[Elecraft] K3 6/10M pre-amp

[Edward R Cole]

>Date: Wed, 10 Jul 2013 00:12:45 -0800
>To: Wayne Burdick <n6kr at elecraft.com>
>From: Edward R Cole <kl7uw at acsalaska.net>
>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
>dubususa at gmail.com
>"Kits made by KL7UW"