[ARC5] BC-221 Testing Results

[Richard Knoppow]

----- Original Message ----- 
From: "Leslie Smith" <vk2bcu at operamail.com>
To: "J. Forster" <jfor at quikus.com>; "ARC-5 List" 
<arc5 at mailman.qth.net>
Sent: Saturday, November 24, 2012 6:18 PM
Subject: Re: [ARC5] BC-221 Testing Results


> Hi John & group,
> My comments below (about wave-forms at different 
> frequencies) are based
> on conjecture, without supporting theory.
> Briefly, I built an interesting oscillator, based on the 
> principle of
> negative resistance.
> This circuit requires a two terminal tank to be connected 
> to the active
> "negative resistance".
> The negative resistance consists of a JFET and a PNP 
> transistor, with 2
> resistors and by-pass caps.
>
> One side of the tank is grounded.  This makes a simple 
> circuit that will
> oscillate over the frequency range from sub-sonic (say 5 
> or 10Hz) to HF.
> Generally the output waveform is sinusoidal (as seen on a 
> CRO), and so
> relative "clean".
> I never put it on a spectrum analyser, but I think a 
> good-looking sin
> wave will be pure on the analyser, because that's what the 
> theory says,
> and I trust the theory.
>
> In general terms the neg resistance circuit will oscillate 
> when the
> reactances of the tank components are as low as 70 to 100 
> ohms, and much
> higher (say 1000 ohms, reactive).  However, at the lower 
> sub-audible
> frequencies the waveform became quite distorted.
> This (distortion) occurred when the reactance of the tank 
> "L" (in this
> case I used a power transformer) was high.
> I put this down to large energy storage in the tank "L" 
> (large "L",
> large reactance) and the same energy amount of energy was 
> then shifted
> to a small "C".
>
> I see a corresponding situation in your high band vs low 
> band
> observation in the BC-224
> It's conjecture, but interesting conjecture, on my part.
>
> BTW, I found your report VERY informative.
> I love this mailing list, for this reason.
> There are so many interesting observations, and they are 
> instructive.
>
>
>  Les
>  vk2bcu at operamail.com
>
    What kind of inductors did you use for higher 
frequencies?  If air core I wonder if the distortion you got 
came from the iron core transformer.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com