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P3 adding rf protection diodes question

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k5oai

P3 adding rf protection diodes question

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?? :-(
--
GB & 73
K5OAI
Sam Morgan
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Joe Subich, W4TV-4

Re: P3 adding rf protection diodes question

On 2014-05-19 9:38 AM, Sam Morgan wrote:
> It was mentioned to put a couple of diodes across the P3's input to
> protect it.

Don't! Back to back diodes will degrade the strong signal handling
of the K3 and the receive inputs already include protection including
gas discharge and a signal level detector that disconnects the input
if the level becomes too high.

73,

... Joe, W4TV

On 2014-05-19 9:38 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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Harlan Sherriff

Re: P3 adding rf protection diodes question

In reply to this post by k5oai

Sam
I would go with the 1N34a. It is a germanium diode and has a lower forward voltage drop than a silicon diode....thus a lower threshold for protection.

Harlan
NC3C

Sent from my Verizon Wireless 4G LTE DROID

Sam Morgan <[hidden email]> 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?? :-(
>--
>GB & 73
>K5OAI
>Sam Morgan
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

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k5oai

Re: P3 adding rf protection diodes question

In reply to this post by Joe Subich, W4TV-4

Joe,
apples and oranges perhaps?
I think you answered the question as if I was asking about the K3's
input...where as I was asking about the *P3* input which had no gas
discharge protection.

Perhaps I should have mentioned I was speaking of using a standalone P3
for the purpose of chasing rfi, as mentioned in a previous thread:

[Elecraft] P3 as a portable RFI bandscope?
by Jim Miller Sat, 17 May 2014 16:48:07 -0700

http://elecraft.365791.n2.nabble.com/P3-as-a-portable-RFI-bandscope-tt7589211.html

On 5/19/2014 9:20 AM, Joe Subich, W4TV wrote:

>
> On 2014-05-19 9:38 AM, Sam Morgan wrote:
> > It was mentioned to put a couple of diodes across the P3's input to
> > protect it.
>
> Don't! Back to back diodes will degrade the strong signal handling
> of the K3 and the receive inputs already include protection including
> gas discharge and a signal level detector that disconnects the input
> if the level becomes too high.
>
> 73,
> ... Joe, W4TV
>
> On 2014-05-19 9:38 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?

--
GB & 73
K5OAI
Sam Morgan
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Kenneth Christiansen

Re: P3 adding rf protection diodes question

Hi Joe.

I think you could use the 1n148 diodes and they should be OK across the input of the Elecraft P3. The problem is from larger static voltages that could destroy the solid state devices in the P3 but with the two diodes back to back the static voltages should be held to 0.6 volts and that low voltage should not cause any failure. The 0.6 volts may even be better than the 0.3 volt of the 1N34A as there will be less chance of inter mod distortion.

73 and good luck finding your noise.

Ken W0CZ w0cz at i29 dot net

Sent from my iPad

> On May 19, 2014, at 10:31 AM, Sam Morgan <[hidden email]> wrote:
>
> Joe,
> apples and oranges perhaps?
> I think you answered the question as if I was asking about the K3's input...where as I was asking about the *P3* input which had no gas discharge protection.
>
> Perhaps I should have mentioned I was speaking of using a standalone P3 for the purpose of chasing rfi, as mentioned in a previous thread:
>
> [Elecraft] P3 as a portable RFI bandscope?
> by Jim Miller Sat, 17 May 2014 16:48:07 -0700
>
> http://elecraft.365791.n2.nabble.com/P3-as-a-portable-RFI-bandscope-tt7589211.html
>
>
>> On 5/19/2014 9:20 AM, Joe Subich, W4TV wrote:
>>
>> On 2014-05-19 9:38 AM, Sam Morgan wrote:
>> > It was mentioned to put a couple of diodes across the P3's input to
>> > protect it.
>>
>> Don't! Back to back diodes will degrade the strong signal handling
>> of the K3 and the receive inputs already include protection including
>> gas discharge and a signal level detector that disconnects the input
>> if the level becomes too high.
>>
>> 73,
>> ... Joe, W4TV
>>
>>> On 2014-05-19 9:38 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?
>
>
> --
> GB & 73
> K5OAI
> Sam Morgan
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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Eric Swartz - WA6HHQ

Re: P3 adding rf protection diodes question

Administrator

In the lab here at Elecraft we took apart a M-F BNC 50 ohm terminator and put the back to back diodes inside. When we need to search the building for RF interference we just add it to the rear of a P3 running on batteries and use it with a collapsable whip and right angle BNC.

For the batteries we placed an 8 cell AA holder inside the cabinet.

73,

Eric
(Not quite awake after a 23 hour day working Dayton and from traveling back to CA last night..)
elecraft.com
_..._
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Fred Townsend-2

Re: P3 adding rf protection diodes question

In reply to this post by k5oai

Eric:
I would suggest an Elecraft adapter kit for the P3. The kit would contain the elements you suggest except an external battery pack and handy carrying handle. I would add ESD protection to the P3A?
I think the P3A and kit would compete favorably with other commercial RFI tools costing 10x$. I can see a book in the future, 'Chasing RFI with the P3' as well.
Wouldn't be cool to see P3 SNs higher than the K3 SNs?
73
Fred, AE6QL

-----Original Message-----

>From: Eric Swartz WA6HHQ - Elecraft <[hidden email]>
>Sent: May 19, 2014 9:35 AM
>To: Kenneth A Christiansen <[hidden email]>
>Cc: "[hidden email]" <[hidden email]>
>Subject: Re: [Elecraft] P3 adding rf protection diodes question
>
>In the lab here at Elecraft we took apart a M-F BNC 50 ohm terminator and put the back to back diodes inside. When we need to search the building for RF interference we just add it to the rear of a P3 running on batteries and use it with a collapsable whip and right angle BNC.
>
>For the batteries we placed an 8 cell AA holder inside the cabinet.
>
>73,
>
>Eric
>(Not quite awake after a 23 hour day working Dayton and from traveling back to CA last night..)
>elecraft.com
>_..._
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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Jim AB3CV

Re: P3 adding rf protection diodes question

In reply to this post by Eric Swartz - WA6HHQ

A BNC T with diodes at one female end and the whip on the other would be an
easy choice.

Now on my ROUNTUIT list.

jim ab3cv

On Mon, May 19, 2014 at 12:35 PM, Eric Swartz WA6HHQ - Elecraft <
[hidden email]> wrote:

> In the lab here at Elecraft we took apart a M-F BNC 50 ohm terminator and
> put the back to back diodes inside. When we need to search the building for
> RF interference we just add it to the rear of a P3 running on batteries and
> use it with a collapsable whip and right angle BNC.
>
> For the batteries we placed an 8 cell AA holder inside the cabinet.
>
> 73,
>
> Eric
> (Not quite awake after a 23 hour day working Dayton and from traveling
> back to CA last night..)
> elecraft.com
> _..._
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
>

Alan Bloom-2

Re: P3 adding rf protection diodes question

In reply to this post by k5oai

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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