[Hallicrafters] 7059 substitute

[Jim Liles]

Hi Walt:
The 6HL8 is a sorta substitute for the 7059.  Their transconductance is 
10,000 for the tetrode and 7,000 for the triode whereas the 7059 is 5,200 
tetrode and 8,500 triode.  We've tried them in the V3 and V7 positions of 
the SR-2000 and they are a bit unstable and deliver significantly excessive 
gain.  You can make alterations and they will work but using the 6GH8A 
results in a receiver that will outperform most others and equal the rest 
with an MDS of less than -140Dbm in a 2.1Kc band pass and S+N/N of 10Db 
at.less than .15uv.  A better way to quantify this is to say that with a 
.02uv AM signal applied, you can clearly distinguish the carrier and 
sidebands.  Anything better than that will simply be noisy.  The SR-400A 
uses a 6HL8 in the V3 position but does not change out V7, it is still a 
7059.  The use of the quieter 6GH8A configuration in the V3 and V7 positions 
provides the same amplification as the 6HL8 in V3.  When you use the 6HL8 in 
the V3 position, you will be forced to get the spectrum analyzer out, seek 
out the natural feed back loops, reposition wires, and install traps to make 
it work right.  Kindest regards Jim K9AXN