[Elecraft] K3: PRE/ATT Bug or feature?

[drewko]

You are right about the ATU. It was my mistake comparing the ATU-ON
which had been tuned at other than 50 ohm load compared to the
ATU-OFF. 

As for PRE+ATT, I just measured MDS with the  PRE and ATT settings
either both on or both off. Having both PRE and ATT switched on gives
2 db poorer MDS than having both off. That is unnoticeable of course,
just a point of interest since the specs would seem to indicate it
should be a couple of db better. 

Does anyone use both PRE+ATT ON and find it noticeably better? I can't
hear any difference myself.

73,
Drew
AF2Z



On Wed, 11 Aug 2010 06:21:05 -0700 (PDT), AB2TC - Knut wrote:

>
>Why do you think you gain in MDS (presumably you mean a *lower* MDS) by
>bypassing the ATU? If the ATU is needed for transmit, it will also be
>benficial in receive. I don't have the K3 ATU, but both manual and automatic
>tuners in my antenna system and can certainly certify that when switching in
>the tuner when needed, the receive signal goes up (mismatch loses receive
>signal too).
>
>AB2TC - Knut
>
>
>drewko wrote:
>> 
>> Actually, you will probably LOSE a couple of db by switching on both
>> preamp and attenuator compared to having both switched off. (Measure
>> your MDS and compare results if you don't believe...)
>> 
>> Regarding weak signals, one factor that is overlooked is the ATU. By
>> switching it to bypass you can gain 5 or 6 db in MDS. Of course, you
>> would want to switch it back on when you transmit. 
>> 
>> I wonder if the ATU could be programmed to automatically be bypassed
>> on receive? You would perhaps not want the ATU to be switched in and
>> out at break-in speeds, but after a suitable semi-breakin delay. I
>> think that would be a handy option for weak signal work for those of
>> us who must use the ATU.
>> 
>> 73,
>> Drew
>> AF2Z
>> 
>> 
>> <snip
>>