[Hallicrafters] SX115 variations in serial numbers

[Grant Youngman]

> wondering if there are any major qualitative differences in 
> this series of receiver based on serial number, 

I've never heard of any, and never seen any factory service bulletins on the
SX-115, but that doesn't mean there aren't any :-)
 
> Also wonder how this receiver stacks up against a Collins 75A4?

I suspect you're going to get a lot of different views there.  I have both,
and virtually always have the SX-115 powered up and almost never turn on the
75A4.  The 115 isn't quite as selective as the A4 since it uses LC filtering
instead of mechanical filters.  But generally, I think it plays better.  The
SX-115 is quite a bit later on the time-line, and benefits greatly in areas
like AGC performance.  Both are good radios, but if I had to choose one of
them to keep, the 75A4 would be the one to go.

YMMV, of course :-)

Grant/NQ5T
http://www.globeking.com