[Lowfer] 600MRG> Question about parallel diodes

[Andy - KU4XR]

Thanks Paul:

You corrected an incorrect statement I made about the diode " clipping "
the voltage. It acts more as a switch. You lose the .07v in voltage drop
before forward conduction and the diode switches " on ". Thus the
" switching diodes " of today.

Pat mentioned something I read in an article on power supply noise
in active antennas:

--- On Sun, 6/6/10, P.E.Hamel <pehamel at cableone.net> wrote:

> Andy,
> Early on, the semiconductor diode strings were shown with
> equalizing resistors and disk capacitors across each diode.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> but the newer silicon diodes will have much less current than 
> the older diodes and much less noise power will be generated.
> I hope this answers your question.
> 73,
> Pat /6

The article I read, ( and saved ), was about the noise generated
in the power supply used for an active antenna. The writer 
mentioned adding .1µF caps across the diodes to lower the noise 
generated at LF, and VLF. The article was from 2006, so relatively
new. I am curious there now. It might fall into the catagory of
" it won't hurt " BUT; would there be any real world benefit in
adding the capacitors across the diodes, specifically for receivers?
A sidebar thought; at LF and below, Mother Natures noise is probably
by far worse than any noise generated by the power supply diodes,
with the exception of switch mode supplies maybe.


Andy - KU4XR - EM75xr - Friendsville, TN. USA
LOWfer Beacon " XR " @ 185.29875 KHz ( QRSS-60 )
Coordinates:  N:  35º 43' 54" - W:  84º 3' 16"
http://www.myspace.com/beaconxr
http://webpages.charter.net/ku4xr/


--- On Sun, 6/6/10, P.E.Hamel <pehamel at cableone.net> wrote:

> From: P.E.Hamel <pehamel at cableone.net>
> Subject: Re: 600MRG> Question about parallel diodes
> To: "Andy - KU4XR" <ku4xr at Yahoo.com>
> Date: Sunday, June 6, 2010, 1:24 AM
> Andy,
> Early on, the semiconductor diode strings were shown with
> equalizing 
> resistors and disk capacitors across each diode.
> A zener diode is what is used as a noise generator.
> The reverse leakage current and the physics create noise.
> Parallel diodes will each still see some reverse leakage
> current, but the 
> newer silicon diodes will have much less current than the
> older diodes and 
> much less noise power will be generated.
> I hope this answers your question.
> 73,
> Pat /6
> 
> ----- Original Message ----- 
> From: "Andy - KU4XR" <ku4xr at Yahoo.com>
> To: "600 meter group" <SHMRG at piobaire.mines.uidaho.edu>;
> 
> <lowfer at mailman.qth.net>;
> "Part-15 Yahoo" <part15 at yahoogroups.com>
> Sent: Saturday, June 05, 2010 11:48 PM
> Subject: 600MRG> Question about parallel diodes
> 
> 
> > Thanks for any replies: I have just recently come to
> understand that
> > a diode can be, or make noise in a circuit. Frankly, I
> had never
> > considered that before, until Charlie - W5COV began
> discussing it
> > with me on power supply topics. It finally dawned on
> me that a
> > diode " clips " the voltage peaks of a sine wave, this
> inherently
> > creates noise in the process by distortion of the
> signal voltage.
> > OK, my question: In theory, or real world practice,
> would putting
> > 2 diodes in parallel help in any way to lower the
> noise it might
> > generate, OR ::: would it in fact double the noise
> generation.
> > I'm not approaching this concerned about current
> handeling, I'm
> > specifically curious about the diode noise. And to
> clarify; the
> > diodes will be anode to anode / cathode to cathode,
> not anti -
> > parallel.
> > Looking forward to the education; 73 all :::
> >
> >
> >
> > Andy - KU4XR - EM75xr - Friendsville, TN. USA
> > LOWfer Beacon " XR " @ 185.29875 KHz ( QRSS-60 )
> > Coordinates:  N:  35º 43' 54" - W: 
> 84º 3' 16"
> > http://www.myspace.com/beaconxr
> > http://webpages.charter.net/ku4xr/
> >
> >
> >
> > *********** The Primary 600MRG E-mail List Website is:
> **********
> > ******************* http://www.500kc.com/
> ***********************
> > ******* Secondary is: http://www.mines.uidaho.edu/~shmrg/ *******
> > *** Send subscribe and unsubscribe requests to this
> address: ****
> > ************** majordomo at piobaire.mines.uidaho.edu
> **************
> > 
> 
>