sverre Bonsaksen : Your "digital readout wattmeter" seems interesting, do you have information about it?
Ron Taylor : The digital wattmeter is adapted from an article by W8TEE and AC8GY titled “Build an Inexpensive 150 Watt Dummy Load with Wattmeter” published in the Nov 2018 issue of QST magazine.
Ambro Ribo : very good video : thaks for sharing your experience.
Your explanation is very accurate and it will so simple for me to buildup one. The point for me is the output filter since I do not have special instruments available here at my station: could you please post the data to build a power low pass filter for 80, 40 , 20 and 10 meter?
Thanks for all.
Tim F : This is an answer on a filter question which is hidden as a reply below

you either go to QRP labs and buy the filter from there or you use Motorola Application note 267 which is still available on the web. This covers several filter topologies including the Pi type filter which I believe is Net 3 in that note. Look it up and work it out.
Zout for the amplifier (depends on mode - the above is oriented to CW mode but it will operate as a linear at lower power out.

THe output impedance from the amp to match is approximately 2 * (Vcc - 2 ) squared / Pout where Pout is say 30 W for CW use and 16 W for SSB use using much higher bias approx 600 mA total quiescent current through the sum of the Drains. If you are designing a two PI filter you should chose sqrt ( output Z x 50) and match into that using the equations given in the application note. and using a filter Q of either two or three - your choice. Q is defined inn the application note. The RHS filter on the output can be designed using the tables in the Appn note as you know the RHS termination is fifty ohms. You need to have basic EE knowledge to do this ie you need to know how to go from impedance to L and back again and how to do the inductor turns calculations.

Those are covered in the toroid tables of The Toroid king - search on line. Such filters can only be approximate as there is tolerance on the properties of the iron powder material. A size fifty toroid will be adequate for a 30 W rf filter. The capacitors should be either multilayer monolytic or Silver mica. The latter are preferred for low loss. The Toroid king sells them. If you want a seven element filter you have to extend the above description.

THe application note shows how you can subtract Co of the respective Mosfet from the calculated filter C1 capacitor. This is not applicable for a fully isolated OP transformer as used here. It is applicable for class C choke type circuits which is a whole different matter. Basically, the Appn note assumes single ended RF construction so you have to show some initiative when applying it to a push pull RF amplifier.

BTW you may wonder where I got the 16 W above from . Kees Talen used to offer a pretty sophisticated kit with a similar design and it used identical Active devices from MItsubishi. His considered max Pout with full Fcc Compliance was 16W out. This was on the basis of a 2 Pi filter or two section filter following the power amp and 14 V supply. If you take the voltage up to say 16 , which is outside the manufacturer's specification for these devices and if you over drive them (he used just 600mW in) whereas Ron uses one watt, you may well get of order 30 W out on CW but you may not be FCC compliant. The FCC requirements are considerably harsher for transmitters over 5 W out and some people don't allow for this.

In addition of you wire the output transformer for 2T out you will have a nominal output Z of 72 ohms (running the amplifier for 16 W out nominal) and if you treat that as 50 R you get only three percent mismatch loss if you design the filters as 50 R in and 50R out. I think Diz specified 1:3T (I have his original schematic just to try to get a bit more efficiency out of the filter by running it as a higher voltage input device in the first two sections.

Regards TE Fidler Nz.
HufiVideo : Solid good old RF construction technique!
vy 73, HB9BTL

RF 파워 증폭기 특성화 테스트

RF 파워 증폭기의 특성화 테스트 진행시, 기존 박스형 계측기와 비교하여 내쇼날인스트루먼트(NI)의 PXI 계측기를 사용했을 경우 얼마나 빠르고 효율적으로 테스트를 진행할 수 있는지 확인해보십시오.




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