[hpsdr] ALEX - Call for comments - Protection devices.

[Henry Vredegoor]

Hi All, Lyle,

Yes, I found a number of similar diagrams showing the same solution like
yours.
I somehow like the idea of having this in my receiver front-end circuit!

The NE2 can be found easily on the net as well.

A spec of a particular supplier:

<
NEON NE2 120V 0.059W USA bulb specifications:
----------------------------------------------------------------------------
----
 
category:  Glow Lamp 
volt:  120 
watt:  0.059 
base:  1 INCH WIRE 
glass:  T2 
filament:  W11 
m.o.l.:  1.06 inch (26MM) 
d.hours:  6000 

notes: 
 
after 100 hours at design current
DC breakdown volts:70avg
DC maintain volts:59avg
DESIGN CURRENT/MA:0.3
end of life is 5V change in breakdown for maintaining voltage
maximum diameter:0.275inchs
PRE-AGED:NO
VOLTAGE RANGE:105-125V
neon glow lamp 
>



Looking at the website pointed to by Tommy Hollingsworth, KE5LFR, for the
TVR devices, I learned a little bit more about protection in general. (lots
to read!)
These seem to be mainly aimed at protection of data interface lines,
although I could imagine that they would also be useful in radio front-end
circuits - I have no experience in this field.
Anybody?

Another question arises as well: How good are the Janus ADC inputs
protected?
I know there will normally be at least e.g. a RF band pass filter and some
QSD between the antenna and the Janus inputs, but I could imagine that while
experimenting with these (That's what it is all about here with HPSDR....
;-) ) there could be risks of damaging the Janus inputs while connecting and
disconnecting things?
Any thoughts?
(I'll have a look at the diagram of Janus)

73

Henry.

> -----Original Message-----
> From: hpsdr-bounces at hpsdr.org 
> [mailto:hpsdr-bounces at hpsdr.org] On Behalf Of Lyle Johnson
> Sent: dinsdag 6 maart 2007 16:00
> To: hpsdr at hpsdr.org
> Subject: Re: [hpsdr] ALEX - Call for comments - Protection devices.
> 
> 
> ***** High Performance Software Defined Radio Discussion List *****
> 
> >>> Quick search, subject: "Front End Protection"
> >>>
> >>> 1. Good old NE2(A1A) Neon Bulb
> >>> 2. Two diodes antiparalel
> >> The JRC NRD-525 receiver used two anti-paralleled diodes 
> as a mean of input protection, but the common advice on its
> >> Yahoo discussion group was to remove them as soon as 
> possible, as they can generate IMD products in presence of strong
> >> BC stations. I suppose the same holds for two LEDs in 
> anti-parallel.
> 
> A high value resistance to ground to prevent static buildup 
> (100K to 1 
> Meg) in parallel with a spark gap offers no distortion and clamps 
> induced surges (not direct hits by lightning, of course).  
> Caps in the 
> front end filters should be rated somewhat higher than the 
> spark gap - 
> you don't want to use 25V caps in a 70V-protected system!
> 
> Try searching Digikey for "surge arrestor gastube" for EPCOS' 
> offerings. 
>   The lowest voltage ones ought to be suitable.
> 
> 73,
> 
> Lyle KK7P
> 
> 
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