[Elecraft] K3 birdies

[David Gilbert]

When I built my K3 (with the 2nd receiver) well over a year ago I had 
lots of birdies between on most of the bands, although very few on 80m.  
With a dummy load on the antenna port, I logged any birdie S2 or greater 
(I have a really low noise level at this QTH) and then monitored them 
all (yes, all of them) as I played around with various cable positions.  
It soon became obvious that eliminating one birdie often strongly 
accentuated a different one, so I spent a lot of time trying to find a 
decent middle ground and then did my best to hold the cables in those 
positions with cable ties and tape.  The SIG RMV software fix that came 
out a few weeks later was a remarkably innovative godsend and totally 
fixed any remaining issues.

I tried some out-of-the box methods to reduce the birdies before the 
software fix came out.  One was to buy a sheet of anti-static material 
(carbon impregnated foam), cut it into sections that fit into sandwich 
baggies, connect a wire to each of them that could be grounded to the 
case inside the K3, and position them around the various cables.  The 
idea was to create some sort of lossy shielding to reduce the coupling.  
It actually helped a bit, but it made a large difference where I 
connected the wires to ground (understandable since the wire now also 
act as antennas) and the overall improvement wasn't worth the hassle.

By the way, the 2nd receiver is FAR better shielded and I could find 
only a couple of very weak birdies on it, while I had thirty or more S2 
or above (roughly half of which were S3 and about four at S4) on the 
main receiver.  Since I assembled everything before checking for birdies 
I never did a comparison of main receiver birdies with and without the 
2nd receiver installed, but based upon my experience with various cable 
placements it is my strong belief that having the 2nd receiver installed 
makes the birdies worse in the main receiver, presumably because the 
shield of the 2nd receiver creates more coupling between the cables 
behind the front panel.

I still have a couple of birdies on certain frequencies that I never use 
and haven't bothered with, and as might be expected they are STRONGLY 
microphonic.  Tapping on the case while listening to them can be almost 
startling.  It always made me wonder what the transmitted signal would 
sound like on the birdie frequencies if the rig was "physically 
modulated" by other gear on the desk, or even through the air, but I 
haven't walked myself through the frequency chain to see if it would 
even be relevant.

73,
Dave  AB7E


On 4/20/2010 8:26 AM, Guy Olinger K2AV wrote:
> Routing the cables when adding the second RX was very tricky and
> caused birdies to appear and disappear while being moved around.
> Though it is an added cost, a premade wiring harness to enforce a
> tested good routing would be useful.
>
> Or perhaps if there was an actual size template of a wiring harness to
> be assembled as part of the kit, with some pre-printed stickers to put
> on the cables.
>
> Precise routing is fairly left to chance as currently implemented.
>
> I also hear far less birdies (next to none relatively) tuning across
> the band in CW, vs. SSB.
>
> To be fair, most birdies are buried in a busy band without effect, and
> require a dead band to hear them.  In mine there were three that were
> obnoxious enough to bother killing them with the menu device.  I do
> NOT experience related audio gaps as reported by some others.  I DO
> get gaps if I overcorrect.
>
> 73, Guy.