[hpsdr] Front End protection

[Giancarlo Moda]

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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