K3 BUFFER MOD?

[Bill Maddock-2]

Guys,

  Later today I will start building my LP-PAN kit - I was wondering
if the K3 Buffer mod that is recommended will void the warranty
on my radio? Is it really worth the effort? Where is best place to
attain parts? I have the K3 Audio line out mod kit to do figured
I should probably do it all at the same time? My S/N is 1059

Thanks and 73,

Bill N4ZI


     
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[Doug Joyce]

Bill:  I can't comment on the warranty part, but as to the rest -

I just finished my K3 (S/N 2432) and have the LP-Pan up and running with a
Dell D830 notebook and the E-MU 0202 sound card.  While it has only been in
use about a week and I've not completed all the calibration yet, use of the
K3 preamp (as Larry has suggested) seems to provide a noise floor of better
than -110 and I can see just about everything I can hear.  If you decide to
do the mod, the parts are available from Digi-Key.  The 49.9 ohm is P/N
RR12Q49.9DCT-ND and the 15.5K P/N is RR12P15.0KDCT-ND.  These are 1/10W .5%
0805 SMD and less than $4.00 for a qty of 50.

Based on the performance to date and the fact that I'm new to SMD I've not
felt the need to do the mod on my K3 yet, although I did get the parts a
week or so ago.

Hope that helps

73

Doug,  VE3MV


----- Original Message -----
From: "Bill Maddock" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, January 31, 2009 12:58 PM
Subject: [Elecraft] K3 BUFFER MOD?

> Guys,
>
>   Later today I will start building my LP-PAN kit - I was wondering
> if the K3 Buffer mod that is recommended will void the warranty
> on my radio? Is it really worth the effort? Where is best place to
> attain parts? I have the K3 Audio line out mod kit to do figured
> I should probably do it all at the same time? My S/N is 1059
>
> Thanks and 73,
>
> Bill N4ZI
>
>
>
> ______________________________________________________________
> 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
>
>

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[Richard Ferch]

Bill,

I am sure you will get more expert advice than I can give you on this, but
so far I have not found the buffer mod necessary with my LP-PAN - right now
I have only a vertical antenna and have only tried the LP-PAN out on low
bands, where band noise alone is clearly visible on the display even without
the mod. You may feel differently if you are using directional antennas on
quiet bands, but my suggestion would be to start out without the buffer mod
and see how well your LP-PAN works without it.

Although I have installed the Audio line out mod myself, I think it probably
won't make any difference to LP-PAN operation, since the LP-PAN does not use
line out. However, I found that the mod to bypass RF chokes in the ground
return lines made a big difference:
(<http://www.elecraft.com/K3/mods/ELECRAFT_Application_Note_Improving_the_Im
munity_of_the_Rear-Panel_KIO3_RS232_and_Audio_Connectors_to_RF.pdf>, or go
to <http://www.elecraft.com/K3/k3_app_notes.htm> and scroll down to the link
"Improving the Immunity of the Rear-Panel RS232 and Audio Connectors to
RF"). Before making this change, I was seeing a lot of polling noise from
the radio control serial port on the PowerSDR display. Bypassing the choke
in the RS232 ground return seems to have helped a lot in my case - YMMV, of
course.

73,
Rich VE3KI
K3 #1595


N4ZI wrote:

> Guys,
>
>   Later today I will start building my LP-PAN kit - I was wondering
> if the K3 Buffer mod that is recommended will void the warranty
> on my radio? Is it really worth the effort? Where is best place to
> attain parts? I have the K3 Audio line out mod kit to do figured
> I should probably do it all at the same time? My S/N is 1059
>
> Thanks and 73,
>
> Bill N4ZI

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[Bill W4ZV]

Bill Maddock-2 wrote

  Later today I will start building my LP-PAN kit - I was wondering
if the K3 Buffer mod that is recommended will void the warranty
on my radio?

Probably not.  Wayne is well aware of it and has never said the warranty would be voided.

Bill Maddock-2 wrote

Is it really worth the effort? Where is best place to
attain parts?

Unless you want to identify extremely weak signals, perhaps not.  On 160m nearly all DX signals are weak and many were not detectable without the mod.  I robbed junk SMD boards for the two resistors (R8/R9) but most major suppliers carry SMD parts (e.g. Mouser, Newark, etc.)

Bill Maddock-2 wrote

I have the K3 Audio line out mod kit to do figured
I should probably do it all at the same time?

It really doesn't matter.  The mod can be done by removing only the front bottom cover, which is extremely easy to access anytime.

73,  Bill