[Amps] Tuned input design / measurement questions

[Carl]

: [Amps] Tuned input design / measurement questions


>
>
>  16/04/2013 16:34
>
> May I ask a question re my construction of a tuned input circuit? I am
> converting a Henry 2000D RF Generator on 27.12 MHz to (initially) a
> single band (20 meter) linear amp. I am trying to build the tuned
> input circuit, after checking it works on 27 MHz. The 3CX3000A7 valve
> has a cathode input impedance of about 48 Ohms. It has a stock Henry
> Pi input tuned circuit comprising a slug tuned coil on a half inch
> diameter former (about 4 turns 20 gauge wire), and two sets of
> paralleled dipped silver mica caps each side of the coil, to ground. I
> have acquired a new henry former and have wound it to give .475 uH on
> my AIM 4170 analyser. I have a pair of air variable caps of about 350
> PF max each. I have built it as per the photos at:
>
> http://www.chriswilson.tv/pi/input_pi.zip
>
>
> The idea of this Pi circuit came from my reading and is to
> is to add Q and give a flywheel effect, ideally needed in Class AB GG
> linear inputs.
>
> http://www.eham.net/ehamforum/smf/index.php?topic=12665.0
>
> See last post by W8JI Tom Raunch.
>
> You all know this of course, don't get me wrong, just showing my source!


Yeah while his explanation appears OK its this line that gets many laughing:
---------------------
"That may or not be an issue with your SB-200. I can not recall the coponent 
values of the SB-200, it was designed long before I designed products for 
Heath."
----------------------

There werent enough on the Internet in early 2001 to question his resume 
accuracy...........

Carl
KM1H