[Elecraft] K3 Synthesizer Stiffener Plate Mod

Tue Sep 7 17:50:48 EDT 2010

Hello Lou: 

The changes introduced by the stiffener are not consistent over all rigs and
all operating setups. That's why I didn't mention the possibility of
reducing birdies in my earlier e-mail. Clearly additional shielding is
always a good idea and Wayne agrees, although it's impossible to quantify
the improvement for every K3, so it's not mentioned to avoid setting
unrealistic expectations.

The underlying reason for the stiffener is to avoid acoustic modulation of
synthesizer VCO and, as Lyle noted, that can cause some receive issues as
well as transmit issues, so that's another reason to modify both
synthesizers. Again, most K3 owners never noted any issues in transmit or
receive, even though they used the K3's internal speaker.

Following Elecraft's policy of ongoing design improvements, the stiffeners
were introduced into the K3 design and, again according to Elecraft's policy
of not forcing existing rigs to become obsolete, the modification kit was
made available to all current owners who want it. To me, that's one of the
major points the sets Elecraft apart from other manufacturers that I am
aware of. It have K3 S/N 10 dating back to early 2007. It's the K3 you see
in all the assembly manual photos and the various mod kit instructions. With
those mods installed it is functionally and electrically identical to the
K3's being shipped today. 

If you are thinking of Carlos, IK4ISQ, who rerouted his KRX3 cables to
eliminate some birdies, Wayne asked me to try his idea last year. I found an
improvement. Wayne then had a number of other fellows repeat the test and
they found *no* significant change. Go figure, Hi!  That demonstrates just
how "situation specific" this issue remains. So Carlo's mod was not made an
official part of the K3 design. What we do know and can demonstrate is that
the cable routing is important. That's why there are specific routing
instructions in the KRX3 manual. That arrangement is the one Wayne developed
originally as being the best and it's the one the factory assembled K3's
use. But that does not mean that some other routing might help in your case,
just as it obviously helped Carlos. 

Some birdies are inevitable in a complex rig like the K3. You simply cannot
have that many oscillators operating in close proximity and not have them
interact in ways that will occasionally put a mixing product strong enough
to be heard inside the receiver bandpass. And now with the P3 you see
birdies that you would not otherwise ever hear because they remain outside
the bandpass all or most of the time but can be seen on the wideband
display. 

Ron AC7AC

-----Original Message-----
All:

A local friend just received his K3 Kit and took some photos
of the assembly.  I noticed the stiffeners right away and
contacted Gary at Elecraft Support regarding aquiring two
for my rig.  I seem to have some annoying birdies and
figured this shielding would help in at least reducing them.

Gary mentions in his email that they would do nothing for
the birdies.  He sent along a pictorial of a Italian gent
who has rerouted his TMP cables in such a way to
substantially reduce receiver birdies.  This is on my "to
do" list for the radio next time I take it offline.  But,
frankly, its much more fun to USE it than to WORK on it! 
(as an ex Triumph Spitfire owner, I've been there and have
several hundred T-Shirts!) 

I had stopped considering the shields... But Wayne inferred
here that they *DO* add shielding... And with the size of
the birdies, some shielding is better than no shielding!
(PS, I *HATE* the software birdie removal... It punches
holes in the bands! I would rather put up with the birdies
than mask them!)

So, Elecrafters, do we need these "stiffener plates" for
sheilding or for the removal of microphonics, or do they
contribute to both?  (BTW, I dont expect them for free, but
I dont expect to pay $50 plus shipping for them, either!)

I never use the rig with the internal speaker, as I have
external speakers and 99% of the time I use a headset... 
But I might take it portable someday. 

Yes or no on this "modification"?  Will it or will it not
help the annoying birdies?  

I work hard to keep my rig at the latest "factory standard".
 Is this an "elective" or a "requirement"?

-lu-W4LT- 
K3 #3192

***** 

Message: 13
Date: Tue, 07 Sep 2010 08:53:20 -0700
From: Lyle Johnson <kk7p at wavecable.com>
Subject: Re: [Elecraft] K3 Synthesizer Stiffener Plate Mod
To: elecraft at mailman.qth.net
Message-ID: <4C865FF0.9040904 at wavecable.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

  Loud internal speaker audio can cause small VCO sidebands.
 If 
present, it causes them on receive as well as transmit.

73,

Lyle KK7P
> As you say you only transmit on the "main VCO"  so putting
the shield on
the
> main vco would deal with speaker rumble issue so putting
it on the subvco
> maybe to improve shielding?

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