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

[Tom W8JI]

> 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...)

MDS, like dynamic range, can go either direction with changes in gain. It is 
possible to have a gain increase and lose MDS.

This is why it is important to know how things really change in abnormal 
configurations, not how we "feel" they change.

> 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.

That large amount surprises me, although a smaller amount certainly would 
not. Systems with loss are often not bilateral. For example on receiving 
feedline losses associated with feedline SWR are determined by the radio's 
input impedance, not by antenna SWR. On receiving the receiver impedance 
determines feedline SWR.

On transmitting, the antenna is the load and sets feedline SWR....affecting 
feedline losses.

6 dB is a pretty big change. Maybe your receiver input impedance is not so 
close to 50 j0, or your 6 dB is not 6 dB though some sort of errors in 
calibration????

73 Tom