[Hallicrafters] SX-28A "deaf" on higher bands

[Roy Morgan]

At 04:27 PM 4/14/2006, Roger Basford wrote:
>...I've just bought a very nice SX-28A receiver... things are very quiet 
>on the HF bands, falling away to very little on 20 metres.


Roger and others,

The 6SA7 mixer tube used in the SX-28's was followed by a better one later 
on. A plug-in mod is to replace the 6SA7 first mixer with a 6SB7 for better 
performance on the upper one or two HF bands.  You may need to do a small 
bit of alignment, but it should work better at the higher frequencies as is.

(In Rogers case, apparently *all* the HF bands are weak, so that points to 
other difficulties.)

I cannot remember if the 6SB7 is built with the low loss base (tan instead 
of black) or not.  If not, I also don't know if there is a 6SB7-Y which 
would be the low loss base version.

My SX-28's are some ways from overhaul, so I would be glad to hear results 
from  anyone who tries this change.

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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