BNC connectors are designed in such a way that the shield always
connects before the center conductor when you plug it in. The only way
to get a static discharge into a female BNC is to somehow touch the
center conductor (with your finger or whatever) without touching the
shell. You would need to use a tool to do that unless you have REALLY
skinny fingers. :=)
Alan N1AL
On 05/20/2014 11:31 AM, Fred Townsend [email protected]
[Elecraft_K3] wrote:
Alan, thank you for the good information on how to setup the P3 as a
"poor ham's spectrum analyzer". However I must disagree with your first
statement. Diodes for ESD protection are needed in normal use with the
K3. When ESD occures it is frequently at connector interfaces because
the two mating bodies may be at different potentials. Good design
practice for ESD is to protect connector interfaces if the user will be
mateing and un-mateing. This is clearly the case with the K3/P3
combination. Diodes are soo cheap when applied in the SMD process it
seems like a no brainer to include ESD protection. Defeat Murphies law.
73
Fred, AE6QL
-----Original Message-----
From: "Alan Bloom [email protected] [Elecraft_K3]"
Sent: May 20, 2014 10:42 AM
To: [email protected], [email protected]
Subject: [Elecraft_K3] Re: [Elecraft] P3 adding rf protection diodes
question
The diodes are not needed in the normal situation where the P3 is
connected to the K3 IF output.
You can use the P3 as a kind of "poor ham's spectrum analyzer" by going
into the menu and setting "Xcvr Sel" to the last item in the list,
labeled "0 Hz". Now the frequency displayed is the actual RF frequency
of the IF input, not the K3 frequency. The "XCVR" RS-232 connector
should be disconnected from the K3 in this case. Tune the frequency
with the CENTER control. (Make sure the "CenterEn" menu item is "ON".)
If you do that you should add the back-to-back diodes in parallel with
the input BNC connector. Standard 1N4148 or similar switching diodes
are
fine. If you don't want to modify the P3 you can do what I did: Add
the back-to-back diodes to a male BNC connector and connect that to a
BNC "T" plugged into the P3 IF IN.
There may be some slight degradation of dynamic range. The third-order
intercept of the P3'! s preamplifier is about +9 dBm (0.6 Vrms). If
you're worried about it you can use two diodes in series in each leg (4
diodes total) to reduce the distortion contribution from the diodes.
Alan N1AL
On 05/19/2014 06:38 AM, Sam Morgan wrote:
> It was mentioned to put a couple of diodes across the P3's input to
> protect it. Do the diodes need to be 1n34a's or would 1n4148's be
ok for
> that application?
>
> I had tried repeatedly to ask Don W3FPR this question off list via
> direct email, but I guess all my efforts have ended up in his spam
> folder?? :-(
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