The 10 meter sensitivity of the K2 is normally quite good.
I would suggest checking the tuning of the bandpass filters.
When tuning the bandpass filters, remember that they are shared by 2
bands, and you must tune the inductors first, and after that, tune the
capacitors. Do 10 meters first, then 12 meters -- do 15 meters first
and after than do 17 meters.
Set the K2 power to 2 watts, connect a dummy load and adjust the proper
bandpass filter element for a peak in the power output. If the power
increases dramatically, exit tune and then re-enter to drop the starting
power back down to the 2 watt level.
After adjusting the bandpass filters to a peak during a transmit (or
tune), they are properly tuned for receive too.
You will need to buy or borrow a calibrated signal generator to make any
definitive measurements of the sensitivity. It is difficult to make a
judgement based on antenna noise alone without some instrumentation.
The Elecraft XG3 is a great tool to do exactly that - it has controlled
output levels and can be used to make MDS measurements, and you can use
it to properly set your S-meter.
73,
Don W3FPR
On 6/6/2011 3:36 AM, Alastair Couper wrote:
I have just received a new old K2 here. It has most of the important mods,
AtoB upgrade, and is working as well as it can, as best I am able to
determine. The alignment is fine, and it puts out OK on all bands. I have
not been able to find any posts about the sensitivity on 15m-12m-10m being
not so great. On 40m-80m-160m it is what I would expect. 20m it's just OK
with wider filters, but there is plenty of internal noise with the
narrower filters.
I don't have a microvolt source to get a precise reading. But with a 5 el
yagi on 10m, band noise completely covers internal noise on my Yaesu. On
the K2, I can hear the band noise, but the internal noise is rather more
than I like. Even strong signals don't move the S meter much, and that is
after I have tweaked the settings, and adjusted the AGC threshold.
I know audio filtering will help with this. I also did the mod to increase
the gain of the RF preamp. I wonder if anyone else sees the 10m
sensitivity as a problem? Is there perhaps a wider bandwidth transistor to
use in place of the 2n5109?
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