little rf amplifier

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radium98
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little rf amplifier

Post by radium98 » Tue Aug 29, 2023 7:43 pm

Question
i need to make a little amplifier on 210mhz about a half to 1w . i have consulted the datasheet of both transistors wich i have , for 2n4427 wich i have one left and it say Ft transistion175mhz and another say up to 400 mhz .A 2n st 2n3866 1w 400mhz ft .wich one is better , could i also try a 2n2219a ? general purpose up to 250mhz
and a 2sc1971 will work with less power prediction i know it is 175 but i mean for 210 mhz .The excitation of the pll board is S9018 then maybe i will use in between steps a bfr96ts wich i have .
what do you suggest . :tup

radium98
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Re: little rf amplifier

Post by radium98 » Tue Aug 29, 2023 7:44 pm

i forget to say that i have an mrf517 , can this be used as a final .

Albert H
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Re: little rf amplifier

Post by Albert H » Thu Aug 31, 2023 3:37 am

I always preferred the 2N3866. The ones I used to use were TRW ones, and their Ft was higher than most of the other manufacturer's versions. Unfortunately, the '3866 is a 28V device, and you have to use at least 18V to get useful gain out of them at higher frequencies. My little UHF link transmitters used to have a pair of 2N3866s running in parallel for about 3 Watts output at 470 MHz.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

radium98
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Re: little rf amplifier

Post by radium98 » Fri Sep 01, 2023 8:04 pm

you are the only one wich i like that , who told me to use 2n3866 i still have 3 , one from ST one rca and the last one i think copy fake mot , but work the better lol .but i tried on fm with 15v . And the last one i have is an mrf517.Albert if can you please drop me a little design with one bfr96 and 2n3866 on the frequency i need , please .205-210mhz

Albert H
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Re: little rf amplifier

Post by Albert H » Sat Sep 02, 2023 2:24 pm

What are you trying to achieve? There are plenty of circuits around for the 225 MHz amateur band. What transmission mode do you intend to use (AM, SSB, FSK, FM, PM etc...)? How much power do you need?
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

radium98
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Re: little rf amplifier

Post by radium98 » Sat Sep 02, 2023 2:56 pm

i need to make an amplifier by hand for this frequency . modulation is fm , i want to amplify a microphone transmitter , can you make me a scheme ? the output will be the 2n3866 and the driver is bfr96 . if you can not i will have to look in an old manual , but this will be extra hard work for me now , other modules or transistor no .

Albert H
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Re: little rf amplifier

Post by Albert H » Mon Sep 04, 2023 1:51 am

The 2N3866 isn't a good choice for this kind of purpose - it's a 28V device and doesn't have much gain if you use it at lower supply voltage. You really need to shop for some more modern lower voltage devices for a battery-powered microphone transmitter amplifier.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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