[ARC5] 10 meter BC-454, a bit more

[Kenneth G. Gordon]

I brought the HP-8640B home, set it on the bench and fired it up.

Results are the same as with the URM-25D: 

In CW, I can still hear a 0.5 microvolt signal over the whole range 28 to 30 MHz.

In AM, with the signal generator being modulated at 0dbM at 400 Hz, it takes 2.5 microvolts 
to be heard as well.

This difference seems to be about right to me.

Secondly, the 12SK7 is much noisier than the 12SG7. There is "tons" more "shot-noise" with 
the 12SK7.

I also replaced that defective BFO transformer with an NOS one I bought from Fair Radio 
Sales. Result: no noticable BFO drift, and the note is now pure, rather than being modulated 
with something as the other one was.

I will test the total drift on 10 meters tomorrow. There is quite a bit of that, but I guess that is 
to be expected.

Ken W7EKB