Date: Wed, 10 Jul 2013 00:12:45 -0800
To: Wayne Burdick <[email protected]>
From: Edward R Cole <[email protected]>
Subject: Re: K3 6/10M pre-amp
Wayne,
I re-tested on 50.120 and was able to reduce the -107 dBm signal
from the XG3 down to -135 dBm at 2.8-KHz bw. Correcting for
bw=500-KHz this results in -142.5 dBm. This is barely detectable so
lets say -140 dBm for copyable CW. Adjusting the step attenuator
further did not change the signal so suspect -135 dBm is the lowest
level I can generate with the current setup. -135 dBm is equivalent
to NF=4 dB. That is surprisingly low for the BDR performance which
usually requires a trade-off with MDS.
Bypassing the ATU did not change the level so I guess the ATU was
already adjusted to 50-ohms.
I did adjust the pitch up to about 700-Hz which made the signal
easier to hear. The other day it was probably about 400-Hz.
I did not verify the 0-dBm output of the XG3 but would not expect
there to be significant level above zero.
The K3+PR6 or other Gasfet preamp will exceed the KX3 so still the
preferred setup for 6m-eme will be the K3. Still -140 dB is no
small achievement for the KX3. My summer project includes getting
the 6-element 6m yagi installed and 800-1000w 6m sspa QRV for eme/ms.
thanks for a really sweet little radio.
Ed - KL7UW
> At 08:31 AM 7/9/2013, you wrote:
>> Typical KX3 MDS with preamp on is about -138 to -140 dBm in a
500-Hz bandwidth, on all bands.
>>
>> If a KX3 is measuring -134 dBm MDS in this bandwidth, chances
are there's a measurement error, or the ATU has been left in-line
at an impedance other than that of the source RF generator, etc.
>>
>> 73,
>> Wayne
>> N6KR
73, Ed - KL7UW
http://www.kl7uw.com
[email protected]
"Kits made by KL7UW"
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