[Milsurplus] TCS Receiver: "More than one way to skin..."

[AKLDGUY .]

Dave
I'm also out and about. You can see where I'm at with the APRS network.

http://aprs.fi/#!mt=roadmap&z=11&call=a%2FZL1ANM-9&timerange=3600&tail=3600

I'm stationary in the mall right now but that map will update automatically
when I get on the move again. You can zoom in/out with the + and - buttons
at left.

If you're that worried about RF, the capacitor could go to ground from the
V2 side of the zener, once again making sure there is no oscillation.

73 DE Neil ZL1ANM
On 14/02/2016 2:58 pm, "David Stinson" <arc5 at ix.netcom.com> wrote:

> Neil:
> I read your letter while out with the wife and got to thinking about it.
> When the B+ rises above the breakdown on the zener, the diode goes into
> conduction.  So any RF rides on the conduction, just like diode switching
> of RF in modern, plastic toy radios.  The cap is not needed.  I did scope
> it as-is and there was no oscillation, but your point is well taken.  Now
> moot, since it's not required and I removed it from the circuit. The thing
> one learns with a hot soldering iron. ;-)
> 73 Dave AB5S
>
> ----- Original Message ----- From: "AKLDGUY ." <neilb0627 at gmail.com>
> Subject: Re: [Milsurplus] TCS Receiver: "More than one way to skin..."
>
>
> I see two problems with the 0.047 capacitor across the zener.
>> The first is that at the instant the B+ is turned on, V2 is subjected
>> to the full 220V B+,
>> since the capacitor is essentially a dead short until charging gets
>> underway.
>> That high voltage may have a detrimental effect on V2's life.
>>
>> The second is that a capacitor placed across a zener or voltage
>> regulator tube may
>> create a relaxation oscillator if the timing constants happen to favour
>> it.
>>
>
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