Sub Receiver I.F. Tap

[wa9fvp]

I notice on the sub-receiver schematic dated 8/18/08 that there was a connector for a plug-in board. I assume it was for an I.F. buffer plug-in circuit that connects to J93 for an I.F. tap.  I didn’t see that on the KRX3A but the jumper W3 is near connector J78. Is it possible to attach a J309 to and duplicate the circuit on the main receiver?

John Albert WA9FVP
WillcoElectronics.

[Elecraft mailing list]

Yes it is possible 
I was going to replacate the buffer amp as it was on the main receiver for my sub receiver 




-------- Original message --------
From: wa9fvp <[hidden email]>
Date: 2017-04-15  11:52 PM  (GMT-05:00)
To: [hidden email]
Subject: [Elecraft] Sub Receiver I.F. Tap

I notice on the sub-receiver schematic dated 8/18/08 that there was a
connector for a plug-in board. I assume it was for an I.F. buffer plug-in
circuit that connects to J93 for an I.F. tap.  I didn’t see that on the
KRX3A but the jumper W3 is near connector J78. Is it possible to attach a
J309 to and duplicate the circuit on the main receiver?

John Albert WA9FVP
WillcoElectronics.





-----
Jack WA9FVP

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--
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[Edward R Cole]

I brought out the 1st IF of the sub receiver from that point using
0.001 uF disc ceramic coupling cap to RG-174 coax snaked out thru a
hole in the sub-Rx shield to a BNC on  back panel of the K3.
http://www.kl7uw.com/LINRAD.htm

scroll down to the heading: Connecting K3 Sub-Receiver IF to LP-Pan


Date: Sat, 15 Apr 2017 20:52:46 -0700 (MST)
From: wa9fvp <[hidden email]>
To: [hidden email]
Subject: [Elecraft] Sub Receiver I.F. Tap
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=UTF-8

I notice on the sub-receiver schematic dated 8/18/08 that there was a
connector for a plug-in board. I assume it was for an I.F. buffer plug-in
circuit that connects to J93 for an I.F. tap.  I didn?t see that on the
KRX3A but the jumper W3 is near connector J78. Is it possible to attach a
J309 to and duplicate the circuit on the main receiver?

John Albert WA9FVP
WillcoElectronics.


73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]
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[wa9fvp]

 Edward R Cole  wrote ;

I brought out the 1st IF of the sub receiver from that point using
0.001 uF disc ceramic coupling cap to RG-174 coax snaked out thru a
hole in the sub-Rx shield to a BNC on  back panel of the K3.

-------------

I think that connecting the coax via a capacitor would load and mistune the I.F..  That's why the main receiver was designed with a buffer JFET.

[Edward R Cole]

Jack,

If by "mistune" you mean that the impedance will be loaded down, yes
that is likely.  A buffer amp following will solve that .  My reply
was merely to indicate tapping the 1st IF at W3 is a good
decision.  I run both main Rx IF and sub Rx IF to LP-Pan that have
the optional IF amps installed (now std in the LP-Pan 2).  Both
appear to work fine bringing out the 1st IF to my LP-Pan which in
turn provide IQ baseband input to a four port soundcard for diversity
reception on 2m-eme (a special application using digital modes).

I did determine that feeding the 1st IF to the 2nd IF of the K3
loaded the panoramic display at frequency zero, so I select a xtal
location that is unfilled to effectively disconnect the 2nd IF.  But
normal use of the K3 using the entire receivers works fine.  I do not
detect any loading of the 1st IF by either LP-Pan.

Now probably one should use a 0.01uF cap instead of 0.001uF for 8.215
MHz.  That will provide a little more RF coupling.

One other item I did omit is the use of a ferrite on the RG-174 for
isolating the shield for any noise introduction to the IF.

73, Ed - KL7UW


From: wa9fvp <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] Sub Receiver I.F. Tap
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=us-ascii

  Edward R Cole  wrote ;

I brought out the 1st IF of the sub receiver from that point using
0.001 uF disc ceramic coupling cap to RG-174 coax snaked out thru a
hole in the sub-Rx shield to a BNC on  back panel of the K3.

-------------

I think that connecting the coax via a capacitor would load and mistune the
I.F..  That's why the main receiver was designed with a buffer JFET.

-----
Jack WA9FVP


73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]

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