[Elecraft] [K2] Preamp?

[Don Wilhelm]

Gil,

Unless your antennas are very inefficient, I would suggest that the 
preamp only does damage to the dynamic range if turned on for the lower 
bands (below 20 meters, 30 meters is a toss-up).

Try this test - connect the antenna and listen to band noise (no 
signals).  Then disconnect the antenna -  if there is a difference 
between antenna connected and antenna disconnected, your receiver front 
end has enough gain.  So turn off the preamp and try the same test 
again.  Similarly, turn on the attenuator and go through the same test.  
At whatever settings you still hear an increase in atmospheric band 
noise when the antenna is connected, that is enough front end gain.  To 
use the preamp when it is not needed will decrease the dynamic range of 
your receiver and reduce the number of weak signals that you can hear.

Of course, if your main operating is working only extra strong signals, 
then you can run the preamp on for all bands and you will not know the 
difference except that your ears will suffer from the excessive 
atmospheric noise that is produced.

73,
Don W3FPR

On 10/29/2012 8:14 PM, Gil G. wrote:
> Hello,
>
> I am curious as to how much of the time you guys have your preamp on?
> Mine is on 100% of the time. I actually never had to turn it off.
> I couldn't dream of ever using the attenuator…
> My K2 seems to hear pretty well, but not without the preamp.
>
> Has anyone heard of changing R76 from 10 Ohms to 6.8 Ohms?
>
> Thanks.
>