Transistors 400mW v5 amplifier

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Re: Transistors 400mW v5 amplifier

Post by Admin on Sun Sep 15, 2013 4:44 pm

Hi Justin,
I do seem to remember your name although the specific conversations I have no recollection of. But it is always nice to hear a voice from the past, especially if that voice expresses so much positive feedback.

Regarding your questions, the 2B2369 works perfectly although my own experiences with that device is that they are cheap but very unforgiving. If you are pushing them towards their limits the just a nearby sneeze can cause them to pop. Otherwise thay are extremely good little devices for VHF. I have used them for a 300MHz stage microphone.

The 2SC3781 is a much better choice as I feel this is more built like brick toilet. I have had those so hot that I burned my finger on the can (no heat-sink) during experiments.

Another device not to underestimate is the IRF510. For 100MHz you MUST feed them with a low input impedance (25 Ohms or so) if you want stability, but remember to use a current limited PSU that will restrict the current to 3A per device. Using these beasties it is easy to get more than 400mW. You can easily get 25 Watts if you have sufficient drive.

Please let me know how you get on.

Keep up the experimenting, and I promise not to "let on" to the wife about your time with the V5 Wink 

Very best regards from Harry - SM0VPO

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Transistors 400mW v5 amplifier

Post by KG4UGI on Tue Sep 10, 2013 6:09 pm

My dear old friend Harry
  It has been many moons since I spoke with you via your message board (roughly 10 Years) I don't expect you to remember me
my name is Justin Roode (KG4UGI) you answered so many questions for me during my college years and I once again thank you so much for your time.
  I'm very pleased to see your site and message board is still up and running, I think I have been to every instructional, "electronics project" site on the web and in my opinion yours is by far the best and my personal favorite.

 I have been playing with my breadboard again lately and I see you have a 400mW amplifier geared towards amplifying the V5's RF output. I have to admit the V5 has entertained me for more Hours than I'll ever tell my wife, lol (I thank you for that)

My question today is about the transistors you used in the amplifier circuit, I have a bunch of 2n3866 laying around and I'm wondering if I could use those in place of the 2n2369 and 2SC3781 you used?

It's good to talk to you again Harry!!
 Thank You
  Justin R.
  KG4UGI

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