[Elecraft] L34 on K2 tuning question?

[Geoffrey Mackenzie-Kennedy]

Kevin,

When I first aligned my K2 I followed the instructions written in the manual
for tuning L34 using the quote 'weak' 7 MHz birdie - more like a angry
elephant. After doing some work to reduce the number of K2  receiver
birdies, it struck me that the 7 MHz birdie signal is entering the receiver
chain at not just one place, or could be perhaps two separate signals from
different sources.  If one 'birdie' signal had established itself in the
receiver chain before L34 and another 'birdie' signal  entered the chain
AFTER L34, then tuning L34 as suggested in the manual using the birdie might
not result in best overall receiver performance in terms of noise floor.
Tuning L34 will have an effect on the combined level of the two birdie
signals as seen by Spectrogram as a single signal (tuning birdie against
birdie),  and some effect on the observed noise floor, but not necessarily
result in the overall noise figure which the receiver is capable of
'delivering' at 7 MHz and other bands. Tuning the 40m bandpass filter does
affect the 'before L34 birdie', an effect noted by Bill KE5KWE.

Using a signal generator connected to the antenna input running at a
frequency further up the 40m band, to separate the observed signal from that
wretched 7 MHz birdie, and setting the generator level so that the observed
output signal was about 10db IIRC above noise, I found the optimum position
of L34's slug to be near the top of the can but not at same place as when
using the birdie, about 1/2 turn below IIRC. With L34 tuned this way,
antenna noise can be heard on all bands 80m - 10m when using my K2 with a
400 Hz filter setting at this very quiet rural location.

73,
Geoff
GM4ESD


Kevin Cozens  <kevin at ve3syb.ca>  wrote.

> bill KE5KWE wrote:
>> I went through the same thing just today.  We also used a spectogram but
>> after failing to hear an apreciable change we followed the next
>> suggestion,
>> alligning the 40-meter band pass filter.  Once this was aligned we were
>> able
>> to tune L-34 by ear. It did indeed occur near the top of the can, as
>> stated
>> in the text.
>
> The internal signal on my K2 had peaked around the time that L34 was
> half-way down but the noise to the right of the internal signal didn't
> drop until about the time the slug hit the bottom of the can. Unless you
> use Spectogram to you may be close to the best position of the L34 slug
> but not at the ideal spot.
>
> One thing I'm interested in is the difference between the peak of the
> internal signal and the peak of the noise floor on K2 radios. On my radio
> I see a difference (between the black cross and red cross on the screen
> capture at http://www.ve3syb.ca/tmp/K2-L34.jpg) of about 17db as seen with
> Spectogram.
>
> Is this typical, above average, or below average of what other K2 owners
> have noticed? I'm still trying to convince myself that my K2 is hearing as
> well as it should. So far, it seems to be hearing everything I can hear on
> my shortwave radio.
>
> -- 
> Cheers!
>
> Kevin.