[hpsdr] Front End protection

[Hollingsworth, Tommy]

Has anyone considered the low voltage TVS parts from Semtech?
This is a 5 volt clamp with 5 uA leakage.  It was designed for this purpose.

Part no  uClamp0524P

http://www.semtech.com/products/product-detail.jsp?navId=H0,P3077
 
Tommy Hollingsworth KE5LFR

-----Original Message-----
From: hpsdr-bounces at hpsdr.org [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of
Giancarlo Moda
Sent: Thursday, February 22, 2007 9:25 AM
To: hpsdr at hpsdr.org
Subject: Re: [hpsdr] Front End protection

***** High Performance Software Defined Radio Discussion List *****

Hi  all,

Cerberus or Kerberos (Greek ÊÝñâåñïò, Kerberos, "demon of the pit") was the
hound of Hades, a monstrous three-headed dog with a snake for a tail and
serpentine mane.

Our ADC may need something better than Cerberus as he was overcome several
times:

* Hercules' final labour was to capture Cerberus, which he did by wrestling
it into submission.
Fightings between old mixers, qsd and adc could give highly distorted and
spured signals.

* Orpheus used his musical skills to lull Cerberus to sleep.
This could be a danger coming on 40m from Broadcasters splatters and signals
... and IMD !!!

* Hermes put him to sleep with water from the river Lethe.
Water should not be a problem.

* In Roman mythology, The Sybil of Cumae lulled Cerberus to sleep with
drugged honeycakes in order to permit Aeneas fuller entry to the underworld.
Maybe today we could use some good original italian spaghetti  and good
wines ... still through advertisements on broadcast  transmissions ... lot
of IMD !!!.

* In a Greek tale, Psyche also lulled Cerberus to sleep with drugged
honeycakes.
Maybe we will have to watch some of those sweety, flashy and porno electrons
flying in the air...

Any addition to the front end wiull bring possible noise figure increase,
attenuation, distortion.. ??
Maybe we could use a couple of LEDs like the old NE-2 gas lamp used with
valve/tube RXs (my homebrew RX 17 valves plus a nuvistor had an NE-2 ...not
only Drake .. hi). Two leds in parallel but opposite pinsconnection could
work ... flashing and or blowing.... these are only two heads of our
electronic cerberus .... people that can afford it could test them in such
an application.

73

Gian
I7SWX
  

Message: 12
Date: Thu, 22 Feb 2007 12:14:02 +0100
From: Jeroen Bastemeijer <J.Bastemeijer at TUDelft.nl>
Subject: Re: [hpsdr] Front End protection
To: FRANCIS CARCIA <carcia at sbcglobal.net>
Cc: hpsdr at hpsdr.org
Message-ID: <45DD7AFA.40408 at TUDelft.nl>
Content-Type: text/plain; charset="us-ascii"

Hi Francis,

It wasn't a god, but a dog-like creature called Ceberus (if my memory serves
me well).

In my opninion a combination of resistors and diodes (to the power suply
lines) is the best solution. The resistors will limit the current and
provide some "soft clipping". By soft-clipping all sorts of distortion
generated by the receiver are avoided.

Regards, Jeroen PE1RGE

FRANCIS CARCIA wrote:

>***** High Performance Software Defined Radio
Discussion List *****
>
>  
>
>
> 
------------------------------------------------------------------------
>
> I don't know which Greek God guarded the gate but
how are we going to 
> protect this fast A/D from static and lightning
transients? Racal
used 
> an interesting active limiter ahead of the RA6830
because the older 
> RA6790 had real bad burnout problems with the FETs
in the first
mixer. 
> I would think we need more than a NE2 across the
input.  Frank WA1GFZ
>
>-----------------------------------------------------------------------
>-
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--
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl




 
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