Paul,
Check out Jack Smith's website for a fairly simple method of
determining the sensitivity of your K2. There are some readings that Jack
took of his K2, and also readings that I took on my K2. I've provided a link
to the page so you should be able to go right to it.
http://www.cliftonlaboratories.com/k2_rx_sensitivity.htm
You can also check out the rest of his website while you are there. He has
some interesting information on the K2, as well as a nice Panadapter that
you might want to take a look at.
Stan Rife
W5EWA
Houston, TX
K2 S/N 4216
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Don Wilhelm
Sent: Tuesday, January 16, 2007 10:07 AM
To: Paul Del Negro; elecraft@mailman.qth.net
Subject: RE: [Elecraft] K2 receive sensitivity
Paul,
I do not have 10 meter specific MDS measurements handy. I can measure 2 K2s
sometime in th efuture if it is necessary, but it will be after I get the
workbench cleared.
If you have the equipment, measure the RX VFO injection level to the mixer
(TP1) - it should be +7 dBm for good mixer performance. Assuming the mixer
presents a 50 ohm load to the VFO signal and your measurement does not
interfere with the loading, you should see a 500 mVrms voltage at the mixer
port or 1.416 volts peak to peak on a 'scope. In-situ measurement is not
the best for this, substitution would be better, but you can draw some
conclusions based on the in-situ measurement if the input impedance to the
measuring device is high enough (you will be measuring in the 23 to 24 MHz
range, so be certain the instrument is capable of accurate readings at that
frequency (a 150 MHz 'scope with 150 MHz 10X probe should give good
measurements).
If the 10 meter VFO input is sufficient, you should be getting full benefit
from the mixer, and there is nothing short of reducing the losses in the
bandpass filters, T-R switch, and Low Pass Filter that will improve the MDS
on 10 meters. If you find the mixer input level low, it can be adjusted by
changing the resistors on the U2 buffer, but check all bands so you don't
overdrive the mixer if you change the level. If the VFO level changes
between bands, look for some frequency dependency in the VFO ALC circuit.
My reasoning: - beyond the mixer, the K2 response should be the same from
band to band, the only thing that will make changes on one band and not
others is between the antenna jack and the mixer.
73,
Don W3FPR
> -----Original Message-----
> I do own the XG2 and have performed MDS measurements on my K2 using the
> XG2 and also a milspec signal generator I have. The numbers agree very
> closely with published specs ON 20 METERS. On ten meters I measured an
> MDS of -124 dbm (preamp off) and -130dbm (preamp on). IMHO, an MDS less
> than -130 dbm is not acceptable for weak signal reception. Which means
> to me that on 10 meters the preamp is absolutely required.
snip...
> I just want to know if my K2 is healthy
> or not.
> I think the K2 is a masterpiece of 'elegant simplicity' and my intent is
> not to knock the rig. I've had more fun since the my kit arrived than
> I've had since the heathkit days.
> 73, Paul, N2PD
>
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